U.S. patent application number 11/421057 was filed with the patent office on 2007-12-06 for venting of on-board vehicle emissions treatment system.
This patent application is currently assigned to FORD GLOBAL TECHNOLOGIES, LLC. Invention is credited to David Cook, Kent Dawson, Daniel Kabat, Michael Levin, Furqan Zafar Shaikh.
Application Number | 20070277505 11/421057 |
Document ID | / |
Family ID | 38135076 |
Filed Date | 2007-12-06 |
United States Patent
Application |
20070277505 |
Kind Code |
A1 |
Dawson; Kent ; et
al. |
December 6, 2007 |
VENTING OF ON-BOARD VEHICLE EMISSIONS TREATMENT SYSTEM
Abstract
A system and method for controlling venting of an on-board
vehicle emissions treatment substance storage and distribution
system that selectively dispenses an emissions treatment substance
from a storage tank on the vehicle to an exhaust system of the
vehicle include selectively coupling the storage tank to the
exhaust system when pressure in the storage tank exceeds a
predetermined pressure associated with the exhaust system. The
invention may also include selectively coupling the storage tank to
atmosphere when a pressure differential between the storage tank
and atmosphere exceeds a predetermined pressure differential.
Inventors: |
Dawson; Kent; (Romeo,
MI) ; Shaikh; Furqan Zafar; (Troy, MI) ;
Levin; Michael; (Ann Arbor, MI) ; Cook; David;
(Albuquerque, NM) ; Kabat; Daniel; (Oxford,
MI) |
Correspondence
Address: |
BIR LAW, PLC/FGTL
13092 GLASGOW CT.
PLYMOUTH
MI
48170-5241
US
|
Assignee: |
FORD GLOBAL TECHNOLOGIES,
LLC
FAIRLANE PLAZA SOUTH, STE. 800 330 TOWN CENTER DRIVE
DEARBORN
MI
|
Family ID: |
38135076 |
Appl. No.: |
11/421057 |
Filed: |
May 30, 2006 |
Current U.S.
Class: |
60/281 ;
60/285 |
Current CPC
Class: |
F01N 2610/06 20130101;
Y02A 50/20 20180101; B01D 2251/2067 20130101; Y02A 50/2322
20180101; F01N 3/206 20130101; F01N 2610/1466 20130101; B01D 53/90
20130101 |
Class at
Publication: |
060/281 ;
060/285 |
International
Class: |
F01N 5/00 20060101
F01N005/00; F01N 3/00 20060101 F01N003/00 |
Claims
1. A method for controlling an on-board vehicle emissions treatment
system that selectively dispenses an emissions treatment substance
from a storage tank to an exhaust system of the vehicle, the method
comprising: selectively coupling the storage tank to the exhaust
system in response to pressure in the storage tank exceeding a
predetermined pressure associated with the exhaust system and
decoupling the storage tank from the exhaust system otherwise to
reduce or eliminate backflow of exhaust into the storage tank.
2. The method of claim 1 wherein the exhaust system includes a
catalyst and wherein the step of selectively coupling comprises
selectively coupling a portion of the storage tank above a maximum
level of the emissions treatment substance to the exhaust system
upstream of the catalyst to selectively deliver vapors from the
storage tank to the exhaust system.
3. The method of claim 1 wherein the predetermined pressure
associated with the exhaust system corresponds to a maximum
anticipated exhaust pressure and wherein the step of selectively
coupling comprises positioning a passive valve between the storage
tank and the exhaust system that operates solely in response to a
pressure differential across the valve to open when the pressure in
the storage tank exceeds the predetermined pressure and to close
when the pressure in the storage tank is less than the
predetermined pressure.
4. The method of claim 1 wherein the step of selectively coupling
comprises positioning a one-way valve between the storage tank and
the exhaust system wherein the one-way valve opens when the
pressure in the storage tank exceeds the predetermined
pressure.
5. The method of claim 1 wherein the step of selectively coupling
comprises controlling a solenoid valve disposed between the storage
tank and the exhaust system such that the solenoid valve opens when
the pressure in the storage tank exceeds the predetermined pressure
associated with the exhaust system.
6. The method of claim 1 further comprising selectively coupling
the storage tank to atmosphere when a pressure differential between
the storage tank and atmosphere exceeds a predetermined pressure
differential.
7. The method of claim 6 wherein the step of selectively coupling
the storage tank to atmosphere comprises positioning a one-way
valve between the storage tank and atmosphere, the one-way valve
opening when the pressure differential between the storage tank and
atmosphere exceeds the predetermined pressure differential to
provide air from atmosphere to the storage tank, and closing when
the pressure differential between the storage tank and atmosphere
is less than the predetermined pressure differential to prevent
vapor egress from the storage tank.
8. The method of claim 6 wherein the step of selectively coupling
the storage tank to atmosphere comprises controlling a solenoid
valve positioned between the storage tank and atmosphere to
selectively provide air to the storage tank.
9. An on-board vehicle emissions treatment system that selectively
dispenses an emissions treatment substance from a storage tank on
the vehicle to an exhaust system of the vehicle, the emissions
treatment system comprising: a venting valve disposed between the
storage tank and the exhaust system, the venting valve selectively
coupling the storage tank to the exhaust system when pressure in
the storage tank exceeds a predetermined pressure associated with
the exhaust system, and decoupling the storage tank from the
exhaust system otherwise to reduce or eliminate exhaust backflow
toward the storage tank.
10. The emissions treatment system of claim 9 further comprising: a
vacuum release valve disposed between the storage tank and
atmosphere, the vacuum release valve selectively coupling
atmosphere to the storage tank when a pressure differential between
atmosphere and the storage tank exceeds a predetermined level and
decoupling the storage tank from atmosphere otherwise.
11. The emissions treatment system of claim 10 wherein the vacuum
release valve operates solely in response to the pressure
differential between the storage tank and atmosphere.
12. The emissions treatment system of claim 9 wherein at least one
of the venting valve and the vacuum release valve comprises a
solenoid valve, the emissions treatment system further comprising:
a controller in communication with the at least one valve for
selectively controlling the valve in response to current operating
conditions.
13. The emissions treatment system of claim 9 wherein the venting
valve operates solely in response to a pressure differential
between the storage tank and the exhaust system.
14. The emissions treatment system of claim 9 further comprising: a
catalyst disposed downstream of an internal combustion engine,
wherein the venting valve selectively couples the storage tank to
the exhaust system upstream of the catalyst.
15. The emissions treatment system of claim 9 wherein the venting
valve opens when the pressure in the storage tank exceeds a maximum
exhaust pressure associated with operation of an internal
combustion engine of the vehicle.
16. A computer readable storage medium having stored data
representing instructions executable by a computer to control an
emissions treatment system of a vehicle, the emissions treatment
system selectively dispensing an emissions treatment substance from
a storage tank on the vehicle to an exhaust system of the vehicle,
the emissions treatment system including a conduit with a
controllable valve disposed between the storage tank and the
exhaust system for selectively venting vapors from the storage tank
to the exhaust system, the computer readable storage medium
comprising: instructions for controlling the valve to open in
response to pressure in the storage tank exceeding exhaust system
pressure to reduce or prevent backflow of exhaust into the storage
tank.
17. The computer readable storage medium of claim 16 wherein the
predetermined pressure corresponds to a maximum anticipated exhaust
pressure to prevent exhaust from entering the storage tank when the
valve is open.
18. The computer readable storage medium of claim 16 wherein the
emissions treatment system includes a controllable vacuum release
valve and wherein the computer readable storage medium comprises
instructions for controlling the vacuum release valve in response
to atmospheric pressure exceeding pressure of the storage tank by a
predetermined amount.
19. The computer readable storage medium of claim 16 further
comprising instructions for periodically opening the valve to
deliver vapor from the storage tank to the exhaust system.
20. The computer readable storage medium of claim 16 further
comprising instructions for opening the valve in response to
temperature of at least one exhaust system component.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to systems and methods for
controlling venting of an on-board emissions treatment system of a
vehicle.
[0003] 2. Background Art
[0004] Various types of vehicle emission control systems introduce
one or more substances directly or indirectly to the engine via the
fuel supply, air/fuel intake, exhaust, or directly to an engine
cylinder or emissions control device, such as a catalyst. For
example, substances acting as reducing agents or reductants, such
as aqueous urea or hydrocarbons (other than fuel) may be used in
lean air/fuel ratio engine applications including diesel engines in
combination with lean NOx catalysts (or selective catalytic
reduction (SCR)) to treat nitrous oxide feedgas emissions. These
substances generally require a storage and distribution system
separate from the primary fuel storage and distribution system.
[0005] Liquid urea selective catalytic reduction (SCR) is a method
of mobile exhaust aftertreatment particularly suited for diesel
engines for treating oxides of nitrogen (NOx) emissions. In a
representative liquid urea SCR application, a urea solution,
typically 33% urea in water, is stored on board the vehicle and
metered or dosed by a pump and injector into the exhaust where it
decomposes by thermal hydrolysis to ammonia and carbon dioxide.
Ammonia then reacts over the SCR catalyst to reduce NOx compounds
to nitrogen, oxygen, and water before being released to
atmosphere.
[0006] Urea stored on-board the vehicle poses unique technical
challenges. For example, when subjected to temperatures common for
underbody exhaust components, urea stored in the tank may begin to
decompose and release ammonia to the air space above the liquid. In
an open vented tank system, some ammonia, which is lighter than
air, may travel up and out the tank vent. Because ammonia has a
pungent odor that most humans can detect in concentrations as low
as 5-20 ppmv, it is desirable to minimize or eliminate ammonia
escaping from the emissions treatment system. Prior art approaches
have employed a selectively operable fan to introduce air into the
reductant storage tank or to remove vapors from the tank as
disclosed in US2003/0213234 and WO2005/028826, for example.
SUMMARY OF THE INVENTION
[0007] A system and method for controlling venting of an on-board
vehicle emissions treatment substance storage and distribution
system that selectively dispenses an emissions treatment substance
from a storage tank on the vehicle to an exhaust system of the
vehicle include selectively coupling the storage tank to the
exhaust system when pressure in the storage tank exceeds a
predetermined pressure associated with the exhaust system. The
invention may also include selectively coupling the storage tank to
atmosphere when a pressure differential between the storage tank
and atmosphere exceeds a corresponding predetermined pressure
differential. The emissions treatment substance storage tank may be
coupled to the exhaust system upstream of a catalyst that may store
ammonia or facilitate its decomposition to reduce or eliminate
ammonia escaping from the vehicle.
[0008] Embodiments of the present invention include an on-board
emissions treatment system having a first valve for selectively
coupling a vehicle emissions treatment substance storage tank to a
vehicle exhaust system when pressure in the storage tank exceeds a
predetermined threshold. A passive one-way check valve may be used
with a predetermined crack or opening pressure selected to be above
the highest anticipated exhaust system pressure to allow selective
venting of the storage tank while reducing or eliminating exhaust
flow into the storage tank. Alternatively, a computer controlled
solenoid valve may be used to selectively couple the storage tank
to the vehicle exhaust system based on current engine, vehicle,
and/or ambient operating conditions. A second check valve or
solenoid valve may be used to selectively couple the storage tank
to atmosphere to reduce or eliminate vacuum and associated vacuum
lock in the emissions treatment storage and distribution
system.
[0009] The present invention provides a number of advantages. For
example, the present invention provides a passive control for
venting a vehicle emissions treatment system to provide storage
and/or treatment of any vapors before being released to atmosphere.
The present invention reduces or eliminates detectable odor
associated with the release of untreated vapors from a vehicle
emissions treatment system. In addition, the invention provides an
alternative to open venting without inducing vacuum lock in the
emission treatment system.
[0010] The above advantages and other advantages and features of
the present invention will be readily apparent from the following
detailed description of the preferred embodiments when taken in
connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a block diagram illustrating one embodiment of a
system or method for controlling venting of an on-board vehicle
emissions treatment system according to the present invention;
and
[0012] FIG. 2 is flow chart illustrating operation of one
embodiment of a system or method for controlling venting of an
on-board emissions treatment system according to the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0013] As those of ordinary skill in the art will understand,
various features of the present invention as illustrated and
described with reference to any one of the Figures may be combined
with features illustrated in one or more other Figures to produce
embodiments of the present invention that are not explicitly
illustrated or described. The combinations of features illustrated
provide representative embodiments for typical applications.
However, various combinations and modifications of the features
consistent with the teachings of the present invention may be
desired for particular applications or implementations.
[0014] Referring now to FIG. 1, a block diagram illustrating one
embodiment of a system or method for controlling an on-board
vehicle emissions treatment system according to the present
invention is shown. System 10 includes an emissions treatment
substance storage tank 12 mounted on a vehicle (not shown). Storage
tank 12 may be used to store an emissions treatment substance 14,
which may include, but is not limited to various reducing agents or
reductants such as aqueous urea, hydrocarbons (other than the
primary fuel), etc. Storage tank 12 may be a single or multiple
wall storage tank having a generally rigid exterior and may
optionally include an interior bladder that contains emissions
treatment substance 14. However, the present invention is
independent of the particular type of storage tank 12. Storage tank
12 includes a vapor/air space 16 that varies in volume relative to
the quantity of emissions treatment substance 14 in tank 12. A fill
pipe (not shown) extends from storage tank 12 and terminates at a
filler neck adapted for receiving a filling nozzle to add emissions
treatments substance 14 to storage tank 12.
[0015] Pump 20 is fluidly coupled to storage tank 12 and in
communication with controller 50, which controls operation of pump
20. During operation, pump 20 pumps emissions treatment substance
14 from tank 12 to pressurize a supply line 22. A dosing or
metering valve 24 is selectively controlled by controller 50 in
response to current operating conditions or parameters of exhaust
system 30 and/or engine 80 to deliver emissions treatment substance
14 via a corresponding nozzle or injector 26 to exhaust system 30
upstream of a mixing element or mixer 34, which mixes exhaust flow
from engine 80 with injected emissions treatment substance 14.
Exhaust system 30 includes various emissions control/treatment
devices that may include a pre-oxidation catalyst 40, a selective
catalytic reduction (SCR) catalyst 42, and a diesel particulate
filter (DPF) 44, for example. Of course, the presence and/or
sequence of particular emissions treatment/control devices may vary
depending upon the particular type of fuel, engine control
strategy, and other factors affecting a particular application or
implementation and the present invention is independent of the
particular types or sequence of emissions treatment/control
devices.
[0016] As also illustrated in FIG. 1, system 10 includes a venting
valve 60 disposed between storage tank 12 and exhaust system 30.
Venting valve 60 opens to selectively fluidly couple space 16,
preferably above a maximum level of emissions treatment substance
14, of storage tank 12 to exhaust system 30 when pressure in
storage tank 12 exceeds a predetermined pressure, such as a
pressure associated with exhaust system 30, for example. Venting
valve 60 closes to decouple space 16 of storage tank 12 from
exhaust system 30 when pressure in exhaust system 30 is greater
than pressure within storage tank 12. In one embodiment, venting
valve 60 is implemented by a passive mechanical valve that operates
solely in response to the pressure in storage tank 12 to open when
the pressure in tank 12 exceeds a predetermined pressure and to
close when the pressure in tank 12 is less than the predetermined
pressure. For example, a passive one-way mechanical valve may be
implemented by a spring-biased ball check valve that has a selected
opening or crack pressure associated with the spring constant and
aperture size. The opening or crack pressure of venting valve 60
may be selected or determined based on the maximum anticipated
pressure in exhaust system 30 so that valve 60 opens only when tank
pressure exceeds exhaust pressure to prevent the flow of exhaust
into tank 12. In an alternative embodiment, venting valve 60 is
implemented by an active/controllable valve, such as a solenoid
valve, in communication with controller 50 and may be electrically,
pneumatically, or electromagnetically actuated in response to one
or more vehicle and/or ambient operating conditions, modes, and/or
parameters. For example, an active venting valve 60 may be
selectively operated directly or indirectly in response to a
temperature sensor 62 and/or pressure sensor 64, which may trigger
operation of venting valve 60 directly, or may communicate with a
dedicated or general purpose controller 50 that actuates venting
valve 60 in response to signals received from sensors 62, 64,
and/or other sensors 66 and/or other actuators 68.
[0017] In the representative embodiments illustrating the present
invention, space 16 of storage tank 12 is vented to exhaust system
30 via selective fluid coupling facilitated by venting valve 60.
Fluid coupling of space 16 to exhaust system 30 directs vapors away
from the vehicle, particularly during filling of emissions
treatment substance storage tank 12. While venting of tank 12 away
from an associated filling tube (not shown) according to the
present invention reduces or eliminates detection of odor during
filling of tank 12 by vehicle operators/occupants, additional
benefits of the invention may be provided by venting tank 12 to a
device that can decompose or store the vapor for future treatment
to reduce or eliminate vapor escape from system 10. In the
representative embodiment illustrated in FIG. 1, tank 12 is
selectively coupled to exhaust system 30 upstream of a vapor
storage/decomposition device implemented by SCR catalyst 42.
Depending upon the current operating temperature of SCR catalyst
42, vapor from tank 12 will react with exhaust flow from engine 80
in exhaust system 30, or may be stored by SCR catalyst 42 and
subsequently reacted when a suitable operating temperature is
reached. For example, if valve 60 opens while engine 80 is
operating or has just been shut off and SCR catalyst 42 has reached
an appropriate operating temperature, vapor from tank 12 will be
reacted with exhaust constituents in SCR catalyst 42. If valve 60
opens based on pressure in tank 12 exceeding a predetermined
pressure threshold due to refilling of substance 14, or due to
increasing temperature of tank 12 when SCR catalyst 42 is below
operating temperature, vapor is stored by SCR catalyst 42 for
subsequent reaction.
[0018] As also illustrated in FIG. 1, system 10 may include a
vacuum release valve disposed between storage tank 12 and
atmosphere. Vacuum release valve 70 selectively couples atmosphere
to space 16 of storage tank 12 when a pressure differential between
atmosphere and storage tank 12 exceeds a predetermined level or
threshold. Vacuum release valve 70 closes to decouple space 16 of
storage tank 12 from atmosphere when the differential pressure is
below the predetermined threshold. Vacuum release 70 may be
implemented by a passive one-way mechanical device that operates
solely in response to the pressure differential between storage
tank 12 and atmosphere, or may be actively controlled by a sensor
or controller, such as pressure sensor 64 or controller 50, for
example, in response to one or more operating conditions, modes,
and/or parameters. In one embodiment, a vacuum release device 70 is
implemented by a mechanical device such as a spring-biased check
valve that allows air to enter space 16 while preventing vapor
egress from space 16 of tank 12 to atmosphere. Preferably, the
opening or cracking pressure of vacuum release valve or device 70
is selected to allow air to enter space 16 when even a small
pressure differential, such as 1/3 psig is present to avoid vacuum
lock of pump 20. Those of ordinary skill in the art will recognize
that various other types of valves or flow control devices may be
used depending upon the particular application to provide the
features and advantages of the present invention that may include
but are not limited to mechanically, electrically, magnetically,
electromagnetically, or pneumatically actuated valves, for
example.
[0019] As those of ordinary skill in the art will appreciate,
system 10 includes various conventional sensors 66 and actuators 68
in addition to those specifically illustrated in FIG. 1 to control
system 10. Various sensors and actuators may communicate with at
least one dedicated or general-purpose controller 50 that includes
a microprocessor 92, also called a central processing unit (CPU),
in communication with a memory management unit (MMU) 94. MMU 94
controls movement of data and/or instructions among various
computer readable storage media 96 and communicates data to and
from CPU 92. The computer readable storage media preferably include
volatile and nonvolatile or persistent storage in read-only memory
(ROM) 98, keep-alive memory (KAM) 100, and random-access memory
102, for example. KAM 100 may be used to store various engine
and/or ambient operating variables while CPU 92 is powered down.
Computer-readable storage media 96 may be implemented using any of
a number of known memory devices such as PROMs (programmable
read-only memory), EPROMs (electrically PROM), EEPROMs
(electrically erasable PROM), flash memory, or any other electric,
magnetic, optical, or combination memory devices capable of storing
data, some of which represent executable instructions, used by CPU
92 in controlling system 10. Computer-readable storage media 96 may
also include floppy disks, CD-ROMs, hard disks, and the like
depending upon the particular application. CPU 92 communicates with
the sensors and actuators via an input/output (I/O) interface 104.
Interface 104 may be implemented as a single integrated interface
that provides various raw data or signal conditioning, processing,
and/or conversion, short-circuit protection, and the like.
Alternatively, one or more dedicated hardware or firmware chips may
be used to condition and process particular signals before being
supplied to CPU 92. Some controller architectures do not contain an
MMU 94. If no MMU 94 is employed, CPU 92 manages data and connects
directly to ROM 98, KAM 100, and RAM 102. Of course, the present
invention could utilize more than one controller 90 or more than
one CPU 92 to provide system control and each controller 90 may
contain multiple ROM 98, KAM 100, and RAM 102 coupled to MMU 94 or
CPU 92 depending upon the particular application.
[0020] FIG. 2 is a flow chart illustrating operation of a system or
method for controlling venting of an on-board vehicle emissions
treatment substance storage and distribution system according to
one embodiment of the present invention. As those of ordinary skill
in the art will appreciate, the diagram of FIG. 2 generally
represents a control process or logic, some of which may be
implemented by any one or more of a number of known processing
strategies such as event-driven, interrupt-driven, multi-tasking,
multi-threading, and the like. As such, various steps 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 invention, but is provided for ease of
illustration and description. Although not explicitly illustrated,
one of ordinary skill in the art will recognize that one or more of
the illustrated steps or functions may be repeatedly performed
depending upon the particular processing strategy or
implementation.
[0021] Steps of the process performed by a controller may be
implemented primarily in software executed by a
microprocessor-based controller that may be dedicated to
controlling the emissions treatment system, or may also be used to
control the engine and/or vehicle. Of course, these steps may be
implemented in software, hardware, or a combination of software and
hardware depending upon the particular application. When
implemented in software, the control logic is preferably provided
in a computer-readable storage medium having stored data
representing instructions executed by a computer or controller to
control the system. The computer-readable storage medium or media
may be any of a number of known physical devices which utilize
electric, magnetic, and/or optical devices to temporarily or
persistently store executable instructions and associated
calibration information, operating variables, and the like.
[0022] Block 200 represent of FIG. 2 represents optionally
determining operating and/or ambient parameters associated with the
engine, vehicle, and/or emissions treatment system and may include
determining pressure(s) 202 and/or temperature(s) 204 associated
with an emissions treatment system including an emissions treatment
substance storage tank and/or one or more exhaust system
components, such as catalysts. Temperature(s) and/or pressure(s)
may be measured by corresponding sensors and/or inferred based on
one or more operating modes, conditions, or parameters. Of course,
for implementations using a passive flow control device for
selective coupling of the emissions treatment storage tank, this
step is unnecessary. Block 206 generally represents a determination
of whether to vent the emissions treatment substance storage tank
in response to current operating conditions or modes. If block 206
determines that venting of the tank is desired, block 208 actuates
one or more flow control devices to selectively couple the on-board
vehicle emissions treatment substance storage tank to the exhaust
system of the vehicle in response to at least one operating
condition and/or parameter. For example, the selective coupling may
be performed by actuating a solenoid valve in response to operating
and/or ambient conditions as determined by corresponding sensors
and/or actuators. Alternatively, selective coupling represented by
block 208 may be performed by a mechanical device operating solely
in response to one or more operating conditions, such as
temperature and/or pressure within the emissions treatment
substance storage tank and/or exhaust system. Depending upon the
particular application and implementation, the selective coupling
may be performed in response to a predetermined pressure or
pressure differential exceeding a predetermined threshold with the
threshold based on an absolute or differential pressure associated
with the exhaust system of the vehicle to reduce or eliminate
exhaust flow into the storage tank. As also generally represented
by block 208, a space above the maximum fluid fill level of the
storage tank is preferably selectively connected to the exhaust
system upstream of a treatment device capable of storing and/or
treating vapors exiting the emissions treatment substance storage
tank. In one embodiment, vapors from the emissions treatment
substance storage tank are selectively introduced to the exhaust
system upstream of an SCR catalyst and downstream of the emissions
treatment substance injector and mixing device.
[0023] If block 206 determines that current operating conditions
and/or mode are not favorable or do not require tank venting, the
system and method decoupling the storage tank from the exhaust
system in response as represented by block 210. This step or
function may include controlling one or more devices to decouple or
block flow between the storage tank and exhaust system. For
example, the system or method may decouple the storage tank space
from the exhaust system when the storage tank pressure is below a
predetermined pressure or pressure differential that may be
selected to include hysteresis for actively controlled valve
applications.
[0024] As also illustrated in FIG. 2, the present invention may
include a determination for selectively coupling the emissions
treatment substance storage tank to atmosphere as represented by
block 212. If current operating conditions and/or operating mode
are suitable for vacuum release, then the emissions treatment
substance storage tank is coupled to atmosphere as represented by
block 214. Operating conditions may include ambient and/or system
temperature(s) and/or pressure(s), operating state of pump 20,
engine 80, and the like.
[0025] Preferably, a vacuum release device operates in response to
a pressure differential between the storage tank and atmosphere to
couple the storage tank to atmosphere and allow air to enter the
storage tank and to subsequently decouple the storage tank from
atmosphere as represented by block 216 to stop vapor egress from
the storage tank to atmosphere.
[0026] Although described with reference to coupling and decoupling
the storage tank space to the exhaust system and/or atmosphere,
those of ordinary skill in the art will recognize that these
features of the invention may be stated differently as controlling
egress of vapors from the storage tank while allowing ingress of
air to prevent vacuum lock of an associated emissions treatment
system pump.
[0027] As such, the present invention provides a passive or active
control for venting a vehicle emissions treatment system to provide
storage and/or treatment of any vapors before being released to
atmosphere. The present invention reduces or eliminates detectable
odor associated with the release of untreated vapors from a vehicle
emissions treatment system. In addition, the invention provides an
alternative to open venting without inducing vacuum lock in the
emission treatment system.
[0028] While the best mode for carrying out the invention has 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 as defined by the
following claims.
* * * * *