U.S. patent application number 12/844991 was filed with the patent office on 2012-02-02 for apparatus and method for monitoring regeneration frequency of a vehicle particulate filter.
This patent application is currently assigned to GM GLOBAL TECHNOLOGY OPOERATIONS, INC.. Invention is credited to Steve L. Melby, Rebecca A. Oemke, Cheryl J. Stark.
Application Number | 20120023903 12/844991 |
Document ID | / |
Family ID | 45471289 |
Filed Date | 2012-02-02 |
United States Patent
Application |
20120023903 |
Kind Code |
A1 |
Oemke; Rebecca A. ; et
al. |
February 2, 2012 |
APPARATUS AND METHOD FOR MONITORING REGENERATION FREQUENCY OF A
VEHICLE PARTICULATE FILTER
Abstract
A vehicle includes an engine, a regenerable exhaust stream
particulate filter, and a host machine. The host machine has a pair
of soot models providing respective actual and modeled soot mass
values for the soot contained in the particulate filter, calculates
a ratio of a change in the actual and modeled soot masses, and
executes a control action when the ratio exceeds a calibrated
threshold. A diagnostic code and/or activation of an indicator
device may be part of the control action. A system includes the
particulate filter and host machine noted above. A method for use
aboard the vehicle includes determining the actual and modeled soot
mass values using first and second soot models, respectively,
calculating a ratio of a change in the actual and modeled soot
mass, comparing the ratio to a calibrated threshold, and executing
a control action when the ratio exceeds the threshold.
Inventors: |
Oemke; Rebecca A.;
(Plymouth, MI) ; Stark; Cheryl J.; (Canton,
MI) ; Melby; Steve L.; (Howell, MI) |
Assignee: |
GM GLOBAL TECHNOLOGY OPOERATIONS,
INC.
Detroit
MI
|
Family ID: |
45471289 |
Appl. No.: |
12/844991 |
Filed: |
July 28, 2010 |
Current U.S.
Class: |
60/274 ;
60/295 |
Current CPC
Class: |
F01N 9/005 20130101;
F01N 3/023 20130101; F01N 9/002 20130101; Y02T 10/47 20130101; Y02T
10/40 20130101; F01N 2900/1606 20130101; F01N 11/00 20130101 |
Class at
Publication: |
60/274 ;
60/295 |
International
Class: |
F01N 3/023 20060101
F01N003/023 |
Claims
1. A vehicle comprising: an engine; a particulate filter which
collects particulate matter from an exhaust stream of the engine,
and which is selectively regenerable using heat; and a host machine
having a first soot model and a second soot model, with the first
and the second soot models respectfully providing an actual soot
mass and a modeled soot mass contained in the particulate filter;
wherein the host machine is operable for calculating a ratio of a
change in the actual soot mass to a change in the modeled soot mass
since an immediately prior regeneration event of the particulate
filter, and for executing a control action when the ratio exceeds a
calibrated threshold.
2. The vehicle of claim 1, wherein the first soot model indexes a
differential pressure across the particulate filter to the actual
soot mass, and wherein the second soot model determines the modeled
soot mass with respect to a set of current vehicle operating
conditions not including the differential pressure across the
particulate filter.
3. The vehicle of claim 1, wherein the host machine generates a
diagnostic code as at least part of the control action.
4. The vehicle of claim 3, wherein the host machine activates an
indicator device as an additional part of the control action.
5. The vehicle of claim 1, wherein the engine is a diesel engine
and the particulate filter is a diesel particulate filter.
6. A system for use aboard a vehicle having an internal combustion
engine, the system comprising: a particulate filter which collects
particulate matter from an exhaust stream of the engine, and which
is selectively regenerable using heat; and a host machine having a
first soot model and a second soot model, with the first and the
second soot models respectfully providing an actual soot mass and a
modeled soot mass contained in the particulate filter; wherein the
host machine is operable for calculating a ratio of a change in the
actual soot mass to a change in the modeled soot mass since an
immediately prior regeneration event of the particulate filter, and
for executing a control action when the ratio exceeds a calibrated
threshold.
7. The system of claim 6, wherein the first soot model indexes
differential pressure across the particulate filter to the actual
soot mass, and wherein the second soot model determines the modeled
soot mass with respect to a set of vehicle operating conditions not
including the differential pressure across the particulate
filter.
8. The vehicle of claim 6, wherein the host machine generates a
diagnostic code as at least part of the control action.
9. The vehicle of claim 8, wherein the host machine activates an
indicator device as an additional part of the control action.
10. The vehicle of claim 6, wherein the engine is a diesel engine
and the particulate filter is a diesel particulate filter.
11. A method for use aboard a vehicle having an internal combustion
engine, a particulate filter which is regenerable using heat, and a
host machine, the method comprising: determining an actual soot
mass value in the particulate filter using a first soot model;
determining a modeled soot mass value in the particulate filter
using a second soot model, wherein the second soot model provides
an estimated soot mass value contained in the particulate filter;
calculating a ratio of a change in the actual soot mass to a change
in the modeled soot mass; comparing the ratio to a calibrated
threshold; and executing a control action when the ratio exceeds a
calibrated threshold.
12. The method of claim 11, wherein the first soot model indexes
differential pressure across the particulate filter to the actual
soot mass value.
13. The method of claim 12, further comprising determining a set of
current vehicle operating conditions not including the differential
pressure across the particulate filter, wherein the second soot
model determines the modeled soot mass with respect to the set of
current vehicle operating conditions.
14. The method of claim 11, further comprising: generating a
diagnostic code as at least part of the control action.
15. The method of claim 14, further comprising: activating an
indicator device as an additional part of the control action.
Description
TECHNICAL FIELD
[0001] The present invention relates to an apparatus and method for
monitoring the regeneration frequency of a particulate filter
adapted for removing soot from a vehicle exhaust stream.
BACKGROUND
[0002] Particulate filters are designed to remove microscopic
particles of soot, ash, metal, and other suspended matter from an
exhaust stream of a vehicle. Over time, the particulate matter
accumulates on a substrate within the filter. In order to extend
the life of the particulate filter and to further optimize engine
functionality, some filters are designed to be selectively
regenerated using heat.
[0003] Temperatures within the particulate filter can be
temporarily increased to between approximately 450.degree. C. to
600.degree. C. by directly injecting and igniting fuel, either in
the engine's cylinder chambers or in the exhaust stream upstream of
the filter. The spike in exhaust gas temperature may be used in
conjunction with a suitable catalyst, e.g., palladium or platinum,
wherein the catalyst and heat act together to reduce the
accumulated particulate matter to relatively inert carbon soot via
a simple exothermic oxidation process.
SUMMARY
[0004] A vehicle as disclosed herein includes an engine, a
particulate filter that is regenerable using heat, and a host
machine. The host machine accesses a first soot model to determine
an actual soot mass in the particulate filter, e.g., a lookup table
indexed by a calculated or measured differential pressure across
the filter, and a second soot model to determine a modeled soot
mass in the filter. The second soot model provides the modeled soot
mass relative to a set of current vehicle operating points or
conditions. The host machine then calculates a ratio of a change in
the actual soot mass to a change in the modeled soot mass. The host
machine compares the calculated ratio to a calibrated threshold,
and automatically executes a control action when the calculated
ratio exceeds the calibrated threshold.
[0005] The method may be embodied as an algorithm executable by the
host machine. By executing the algorithm as disclosed herein, the
host machine can account for varying filter regeneration trigger
points, i.e., sets of generated or related signals initiating a
heat-based regeneration of the particulate filter. The host machine
can also account for the varying soot masses remaining in the
particulate filter subsequent to an immediately prior filter
regeneration event.
[0006] Suitable control actions may include setting a first
diagnostic code when the calculated ratio exceeds the calibrated
threshold, activating an indicator device, transmitting a message,
etc. As the actual and modeled soot values can vary with vehicle
operating conditions, conventional monitoring methods that set an
arbitrary threshold to cover a worst case scenario may be less than
optimal. The present method may therefore improve the robustness of
any regeneration frequency monitoring algorithm.
[0007] A system is also provided for use aboard the vehicle noted
above. The system includes a host machine and a particulate filter,
which is regenerable using heat. The host machine accesses a first
soot model which provides an actual soot mass remaining in the
particulate filter, and a second soot model which provides a
modeled soot mass remaining in the filter using a set of current
vehicle operating conditions. The host machine also calculates a
ratio of a change in the measured soot mass to a change in the
modeled soot mass. The host machine then compares the calculated
ratio to a calibrated threshold, and executes a suitable control
action when the ratio exceeds the threshold.
[0008] A method is also provided that may be embodied as an
algorithm and used aboard the vehicle noted above. The method
includes using a first soot model to determine an actual soot mass
remaining in the particulate filter, and using a second soot model
to determine a modeled soot mass remaining in the filter, with the
second soot model using a set of current vehicle operating
conditions. The method also includes calculating a ratio of a
change in the actual soot mass to a change in the modeled soot
mass, comparing the ratio to a calibrated threshold, and executing
a control action when the ratio exceeds the calibrated
threshold.
[0009] The above features and advantages and other features and
advantages of the present invention are readily apparent from the
following detailed description of the best modes for carrying out
the invention when taken in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic illustration of a vehicle having an
internal combustion engine and a regenerable particulate filter;
and
[0011] FIG. 2 is a flow chart describing a method for monitoring
filter regeneration frequency aboard the vehicle shown in FIG.
1.
DESCRIPTION
[0012] Referring to the drawings, wherein like reference numbers
correspond to like or similar components throughout the several
figures, a vehicle 10 is shown schematically in FIG. 1. The vehicle
10 includes a host machine 40 having an algorithm 100 adapted to
monitor a frequency of regeneration of a heat-regenerable
particulate filter 34 as explained below, and to execute a control
action as needed depending on the frequency of regeneration.
Algorithm 100 is explained in detail below with reference to FIG.
2.
[0013] Vehicle 10 includes an internal combustion engine 12, such
as a diesel engine or a direct injection gasoline engine, an
oxidation catalyst (OC) system 13 having the particulate filter 34,
and a transmission 14. The engine 12 combusts fuel 16 drawn from a
fuel tank 18. In one possible embodiment, the fuel 16 is diesel
fuel, the oxidation catalyst system 13 is a diesel oxidation
catalyst (DOC) system, and the particulate filter 34 is a diesel
particulate filter (DPF), although gasoline or other fuel types may
be used depending on the design of engine 12.
[0014] As noted above, algorithm 100 is executed by the host
machine 40 in order to detect a condition in which a frequency of
regeneration of the particulate filter 34 is higher than a
threshold level required by design standards, doing so using first
and second soot models 50 and 60, respectively, as set forth
herein. In particular, host machine 40 directly monitors
regeneration frequency using a calculated ratio of the difference
in a measured or actual soot level to a simulated or modeled soot
level from the first and second soot models 50 and 60,
respectively, with the two models determining soot levels remaining
in the particulate filter 34 in different ways, and by comparing
the calculated ratio to a calibrated threshold as explained below
with reference to FIG. 2.
[0015] Host machine 40 may be configured as a digital computer
acting as a vehicle controller, and/or as a
proportional-integral-derivative (PID) controller device having a
microprocessor or central processing unit (CPU), read-only memory
(ROM), random access memory (RAM), electrically erasable
programmable read only memory (EEPROM), a high-speed clock,
analog-to-digital (A/D) and/or digital-to-analog (D/A) circuitry,
and any required input/output circuitry and associated devices, as
well as any required signal conditioning and/or signal buffering
circuitry. Algorithm 100 and any required reference calibrations
are stored within or readily accessed by host machine 40 to provide
the functions described below with reference to FIG. 2.
[0016] Vehicle 10 also includes a throttle 20 which selectively
admits a predetermined amount of the fuel 16 and air into engine 12
as needed. Combustion of fuel 16 by the engine 12 generates an
exhaust stream 22, which passes through the exhaust system of the
vehicle before it is ultimately discharged into the surrounding
atmosphere as shown. Energy released by the combustion of fuel 16
ultimately produces torque on an input member 24 of transmission
14. The transmission 14 in turn transfers torque from the engine 12
to an output member 26 in order to propel the vehicle 10 via a set
of wheels 28, only one of which is shown in FIG. 1 for
simplicity.
[0017] The OC system 13 as shown in FIG. 1 cleans and conditions
the exhaust stream 22 as it passes from exhaust ports 17 of engine
12 through the vehicle's exhaust system. To this end, OC system 13
may include an oxidation catalyst 30, a selective catalytic
reduction (SCR) device 32, and the particulate filter 34 noted
above. SCR device 32 may be positioned between the oxidation
catalyst 30 and the particulate filter 34. As understood in the
art, an SCR device converts nitrogen oxide (NOx) gasses into water
and nitrogen as inert byproducts using an active catalyst. SCR
device 32 may be configured as a ceramic brick or a ceramic
honeycomb structure, a plate structure, or any other suitable
design.
[0018] Regeneration of the particulate filter 34 may be active or
passive. As understood in the art, passive regeneration requires no
additional control action for regeneration. Instead, the
particulate filter is installed in place of the muffler, and at
idle or low power operations, particulate matter is collected on
the filter. As the engine exhaust temperatures increase, the
collected material is then burned or oxidized by the exhaust stream
22. Active regeneration adds an external source of heat to complete
the regeneration, along with additional control methodology.
[0019] However configured, the particulate filter 34 may be
constructed of a suitable substrate constructed of, by way of
example, ceramic, metal mesh, pelletized alumina, or any other
temperature and application-suitable material(s). As the
temperature of the exhaust stream 22 increases, particulate matter
previously entrapped within the particulate filter 34 is burned or
oxidized by the hot exhaust gas to form soot within the particulate
filter.
[0020] Vehicle 10 may also include a fuel injection device 36 in
electronic communication with the host machine 40 via control
signals 15, and in fluid communication with fuel tank 18. Fuel
injection device 36 selectively injects fuel 16 into the oxidation
catalyst 30 or engine cylinders (not shown) when determined by the
host machine 40. The injected fuel 16 is then ignited and burned in
a controlled manner to generate the increased levels of heat
necessary for regenerating the particulate filter 34.
[0021] Still referring got FIG. 1, the respective first and second
soot models 50, 60 may be in the form of lookup tables and/or a
series of calculations suitable for determining in different
respective manners the remaining mass of soot in the particulate
filter 34. In one embodiment, the first soot model 50 provides a
measured or actual soot mass value using the measured or calculated
differential pressure across the particulate filter 34, with the
first soot model indexing a differential pressure across the
particulate filter to the actual soot mass.
[0022] The second soot model 60 provides the modeled soot mass in a
different manner, i.e., doing so using a set of current vehicle
operating conditions and not using the differential pressure across
the particulate filter 34. Second soot model 60 uses feedback
signals 44 describing the operating point of engine 12 and other
suitable vehicle operating data points. Such points may include
oxygen levels, throttle position, engine speed, accelerator pedal
position, fueling quantity, requested engine torque, exhaust
temperatures, elapsed time since the start of the last regeneration
event, the particular driving mode such as highway driving, city
driving, and/or other recognized modes or combinations of modes as
determined by monitoring parameters such as engine speed, engine
loading, braking, etc.
[0023] Host machine 40 also receives signals 11 from various
sensors 42 positioned throughout the vehicle 10 describing various
measured values, e.g., exhaust temperatures, pressure, oxygen
levels, etc., at different locations within the OC system 13,
including directly upstream and downstream of the oxidation
catalyst 30 and directly upstream and downstream of the particulate
filter 34. These signals 11 are each transmitted by or relayed to
the host machine 40. Host machine 40 is also in communication with
the engine 12 to receive the feedback signals 44 indentifying the
operating point of the engine, values which are used in particular
by the second soot model 60 as described below.
[0024] Referring to FIG. 2, the host machine 40 executes algorithm
100 aboard the vehicle 10 of FIG. 1 to monitor regeneration
frequency of the particulate filter 34. In general, the host
machine 40 determines a measured or actual soot mass using the
first soot model 50, with the actual soot mass being based on a
differential pressure across the particulate filter 34 according to
one possible embodiment. The host machine 40 then determines a
modeled soot mass in the particulate filter 34, e.g., by
referencing the second soot model 60 using vehicle operating data.
Next, a ratio of a change in the actual soot mass is calculated and
compared to a change in the modeled soot mass, with the ratio
compared to a calibrated threshold. Host machine 40 can execute a
control action when the ratio exceeds the threshold.
[0025] In particular, beginning at step 102 the host machine 40
first determines whether a set of initialization conditions are
present, i.e., whether a regeneration event is presently commanded.
Step 102 may be satisfied by detecting a discrete on/off
regeneration trigger signal generated internally by the host
machine if the host machine is configured to control the
regeneration process, or by another vehicle controller if
configured otherwise. The algorithm 100 proceeds to step 104 after
detection of the regeneration trigger signal or other
initialization condition.
[0026] At step 104, the host machine 40 determines the actual soot
mass in the particulate filter 34. In one possible embodiment, the
host machine 40 directly reads or calculates the differential
pressure across the particulate filter 34 using signals 11 from the
sensors 42 positioned at the inlet and outlet sides of the
particulate filter, in this case configured as temperature
transducers or other suitable temperature sensors, and then
references the first soot model 50 using the pressure drop to
determine an actual soot mass value. This value is temporarily
recorded in memory, and the algorithm 100 proceeds to step 106.
[0027] At step 106, the host machine 40 processes the feedback
signals 44 and any other required signals 11 to calculate a change
in the modeled soot mass, with the modeled soot mass determined
with reference to the second soot model 60 described above. This
change occurs over the time interval between the present
regeneration trigger signal and the initiation of the immediately
prior filter regeneration event. Host machine 40 also calculates
the change in actual soot mass within the particulate filter 34
over the same time interval, this time with reference to first soot
model 50, and then proceeds to step 108 after temporarily recording
the two change values in memory.
[0028] At step 108, the host machine 40 calculates a ratio of the
change values calculated at step 106, i.e., the change in modeled
soot mass and the change in actual soot mass in the elapsed
interval since the last regeneration event, and temporarily records
the value of this ratio in memory before proceeding to step
110.
[0029] At step 110, the host machine 40 compares the ratio from
step 108 to a calibrated threshold. If the recorded ratio exceeds
the calibrated threshold, the host machine 40 proceeds to step 112,
and otherwise proceeds to step 114.
[0030] At step 112, host machine 40 sets a first diagnostic code
indicating that the ratio exceeds the calibrated threshold. Such a
result could mean that there is more soot present within the
particulate filter 34 than expected by the second soot model 60, a
result which may be caused by an air leak or an engine malfunction,
and which therefore warrants further investigation. Additional
control actions at step 112 may include activating an indicator
device 38 to alert an operator, transmitting a message within
vehicle 10, transmitting a message outside of the vehicle using a
vehicle telematics unit, and/or taking any other action suitable
for signaling the need to inspect, maintain, or replace the
particulate filter 34.
[0031] At step 114, the host machine 40 sets a second diagnostic
code indicating that the calculated ratio does not exceed the
calibrated threshold. Algorithm 100 may continue to execute in a
suitable control loop to minimize variability, i.e., all
regeneration events must maintain at least a minimum level of
efficiency, thus making the algorithm robust for any given control
system calibration, as well as a wider variety of control system
calibrations.
[0032] While the best modes for carrying out the invention have
been described in detail, those familiar with the art to which this
invention relates will recognize various alternative designs and
embodiments for practicing the invention within the scope of the
appended claims.
* * * * *