U.S. patent application number 11/423687 was filed with the patent office on 2007-12-13 for cold start emission reduction monitoring system and method.
Invention is credited to Robert Baskins, Michael J. Cullen, Marsha Kapolnek, John Rollinger, Karen Willard.
Application Number | 20070283682 11/423687 |
Document ID | / |
Family ID | 38820500 |
Filed Date | 2007-12-13 |
United States Patent
Application |
20070283682 |
Kind Code |
A1 |
Cullen; Michael J. ; et
al. |
December 13, 2007 |
Cold Start Emission Reduction Monitoring System and Method
Abstract
An engine emissions diagnostic is disclosed that utilizes
parameters correlating to catalyst temperature to identify when an
indication of degraded performance may be generated.
Inventors: |
Cullen; Michael J.;
(Northville, MI) ; Rollinger; John; (Sterling
Heights, MI) ; Kapolnek; Marsha; (Dearborn, MI)
; Baskins; Robert; (Grass Lake, MI) ; Willard;
Karen; (Grosse Point Farms, MI) |
Correspondence
Address: |
ALLEMAN HALL MCCOY RUSSELL & TUTTLE, LLP
806 S.W. BROADWAY, SUITE 600
PORTLAND
OR
97205
US
|
Family ID: |
38820500 |
Appl. No.: |
11/423687 |
Filed: |
June 12, 2006 |
Current U.S.
Class: |
60/284 ;
60/285 |
Current CPC
Class: |
Y02T 10/47 20130101;
F01N 11/002 20130101; F01N 2550/02 20130101; Y02T 10/40 20130101;
F01N 11/005 20130101 |
Class at
Publication: |
60/284 ;
60/285 |
International
Class: |
F01N 3/00 20060101
F01N003/00 |
Claims
1. A method for controlling a vehicle having an engine, the engine
having an exhaust with an emission control device, comprising:
during an engine start, at least temporarily adjusting an operating
parameter of the engine to increase exhaust mass flow or
temperature when needed to more rapidly heat the emission control
device; estimating temperature of the emission control device
during said engine start; and comparing said estimated temperature
to a reference catalyst temperature required to achieve an emission
threshold.
2. The method of claim 1 wherein said reference catalyst
temperature is based on a desired engine idle speed.
3. The method of claim 2 wherein said reference catalyst
temperature is further based on an estimated airflow based on the
desired engine speed.
4. The method of claim 3 wherein said reference catalyst
temperature is based on an expected spark value for current
conditions.
5. The method of claim 4 wherein actual spark timing is adjusted
based on fuel quality.
6. The method of claim 1 wherein said emission threshold is based
on engine coolant temperature at start.
7. A method for controlling a vehicle having an engine, the engine
having an exhaust with an emission control device, comprising:
during an engine start, at least temporarily adjusting at least
engine airflow and spark timing to increase exhaust mass flow and
temperature when needed to more rapidly heat the emission control
device; overriding at least one of said engine airflow and spark
timing adjustments to compensate for an operating condition; and
setting a diagnostic indication when said override has caused
temperature of the emission control device to be lower than desired
to meet an emission level.
8. A method for controlling a vehicle having an engine, the engine
having an exhaust with an emission control device, comprising:
during an engine cold start, at least temporarily adjusting at
least engine airflow and spark timing to increase exhaust mass flow
and temperature when needed to more rapidly heat the emission
control device; overriding at least one of said engine airflow and
spark timing adjustments to compensate for fuel quality effects on
combustion; and setting a diagnostic indication when said override
has caused temperature of the emission control device to be lower
than desired to meet an emission level.
9. The method of claim 8 wherein said override compensates for
hesitation fuel.
10. The method of claim 8 wherein said override compensates for
engine speed falling below a selected engine speed profile during
said start.
11. The method of claim 8 wherein said diagnostic indication sets a
code in a controller of the vehicle.
12. The method of claim 8 wherein said emission level is based on
engine coolant temperature at start.
Description
BACKGROUND AND SUMMARY
[0001] Vehicles may be required to meet certain emission
thresholds. As such, some vehicles may use emission control
devices, such as catalytic converters, to reduce engine emissions.
These devices may provide various levels of emission reduction
depending on exhaust temperature. As such, engine operation may be
adjusted during an engine start to increase temperature of the
device to thereby reduce emissions by achieving earlier catalyst
light-off, for example.
[0002] However, the various factors can affect performance of the
above adjustments to increase catalyst temperature. For example,
degradation of components may result in less airflow than desired,
for example, which may reduce exhaust gas heat. Further, engine
speed control operation may result in adjustment of spark timing to
such a degree that spark retard is sufficiently reduced or
eliminated thus resulting in reduced exhaust gas temperature and
delayed catalyst light-off.
[0003] As such, in one example, the above conditions causing
reduced catalyst light-off performance via reduced catalyst
temperature may be detected and utilized to indicate that vehicle
emission control performance has degraded.
DESCRIPTION OF THE FIGURES
[0004] FIG. 1 shows a schematic engine diagram;
[0005] FIG. 2 shows an example cold start emissions reduction
monitoring routine; and
[0006] FIG. 3 shows an example graph plotting the catalyst delta
ratio against the engine coolant temperature at start.
DETAILED DESCRIPTION
[0007] Internal combustion engine 10 comprising a plurality of
cylinders, one cylinder of which is shown in FIG. 1, is controlled
by electronic engine controller 12. Engine 10 includes combustion
chamber 30 and cylinder walls 32 with piston 36 positioned therein
and connected to crankshaft 13. Combustion chamber 30 communicates
with intake manifold 44 and exhaust manifold 48 via respective
intake valve 52 and exhaust valve 54. Exhaust gas oxygen sensor 16
is coupled to exhaust manifold 48 of engine 10 upstream of
catalytic converter 20.
[0008] Intake manifold 44 communicates with throttle body 64 via
throttle plate 66. Throttle plate 66 is controlled by electric
motor 67, which receives a signal from ETC driver 69. ETC driver 69
receives control signal (DC) from controller 12. Intake manifold 44
is also shown having fuel injector 68 coupled thereto for
delivering fuel in proportion to the pulse width of signal (fpw)
from controller 12. Fuel is delivered to fuel injector 68 by a
conventional fuel system (not shown) including a fuel tank, fuel
pump, and fuel rail (not shown).
[0009] Engine 10 further includes conventional distributorless
ignition system 88 to provide ignition spark to combustion chamber
30 via spark plug 92 in response to controller 12. In the
embodiment described herein, controller 12 is a conventional
microcomputer including: microprocessor unit 102, input/output
ports 104, electronic memory chip 106, which is an electronically
programmable memory in this particular example, random access
memory 108, and a conventional data bus. The controller may further
include a keep alive memory (not shown) for storing adaptive
parameters.
[0010] Controller 12 receives various signals from sensors coupled
to engine 10, in addition to those signals previously discussed,
including: measurements of inducted mass air flow (MAF) from mass
air flow sensor 110 coupled to throttle body 64; engine coolant
temperature (ECT) from temperature sensor 112 coupled to cooling
jacket 114; a measurement of throttle position (TP) from throttle
position sensor 117 coupled to throttle plate 66; a measurement of
turbine speed (Wt) from turbine speed sensor 119, where turbine
speed measures the speed of a torque converter output shaft, and a
profile ignition pickup signal (PIP) from Hall effect sensor 118
coupled to crankshaft 13 indicating an engine speed (N).
Alternatively, turbine speed may be determined from vehicle speed
and gear ratio.
[0011] Controller 12 may include various control routines, such as
cold start rapid catalyst heating routines that adjust various
engine and/or vehicle operating parameters to more rapidly raise
exhaust gas temperature. For example, ignition timing of one or
more cylinders may be retarded from peak torque timing during cold
starting operating to increase exhaust gas heat generation.
Further, engine idle speed may be temporarily elevated after a cold
start to further increase exhaust gas heat generation. Still other
actions may be taken, such as air-fuel ratio adjustments, valve
timing adjustments, fuel injection timing adjustments, and the
like. In one particular embodiment, engine idle speed, spark
timing, and engine airflow, may be adjusted during a cold start to
increase exhaust gas temperature. In another embodiment, intake
valve advance and/or retard may be used, along with spark retard
and fuel injection timing and amount variations. For example, the
controller may adjust a variable valve timing system to increase
positive valve overlap (e.g., via an intake only variable valve
timing unit) of at least one cylinder during a cold start, and then
adjust a fuel injection amount and/or timing and/or spark
timing.
[0012] However, other control routines may be present which may
limit or vary the above exhaust heat generation adjustments. For
example, detection of low fuel quality, such as hesitation fuel,
may reduce or eliminate spark retard (in order to maintain
combustion and minimum engine speed). As another example, flow
blockages or plugs, may limit airflow increases. As still another
example, variable valve unit degradation may limit or affect valve
timing adjustments or positive overlap generation. As such,
diagnostic routines may be used to detect such system overrides and
the corresponding effects on exhaust gas temperature and/or
catalyst light off during at least the first 15 seconds of vehicle
operation from a cold start under selected conditions, such as
standard air temperatures near 70 degrees F. and barometric
pressure near sea level.
[0013] Continuing with FIG. 1, accelerator pedal 130 is shown
communicating with the driver's foot 132. Accelerator pedal
position (PP) is measured by pedal position sensor 134 and sent to
controller 12.
[0014] In an alternative embodiment, where an electronically
controlled throttle is not used, an air bypass valve (not shown)
can be installed to allow a controlled amount of air to bypass
throttle plate 62. In this alternative embodiment, the air bypass
valve (not shown) receives a control signal (not shown) from
controller 12. In another alternative embodiment, where a mass air
flow sensor is not used, inducted mass air flow may be determined
using a variety of computational methods.
[0015] In an exemplary embodiment, electronic engine controller 12
may further include an on-board diagnostic (OBD) system (not
shown). The OBD system may detect operating component degradation
through various diagnostic routines. In some instances, if a
routine detects degradation, the routine may set a diagnostic
trouble code (alternatively referred to as a service code) in the
electronic engine controller. Many routines within the on-board
diagnostics system may detect emission related degradations in a
range of operating condition of the engine.
[0016] One embodiment advantageously implements a routine to
monitor hydrocarbon emissions during various operating conditions,
such as during engine cold start conditions. Such a monitoring
routine may detect, whether various cold start emissions reduction
(CSER) engine control strategies are effective in heating a
catalyst to a desired light-off temperature and reducing
hydrocarbon emissions. Specifically, the routine may determine if
particular ignition spark retard and/or elevated idle speed
strategies are effectively reducing cold start emissions. However,
it should be appreciated that in some embodiments the routine may
demonstrate the effectiveness of other CSER control strategies as
well.
[0017] Referring to FIG. 2, an exemplary cold start emissions
reduction (CSER) monitoring routine is shown. Specifically, routine
200 monitors catalyst temperature via a catalyst temperature
warm-up index calculation. Furthermore the monitoring system may
make a degradation determination regarding CSER related components
based on whether actual emissions exceed a predetermined threshold
when compared to reference emissions standards. The determined
degradation may result in setting a CSER service code in the
electronic engine controller. Additionally, in some embodiments the
degradation determination may result in a change in operating
parameter.
[0018] Referring back to FIG. 2, the routine begins at 210 where it
is determined if the engine is in a start condition. In one
embodiment, the CSER monitor routine may be configured to monitor
emissions conditions for fifteen seconds following the start of the
engine. Thus, the determination made at 210 may judge whether or
not fifteen seconds have elapsed since the start of the engine. In
some embodiments, the CSER monitor routine may further be limited
to running only when the engine is started and the transmission is
in a neutral position. As such, the engine may be judged to be in a
start condition only when the transmission is in neutral and less
than fifteen seconds have elapsed since the start of the
engine.
[0019] It should be appreciated that in some embodiment, the CSER
monitor routine may run for a desired longer or shorter amount of
time, and/or may run during driving conditions as well.
[0020] Continuing with 210, if it is determined that the engine is
not in a start condition, the routine ends, otherwise the routine
moves to 220. In the illustrated embodiment, the routine may be
configured to make diagnostic calculations at predetermined
intervals during the CSER monitoring time period, for example, a
calculation cycle may be carried out every one hundred
milliseconds. In some embodiments, the diagnostic interval may be
adjusted to desired longer or shorter lengths based on a desired
diagnostic resolution.
[0021] Continuing with 220, if it is determined that the
predetermined amount of time has not elapsed, the routine loops
until it is determined that the predetermined amount of time has
elapsed. Once the predetermined amount of time has elapsed the
routine moves to 230.
[0022] At 230, the routine may calculate a reference catalyst
temperature estimate (ext_cmd_wavg_ref). The reference catalyst
temperature estimate may represent the temperature of the catalyst
based on performance as if there are no hardware problems or
unintended software algorithms. In other words, the reference
catalyst temperature estimate may represent the temperature of the
catalyst during fully functioning conditions. The reference
catalyst temperature estimate may be calculated from several
operating parameters including, a desired idle rpm (dsdrpm) which
may be increased during CSER conditions to heat the catalyst; an
estimated airflow (am_ref) based on the above desired engine speed
(dsdrpm (am_ref)); and the spark timing (spk_lold_cld). In some
embodiments the airflow estimation may be made based on a subset of
an idle speed control open loop airflow calculation. Further, the
reference temperature may be a required temperature needed to
achieve a given emissions level for the current engine starting
conditions, which may include engine coolant temperature,
barometric pressure, air temperature, or combinations thereof. As
such, the reference temperature may be a function of these and
other parameters.
[0023] Once the reference catalyst temperature estimate has been
calculated the routine moves to 240, where the current catalyst
temperature estimate (ext_cmd_wavg) may be calculated. The current
catalyst temperature estimate may be calculated from several
measured or estimated operating parameters including, engine speed
(N); spark estimate (saftot); and the observed airmeter estimate
(load). In some embodiments, the current catalyst temperature
estimate calculation may represent the actual temperature of the
catalyst during a start condition of the engine.
[0024] It should be appreciated that the above described input
operating parameters are purely exemplary, and in some embodiments
other operating parameters may be utilized as inputs for
measurements, derivations, and calculations of the exemplary
routine.
[0025] Next at 250, the delta reference catalyst temperature
estimate (Delta_Ref) may be made based on the change in reference
temperature estimation from the beginning of a calculation cycle to
the end of a calculation cycle. The delta reference catalyst
temperature estimate may indicate the expected catalyst temperature
change according to CSER control strategies. Specifically, the
delta reference catalyst temperature estimate (Delta_Ref) may be
calculated by subtracting the reference catalyst temperature
estimate (ext_cmd_wavg_ref(beg)) calculated at the beginning of the
calculation cycle from the reference catalyst temperature estimate
(ext_cmd_wavg_ref(end)) calculated at the end of the calculation
cycle.
[0026] Next at 260, the delta current catalyst temperature estimate
(Delta_CMD) may be made based on the change in actual temperature
estimation from the beginning of a calculation cycle to the end of
a calculation cycle. The delta current catalyst temperature
estimate may indicate the actual catalyst temperature change
according to CSER control strategies. Specifically, the delta
current catalyst temperature estimate (Delta_CMD) may be calculated
by subtracting the current catalyst temperature estimate
(ext_cmd_wavg_ref(beg)) calculated at the beginning of the
calculation cycle from the current catalyst temperature estimate
(ext_cmd_wavg_ref(end)) calculated at the end of the calculation
cycle.
[0027] Now referring to 270, the temperature warm-up index
calculation may be made. A catalyst delta ratio (CDR) may be
calculated by subtracting the delta current catalyst temperature
estimate (Delta_CMD) from the delta reference catalyst temperature
estimate (Delta_Ref). The difference of two estimates may be
further divided by the delta reference catalyst temperature
estimate (Delta_Ref) to produce the catalyst delta ratio. In some
embodiment, the routine may include a normalization step which may
create a catalyst delta ratio ranging from zero to one. Moreover,
the normalized catalyst delta ratio calculation may indicate the
percent of heating loss in the catalyst between the reference
estimate and the actual estimate. For example, a catalyst delta
ratio of `0.5` may indicate that the catalytic temperature may have
achieved only 50% of expected temperature value.
[0028] Continuing to 280, the calculated catalyst delta ratio can
be compared to a predetermined threshold value. In the illustrated
embodiment, the threshold value may correspond to one and a half
times the expected emission value. Further, the degradation
threshold may be determined based on a function of the engine
coolant temperature at start. Thus, by plotting the catalyst delta
ratio against the engine coolant temperature at start, it can be
determined whether the catalyst delta ratio is above the threshold.
If it is determined that the catalyst delta ratio is below the
threshold value the routine loops back to the beginning of the
routine for another cycle of calculations. If it is determined that
the catalyst delta ratio is above the threshold, the routine moves
to 290.
[0029] At 290, a service code may be set in the electronic engine
controller. In some embodiments, the service code may be related to
CSER, for example, the code may state "cold start engine exhaust
temperature out of range". Furthermore, in some embodiments,
setting the service code may result in a "check engine" light to
illuminate and/or other diagnostic routines to be initiated. Once
the service code has been set the routine ends.
[0030] The routine shown in FIG. 2 is just one example of a cold
start emission reduction engine monitoring strategy. In some
embodiments the routine may include more or less diagnostic modes
than shown in FIG. 2.
[0031] It should also be appreciated that the example
control/diagnostic routines described herein are dependant upon the
configuration of the vehicle control system. Note that the example
control and estimation routines included herein can be used with
various engine and/or vehicle propulsion system configurations. 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 steps, acts, 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 steps,
acts, or functions may be repeatedly performed depending on the
particular strategy being used. Further, the described steps may
graphically represent code to be programmed into the computer
readable storage medium in controller 12.
[0032] FIG. 3 shows an exemplary graph of catalyst delta ratio
calculations plotted against the engine coolant temperature at
start during a cold start condition according to the above
described monitoring routine. The example graph show results
compiled over multiple tests. As shown, the plots determined by the
monitoring routine to be above the threshold, are plotted as
circles and may be judged to be degradations. Furthermore, the
plots determined by the monitoring routine to be below the
threshold, are plotted as squares and may be judged to fall within
acceptable operating conditions.
[0033] The results illustrated in the example graph demonstrate the
accurate and robust nature of the monitoring routine. For example,
the appropriation of the threshold value within the routine may
allow for clear determinations of whether or not a CSER engine
strategy may be functioning effectively. It should be noted that in
embodiments where engines are equipped with electronic throttle
control, degradation determinations may occur less frequently
because the electronically controlled throttle may have a large
dynamic range of operation, resulting in more airflow and faster
catalyst temperature increase.
[0034] Further, 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.
[0035] The subject matter of the present disclosure includes all
novel and nonobvious combinations and subcombinations of the
various systems and configurations, and other features, functions,
and/or properties disclosed herein.
[0036] The following claims particularly point out certain
combinations and subcombinations regarded as novel and nonobvious.
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
subcombinations 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.
* * * * *