U.S. patent application number 14/775376 was filed with the patent office on 2016-02-04 for reintroduction of air in delivery system accumulator.
This patent application is currently assigned to Cummins IP, Inc.. The applicant listed for this patent is CUMMINS IP, INC.. Invention is credited to Yongquan Chai, Wei Huang, Li Wang, Shu Zhang.
Application Number | 20160032805 14/775376 |
Document ID | / |
Family ID | 51580598 |
Filed Date | 2016-02-04 |
United States Patent
Application |
20160032805 |
Kind Code |
A1 |
Huang; Wei ; et al. |
February 4, 2016 |
Reintroduction of Air in Delivery System Accumulator
Abstract
According to one embodiment, an apparatus for reintroducing air
includes a bypass valve that reduces pressure in an accumulator
that stores reductant to less than an air supply pressure of an air
supply. The apparatus also includes a metering valve that fills the
accumulator with air from the air supply at the air supply
pressure, and a pump that pumps reductant into the accumulator.
Inventors: |
Huang; Wei; (Columbus,
IN) ; Chai; Yongquan; (Columbus, IN) ; Wang;
Li; (Columbus, IN) ; Zhang; Shu; (Columbus,
IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CUMMINS IP, INC. |
Columbus |
IN |
US |
|
|
Assignee: |
Cummins IP, Inc.
Columbus
IN
|
Family ID: |
51580598 |
Appl. No.: |
14/775376 |
Filed: |
February 17, 2014 |
PCT Filed: |
February 17, 2014 |
PCT NO: |
PCT/US14/16720 |
371 Date: |
September 11, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61788484 |
Mar 15, 2013 |
|
|
|
Current U.S.
Class: |
60/274 ;
60/295 |
Current CPC
Class: |
F01N 2610/144 20130101;
F01N 2610/1466 20130101; F01N 2610/1473 20130101; F01N 3/208
20130101; Y02T 10/24 20130101; Y02T 10/12 20130101; F01N 2610/1433
20130101 |
International
Class: |
F01N 3/20 20060101
F01N003/20 |
Claims
1. An apparatus for reintroducing air, comprising: a bypass valve
downstream of an accumulator for reducing pressure in the
accumulator storing reductant to less than an air supply pressure
of an air supply; a metering valve filling the accumulator with air
from the air supply at the air supply pressure; and a pump pumping
reductant into the accumulator.
2. The apparatus of claim 1, wherein the bypass valve reduces
pressure in the accumulator to less than the air supply pressure of
the air supply in response to a timer exceeding a predetermined
threshold.
3. The apparatus of claim 2, wherein the predetermined threshold
comprises an upper pressure threshold and a lower pressure
threshold, and the timer increments when the pressure in the
accumulator is more than the upper pressure threshold or the
pressure in the accumulator is less than the lower pressure
threshold.
4. The apparatus of claim 3, wherein the upper pressure threshold
is associated with a first predetermined percentage of a target
pressure greater than the target pressure, and the lower pressure
threshold is associated with a second predetermined percentage of a
target pressure lower than the target pressure.
5. The apparatus of claim 4, wherein the first and second
predetermined percentages are between about 10% and about 30%.
6. The apparatus of claim 1, wherein the bypass valve reduces
pressure in the accumulator to less than the air supply pressure of
the air supply in response to an expiration of a priming time
interval.
7. The apparatus of claim 6, wherein the priming time interval is
between about 4 hours and about 16 hours.
8. The apparatus of claim 1, wherein the bypass valve reduces
pressure in the accumulator by opening to allow reductant in the
accumulator to drain from the accumulator.
9. The apparatus of claim 8, wherein the metering valve closes to
prevent filling the accumulator with air from the air supply while
the bypass valve is opened.
10. The apparatus of claim 9, wherein the pump stops pumping
reductant into the accumulator while the bypass valve is open and
when the metering valve is filling the accumulator with air.
11. An internal combustion engine system, comprising: an internal
combustion engine; an exhaust after-treatment system treating
exhaust gas from the internal combustion engine; a reductant
delivery system providing reductant to the exhaust after-treatment
system and comprising: a reductant source; an accumulator storing
reductant; a bypass valve downstream of the accumulator and
upstream of the reductant source, the bypass valve operable to
reduce pressure in the accumulator to less than an air supply
pressure of an air supply downstream of the bypass valve; a
metering valve downstream of the accumulator and the bypass valve
and upstream of the air supply, the metering valve being operable
to fill the accumulator with air from the air supply at the air
supply pressure; and a pump downstream of the reductant source and
upstream of the accumulator, the pump being operable to pump
reductant from the reductant source into the accumulator.
12. The internal combustion engine system of claim 11, further
comprising a controller monitoring a pressure within the
accumulator, and stopping the pump, closing the metering valve, and
opening the bypass valve when a magnitude of pressure oscillations
within the accumulator meets a threshold.
13. The internal combustion engine system of claim 12, wherein a
timer increments when the pressure in the accumulator is more than
an upper pressure threshold or the pressure in the accumulator is
less than a lower pressure threshold, and the magnitude of pressure
oscillations is determined using the timer.
14. The internal combustion engine system of claim 12, further
comprising a reductant nozzle injecting reductant into the exhaust
gas from the internal combustion engine.
15. The internal combustion engine system of claim 12, wherein the
controller closes the bypass valve and opens the metering valve
after reductant has drained from the accumulator through the bypass
valve.
16. The internal combustion engine system of claim 15, wherein the
controller closes the metering valve and starts the pump when the
pressure within the accumulator is equal to or less than the air
supply pressure.
17. A method for reintroducing air, comprising: reducing pressure
in an accumulator storing reductant to less than an air supply
pressure of an air supply via a bypass valve downstream of the
accumulator; filling the accumulator with air at the air supply
pressure through a metering valve connecting the accumulator to the
air supply; and pumping reductant into the accumulator from a
pump.
18. The method of claim 17, further comprising: detecting an air
volume in the accumulator; stopping the pump in response to the
detected air volume indicating a low air volume; closing the
metering valve in response to the detected air volume indicating a
low air volume; and opening the bypass valve to drain reductant
from the accumulator in response to stopping the pump and closing
the metering valve.
19. The method of claim 18, further comprising closing the bypass
valve after reductant has been drained from the accumulator.
20. The method of claim 19, further comprising: opening the
metering valve after reductant has been drained from the
accumulator; supplying air at the air supply pressure to the
accumulator through the metering valve after reductant has been
drained from the accumulator until the air pressure within
accumulator reaches the air supply pressure; closing the metering
valve after the air pressure within the accumulator reaches the air
supply pressure; and pumping reductant into the accumulator from
the pump after the accumulator reaches the air supply pressure and
the metering valve is closed.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 61/788,484, filed Mar. 15, 2013, which is
incorporated herein by reference
FIELD
[0002] This application relates generally to internal combustion
engine systems, and more particularly to reductant delivery systems
for exhaust gas after-treatment systems.
BACKGROUND
[0003] Typical exhaust after-treatment systems include components
that reduce the level of harmful exhaust emissions present in the
exhaust gas. Emission requirements vary according to engine type.
For example, emissions tests for compression-ignited engines (e.g.,
diesel-powered engines) typically monitor the concentration of
carbon monoxide, nitrogen oxides (NOx), and unburned hydrocarbons
(UHC) that are released from the tail-pipe to make sure that the
concentrations of such compounds leaving the tail-pipe are within
certain emissions standards. An exhaust after-treatment system may
employ selective catalytic reduction (SCR) components to convert
NOx to Nitrogen and other compounds.
[0004] Conventional exhaust after-treatment systems utilize a
reductant, typically a diesel exhaust fluid (DEF), such as aqueous
urea, ammonia, and the like as a reagent to reduce the NOx in the
exhaust gas. The reductant is dosed into an exhaust gas stream to
convert the harmful emissions. The exhaust after-treatment system
may employ a reductant delivery system with an accumulator and
pressurized air to deliver pressurized reductant for dosing the
exhaust gas. Air within the accumulator may stabilize the pressure
of the reductant. Unfortunately, during dosing the air may migrate
from the accumulator.
SUMMARY
[0005] The subject matter of the present application has been
developed in response to the present state of the art, and in
particular, in response to the problems and needs in the art that
have not yet been fully solved by currently available exhaust
after-treatment systems. Accordingly, the subject matter of the
present application has been developed to provide an apparatus,
method, and system for reintroducing air into a reductant delivery
system accumulator.
[0006] According to one embodiment, an apparatus for reintroducing
air includes a bypass valve that reduces pressure in an accumulator
that stores reductant to less than an air supply pressure of an air
supply. The apparatus also includes a metering valve that fills the
accumulator with air from the air supply at the air supply
pressure, and a pump that pumps reductant into the accumulator.
[0007] In some implementations of the apparatus, the bypass valve
reduces pressure in the accumulator to less than the air supply
pressure of the air supply in response to a timer exceeding a
predetermined threshold. The predetermined threshold can include an
upper pressure threshold and a lower pressure threshold. The timer
will increment when the pressure in the accumulator is more than
the upper pressure threshold or the pressure in the accumulator is
less than the lower pressure threshold. In certain implementations,
the upper pressure threshold is associated with a first
predetermined percentage of a target pressure greater than the
target pressure, and the lower pressure threshold is associated
with a second predetermined percentage of a target pressure lower
than the target pressure. The first and second predetermined
percentages can be between about 10% and 30%
[0008] According to certain implementations of the apparatus, the
bypass valve reduces pressure in the accumulator to less than the
air supply pressure of the air supply in response to the expiration
of a priming time interval. The priming time interval can be
between about 4 hours and about 16 hours.
[0009] In some implementations, the bypass valve reduces pressure
in the accumulator by opening to allow reductant in the accumulator
to drain from the accumulator. Further, the metering valve may
close to prevent filling the accumulator with air from the air
supply while the bypass valve is opened. Additionally, the pump can
stop pumping reductant into the accumulator while the bypass valve
is open and when the metering valve is filling the accumulator with
air.
[0010] According to another embodiment, an internal combustion
engine system includes an internal combustion engine and an exhaust
after-treatment system that treats exhaust gas from the internal
combustion engine. The engine system further includes a reductant
delivery system that provides reductant to the exhaust
after-treatment system. The reductant delivery system also includes
a reductant source, an accumulator that stores reductant, and a
bypass valve downstream of the accumulator and upstream of the
reductant source. The bypass valve is operable to reduce pressure
in the accumulator to less than an air supply pressure of an air
supply downstream of the bypass valve. The reductant delivery
system further includes a metering valve downstream of the
accumulator and the bypass valve and upstream of the air supply.
The metering valve is operable to fill the accumulator with air
from the air supply at the air supply pressure. Additionally, the
reductant delivery system includes a pump downstream of the
reductant source and upstream of the accumulator. The pump is
operable to pump reductant from the reductant source into the
accumulator.
[0011] In some implementations, the internal combustion engine
further includes a controller that monitors a pressure within the
accumulator, and stops the pump, closes the metering valve, and
opens the bypass valve when a magnitude of pressure oscillations
within the accumulator meets a threshold. A timer increments when
the pressure in the accumulator is more than an upper pressure
threshold or the pressure in the accumulator is less than a lower
pressure threshold. The magnitude of pressure oscillations may be
determined using the timer. The engine system may further include a
reductant nozzle that injects reductant into the exhaust gas from
the internal combustion engine. The controller may close the bypass
valve and open the metering valve after reductant has drained from
the accumulator through the bypass valve. In some implementations,
the controller closes the metering valve and starts the pump when
the pressure within the accumulator is equal to or less than the
air supply pressure.
[0012] According to yet another embodiment, a method for
reintroducing air includes reducing pressure in an accumulator
storing reductant to less than an air supply pressure of an air
supply. The method also includes filling the accumulator with air
at the air supply pressure through a metering valve connecting the
accumulator to the air supply. Additionally, the method includes
pumping reductant into the accumulator from a pump.
[0013] In some implementations, the method includes detecting an
air volume in the accumulator, stopping the pump in response to the
detected air volume indicating a low air volume, closing the
metering valve in response to the detected air volume indicating a
low air volume, and opening a bypass valve to drain reductant from
the accumulator in response to stopping the pump and closing the
metering valve. The method may include closing the bypass valve
after reductant has been drained from the accumulator.
Additionally, the method may include opening the metering valve
after reductant has been drained from the accumulator, supplying
air at the air supply pressure to the accumulator through the
metering valve after reductant has been drained from the
accumulator until pressure within accumulator reaches the air
supply pressure, closing the metering valve after the air pressure
within the accumulator reaches the air supply pressure, and pumping
reductant into the accumulator from the pump after the accumulator
reaches the air supply pressure and the metering valve is
closed.
[0014] Reference throughout this specification to features,
advantages, or similar language does not imply that all of the
features and advantages that may be realized with the subject
matter of the present disclosure should be or are in any single
embodiment. Rather, language referring to the features and
advantages is understood to mean that a specific feature,
advantage, or characteristic described in connection with an
embodiment is included in at least one embodiment of the present
disclosure. Thus, discussion of the features and advantages, and
similar language, throughout this specification may, but do not
necessarily, refer to the same embodiment.
[0015] The described features, structures, advantages, and/or
characteristics of the subject matter of the present disclosure may
be combined in any suitable manner in one or more embodiments
and/or implementations. In the following description, numerous
specific details are provided to impart a thorough understanding of
embodiments of the subject matter of the present disclosure. One
skilled in the relevant art will recognize that the subject matter
of the present disclosure may be practiced without one or more of
the specific features, details, components, materials, and/or
methods of a particular embodiment or implementation. In other
instances, additional features and advantages may be recognized in
certain embodiments and/or implementations that may not be present
in all embodiments or implementations. Further, in some instances,
well-known structures, materials, or operations are not shown or
described in detail to avoid obscuring aspects of the subject
matter of the present disclosure. The features and advantages of
the subject matter of the present disclosure will become more fully
apparent from the following description and appended claims, or may
be learned by the practice of the subject matter as set forth
hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] In order that the advantages of the subject matter may be
more readily understood, a more particular description of the
subject matter briefly described above will be rendered by
reference to specific embodiments that are illustrated in the
appended drawings. Understanding that these drawings depict only
typical embodiments of the subject matter and are not therefore to
be considered to be limiting of its scope, the subject matter will
be described and explained with additional specificity and detail
through the use of the drawings, in which:
[0017] FIG. 1 is a schematic block diagram illustrating one
embodiment of an internal combustion engine system;
[0018] FIG. 2 is a schematic block diagram illustrating one
embodiment of a reductant delivery system;
[0019] FIG. 3 is a flow chart diagram illustrating one embodiment
of a method for reintroducing air; and
[0020] FIG. 4 is a chart illustrating one embodiment of
reintroducing air.
DETAILED DESCRIPTION
[0021] FIG. 1 is a schematic block diagram illustrating one
embodiment of an internal combustion engine system 190. The system
190 includes an internal combustion engine 195, an exhaust
after-treatment system 180, and a reductant delivery system 100.
The internal combustion engine 195 combusts fuel, producing
mechanical energy and exhaust gas. The exhaust gas includes
components such as NOX that are harmful to the environment. As a
result, the system 100 converts these components into less harmful
byproducts.
[0022] The exhaust gas is treated by the exhaust after-treatment
system 180. In one embodiment, the exhaust after-treatment system
180 douses the exhaust gas with a reductant. The reductant may be a
diesel exhaust fluid (DEF). The reductant delivery system 100 may
supply the reductant to the exhaust after-treatment system 180.
[0023] FIG. 2 is a schematic block diagram illustrating one
embodiment of the reductant delivery system 100. The system 100
includes a reductant tank 110, a pump 115, an accumulator 120, a
metering valve 130, an air supply 125, a controller 155, and a
nozzle 160.
[0024] The reductant tank 110 stores reductant and provides
reductant to the pump 115. The reductant in the reductant tank 110
may be at an input pressure P.sub.in 140. In one embodiment,
P.sub.in 140 is ambient pressure. The pump 115 pumps the reductant
into the accumulator 120. The pump 115 may pump the reductant at a
first pressure P.sub.1 145. The first pressure 145 may be in the
range of 450 to 650 kilopascals (kPa). In one embodiment, a target
first pressure 145 is 500 kPa.
[0025] The accumulator 120 is primed with air. The air resides in
an upper portion of a cavity within the accumulator 120 as is well
known to those of skill in the art. The reductant enters and exits
the accumulator 120 through ports that are below the level of the
air. As a result, the air is prevented from flowing directly out of
port.
[0026] The metering valve 130 meters the reductant from the
accumulator 120 to the nozzle 160. The reductant may be mixed with
pressurized air from the air supply 125. The air supply pressure
P.sub.2 150 of the air supply 125 may be in the range of 350 to 450
kPa. In one embodiment, the air supply pressure 150 may be 400 kPa.
The nozzle 160 may dose the exhaust gas with the reductant. The air
supply 125 may be a brake air supply. A pressure sensor 175 may
measure the air supply pressure P.sub.2 150 of the air supply 125.
The pressure sensor 175 may communicate a pressure value to the
controller 155.
[0027] The bypass valve 135 may open to allow reductant to flow
from the accumulator 122 the reductant tank 110. The bypass valve
135 and the metering valve 130 may open and close in response to
commands from the controller 155. The controller 155 may control
the operation of the pump 115, and the opening and closing of the
metering valve 130 and the bypass valve 135. In addition, the
controller 155 may receive pressure values from the pressure
sensors 170, 175.
[0028] The controller 155 may include a processor and a computer
readable storage medium. The computer readable storage medium may
store computer readable program code. The processor may execute the
computer readable program code to perform the functions of the
controller 155.
[0029] The accumulator 120 stabilizes the first pressure 145 of the
reductant. When the first pressure 145 increases, such as when the
metering valve 130 is closed, the air is compressed, dampening the
increase in the first pressure 145. Similarly, when the first air
pressure 145 decreases, such as when the metering valve 130 is
opened, the air in the accumulator 120 expands, dampening the
decrease in the first pressure 145. The pressure sensor 170 may
measure the first pressure 145.
[0030] In one embodiment, the metering valve 130 precisely meters
the reductant to ensure that the exhaust gas is not dosed with
insufficient reductant or that too much reductant is not applied.
Yet the reductant cannot be precisely metered if the first pressure
145 oscillates significantly. As a result, the air in the
accumulator 120 dampens the first pressure 145 so that the
reductant can be metered more precisely.
[0031] Unfortunately, although the air cannot flow directly out of
the ports of the accumulator 120, the air does dissolve into the
reductant and flow out of the accumulator 120 with the reductant.
As a result, over time the volume of air in the accumulator 120
decreases. For example, the air in accumulator 120 may have
insufficient volume to dampen the first air pressure 145 after 8 to
12 hours of operation of the internal combustion engine system
190.
[0032] When there is insufficient air in the accumulator 120,
oscillations of the first pressure 145 increase. As a result, the
metering of the reductant from the metering valve 130 to the nozzle
160 is less precise.
[0033] The accumulator 120 could be re-primed with air from a
dedicated, pressurized priming air line. However, the addition of
such a dedicated air line along with the required valves, controls,
and air supply may increase the cost and reduce the reliability of
the accumulator 120. The embodiments described herein reintroduce
air into the accumulator 120 without a dedicated priming line. As a
result, the accumulator 120 may be regularly re-primed with air as
will be described hereafter. In one embodiment, the reintroduction
of the air is performed by an apparatus 175 made up of the pump
115, the accumulator 120, the metering valve 130, the bypass valve
135, and the controller 155.
[0034] FIG. 3 is a flow chart diagram illustrating one embodiment
of a method 500 for reintroducing air. The method 500 may be
performed by the apparatus 175, the reductant delivery system 100,
and the internal combustion engine system 190. In one embodiment,
the controller 155 controls functions of the pump 115, the metering
valve 130, and the bypass valve 135 to perform the method 150.
[0035] The method 500 starts, and in one embodiment the controller
155 detects 502 the air volume in the accumulator 120. The
controller 155 may detect 502 the air volume based on oscillations
in the first pressure 145. The controller 155 may record pressure
values from the pressure sensor 170. In some implementations, the
controller 155 may record the oscillations in the first pressure
145 using a timer or counter. When the first pressure 145 exceeds
an upper pressure threshold or when the first pressure falls below
a lower pressure threshold, the timer or counter is incremented. If
the pressure oscillations, as indicated by the timer or counter,
exceed a threshold, the controller 155 may detect 502 a low air
volume condition as will be described hereafter.
[0036] The pressure threshold may be in the range of 10 to 30
percent greater than or less than a target pressure. For example,
if the target pressure for the first pressure 145 is 500 kPa, the
pressure threshold may be plus and minus 10 percent of the target
pressure, or plus and minus 150 kPa.
[0037] In one embodiment, the controller 155 detects 502 the air
volume in the accumulator 120 in response to a priming time
interval expiring. The priming time interval may be in the range of
4 to 16 hours. In a certain embodiment, the priming time interval
is in the range of 6 to 10 hours. For example, if the priming time
interval is eight hours, the controller 155 may detect 502 the air
volume every eight hours.
[0038] In one embodiment, the controller 155 stops 504 the pump
115. Thus the pump 115 does not pressurize the reductant in the
accumulator 122 to the first pressure 145. In addition, the
controller 155 may close the metering valve 130.
[0039] The bypass valve 135 may reduce 506 the first pressure 145
in the accumulator 120. In one embodiment, the controller 155 opens
the bypass valve 135, allowing the reductant in the accumulator 120
to flow from the accumulator 120 into the reductant tank 110 to
reduce 506 the first pressure 145. The bypass valve 135 may reduce
506 the first pressure 145 until the first pressure 145 is less
than the air supply pressure 150. In one embodiment, the reductant
drains from the accumulator 120 into the reductant tank 110.
[0040] The bypass valve 135 may close 508 in response to a command
from the controller 155. The controller 155 may only close 508 the
bypass valve 135 if the first pressure 145 is less than the air
supply pressure 150. In one embodiment, the controller 155 closes
508 the bypass valve 135 if the first pressure 145 is a pressure
difference less than the air supply pressure 150. The pressure
difference may be in the range of 5 to 25 percent of the air supply
pressure 150.
[0041] The metering valve 130 may open 510. In one embodiment, the
controller 155 opens 510 the metering valve 130 if the bypass valve
135 is closed and if the first pressure 145 is less than the air
supply pressure 150.
[0042] The metering valve 130 may fill 512 the accumulator 120 with
air from the air supply 125 at the air supply pressure 150. In one
embodiment, the metering valve 130 opens to fill 512 the
accumulator 124 for a specified reintroduction time interval. The
reintroduction time interval may be in the range of 2 to 20
seconds. Because the air supply pressure 150 is greater than the
first pressure 145, the air flows through the metering valve 130
and into the accumulator 120.
[0043] In one embodiment, the controller 155 closes 514 the
metering valve 130 after the expiration of the reintroduction time
interval. Alternatively, the controller 155 closes 514 the metering
valve 130 when the first pressure 145 is equal to the air supply
pressure 150.
[0044] The pump 115 may pump 516 reductant into the accumulator 120
and the method 500 ends. Some of the air in the accumulator 120
remains when the reductant is pumped into the accumulator 120 and
is pressurized to the first pressure 145. Thus air is reintroduced
to the accumulator 120 and the accumulator 120 has sufficient air
volume to effectively dampen oscillations of the first pressure
145.
[0045] FIG. 4 is a chart 200 illustrating one embodiment of
reintroducing air. The chart 200 shows the first pressure 145 of
the reductant and the air supply pressure 150 of the mix of
reductant and pressurized air that is fed to the nozzle 160. The
chart 200 also depicts the transitions of the bypass valve 135 and
the metering valve 130 between open and closed positions.
[0046] As depicted, the metering valve 130 opens to supply
reductant to the nozzle 160. When the air volume of the accumulator
120 is low, as shown in seconds 100 to 190, the accumulator 120
does not sufficiently reduce the oscillations 225 of the first
pressure 145 as the metering valve 130 opens to release reductant
and closes to retain reductant.
[0047] In the depicted embodiment, the oscillations 225 of the
first pressure 145 exceed a pressure threshold range defined by
upper and lower thresholds 220a, 220b. The controller 155 may
determine from the oscillations of the first pressure 145 exceeding
the pressure threshold 220 that the air volume within the
accumulator 120 is low. The controller 155 may use a timer or
counter that increments each time the first pressure 145 exceeds or
falls below the upper and lower thresholds 220a, 220b. Once the
timer or counter meets or exceeds a threshold value, a low air
volume condition may be detected for the accumulator 120. In
response to detecting the low air volume in the accumulator 120,
the controller 155 may close 205 the metering valve 130. In
addition, the controller 155 may stop the pump 115.
[0048] The bypass valve 135 opens 210 to reduce the first pressure
145. In one embodiment, the controller 155 opens the bypass valve
135 until the first pressure 145 is less than 215 the air supply
pressure 150. The controller 155 may further close 211 the bypass
valve 135 when the first pressure 145. In one embodiment the
controller 155 closes 211 the bypass valve 135 when the first
pressure 145 is less than 215 the air supply pressure 150.
[0049] The metering valve 130 fills the accumulator 120 with air
from the air supply 125 at the air supply pressure 150. The
controller 155 may open the metering valve 130 if the first
pressure 145 is less than 215 the air supply pressure 150. Because
the air supply pressure 150 is greater than the first pressure 145,
air flows from the air supply 125 through the metering valve 130
into the accumulator 120, reintroducing air into the accumulator
120.
[0050] The controller 155 closes 235 the metering valve 130. The
controller 155 may close 235 the metering valve 130 after the
expiration of the reintroduction time interval. Alternatively, the
controller 155 may close 235 the metering valve 130 when the first
pressure 145 is equal to the air supply pressure 150.
[0051] The pump 115 pumps 240 the reductant into the accumulator
120 at the first pressure 145, with the first pressure 145
stabilizing near a target pressure. Because the accumulator 120 has
been re-primed with air, when the metering valve 130 resumes
opening 245, the oscillations 255 of the first pressure 145 are
greatly reduced.
[0052] By reintroducing air into the accumulator 120, the
embodiments mitigate the depletion of air from the accumulator 120
as the air is dissolved into the reductant and removed from the
accumulator 120. As a result, the accumulator 120 stabilizes the
first pressure of the reductant and the reductant delivery system
100 more precisely supplies the reductant to the nozzle 160 and the
exhaust after-treatment system 180. The exhaust after-treatment
system 180 operates more efficiently, reducing environmental
pollutants. In addition, by reducing peaks of the first pressure
145, components operate within design pressure ranges and are less
susceptible to wear and failure.
[0053] The schematic flow chart diagrams and method schematic
diagrams described above are generally set forth as logical flow
chart diagrams. As such, the depicted order and labeled steps are
indicative of representative embodiments. Other steps, orderings
and methods may be conceived that are equivalent in function,
logic, or effect to one or more steps, or portions thereof, of the
methods illustrated in the schematic diagrams.
[0054] Additionally, the format and symbols employed are provided
to explain the logical steps of the schematic diagrams and are
understood not to limit the scope of the methods illustrated by the
diagrams. Although various arrow types and line types may be
employed in the schematic diagrams, they are understood not to
limit the scope of the corresponding methods. Indeed, some arrows
or other connectors may be used to indicate only the logical flow
of a method. For instance, an arrow may indicate a waiting or
monitoring period of unspecified duration between enumerated steps
of a depicted method. Additionally, the order in which a particular
method occurs may or may not strictly adhere to the order of the
corresponding steps shown.
[0055] Many of the functional units described in this specification
have been labeled as functions, in order to more particularly
emphasize their implementation independence. For example, a
function may be implemented as a hardware circuit comprising custom
VLSI circuits or gate arrays, off-the-shelf semiconductors such as
logic chips, transistors, or other discrete components. A function
may also be implemented in programmable hardware devices such as
field programmable gate arrays, programmable array logic,
programmable logic devices or the like.
[0056] Functions may also be implemented in software for execution
by various types of processors. An identified function of
executable code may, for instance, comprise one or more physical or
logical blocks of computer instructions, which may, for instance,
be organized as an object, procedure, or function. Nevertheless,
the executables of an identified function need not be physically
located together, but may comprise disparate instructions stored in
different locations which, when joined logically together, comprise
the function and achieve the stated purpose for the function.
[0057] Indeed, a function of computer readable program code may be
a single instruction, or many instructions, and may even be
distributed over several different code segments, among different
programs, and across several memory devices. Similarly, operational
data may be identified and illustrated herein within functions, and
may be embodied in any suitable form and organized within any
suitable type of data structure. The operational data may be
collected as a single data set, or may be distributed over
different locations including over different storage devices, and
may exist, at least partially, merely as electronic signals on a
system or network. Where a function or portions of a function are
implemented in software, the computer readable program code may be
stored and/or propagated on in one or more computer readable
storage medium(s).
[0058] The computer readable medium may be a tangible computer
readable storage medium storing the computer readable program code.
The computer readable storage medium may be, for example, but not
limited to, an electronic, magnetic, optical, electromagnetic,
infrared, holographic, micromechanical, or semiconductor system,
apparatus, or device, or any suitable combination of the
foregoing.
[0059] More specific examples of the computer readable medium may
include but are not limited to a portable computer diskette, a hard
disk, a random access memory (RAM), a read-only memory (ROM), an
erasable programmable read-only memory (EPROM or Flash memory), a
portable compact disc read-only memory (CD-ROM), a digital
versatile disc (DVD), an optical storage device, a magnetic storage
device, a holographic storage medium, a micromechanical storage
device, or any suitable combination of the foregoing. In the
context of this document, a computer readable storage medium may be
any tangible medium that can contain, and/or store computer
readable program code for use by and/or in connection with an
instruction execution system, apparatus, or device.
[0060] The computer readable medium may also be a computer readable
signal medium. A computer readable signal medium may include a
propagated data signal with computer readable program code embodied
therein, for example, in baseband or as part of a carrier wave.
Such a propagated signal may take any of a variety of forms,
including, but not limited to, electrical, electro-magnetic,
magnetic, optical, or any suitable combination thereof. A computer
readable signal medium may be any computer readable medium that is
not a computer readable storage medium and that can communicate,
propagate, or transport computer readable program code for use by
or in connection with an instruction execution system, apparatus,
or device. Computer readable program code embodied on a computer
readable signal medium may be transmitted using any appropriate
medium, including but not limited to wireless, wireline, optical
fiber cable, Radio Frequency (RF), or the like, or any suitable
combination of the foregoing
[0061] In one embodiment, the computer readable medium may comprise
a combination of one or more computer readable storage mediums and
one or more computer readable signal mediums. For example, computer
readable program code may be both propagated as an electro-magnetic
signal through a fiber optic cable for execution by a processor and
stored on RAM storage device for execution by the processor.
[0062] Computer readable program code for carrying out operations
for aspects of the present invention may be written in any
combination of one or more programming languages, including an
object oriented programming language such as Java, Smalltalk, C++
or the like and conventional procedural programming languages, such
as the "C" programming language or similar programming languages.
The computer readable program code may execute entirely on the
user's computer, partly on the user's computer, as a stand-alone
software package, partly on the user's computer and partly on a
remote computer or entirely on the remote computer or server. In
the latter scenario, the remote computer may be connected to the
user's computer through any type of network, including a local area
network (LAN) or a wide area network (WAN), or the connection may
be made to an external computer (for example, through the Internet
using an Internet Service Provider).
[0063] Reference throughout this specification to "one embodiment,"
"an embodiment," or similar language means that a particular
feature, structure, or characteristic described in connection with
the embodiment is included in at least one embodiment of the
present invention. Thus, appearances of the phrases "in one
embodiment," "in an embodiment," and similar language throughout
this specification may, but do not necessarily, all refer to the
same embodiment. Similarly, the use of the term "implementation"
means an implementation having a particular feature, structure, or
characteristic described in connection with one or more embodiments
of the present disclosure, however, absent an express correlation
to indicate otherwise, an implementation may be associated with one
or more embodiments.
[0064] In the above description, certain terms may be used such as
"up," "down," "upper," "lower," "horizontal," "vertical," "left,"
"right," and the like. These terms are used, where applicable, to
provide some clarity of description when dealing with relative
relationships. But, these terms are not intended to imply absolute
relationships, positions, and/or orientations. For example, with
respect to an object, an "upper" surface can become a "lower"
surface simply by turning the object over. Nevertheless, it is
still the same object. Further, the terms "including,"
"comprising," "having," and variations thereof mean "including but
not limited to" unless expressly specified otherwise. An enumerated
listing of items does not imply that any or all of the items are
mutually exclusive and/or mutually inclusive, unless expressly
specified otherwise. The terms "a," "an," and "the" also refer to
"one or more" unless expressly specified otherwise.
[0065] Additionally, instances in this specification where one
element is "coupled" to another element can include direct and
indirect coupling. Direct coupling can be defined as one element
coupled to and in some contact with another element. Indirect
coupling can be defined as coupling between two elements not in
direct contact with each other, but having one or more additional
elements between the coupled elements. Further, as used herein,
securing one element to another element can include direct securing
and indirect securing. Additionally, as used herein, "adjacent"
does not necessarily denote contact. For example, one element can
be adjacent another element without being in contact with that
element.
[0066] As used herein, the phrase "at least one of", when used with
a list of items, means different combinations of one or more of the
listed items may be used and only one of the items in the list may
be needed. The item may be a particular object, thing, or category.
In other words, "at least one of" means any combination of items or
number of items may be used from the list, but not all of the items
in the list may be required. For example, "at least one of item A,
item B, and item C" may mean item A; item A and item B; item B;
item A, item B, and item C; or item B and item C. In some cases,
"at least one of item A, item B, and item C" may mean, for example,
without limitation, two of item A, one of item B, and ten of item
C; four of item B and seven of item C; or some other suitable
combination.
[0067] The present disclosure may be embodied in other specific
forms without departing from its spirit or essential
characteristics. The described embodiments are to be considered in
all respects only as illustrative and not restrictive. The scope of
the disclosure is, therefore, indicated by the appended claims
rather than by the foregoing description. All changes which come
within the meaning and range of equivalency of the claims are to be
embraced within their scope.
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