U.S. patent application number 11/899107 was filed with the patent office on 2008-03-06 for procedure for the dynamic diagnosis of an exhaust gas probe.
This patent application is currently assigned to Robert Bosch GmbH. Invention is credited to Andreas Koring.
Application Number | 20080053187 11/899107 |
Document ID | / |
Family ID | 38989690 |
Filed Date | 2008-03-06 |
United States Patent
Application |
20080053187 |
Kind Code |
A1 |
Koring; Andreas |
March 6, 2008 |
Procedure for the dynamic diagnosis of an exhaust gas probe
Abstract
The invention concerns a procedure for the dynamic diagnosis of
an exhaust gas probe disposed in an exhaust gas duct of an internal
combustion engine after the emission control system. Provision is
made according to the invention for the dynamic diagnosis to be
implemented simultaneously with a precipitous change of a Lambda
value of the exhaust gas from rich to lean or from lean to rich.
During the operating time of an internal combustion engine, step
changes in the mixture composition occur for different reasons from
rich to lean and from lean to rich. If a dynamic diagnosis of the
exhaust gas probe is implemented during such a step change of the
mixture composition, provision must not be specially made for such
a step change in the diagnosis, which can lead to increased
emissions. It is simply to be taken into regard that the mixture
composition is suited to the effect that the diffusion barrier is
not eliminated due to mixture displacements, which are too
large.
Inventors: |
Koring; Andreas;
(Reutlingen, DE) |
Correspondence
Address: |
MERCHANT & GOULD PC
P.O. BOX 2903
MINNEAPOLIS
MN
55402-0903
US
|
Assignee: |
Robert Bosch GmbH
Stuttgart
DE
|
Family ID: |
38989690 |
Appl. No.: |
11/899107 |
Filed: |
September 4, 2007 |
Current U.S.
Class: |
73/1.06 |
Current CPC
Class: |
Y02T 10/40 20130101;
F02D 41/1495 20130101; F01N 11/00 20130101; Y02T 10/47 20130101;
F02D 41/1408 20130101 |
Class at
Publication: |
073/001.06 |
International
Class: |
F01N 11/00 20060101
F01N011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 5, 2006 |
DE |
10 2006 041 477.2 |
Claims
1. A method of diagnosing an exhaust gas probe disposed in an
exhaust gas duct of an internal combustion engine, the method
comprising dynamically diagnosing the exhaust gas probe
simultaneously with a precipitous change of a Lambda value of an
exhaust gas from rich to lean or from lean to rich.
2. A method according to claim 1, wherein dynamically diagnosing
includes dynamicaly diagnosing simultaneously with a diagnosis of
an emission control system and with a precipitous change of the
Lambda value of the exhaust gas.
3. A procedure according to claim 2, wherein dynamically diagnosing
includes diagnosing after a change of an exhaust gas composition
from a Lambda smaller than 1 to a Lambda greater than 1.
4. A method according to claim 1, further comprising determining a
step function response from rich to lean based on a rich
conditioning of an emission control system and the immediately
subsequent precipitous change of an exhaust gas composition from a
Lambda smaller than 1 to a Lambda greater than 1.
5. A method according to claim 2, wherein dynamically diagnosing is
implemented after a change of an exhaust gas composition from a
Lambda greater than 1 to a Lambda smaller than 1.
6. A method according to claim 1, further comprising determining a
response diagnosis from lean to rich from a gutting of an emission
control system and a lean-rich step change, which occurs in the
process.
7. A method according to claim 1, wherein dynamically diagnosing is
discontinued, if a diagnosis of an emission control system
recognizes it to be in good working order, and the diagnosis of the
emission control system is completed ahead of time.
Description
BRIEF DESCRIPTION OF THE INVENTION
[0001] The invention concerns a procedure for the dynamic diagnosis
of an exhaust gas probe disposed behind the emission control system
in the exhaust gas duct of an internal combustion engine.
[0002] The storage capability for oxygen of an emission control
system is utilized for the purpose of accumulating oxygen in the
lean phases and giving it off in the rich phases. The ability to
convert oxidable toxic gas components is thereby achieved. An
exhaust gas probe located downstream from the emission control
system serves then to monitor the oxygen storage capability of the
emission control system. The oxygen storage capability must be
monitored within the framework of the On-Board-Diagnosis because it
represents a measurement for the conversion capability of the
emission control system. In order to determine the oxygen storage
capability, the emission control system is either initially filled
with oxygen in a lean phase, and in a rich phase is subsequently
emptied of an exhaust gas of a known Lambda while taking into
consideration the amount of exhaust gas which has passed through
the emission control system; or the emission control system is
initially emptied of oxygen in a rich phase and subsequently in a
lean phase is filled with an exhaust gas of a known Lambda taking
into consideration the amount of exhaust gas which has passed
through the emission control system. The lean phase is terminated
if the exhaust gas probe downstream from the emission control
system detects the oxygen, which can no longer be stored by the
emission control system. Likewise a rich phase is terminated if the
exhaust gas probe detects the passage of rich exhaust gas.
Furthermore, an output signal of the exhaust gas probe serves as
additional information for a closed-loop Lambda control, which,
however, to a great extent relies on the output signal of a Lambda
probe disposed before the emission control system.
[0003] If the exhaust gas probe ages, the output signal of the
exhaust gas probe reacts more slowly to changes in the exhaust gas
composition, and deviations in the diagnosis or the emission
control system can occur. These deviations can lead to the point,
where an emission control system, which is no longer correctly
working, is wrongly evaluated to be operative. A known procedure
for the diagnosis of an emission control system evaluates the ratio
of the amplitudes of the output signals of the Lambda probe
disposed before emission control system to those of the exhaust gas
probe downstream from the emission control system. An operative
emission control system dampens by means of its storage capability
the amplitude of an oscillation of the oxygen content of the
exhaust gas at the outlet of the internal combustion engine, so
that the ratio of the amplitudes before and after the emission
control system result in a high value. A delayed reaction of the
exhaust gas probe downstream from the emission control system
leads, however, likewise to a reduction of the amplitude of its
output signal, whereby the oxygen storage capability of the
emission control system is assessed as being too high. An emission
control system no longer corresponding to the demands can, thus,
under certain circumstances wrongly be classified as being in
correct working order.
[0004] A dynamic diagnosis is complicated due to the fact that the
output signal of the exhaust gas probe is dependent on the
beginning and final Lambda value in the case of a rich-lean or
lean-rich step change. Moreover the influence of the emission
control system described above factors in, which is affected
further by the influences of temperature and age on the emission
control system.
[0005] A procedure for the dynamic diagnosis of an exhaust gas
probe is put forth in the German patent DE 19722334. The exhaust
gas probe is disposed in the exhaust gas behind the emission
control system. The rate of change of an output signal of the
exhaust gas probe is used as an assessment criterion, which, for
example, occurs after the beginning of a phase in the coasting
(overrun) mode. It is a disadvantage in this case that this
procedure works only when a very large air mass flow (>>50
kg/h) is present, as only then the effect of the catalytic
converter can be disregarded. In such operating states, undesirable
conditions can, however, emerge when resetting after the coasting
(overrun) phase.
[0006] It is the task of the invention to provide a procedure for
the dynamic diagnosis of an exhaust gas probe disposed behind an
emission control system, which allows for a reliable
evaluation.
SUMMARY OF THE INVENTION
[0007] The task is thereby solved, in that the dynamic diagnosis is
implemented simultaneously with a precipitous change of the Lambda
value of the exhaust gas from rich to lean or from lean to rich.
During the operating time of an internal combustion engine, step
changes of the mixture composition from rich to lean and from lean
to rich occur for different reasons. If the dynamic diagnosis of
the exhaust gas probe is implemented during one such step change of
the mixture composition, provision does not have to be specially
made for such a step change in the diagnosis, which can lead to
increased emissions. It is simply important to pay attention that
the mixture composition is sufficiently suited to prevent the
diffusion barrier from being disabled by mixture displacements,
which are too large.
[0008] If the dynamic diagnosis is simultaneously implemented with
a diagnosis of the emission control system with a precipitous
change of a Lambda value, the fact that the state of the emission
control system is known can be advantageously utilized and
perturbations can be eliminated as far as possible. Moreover, it is
advantageous that no additional emissions are generated, as would
be the case when implementing a rich phase, which is specially
conducted for the diagnosis of the exhaust gas probe with a passage
of rich exhaust gas through the emission control system.
[0009] If the dynamic diagnosis is implemented after a change of
the exhaust gas composition from a Lambda smaller than 1 to a
Lambda greater than 1, the dynamic diagnosis to determine a step
function response to an output signal of the probe during a step
change from rich to lean can be implemented after a rich
conditioning of the emission control system during the subsequent
rich-lean step change.
[0010] If a rich conditioning of the emission control system and
the precipitous change immediately following of the exhaust gas
composition from a Lambda smaller than 1 to a Lambda greater than 1
are used to determine a response rate diagnosis from rich to lean,
the response rate diagnosis can be implemented without provision
being made for a special alteration of the exhaust gas composition
within the scope of the diagnosis of the emission control
system.
[0011] If the dynamic diagnosis is implemented after a change of
the exhaust gas composition from a Lambda greater than 1 to a
Lambda smaller than 1, a dynamic diagnosis can be implemented after
a cat gutting and the lean-rich step change, which occurs in the
process, to determine the step function response from lean to
rich.
[0012] If a gutting of the emission control system and the
lean-rich step change, which occurs in the process, are used for
the determination of a step function response from lean to rich, an
emission of toxic pollutants can be reduced, as the response
diagnosis can be simultaneously implemented with the diagnosis of
the emission control system.
[0013] If the dynamic diagnosis is discontinued when the diagnosis
of the emission control system recognizes it to be in good working
order and the diagnosis of the emission control system is completed
ahead of time, an unnecessary emission of exhaust gas can be
avoided. In so doing, the principle is utilized that in the case of
emission control systems with a sufficient conversion capability,
the dynamics of the exhaust gas probe located downstream from the
emission control system are not relevant.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The invention is explained in detail below using an example
of embodiment depicted in the figures. The following are shown:
[0015] FIG. 1 a technical layout in schematic representation, in
which the procedure according to the invention can be applied,
[0016] FIG. 2 a probe output signal of the exhaust gas probe during
a dynamic diagnosis
DETAILED DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 schematically shows the technical layout, in which
the procedure according to the invention can be deployed for the
dynamic diagnosis of an exhaust gas probe 17. Air is supplied to an
internal combustion engine 10 by way of an air feed 11, and its
mass is determined with an air mass meter 12. The air mass meter 12
can be embodied as a hot film air mass meter. The exhaust gas of
the internal combustion engine 10 is discharged via an exhaust gas
duct 18, whereby provision is made for an emission control system
16 behind the internal combustion engine 10 in the direction of
flow of the exhaust gas. Provision is made for an engine management
system 14 to control the internal combustion engine 10. The engine
management system 14 delivers on the one hand fuel to the internal
combustion engine 10 by way of a fuel metering 13 and on the other
hand is provided with signals from the air mass meter 12 and a
Lambda probe 15 disposed in the exhaust gas duct 18 as well as from
an exhaust gas probe 17 disposed in the exhaust gas discharge pipe
18. The Lambda probe 15 determines a Lambda actual value of a
fuel-air-mixture delivered to the internal combustion engine 10.
The Lambda probe 15 can be embodied as a wide band Lambda probe.
The exhaust gas probe 17 determines the exhaust gas composition
after the emission control system 16. The exhaust gas probe 17 can
be designed as a step change probe.
[0018] A time sequence diagram 20 in FIG. 2 shows a progression of
a probe output signal 21 of the exhaust gas probe 17 in operating
cases, which are suited to a dynamic diagnosis in accordance with
the procedure according to the invention. All of the signals and
operating phases are plotted along a time axis 25. Within the scope
of a diagnosis of the emission control system, a rich conditioning
22 is conducted, in which the oxygen present in the emission
control system is removed and in which the probe output signal 21
increases. At the end of a subsequent lean phase 23, lean exhaust
gas is discharged after the emission control system, and a step
change to a smaller voltage occurs in the probe output signal. This
step change can in accordance with the invention be utilized in the
dynamic diagnosis. At the end of a subsequent gutting phase 24, for
which provision has been made and in which the emission control
system is emptied, the probe output signal 21 increases
precipitously. This step change can also in accordance with the
invention be used in the dynamic diagnosis.
* * * * *