U.S. patent application number 14/170857 was filed with the patent office on 2015-08-06 for diesel exhaust fluid filter permeability detection strategy and machine using same.
This patent application is currently assigned to Caterpillar Inc.. The applicant listed for this patent is Caterpillar Inc.. Invention is credited to Jason Wesley Hudgens.
Application Number | 20150218990 14/170857 |
Document ID | / |
Family ID | 53754430 |
Filed Date | 2015-08-06 |
United States Patent
Application |
20150218990 |
Kind Code |
A1 |
Hudgens; Jason Wesley |
August 6, 2015 |
DIESEL EXHAUST FLUID FILTER PERMEABILITY DETECTION STRATEGY AND
MACHINE USING SAME
Abstract
A reductant dosing system for an exhaust aftertreatment system
of a diesel engine includes a reductant tank with an inlet volume
separated from an outlet volume by a sock filter. A filter
permeability condition is detected by the electronic controller
using a filter status algorithm that compares fluid level sensor
data to expected data. A filter permeability condition might be
indicated when the reductant dosing rate exceeds the rate at which
fluid can move through the sock filter from the inlet volume to the
outlet volume. A filter permeability condition may eventually lead
to a system fault.
Inventors: |
Hudgens; Jason Wesley;
(Washington, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Caterpillar Inc. |
Peoria |
IL |
US |
|
|
Assignee: |
Caterpillar Inc.
Peoria
IL
|
Family ID: |
53754430 |
Appl. No.: |
14/170857 |
Filed: |
February 3, 2014 |
Current U.S.
Class: |
423/239.1 ;
422/111 |
Current CPC
Class: |
F01N 2550/05 20130101;
F01N 2900/1808 20130101; Y02T 10/40 20130101; F01N 11/00 20130101;
Y02T 10/47 20130101; Y02T 10/12 20130101; F01N 2610/1426 20130101;
F01N 2900/1812 20130101; F01N 3/2066 20130101; Y02T 10/24 20130101;
F01N 2610/02 20130101 |
International
Class: |
F01N 3/20 20060101
F01N003/20 |
Claims
1. A machine comprising: an engine mounted on a chassis and
including an exhaust after treatment system; the exhaust after
treatment system including a reductant dosing system that includes
a reductant tank with a fluid level sensor in communication with an
electronic controller; the reductant tank including a filter
separating an inlet volume from an outlet volume, and the fluid
level sensor being positioned in the outlet volume, and the
reductant tank including an inlet that opens to the inlet volume
and an outlet that opens to the outlet volume; and the electronic
controller including a filter status algorithm configured to detect
a filter permeability condition based at least in part on data from
the fluid level sensor.
2. The machine of claim 1 wherein the fluid level sensor is a float
sensor; and the filter is a sock filter; and a header of the
reductant tank and the sock filter define the outlet volume.
3. The machine of claim 2 wherein the electronic controller
includes a reductant system fault algorithm configured to log a
reductant system fault responsive to a pressure in a fluid circuit
of the reductant system that is less than a dosing pressure
threshold.
4. The machine of claim 3 wherein the system fault algorithm is
configured to disable the reductant system responsive to a
reductant system fault; and the electronic controller is configured
to maintain the reductant system operational responsive to the
filter permeability condition.
5. The machine of claim 4 wherein the fluid circuit includes the
outlet, a pump and a return line that opens into the outlet volume;
and a second filter positioned in the fluid circuit.
6. The machine of claim 5 wherein the filter status algorithm is
configured to determine a time rate of change in the tank level
data; and the filter status algorithm is configured to log a filter
permeability condition responsive to the time rate of change in the
tank level data being greater than an expected time rate of change
while reductant is being dosed from the reductant system into an
exhaust pipe of the engine.
7. The machine of claim 6 wherein the filter status algorithm is
configured to log a filter permeability condition responsive to an
increase in the tank level data that is greater than an expected
increase threshold after reductant dosing has ceased and the inlet
is closed.
8. The machine of claim 1 wherein the electronic controller
includes a reductant system fault algorithm configured to log a
reductant system fault responsive to a pressure in a fluid circuit
of the reductant system that is less than a dosing pressure
threshold; the system fault algorithm is configured to disable the
reductant system responsive to a reductant system fault; the
electronic controller is configured to maintain the reductant
system operational responsive to the filter permeability condition;
the fluid circuit includes the outlet, a pump and a return line
that opens into the outlet volume; and a second filter positioned
in the fluid circuit.
9. The machine of claim 1 wherein the filter status algorithm is
configured to determine a time rate of change in the tank level
data; the filter status algorithm is configured to log a filter
permeability condition responsive to the time rate of change in the
tank level data being greater than an expected time rate of change
while reductant is being dosed from the reductant system into an
exhaust pipe of the engine; and the filter status algorithm is
configured to log a filter permeability condition responsive to an
increase in the tank level data that is greater than an expected
increase threshold after reductant dosing has ceased and the inlet
is closed.
10. A method of operating a machine, comprising the steps of:
running an engine supported on a chassis of the machine; moving
exhaust through an exhaust pipe from the engine; circulating
reductant around a fluid circuit from an outlet volume of a
reductant tank, through a pump and into a return line that opens
back into the outlet volume; dosing reductant into an exhaust pipe
of the engine; moving reductant from the inlet volume to the outlet
volume through a filter; communicating tank level data from a fluid
level sensor, which is positioned in the outlet volume, to an
electronic controller; comparing the tank level data to expected
data; and logging a filter permeability condition responsive to the
tank level data differing from the expected data by greater than a
predetermined threshold.
11. The method of claim 10 wherein the circulating step includes
pumping the reductant through a second filter fluidly positioned in
the fluid circuit.
13. The method of claim 12 including a step of measuring a system
pressure of the reductant in the fluid circuit; logging a reductant
system fault responsive to the system pressure being below a dosing
pressure threshold.
14. The method of claim 13 including a step of maintaining the
reductant dosing system operational responsive to the filter
permeability condition; and disabling the reductant dosing system
responsive to the reductant system fault.
15. The method of claim 10 wherein the comparing step includes
comparing a time rate of change in the tank level data to an
expected time rate of change.
16. The method of claim 15 including determining a dosing rate; and
determining the expected time rate of change based at least in part
on the dosing rate.
17. The method of claim 16 including ceasing dosing of reductant
into the exhaust pipe; the comparing step includes detecting an
increase in the tank level data that is greater than an expected
increase threshold after the dosing has ceased.
18. The method of claim 15 including ceasing dosing of reductant
into the exhaust pipe; the logging step includes detecting an
increase in the tank level data that is greater than an expected
increase threshold after the dosing has ceased.
19. The method of claim 10 including replacing the sock filter
responsive to the filter permeability condition.
20. The method of claim 19 including adding sock filter replacement
to a previous maintenance schedule for the machine responsive to
the filter permeability condition.
Description
TECHNICAL FIELD
[0001] The present disclosure relates generally to detecting filter
permeability degradation in a reductant dosing system for exhaust
aftertreatment of a diesel engine, and more particularly to a
strategy for detecting degraded permeability of a sock filter in a
reductant tank.
BACKGROUND
[0002] Many machines that utilize a diesel engine for power now
include exhaust aftertreatment systems. One purpose of these
aftertreatment systems is to reduce the presence of NOx at the
exhaust tailpipe. Typically, this is accomplished by injecting a
reductant, such as urea, into the exhaust pipe upstream from a
selective catalytic reduction (SCR) catalyst, where the NOx is
converted to nitrogen and other more acceptable compounds. The
reductant, or urea, utilized for this process is supplied from a
tank carried by the machine. When the tank is in need of being
refilled, dirt and debris can enter the tank along with the
reductant. The risk of dirt and debris entering the reductant tank
can be many times more problematic in the case of off road machines
that must operate in dirt and debris filled environments.
[0003] Soon after the adoption of reductant dosing systems there
were diagnostic strategies to detect faults that would prevent the
system from operating properly. For instance, reductant dosing
injectors require some minimum fluid pressure in order to operate
properly. Furthermore, the nozzle outlets of the reductant injector
must remain open and free of clogs. U.S. Patent Application
Publication 2012/0286063 teaches a urea injector diagnostic
strategy that detects system faults in part by monitoring delivery
line pressure for the reductant dosing injector.
[0004] Regulations and other concerns often require that a faulted
reductant dosing system be serviced as soon as possible in order to
maintain the aftertreatment system in compliance. Thus, when a
reductant system fault is detected, the machine must often be
brought offline for immediate servicing, with the result being an
unexpected loss of work time and expensive repairs, along with a
temporary loss in productivity that can have cascading effects
elsewhere in a larger project involving many machines. These costly
downtimes might be avoided if symptoms that suggest a forthcoming
fault can be detected early so that servicing can be scheduled at a
convenient time, rather than waiting and responding after a fault
occurs.
[0005] The present disclosure is directed toward one or more of the
problems set forth above.
SUMMARY
[0006] In one aspect, an engine is mounted on a chassis and
includes an exhaust aftertreatment system. The exhaust
aftertreatment system includes a reductant dosing system that has a
reductant tank with a fluid level sensor in communication with an
electronic controller. The reductant tank includes a filter
separating an inlet volume from an outlet volume. The fluid level
sensor is positioned in the outlet volume. The tank includes an
inlet that opens to the inlet volume, and an outlet that opens to
the outlet volume. The electronic controller includes a filter
status algorithm configured to detect a filter permeability
condition based at least in part on data from the fluid level
sensor.
[0007] In another aspect, a method of operating a machine includes
running an engine supported on a chassis of the machine. Exhaust is
moved through an exhaust pipe from the engine. Reductant is
circulated around a fluid circuit from an outlet volume of a
reductant tank, through a pump and into a return line that opens
back into the outlet volume. Reductant is dosed into the exhaust
pipe of the engine. Reductant is moved from the inlet volume to the
outlet volume of the reductant tank through a filter. Tank level
data is communicated from a fluid level sensor, which is positioned
in the outlet volume, to an electronic controller. Tank level data
is compared to expected data. A filter permeability condition is
logged responsive to the tank level data differing from the
expected data by greater than a predetermined threshold.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a side view of a machine according to one aspect
of the present disclosure;
[0009] FIG. 2 is a schematic view of an engine and exhaust
aftertreatment system according to the present disclosure;
[0010] FIG. 3 is an exploded view of a reductant tank header and a
sock filter according to the present disclosure;
[0011] FIG. 4 is a schematic view of a reductant tank showing a
filter permeability condition according to the present disclosure;
and
[0012] FIG. 5 is a logic flow diagram of a reductant dosing
algorithm that includes a filter status algorithm according to the
present disclosure.
DETAILED DESCRIPTION
[0013] Referring initially to FIGS. 1 and 2, a machine 10 includes
an engine 15 mounted on a chassis 11. The engine includes an
exhaust aftertreatment system 16. In the illustrated embodiment,
machine 10 is shown as a mobile backhoe loader off-road machine in
which chassis 11 is supported by a conveyance 12. Nevertheless,
those skilled in the art will appreciate that a machine according
to the present disclosure could also be stationary, such that the
engine were supported on a stationary chassis, or the chassis could
be the hull framework of a seagoing vessel without departing from
the present disclosure. Machine 10 includes an operator station 13
that includes various system status displays of a type well known
in the art. Nevertheless, those skilled in the art will appreciate
that in other versions of the invention system status information
may be transmitted to a remote location, such as for instance in
the case of a stationary generator.
[0014] The exhaust aftertreatment system 16 includes a reductant
dosing system 20 that includes a reductant tank 21 with a fluid
level sensor 22 in communication with an electronic controller 23.
As used in this disclosure, "electronic controller" means one or
more electronic controllers that may or may not communicate with
each other in a manner known in the art. When engine 15 is
operating, reductant dosing system 20 injects reductant, such as
urea, into an exhaust pipe 17 to facilitate a NOx reduction
reaction at SCR catalyst 38. Electronic controller 23 may be
configured to control the reductant dosing rate from injector 34 in
order to match the NOx content in the exhaust stream so as to avoid
either ammonia slip or NOx slip at the tailpipe where the exhaust
aftertreatment system vents the treated engine exhaust to
atmosphere.
[0015] The reductant tank 21 includes a filter 24 separating an
inlet volume 25 from an outlet volume 26. The fluid level sensor
22, which may be a float sensor, is positioned in the outlet volume
26. Tank 21 also includes an inlet 27 that opens to the inlet
volume 25 and an outlet 28 that opens to the outlet volume 26. For
illustrative purposes, the inlet 27 to reductant tank 21 is shown
on the outer surface of machine 10 and serves as the means by which
tank 21 may be periodically refilled with reductant as needed. When
inlet 27 is opened for refilling, debris and dirt have an
opportunity to enter inlet volume 25, especially in the case of
off-road machines where both the machine 10 and the reductant
refill location (not shown) are exposed to, and often covered, with
debris and dirt. Filter 24 is included to prevent the dirt and
debris that enters into inlet volume 25 from entering into the
outlet volume 26. In the illustrated embodiment, filter 24 is shown
as a sock filter, but could take other configurations depending
upon the structure of the particular reductant tank. For instance,
the reductant tank could be configured to simply separate the inlet
volume from the outlet volume by a vertical wall which would
include a wall filter without departing from the intended scope of
the present disclosure.
[0016] During typical operation, electronic controller 23 will
activate a reductant pump 31 to begin circulating reductant in a
fluid circuit 30 after engine 15 is started. Fluid circuit 30
includes outlet 28, pump 31 and return line 32 that opens into
outlet volume 26. A second filter 33 is positioned in fluid circuit
30. Pump 31 may draw reductant fluid initially through a screen
filter 39 located in outlet volume 26, past outlet 28 and then
through filter 33 prior to either arriving at injector 34 or being
returned to outlet volume 26 via return line 32. Thus, when no
reductant is being injected from injector 34, all of the reductant
pumped from outlet volume 26 by pump 31 is returned for
recirculation via return line 32. However, when reductant dosing is
active and reductant is being dosed through injector 34 into
exhaust pipe 17, less than all of the reductant leaving outlet
volume 26 is returned via return line 32. When this occurs,
reductant in inlet volume 25 flows through sock filter 24 into
outlet volume 26 in order to maintain the fluid level of reductant
37 in inlet volume 25 equal to that in outlet volume 26. As is
known in the art, filter 33 may be provided to prevent any tiny
particulate matter that passed through both sock filter 24 and
screen filter 39 from potentially plugging the nozzle outlets of
injector 34. A pressure regulator 40, which is shown as a flow
restriction, serves to help maintain injection level pressure in
fluid circuit 30. Electronic controller 23 may monitor pressure and
fluid circuit 30 via a pressure sensor 35. Although not necessary,
pump 31 may have a variable output capability (e.g. variable
speed). This permits electronic controller 23 is in control
communication with pump 31 to increase or decrease the pump rate
responsive to system pressure as communicated by pressure sensor
35. Electronic controller 23 also includes a filter status
algorithm configured to detect a filter permeability condition for
filter 24 based at least in part on data from fluid level sensor 22
communicated to electronic controller 23.
[0017] Referring now in addition to FIG. 3, reductant tank 21 may
include a header 29 with an annular surface that receives the open
end of sock filter 24. Although other strategies could fall within
the scope of the present disclosure, in the illustrated embodiment,
sock filter 24 is attached to header 29 with a suitable clamp 36.
As a reductant dosing system 20 operates over many cycles of being
emptied and refilled with reductant 37, the dirt and debris
entering inlet volume 25 will eventually begin to degrade the
permeability of sock filter 24. When the permeability is
sufficiently degraded, the dosing rate at injector 34 may exceed
the rate at which reductant can flow from inlet volume 25 through
filter 24 and into outlet volume 26. An example circumstance in
which a filter permeability condition exists is shown, for example,
in FIG. 4. Thus, when a filter permeability condition exists, the
reductant dosing system 20 may continue to be fully operational
without any degraded performance. In prior art systems, this system
permeability condition would go undetected and unnoticed. The
present disclosure insightfully recognizes that if the filter
permeability condition can be detected while the reductant system
is fully operational, maintenance on the reductant system 20 can be
scheduled at a convenient time to replace filter 24 before the
filter permeability condition becomes so severe that an actual
system fault Occurs.
[0018] If electronic controller 23 and pump 31 are unable to
maintain system pressure above some minimum injection pressure, a
system fault will be generated and the reductant dosing system may
be disabled. Other fault modes (e.g. plugged injector) are known to
those skilled in the art. A sudden system fault can require that
the machine 10 be shut down for immediate and costly maintenance at
an unscheduled time disrupting worksite organization and
undermining productivity. While reductant dosing systems may be on
some regular maintenance schedule that does or does not take into
account the environment in which the machine 10 is operating,
detection of a filter permeability condition according to the
present disclosure can provide early warning of a forthcoming
system fault while the reductant system 20 remains fully
operational. Thus, electronic controller 23 may include a reductant
system fault algorithm configured to log a reductant system fault
responsive to pressure in fluid circuit 30 of reductant system 20
falling to less than a dosing pressure threshold necessary for
proper operation of injector 34. The reductant system fault
algorithm may be configured to disable the reductant system 20
responsive to the reductant system fault. In contrast, electronic
controller 23 may be configured to maintain the reductant system 20
operational responsive to a filter permeability condition.
[0019] The filter status algorithm according to the present
disclosure may be configured to determine a time rate of change in
the tank level data communicated by float sensor 22. The filter
status algorithm may be configured to log a filter permeability
condition responsive to the time rate of change in the tank level
data being greater than an expected time rate of change while
reductant 37 is being dosed from injector 34 into exhaust pipe 17
of engine 15. In general, electronic controller 23 should know the
reductant dosing rate and can estimate the rate at which the tank
level should fall responsive to that dosing rate. However, if a
filter permeability condition exists, the fluid level in outlet
volume 26 may fall faster than the tank level ought to fall
responsive to that dosing rate. This condition, for instance is
illustrated in FIG. 4. When this occurs, a filter permeability
condition is detected, and the operator may be alerted in a
suitable manner so that changing of the sock filter 24 may be added
to the next regular servicing agenda of machine 10, in order to
avoid unscheduled down time and potentially proactively prevent a
future system fault.
[0020] The present disclosure also contemplates another opportunity
for detecting a filter permeability condition. For instance, when
the engine is changed to a state, such as a shutdown routine, when
reductant dosing is ceased, the filter status algorithm may also be
configured to log a filter permeability condition responsive to an
increase in the tank level data that is greater than an expected
increase threshold, after reductant dosing has ceased and inlet 27
is closed. Such a circumstance is indicated when the reductant in
fluid circuit 30 is evacuated from reductant system 20 during
engine shutdown resulting in excess reductant returning to outlet
volume 26, but the filter permeability condition prevents the
briefly higher fluid level in the outlet volume 26 from passing in
a reverse direction through filter 24 to balance with the fluid
level in inlet volume 25. Again, when a filter permeability
condition is detected in this manner, the operator may be notified
or alerted in a conventional manner, and sock filter replacement
may be added to a next servicing agenda for machine 10 by the
operator or possibly automatically by electronic controller 23 in a
known manner.
INDUSTRIAL APPLICABILITY
[0021] The present disclosure finds potential application in any
machine that includes an engine with a reductant dosing system. The
present disclosure finds specific applicability to machines that
must operate in debris and dirt filled environments that increase
the likelihood of contaminants finding their way into a reductant
tank. Finally, the present disclosure finds application in any
reductant dosing system in which an inlet volume of the tank is
separated from an outlet volume by a serviceable filter
element.
[0022] Referring now in addition to FIG. 5, an example logic flow
diagram of a reductant dosing algorithm 50 that includes both a
system fault algorithm 56 and a filter status algorithm 55
according to the present disclosure. Those skilled in the art will
appreciate that the reductant dosing algorithm 50 may be executed
in conjunction with regular operation of machine 10. At oval 60,
engine 15 is started and proceeds to run in a conventional manner
so that exhaust from engine 15 is moved through exhaust pipe 17. At
box 61, electronic controller 23 activates reductant pump 31. This
results in reductant 37 circulating around fluid circuit 30 from
the outlet volume 26 of reductant tank 21, through pump 31 and into
return line 32, which opens back into outlet volume 26. As engine
15 continues to run, the aftertreatment system 16 is warmed up to
proper treatment temperatures at box 62. At query 63, electronic
controller 23 answers the question of whether the aftertreatment
system 16 is warmed up to proper operational temperatures. If not,
the logic will loop back and continue to warm up the aftertreatment
system at box 62. If affirmative, the logic may advance to box 64
where electronic controller 23 determines a desired dosing rate
using other logic outside the scope of this disclosure. For
instance, this logic may attempt to set a dosing rate to match the
production rate of NOx from engine 15 as discussed earlier. Next at
box 65, the reductant dosing system pressure is measured by
pressure sensor 35. At box 66, the reductant tank level data from
fluid level sensor 22 is communicated to electronic controller 23.
At query 67, the logic determines whether system pressure is too
low for proper operation of injector 34. During normal operation,
as system pressure might incrementally drop, electronic controller
23 may incrementally respond by increasing the speed of pump 31.
However, eventually, the rate of pump 31 will reach its maximum
allowed rate. When the pump 31 can no longer maintain proper system
pressure, query 67 will return a yes and the logic will log a
system fault at box 81. Next, the operator may be alerted at box 82
and the reductant dosing system may be disabled at box 83. Those
skilled in the art will appreciate that the system fault algorithm
56 according to an actual system may be substantially more
complicated and allow for incrementally derating engine 15 as
inducements for the operator to seek servicing prior to completely
disabling the reductant dosing system and completely derate engine
15 in order to force the operator to seek servicing of machine 10.
If a system fault occurs, the logic ends at oval 84.
[0023] If query 67 returns a negative, the logic advances to box 68
and reductant is dosed into exhaust pipe 17 of engine 15. This
should result in movement of reductant from the inlet volume 25
into the outlet volume 26 through filter 24 in order to make up for
the dosed reductant. At box 69, the logic determines a time rate of
change in the tank level data originating from float sensor 22. At
query 70, the logic asks whether the tank level in outlet volume 26
is dropping faster than expected. For instance, if the dosing rate
exceeds the rate at which fluid can pass through filter medium 24,
the level in the outlet volume 26 will drop faster than the level
in inlet volume 25 resulting in a filter permeability condition
schematically illustrated in FIG. 4. If so, the logic advances to
box 71 where a filter permeability condition is logged. Next at box
72, the operator is alerted of the condition. At box 73, a sock
filter 24 change may be added to the next servicing agenda for
machine 10. Thus, the filter status algorithm 55 logs a filter
permeability condition responsive to the tank level data differing
from expected data by greater than some predetermined threshold
that avoids false detections that might otherwise occur due to such
causes as abrupt machine movements and the like. The filter status
algorithm 55 may compare tank level data to expected data. Although
the present disclosure teaches detection of filter permeability
conditions by examining time rate of change in the tank level data,
those skilled in the art will appreciate that properly timed
snapshot data could be used without ever determining time rate of
change and without departing from the present disclosure.
[0024] After query 70, whether or not a filter permeability
condition is detected, the logic may advance to query 74 in order
to determine whether engine shut down has been initiated. Those
skilled in the art will appreciate that in many modern machines,
engine shutdown may constitute a procedure that lasts several
seconds to several minutes in order to properly shut down all of
the engine subsystems before actually stopping the engine. If query
74 returns a negative, the logic loops back to again determine the
dosing rate at box 64 and repeats the determinations measurements
and queries as shown in FIG. 5. If query 74 returns a positive, as
part of the engine shut down reductant dosing is ceased at box 75,
such as when the engine is placed in an idle condition prior to
being completely stopped. At query 76, the filter status algorithm
queries whether the tank level in outlet volume 26 is increasing
too much due to the evacuation of reductant from fluid circuit 30.
This aspect of the logic suggests that the filter status algorithm
23 knows the fluid volume of fluid circuit 30 and the rate by which
that fluid will return to tank 21 when the reductant dosing has
ceased during a normal engine shut down procedure. If that fluid
level in the outlet volume 26 is increasing too much, the query
will move to box 77 and log a filter permeability condition because
that circumstance indicates that fluid is having difficulty moving
from the outlet volume 26 into the inlet volume 25 due to degraded
permeability in filter 24. At box 78, the operator may be alerted
and at box 79 the sock filter change may be added to the next
servicing agenda for machine 10. If query 76 returns a negative,
the logic advance to oval 80 to end indicating that a proper engine
shut down.
[0025] The abbreviated version of a reductant system fault
algorithm 56 is included in the reductant dosing algorithm 50 to
contrast a system fault from a system condition. In other words, a
system fault, if ignored, will eventually result in disabling the
reductant dosing system 20. However, detection of a filter
permeability condition is treated differently in that electronic
controller may maintain the reductance dosing system operational
responsive to a filter permeability condition. In the illustrated
embodiment, the screen filter 39 and the fine particulate filter 33
are identified in order to contrast those known system filters with
the added sock filter and filter status algorithm of the present
disclosure. Thus, pump 31 pumps reductant through filter 33, but
gravity may be responsible for movement of reductant fluid between
inlet volume 25 and outlet volume 26 through sock filter 24. Those
skilled in the art will appreciate that the expected time rate of
change in the tank level data may be based upon the known dosing
rate commanded during normal system operation and an understanding
of the fluid surface area in tank 21.
[0026] By detecting a filter permeability condition, an operator
can be alerted to a forthcoming fault while still being able to
maintain the system fully operational and the machine productive.
This early alert allows reductant system servicing to be added to a
previously scheduled servicing agenda so that a surprise fault and
its accompanying costs and project disruptions are avoided. Thus,
the teachings of the present disclosure may be useful in
proactively planning for proper servicing of the reductant dosing
system 20 prior to an otherwise inevitable fault requiring the
potential disablement of the reductant system and associated taking
of machine 10 offline. Replacement of a sock filter according to
the present disclosure can be accomplished by detaching the head 29
from tank 21, loosening clamp 36 and then sliding sock filter 24
free of head 29. A new sock filter 24 can then be replaced in a
reverse manner. While this is being performed, the technician may
utilize the opportunity to inspect and/or service other aspects of
the reductant dosing system 20 in an effort to maintain machine
10's productivity and avoid untimely reductant system faults.
[0027] The present description is for illustrative purposes only,
and should not be construed to narrow the breadth of the present
disclosure in any way. Thus, those skilled in the art will
appreciate that various modifications might be made to the
presently disclosed embodiments without departing from the full and
fair scope and spirit of the present disclosure. Other aspects,
features and advantages will be apparent upon an examination of the
attached drawings and appended claims.
* * * * *