U.S. patent application number 16/523317 was filed with the patent office on 2021-01-28 for particulate matter sensor hardware protection in after-run.
The applicant listed for this patent is GM Global Technology Operations LLC. Invention is credited to Bryan D. Axe, Francesco Cannarile, Gaetano Di Venti.
Application Number | 20210025312 16/523317 |
Document ID | / |
Family ID | 1000004261395 |
Filed Date | 2021-01-28 |
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United States Patent
Application |
20210025312 |
Kind Code |
A1 |
Axe; Bryan D. ; et
al. |
January 28, 2021 |
PARTICULATE MATTER SENSOR HARDWARE PROTECTION IN AFTER-RUN
Abstract
A method for mitigating against failure of a particulate matter
sensor of an automobile vehicle includes: determining if a key-off
event is present, identifying an engine is off in a vehicle
after-run mode; defining when local environmental conditions are
outside of mechanical limits of a particulate matter (PM) sensor;
identifying input values to reverse the local environmental
conditions of the PM sensor; and controlling operation of a heating
element of the PM sensor to achieve the input values to reverse the
local environmental conditions during the vehicle after-run
mode.
Inventors: |
Axe; Bryan D.; (Farmington
Hills, MI) ; Di Venti; Gaetano; (Enna, IT) ;
Cannarile; Francesco; (Turin, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GM Global Technology Operations LLC |
Detroit |
MI |
US |
|
|
Family ID: |
1000004261395 |
Appl. No.: |
16/523317 |
Filed: |
July 26, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01N 13/008 20130101;
F01N 2550/22 20130101; F01N 2560/20 20130101; F01N 11/007 20130101;
F01N 2560/05 20130101 |
International
Class: |
F01N 11/00 20060101
F01N011/00; F01N 13/00 20060101 F01N013/00 |
Claims
1. A method for mitigating against failure of a particulate matter
sensor of an automobile vehicle, comprising: determining a range of
moisture conditions to identify when liquid water is present in a
particulate matter (PM) sensor and in a vehicle exhaust system;
confirming an engine is in an after-run mode; determining if
enablement criteria for operation of a heating element of the PM
sensor are met by performing a check of a vehicle odometer to
identify if a reading of the vehicle odometer is less than a
predetermined threshold value, wherein if the reading of the
vehicle odometer is less than the predetermined threshold value,
performing a calibration to determine a maximum heating time to
maximize water removal from the PM sensor; initiating operation of
the heating element of the PM sensor; and operating the heating
element for a predetermined period of time less than or equal to
the maximum heating time at a predetermined temperature to remove
the liquid water from the PM sensor while the engine is in the
after-run mode.
2. The method for mitigating against failure of the particulate
matter sensor of the automobile vehicle of claim 1, further
including signaling a predetermined dew point of the vehicle
exhaust system using a modeled dew point location within the
vehicle exhaust system.
3. The method for mitigating against failure of the particulate
matter sensor of the automobile vehicle of claim 2, wherein if the
if the predetermined dew point has not been reached identifying if
the PM sensor is faulted defined as having water in a ceramic layer
of the PM sensor.
4. The method for mitigating against failure of the particulate
matter sensor of the automobile vehicle of claim 3, wherein if the
PM sensor heating element is not faulted performing a battery
voltage determination to identify if a voltage of a vehicle battery
meets a predetermined minimum voltage prior to operating the
heating element and while the engine is in the after-run mode.
5. The method for mitigating against failure of the particulate
matter sensor of the automobile vehicle of claim 2, wherein if the
predetermined dew point has been reached the PM sensor is
considered un-saturated.
6. The method for mitigating against failure of the particulate
matter sensor of the automobile vehicle of claim 5, further
including continuing to monitor dew point conditions effecting the
PM sensor to identify if a subsequent vehicle cool-down period has
occurred which may cause the PM sensor to become saturated.
7. The method for mitigating against failure of the particulate
matter sensor of the automobile vehicle of claim 1, further
including supplying operational power to the heating element of the
PM sensor from a vehicle battery.
8. The method for mitigating against failure of the particulate
matter sensor of the automobile vehicle of claim 7, further
including regulating the operational power using a controllable
relay.
9. The method for mitigating against failure of the particulate
matter sensor of the automobile vehicle of claim 1, further
including: selecting the predetermined temperature; and choosing
the predetermined period of time ranging up to approximately 15
minutes.
10. The method for mitigating against failure of the particulate
matter sensor of the automobile vehicle of claim 1, further
including saving a model including an exhaust system dew point in
an electronic control unit further operated to control operation of
an engine.
11. A method for mitigating against failure of a particulate matter
sensor of an automobile vehicle, comprising: determining if a
key-off event is present, identifying a vehicle engine is off in a
vehicle after-run mode; defining when local environmental
conditions are outside of mechanical limits of a particulate matter
(PM) sensor; calculating input values to reverse the local
environmental conditions of the PM sensor in order to remain within
the mechanical limits of the PM sensor including determining an
amount of energy to remove a saturation level at a predetermined
location within the PM sensor; and controlling operation of a
heating element of the PM sensor to achieve the input values to
reverse the local environmental conditions during the vehicle
after-run mode.
12. The method for mitigating against failure of the particulate
matter sensor of the automobile vehicle of claim 11, wherein if the
key-off event is present, determining if enablement criteria for
operation of the heating element are met.
13. The method for mitigating against failure of the particulate
matter sensor of the automobile vehicle of claim 12, wherein the
determining if enablement criteria for operation of the heating
element are met includes performing a check of a vehicle odometer
to identify if a reading of the vehicle odometer is less than a
predetermined threshold value.
14. The method for mitigating against failure of the particulate
matter sensor of the automobile vehicle of claim 13, wherein if the
reading of the vehicle odometer is less than the predetermined
threshold value, performing a calibration to determine a maximum
heating time to maximize water removal from the PM sensor.
15. The method for mitigating against failure of the particulate
matter sensor of the automobile vehicle of claim 14, wherein the
determining if enablement criteria for operation of the heating
element are met includes reviewing an outside air temperature map
to determine a length of time for operation of the heating element
of the PM sensor to remove water present at the PM sensor from the
PM sensor.
16. (canceled)
17. The method for mitigating against failure of the particulate
matter sensor of the automobile vehicle of claim 11, further
including identifying if environmental conditions occurring at a
predetermined location of the PM sensor between different ceramic
layers of the PM sensor are outside of mechanical limits of a
ceramic material of the different ceramic layers.
18.-20. (canceled)
Description
INTRODUCTION
[0001] The present disclosure relates to particulate matter sensors
used in automobile vehicle exhaust systems.
[0002] Vehicles powered by internal combustion engines including
diesel engines, gasoline engines and hybrid vehicles are typically
equipped with exhaust after-treatment catalysts, filters,
adsorbents, and other devices to comply with regulatory exhaust
emission standards for carbon monoxide (CO), unburned hydrocarbons
(HC), oxides of nitrogen (NOx), particulate matter (PM), and the
like. The effectiveness of exhaust after-treatment devices for
removing the regulated emissions can vary with engine operating
conditions.
[0003] Automobile vehicles and particularly vehicles having diesel
engines commonly use a sensor to determine levels of particulate
matter that accrue in or pass through a vehicle exhaust system
filter during operation. A particulate matter sensor is provided to
meet vehicle emission standards. The particulate matter sensor is
used to identify the health of the particulate matter filter, and
therefore if the particulate matter filter is deteriorating.
Particulate matter sensors commonly include a sensor surface having
a circuitry pattern imprinted on the surface. As particulate
matter, normally in the form of carbon accrues on the particulate
matter sensor, a circuit is completed by the conductive matter of
the exhaust particulates causing a current rise indicative of the
amount of particulate matter accumulation over time. The
particulate matter may be consumed during normal exhaust system
temperature operation or the particulate matter sensor can be
removed and cleaned periodically to remove built-up particulate
matter to ensure accurate sensor readings over time.
[0004] Particulate matter sensors having one or more ceramic
insulation layers are susceptible to delamination cracking of the
ceramic layers due to buildup of water if the water subsequently
freezes. Particulate matter sensor failure can therefore
result.
[0005] Thus, while current vehicle exhaust system particulate
matter sensors achieve their intended purpose, there is a need for
a new and improved system and method for protecting particulate
matter sensors and mitigating the potential for delamination
cracking.
SUMMARY
[0006] According to several aspects, a method for mitigating
against failure of a particulate matter sensor of an automobile
vehicle includes: determining a range of moisture conditions to
identify when liquid water is present in a particulate matter (PM)
sensor in a vehicle exhaust system; confirming an engine is in an
after-run mode; initiating operation of a heating element of the PM
sensor; and operating the heating element for a predetermined
period of time at a predetermined temperature to remove the liquid
water from the PM sensor while the engine is in the after-run
mode.
[0007] In another aspect of the present disclosure, the method
further includes signaling a predetermined dew point of the vehicle
exhaust system using a modeled dew point location of the vehicle
exhaust system.
[0008] In another aspect of the present disclosure, the method
further includes if the predetermined dew point has not been
reached identifying if the PM sensor has water on or in a ceramic
layer of the PM sensor.
[0009] In another aspect of the present disclosure, the method
further includes if the PM sensor is not faulted having water on or
in the ceramic layer of the PM sensor performing a battery voltage
determination to identify if a voltage of a vehicle battery meets a
predetermined minimum voltage prior to operating the heating
element and while the engine is in the after-run mode.
[0010] In another aspect of the present disclosure, the method
further includes: selecting the predetermined temperature; and
choosing the predetermined period of time ranging up to
approximately 15 minutes.
[0011] In another aspect of the present disclosure, the method
further includes if the predetermined dew point has been reached
the PM sensor is considered un-saturated.
[0012] In another aspect of the present disclosure, the method
further includes continuing to monitor dew point conditions
effecting the PM sensor to identify if a subsequent vehicle
cool-down period has occurred which may cause the PM sensor to
become saturated.
[0013] In another aspect of the present disclosure, the method
further includes supplying operational power to the heating element
of the PM sensor from a vehicle battery.
[0014] In another aspect of the present disclosure, the method
further includes regulating the operational power using a
controllable relay.
[0015] In another aspect of the present disclosure, the method
further includes saving a model of the exhaust system in an
electronic control unit further operated to control operation of an
engine.
[0016] According to several aspects, a method for mitigating
against failure of a particulate matter sensor of an automobile
vehicle includes: determining if a key-off event is present,
identifying an engine is off in a vehicle after-run mode; defining
when local environmental conditions are outside of mechanical
limits of a particulate matter (PM) sensor; identifying input
values to reverse the local environmental conditions of the PM
sensor; and controlling operation of a heating element of the PM
sensor to achieve the input values to reverse the local
environmental conditions during the vehicle after-run mode.
[0017] In another aspect of the present disclosure, the method
further includes if the key-off event is present, determining if
enablement criteria for operation of the heating element are
met.
[0018] In another aspect of the present disclosure, the determining
if enablement criteria for operation of the heating element are met
includes performing an odometer check to identify if a vehicle
odometer reading is less than a predetermined threshold value.
[0019] In another aspect of the present disclosure, the method
further includes if the odometer reading is less than the
predetermined threshold, performing a calibration to determine a
maximum heating time to maximize water removal from the PM
sensor.
[0020] In another aspect of the present disclosure, the determining
if enablement criteria for operation of the heating element are met
includes: conducting an ambient temperature check to identify if an
ambient temperature is faulted; and reviewing an outside air
temperature map to determine a length of time for operation of the
heating element of the PM sensor.
[0021] In another aspect of the present disclosure, the method
further includes: calculating the input values to reverse the local
environmental conditions of the PM sensor to remain within the
mechanical limits of the PM sensor; and determining an amount of
energy to remove a saturation level at a predetermined location
within the PM sensor.
[0022] In another aspect of the present disclosure, the method
further includes identifying if environmental conditions occurring
at a predetermined location of the PM sensor between different
ceramic layers of the PM sensor are outside of mechanical limits of
a ceramic material of the different ceramic layers.
[0023] According to several aspects, a particulate matter sensor
protection system includes a particulate matter (PM) sensor in a
vehicle exhaust system. A model having moisture conditions
identifies when liquid water is present at the PM sensor. An
automobile vehicle includes an engine having an after-run mode of
operation. A heating element of the PM sensor is operated for a
predetermined period of time at a predetermined temperature when
liquid water is present to remove the liquid water from the PM
sensor while the engine is in the after-run mode.
[0024] In another aspect of the present disclosure, a vehicle
battery has a predetermined minimum voltage to operate the heating
element while the engine is in the after-run mode. A controllable
relay regulates an operational power provided from the vehicle
battery to the heating element.
[0025] In another aspect of the present disclosure, a modeled dew
point of the vehicle exhaust system signals a predetermined dew
point of the vehicle exhaust system.
[0026] Further areas of applicability will become apparent from the
description provided herein. It should be understood that the
description and specific examples are intended for purposes of
illustration only and are not intended to limit the scope of the
present disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The drawings described herein are for illustration purposes
only and are not intended to limit the scope of the present
disclosure in any way.
[0028] FIG. 1 is a diagrammatic presentation of an automobile
vehicle having a particulate matter sensor protection system
according to an exemplary aspect;
[0029] FIG. 2 is a front elevational view of a particulate matter
sensor used in the particulate matter sensor protection system of
FIG. 1;
[0030] FIG. 3 is an end elevational cross-sectional view taken at
section 3 of FIG. 2;
[0031] FIG. 4A is an end elevational cross-sectional view similar
to section 3 of FIG. 2;
[0032] FIG. 4B is an end elevational cross-sectional view modified
from FIG. 4A;
[0033] FIG. 4C is an end elevational cross-sectional view modified
from FIG. 4B;
[0034] FIG. 4D is an end elevational cross-sectional view modified
from FIG. 4C,
[0035] FIG. 4E is an end elevational cross-sectional view modified
from FIG. 4D;
[0036] FIG. 4F is an end elevational cross-sectional view modified
from FIG. 4E;
[0037] FIG. 5 is a flowchart identifying method steps for use of
the system of FIG. 1;
[0038] FIG. 6 is a system diagram of control elements used in
operation of the particulate matter sensor of FIG. 1;
[0039] FIG. 7 is a system diagram of control elements used in
operation of the particulate matter sensor of FIG. 1;
[0040] FIG. 8 is a graph showing a temperature over a time for
operation of a heating element of the particulate matter sensor of
FIG. 1; and
[0041] FIG. 9 is a flow diagram identifying alternate method steps
for use of the system of FIG. 1.
DETAILED DESCRIPTION
[0042] The following description is merely exemplary in nature and
is not intended to limit the present disclosure, application, or
uses.
[0043] Referring to FIG. 1, a particulate matter sensor protection
system 10 and method for protecting particulate matter sensors
provide a system and a method for mitigating against failure of a
particulate matter (PM) sensor 12 from mechanical damage which may
occur following operation and shutdown of the particulate matter
sensor protection system 10. According to several aspects, the PM
sensor 12 is part of a vehicle combustion system 13 and is
positioned in an exhaust pipe 14 of an automobile vehicle 16 which
receives exhaust gas discharged from an engine 18. The engine 18
may be a diesel engine or a gasoline combustion engine. In the
exhaust pipe 14, the exhaust gas passes through a particulate
matter filter 20 before being discharged to atmosphere. The PM
sensor 12 is provided to determine an operating health of the
particulate matter filter 20. According to several aspects, the
automobile vehicle 16 may include cars, light duty trucks, vans,
sport utility vehicles, and the like. According to further aspects,
the PM sensor 12 may be used in any exhaust system including but
not limited to industrial, heavy equipment and other engine
applications.
[0044] The engine 18 can include multiple cylinders, which in the
example shown include a first cylinder 22, a second cylinder 24, a
third cylinder 26 and a fourth cylinder 28. Exhaust gas from the
cylinders is directed into an exhaust header 30 prior to discharge
into the exhaust pipe 14. Air for combustion of a fossil fuel is
directed into the cylinders via an intake manifold 32. Exhaust gas
recirculation (EGR) may be provided via an EGR line 34 with EGR
flow controlled by an EGR control valve 36. One or more of the
cylinders can be deactivated using individual cylinder deactivation
control devices 38, 40, 42, 44. A catalyst containing device such
as a catalytic converter 46 and a muffler 48 may also be positioned
in the exhaust pipe 14. Multiple sensors in addition to the PM
sensor 12 are also provided in the exhaust pipe 14. These can
include a first temperature sensor 50 and a modeled dew point
location 52 in the vehicle exhaust system.
[0045] Electrical signals generated by the sensors are forwarded to
an electronic control unit (ECU) 54 via a sensor communication path
55. The ECU 54 controls operation of the engine 18 and also
controls EGR operation and is therefore in communication with the
cylinder deactivation control devices 38, 40, 42, 44 whose
quantities are not limiting and are provided for example only, and
the EGR control valve 36. The modeled dew point location 52 of the
vehicle exhaust system may be saved in a memory of the ECU 54.
[0046] The engine 18 provides motive power to a transmission 56
which operates a drivetrain 58. The drivetrain 58 provides power to
a differential 60, at least one drive axle 62 and to at least one
driven wheel 64. Operational control of the transmission 56 is
provided by control signals generated by a transmission electronic
control unit (TECU) 66, which may also communicate with the ECU
54.
[0047] Referring to FIG. 2 and again to FIG. 1, the particulate
matter (PM) sensor 12 includes a sensor body 68 having at least one
layer onto which is printed or is connected a circuit 70. The
circuit 70 is connected to a monitoring unit such as the ECU 54 and
provided with an electrical current. The circuit 70 is normally
open which indicates minimal or no presence of a particulate matter
which has passed un-filtered through the particulate matter filter
20. Particulate matter is commonly carbon-based, which is
electrically conductive. A voltage potential is applied across the
circuit 70. Presence of carbon-based particulate matter on the PM
sensor 12 will therefore close a portion of the circuit 70 and
thereby generate an electrical current whose amplitude is
indicative of a degree of particulate matter buildup on the PM
sensor 12. When the current level exceeds a predetermined
threshold, the PM sensor 12 is deemed to be faulted and an error
code is generated by the ECU 54.
[0048] Referring to FIG. 3 and again to FIGS. 1 and 2, during
operation of the vehicle combustion system 13 exhaust gas
temperature is elevated and therefore precludes formation of liquid
water in the exhaust pipe 14 and on the PM sensor 12 due to
evaporation. Under certain conditions, particularly following a
short engine drive cycle which does not reach normal elevated
engine and exhaust system temperature to evaporate liquid water
which is present, or when a dew point is reached which allows
generation of liquid water in the exhaust system, water can
accumulate in the exhaust pipe 14 and can partially or fully
saturate the PM sensor 12. According to several aspects, the PM
sensor 12 may be manufactured using multiple layers of porous
ceramic material. As shown in FIG. 3, a first layer 72 may contain
the circuit 70, a second layer 74 may contain a heating element 76
and a third layer 78 may contain a temperature sensor 80 used to
sense an operating temperature of the PM sensor 12 and control
current flow to the heating element 76 for regulating a temperature
of the PM sensor 12.
[0049] According to several aspects, the second layer 74 may be
made from a ceramic material having a different porosity than the
first layer 72, and the third layer 78 may be made from a ceramic
material having a different porosity than either the first layer 72
or the second layer 74. This difference in porosity may lead to
delamination between two or more layers of the PM sensor 12 for the
reasons described below.
[0050] Following operation and shutdown of the vehicle combustion
system 13 moisture can collect in the exhaust pipe 14 and the
vehicle combustion system 13. If the PM sensor 12 becomes partially
or fully saturated with this moisture, followed by ambient
temperatures dropping to or below a freezing temperature,
subsequent engine restart heating the PM sensor 12 or subsequent
initiation of the PM sensor heating element 76 when the engine 18
is restarted may cause delamination between any two of the layers
of the PM sensor 12. An exemplary delamination area 82 is shown
between the first layer 72 and the second layer 74, however a
similar delamination and delamination area can occur between any
successive two of the layers. A delamination area 82 can result in
circuit failure of the PM sensor 12.
[0051] Referring generally to FIGS. 4A through 4F sequentially and
again to FIG. 3, the stages of water infiltration and crack
formation in ceramic layers of an exemplary PM sensor 12 are shown.
Referring to FIG. 4A, exemplary layers of ceramic material having
different porosities are indicated by the first layer 72, the
second layer 74 and the third layer 78. No water is as yet present
as shown in FIG. 4A. Referring to FIG. 4B, water 83 has begun to
saturate into the second layer 74. Referring to FIG. 4C, the water
83 is shown fully saturating the second layer 74, which after
freezing expands and pushes the second layer 74 upward toward the
first layer 72. Referring to FIG. 4D, the expansion of frozen water
83 in the second layer 74 displaces the first layer 72 away from
the second layer 74 forming the crack 82. Referring to FIG. 4E,
after the water 83 evaporates from the second layer 74 the crack 82
remains and spatially separates the first layer 72 and the second
layer 74. Referring to FIG. 4F and again to FIG. 4E, a portion of
the first layer 72 has delaminated at the location of the crack 82
and broken away, leaving only a portion 72a of the original first
layer 72.
[0052] Referring to FIG. 5 and again to FIGS. 1 through 3, a flow
diagram defines a dew point program 84 which includes steps taken
by the particulate matter sensor protection system 10 to mitigate
against a delamination caused circuit failure of the PM sensor 12.
In a dew point determination step 86 a model which can be saved in
the ECU 54 determines a range of moisture conditions to identify
when liquid water is present or when liquid water is no longer
present in the vehicle combustion system 13 including the exhaust
pipe 14. The modeled dew point location 52 saved in the memory of
the ECU 54, which may correspond to a location of the PM sensor 12,
may be used to signal when a predetermined dew point has been
reached. If the dew point has not been reached the PM sensor 12 may
be considered partially or fully saturated and the dew point
program 84 in a critical system fault determination step 88 next
identifies if the PM sensor 12 is faulted defined as having water
on or in a ceramic layer of the PM sensor 12.
[0053] If the PM sensor 12 is not faulted having water at, on or in
a ceramic layer of the PM sensor 12 a battery voltage determination
step 90 is performed to identify if a voltage of a vehicle battery
92 meets a predetermined minimum voltage to initiate operation of
the heating element 76 while the engine 18 is in a shutdown or
after-run mode. If the predetermined minimum voltage is present in
the vehicle battery 92, the dew point program 84 initiates a PM
sensor heating action 94 wherein a current is provided to the
heating element 76 to operate the heating element 76 at a
predetermined temperature for a predetermined period of time to
ensure moisture is removed from the PM sensor 12 while the
automobile vehicle 16 is in the after-run mode. According to
several aspects the predetermined temperature may be selected as
approximately 200 degrees Centigrade, however the predetermined
temperature can vary above or below 200 degrees Centigrade. The
predetermined period of time can be chosen from a range of times
ranging up to approximately 15 minutes.
[0054] If following the dew point determination step 86 the dew
point has been reached the PM sensor 12 may be considered
un-saturated or dry and the dew point program 84 in a follow-up
determination step 96 continues to monitor dew point conditions
effecting the PM sensor 12 to identify if a subsequent vehicle
cool-down period has occurred which may cause the PM sensor 12 to
become saturated. Such a vehicle cool-down period may result from
engine operation for a period of time at idle conditions such as
while the operator waits in a parking lot, when the automobile
vehicle 16 is coasting at low engine operating power down an
extended hill or decline, during stop-and-go driving, and the like.
If the determination step 96 identifies the PM sensor 12 continues
to be un-saturated or dry, there is no need to energize the heating
element 76 and the dew point program 84 ends at a do-not-run in
after-run step 98. If the determination step 96 identifies the PM
sensor 12 may be saturated the dew point program 84 shifts in a dew
point lost step 100 to the critical system fault determination step
88.
[0055] If the dew point program 84 in the critical system fault
determination step 88 identifies the PM sensor 12 is faulted having
water at, on or in a ceramic layer of the PM sensor 12, the PM
sensor 12 can no longer be relied on to operate within a
predetermined operating range, in a fault determined step 102 the
dew point program 84 ends at the do-not-run in after-run step 98.
If the dew point program 84 in the battery voltage determination
step 90 identifies the voltage of the vehicle battery 92 does not
meet the predetermined minimum voltage to initiate operation of the
heating element 76 while the engine 18 is in the shutdown or
after-run mode, in a battery-low power step 104 the dew point
program 84 ends at the do-not-run in after-run step 98.
[0056] Referring to FIG. 6 and again to FIGS. 1 through 4, a
vehicle electrical system 106 supplies operational power from the
vehicle battery 92 to the PM sensor 12 for the predetermined period
of time with the automobile vehicle 16 in the after-run mode.
Operational power is regulated using a controllable relay 108.
[0057] Referring to FIG. 7 and again to FIGS. 1 through 5, an ECU
54 to sensor communication 110 provides command signals from the
ECU 54 for a heater request 112 and a sensor state request 114. The
ECU 54 to sensor communication 110 initiates or stops operation of
the heating element 76 of the PM sensor 12 with the engine 18 in
the after-run mode.
[0058] Referring to FIG. 8 and again to FIG. 6, a graph 116
identifies a temperature 118 and a time 120 for operation of the
heating element 76. The heating element 76 is operated for a target
time 122 at a target temperature 124 to remove moisture from the PM
sensor 12. As previously noted, the target time 122 may range up to
approximately 15 minutes and the target temperature selected may be
approximately 200 degrees Centigrade or can vary above or below 200
degrees Centigrade. It is also noted other target times and target
temperatures may be selected.
[0059] To prevent a mechanical failure of the PM sensor 12, an
algorithm detects when the conditions are correct for particulate
matter sensor failure and executes an intervention strategy defined
by the dew point program 84 during a vehicle after-run period which
modifies localized environmental conditions within the PM sensor 12
to a state of the PM sensor 12 that will not fail. The vehicle
electrical system 106 supplies power to the controllable relay 108
for the predetermined amount of time while the automobile vehicle
16 is turned off. The ECU to sensor communication 110 commands the
sensor heating element 76 to be activated also while the vehicle is
turned off, which operates the heating element 76 to the target
temperature setpoint.
[0060] The intervention strategy defined by the dew point program
84 for the particulate matter sensor protection system 10 operates
in three principle steps. In a first step, the criteria when the
local environmental conditions are outside of the hardware limits
of the PM sensor 12 are defined. A model which may be saved in the
ECU 54 is used to predict when the local environmental conditions
of the PM sensor 12 are outside of the mechanical limits of the PM
sensor 12. For example, the first step identifies if the
environmental conditions occurring at a predetermined location such
as between different layers of different ceramic material of the PM
sensor 12 are outside of mechanical durability limits of the
ceramic material. This information may be saved in a memory of the
ECU 54. In addition, the first step identifies if the measured or
estimated saturation level at the predetermined location is beyond
a predetermined limit saved in a memory of the ECU 54.
[0061] In a second step, input values to reverse the local
environmental conditions of the PM sensor 12 are defined. The model
is again used to calculate the inputs to reverse the local
environmental conditions of the PM sensor 12 to remain within the
mechanical limits of the PM sensor 12. During this step an amount
of energy to remove the measured or estimated saturation level at
the predetermined location is determined or may be retrieved from a
lookup table.
[0062] In a third step, the component to the target input
conditions are controlled. The remedial action is then executed to
reverse the detrimental local environmental conditions in the
vehicle after-run mode to not interfere with daily vehicle
operation.
[0063] Referring to FIG. 9 and again to FIGS. 1 through 8, a flow
diagram 126 presents steps for use of the particulate matter sensor
protection system 10. In an initiating step 128 a determination is
made if a key-off event is present, indicating that the engine 18
is off. If the key-off event is present, in an enablement step 130
a determination is made if enablement criteria for operation of the
system are met. The initiating step 128 defines one of the criteria
defined when local environmental conditions are outside of the
hardware limits of the PM sensor 12.
[0064] If the enablement criteria are met an odometer check step
132 is performed to identify if the vehicle odometer reading is
less than a predetermined threshold value. The odometer check step
132 identifies if the automobile vehicle 16 is new, wherein vehicle
operation at a dealership is commonly limited to very short
operational periods and therefore when greater water volumes may be
present in the vehicle combustion system 13 in the after run mode,
or if the automobile vehicle 16 is being used by an owner operator
for longer periods of time when less water volume is anticipated to
be present in the after run mode. If the odometer reading is less
than the predetermined threshold a calibration step 134 is
performed to determine a maximum heating time to maximize water
removal from the system and from the PM sensor 12. The calibration
step 134 is one of the steps defining input values to reverse local
environmental conditions impacting the PM sensor 12.
[0065] The calibration step 134 is followed by a functionality step
136 wherein a sensor bus for the PM sensor 12 is confirmed to be
active and the PM sensor 12 is energized in a protective heating
mode with full functionality. The odometer check step 132 provides
one of the criteria defined when local environmental conditions are
outside of the hardware limits of the PM sensor 12.
[0066] If the odometer reading is greater than the predetermined
threshold in a following ambient temperature check step 138, a
determination is made if an ambient temperature is faulted. The
ambient temperature check step 138 provides one of the criteria
defined when local environmental conditions are outside of the
hardware limits of the PM sensor 12.
[0067] If during the ambient temperature check step 138 the ambient
temperature is identified as faulted, in an outside air temperature
check 140 an outside air temperature map may be reviewed to
determine a recommended length of time for operation of the PM
sensor heating element 76, and the functionality step 136 is then
performed. The outside air temperature check 140 may be one of the
steps defining input values to reverse local environmental
conditions impacting the PM sensor 12.
[0068] If during the ambient temperature check step 138 the ambient
temperature is not identified as faulted a dew point reached step
142 is performed. The dew point reached step 142 provides one of
the criteria defined when local environmental conditions are
outside of the hardware limits of the PM sensor 12.
[0069] During the dew point reached step 142 a map 144 based on dew
point percentage is consulted to determine a recommended length of
time for operation of the PM sensor heating element 76 to remove
remaining water at the PM sensor 12, and the functionality step 136
is then performed. Consulting the map 144 based on dew point
percentage is performed as one of the steps defining input values
to reverse local environmental conditions impacting the PM sensor
12.
[0070] If during the ambient temperature check step 138 the ambient
temperature is not identified as faulted, in lieu of the dew point
reached step 142 a measurement lost step 146 is performed. As used
herein, "measurement lost" is defined as a condition when after the
dew point temperature has been reached the PM sensor 12
subsequently cools down and a PM sensor temperature falls below the
dew point temperature. During the measurement lost step 146 a
determination is made if the dew point has been lost by determining
if the dew point temperature is less than a predetermined threshold
dew point temperature. The measurement lost step 146 provides a
final one of the criteria defined when local environmental
conditions are outside of the hardware limits of the PM sensor
12.
[0071] A particulate matter sensor protection system 10 of the
present disclosure offers several advantages. These include
definition of criteria when local environmental conditions are
outside of the limits of a PM sensor, definition of input values to
reverse the local environmental conditions, and provision of
control criteria to control the PM sensor to achieve target input
conditions. A method is provided for mitigating failure of a
particulate matter sensor 12 from mechanical damage which may occur
following operation and shutdown of the particulate matter
contamination recovery system due to water saturation of different
porosity ceramic material layers of the PM sensor.
[0072] The description of the present disclosure is merely
exemplary in nature and variations that do not depart from the gist
of the present disclosure are intended to be within the scope of
the present disclosure. Such variations are not to be regarded as a
departure from the spirit and scope of the present disclosure.
* * * * *