U.S. patent application number 11/413163 was filed with the patent office on 2007-11-01 for system and method for monitoring a filter.
Invention is credited to Darrel W. Berglund, Andrew A. Knitt, Kevin J. Lueschow.
Application Number | 20070251221 11/413163 |
Document ID | / |
Family ID | 38327028 |
Filed Date | 2007-11-01 |
United States Patent
Application |
20070251221 |
Kind Code |
A1 |
Lueschow; Kevin J. ; et
al. |
November 1, 2007 |
System and method for monitoring a filter
Abstract
An engine assembly may include an internal combustion engine
configured to combust fuel. The combustion of fuel may produce
exhaust and sound waves that may be directed into an exhaust line.
A particulate filter may be operatively coupled to the exhaust
line, and the particulate filter may be configured to filter the
exhaust. The engine assembly may also include a sensor package
operatively coupled to the exhaust line. At least a portion of the
sensor package may extend into the exhaust line at a location
downstream from the particulate filter. The sensor package may be
configured to monitor the sound waves passing through the
particulate filter and to produce an electrical signal indicative
of the intensity of the sound waves.
Inventors: |
Lueschow; Kevin J.;
(Elmwood, IL) ; Berglund; Darrel W.; (Peoria,
IL) ; Knitt; Andrew A.; (Deer Creek, IL) |
Correspondence
Address: |
CATERPILLAR/FINNEGAN, HENDERSON, L.L.P.
901 New York Avenue, NW
WASHINGTON
DC
20001-4413
US
|
Family ID: |
38327028 |
Appl. No.: |
11/413163 |
Filed: |
April 28, 2006 |
Current U.S.
Class: |
60/297 |
Current CPC
Class: |
F01N 2550/04 20130101;
F02D 2200/0812 20130101; F01N 2560/05 20130101; G01N 29/44
20130101; B01D 46/0086 20130101; B01D 46/46 20130101; F01N 2560/12
20130101; F02D 2200/025 20130101; G01N 29/14 20130101; F01N 9/002
20130101; F01N 11/00 20130101; F01N 3/035 20130101; Y02T 10/47
20130101; F01N 2560/14 20130101; G01N 29/223 20130101; B01D 2279/30
20130101; Y02T 10/40 20130101; G01N 29/4454 20130101 |
Class at
Publication: |
060/297 |
International
Class: |
F01N 3/00 20060101
F01N003/00 |
Claims
1. An engine assembly, comprising: an internal combustion engine
configured to combust fuel, wherein the combustion of fuel produces
exhaust and sound waves that are directed into an exhaust line; a
particulate filter operatively coupled to the exhaust line, the
particulate filter being configured to filter the exhaust; and a
sensor package operatively coupled to the exhaust line, wherein at
least a portion of the sensor package extends into the exhaust line
at a location downstream from the particulate filter, the sensor
package being configured to monitor the sound waves passing through
the particulate filter and to produce an electrical signal
indicative of the intensity of the sound waves.
2. The engine assembly of claim 1, wherein the exhaust line further
includes an opening at a downstream end, and wherein the portion of
the sensor package is configured to be inserted into the exhaust
line through the opening.
3. The engine assembly of claim 1, wherein the sensor package
further includes: a microphone configured to receive the sound
waves and convert the sound waves into a signal; a first filter
configured to receive the signal and reduce frequencies of the
signal that are below a first cutoff frequency, while allowing
frequencies above the first cutoff frequency to pass, to produce a
filtered signal; and an envelope detector configured to receive the
filtered signal and convert the filtered signal into the electrical
signal.
4. The engine assembly of claim 3, wherein the envelope detector
further includes: a rectifier configured to receive the filtered
signal and convert the filtered signal into one of an entirely
positive waveform and an entirely negative waveform, to produce a
rectified signal; and a second filter configured to receive the
rectified signal and reduce frequencies of the rectified signal
that are above a second cutoff frequency, while allowing
frequencies below the second cutoff frequency to pass, to produce
the electrical signal.
5. The engine assembly of claim 1, wherein the electrical signal is
received by a signal detector operatively coupled to the sensor
package, and the signal detector is set with at least one of a high
signal level, indicative of the particulate filter being clean, and
a low signal level, indicative of the particulate filter being
loaded.
6. The engine assembly of claim 5, wherein the signal detector is
configured to automatically trigger regeneration of the particulate
filter when the electrical signal falls below the low signal
level.
7. The engine assembly of claim 5, wherein at least one of the high
signal level and the low signal level is selectively adjusted based
at least in part on the intensity of the sound waves produced by
the internal combustion engine.
8. A method of monitoring a particulate filter, comprising:
producing exhaust and sound waves by combusting fuel with an
internal combustion engine; directing the exhaust and sound waves
through the particulate filter; converting the sound waves into an
electrical signal with a sensor package, the sensor package being
operatively coupled to an exhaust line of the internal combustion
engine at a location downstream from the particulate filter, and
wherein at least a portion of the sensor package extends into the
exhaust line; and regenerating the particulate filter if the
electrical signal falls outside a predetermined range.
9. The method of claim 8, further including receiving the sound
waves with a microphone of the sensor package, wherein the
microphone produces a signal.
10. The method of claim 9, further including reducing frequencies
of the signal that are below a first cutoff frequency, while
allowing frequencies above the first cutoff frequency to pass, to
produce a filtered signal.
11. The method of claim 10, further including converting the
filtered signal into one of an entirely positive waveform and an
entirely negative waveform, to produce a rectified signal.
12. The method of claim 11, further including reducing frequencies
of the rectified signal that are above a second cutoff frequency,
while allowing frequencies below the second cutoff frequency to
pass, to produce the electrical signal.
13. The method of claim 8, further including selectively adjusting
the predetermined range based at least in part on the intensity of
the sound waves produced by the internal combustion engine.
14. A machine comprising: an internal combustion engine configured
to combust fuel, wherein the combustion of fuel produces exhaust
and sound waves that are directed into an exhaust line; a
particulate filter operatively coupled to the exhaust line, the
particulate filter being configured to filter the exhaust; and a
sensor package operatively coupled to the exhaust line, wherein at
least a portion of the sensor package extends into the exhaust line
at a location downstream from the particulate filter, the sensor
package being configured to convert the sound waves passing through
the particulate filter into a voltage signal indicative of the
intensity of the sound waves.
15. The machine of claim 14, wherein the exhaust line further
includes an opening at a downstream end, and wherein the portion of
the sensor package is configured to be inserted into the exhaust
line through the opening.
16. The machine of claim 14, wherein the sensor package further
includes: a piezoelectric microphone configured to receive the
sound waves and convert the sound waves into a signal; a high-pass
filter configured to receive the signal and reduce frequencies of
the signal that are below a first cutoff frequency, while allowing
frequencies above the first cutoff frequency to pass, to produce a
filtered signal; and an envelope detector configured to receive the
filtered signal and convert the filtered signal into the voltage
signal.
17. The machine of claim 16, wherein the envelope detector further
includes: a full wave rectifier configured to receive the filtered
signal and convert the filtered signal into one of an entirely
positive waveform and an entirely negative waveform, to produce a
rectified signal; and a low-pass filter configured to receive the
rectified signal and reduce frequencies of the rectified signal
that are above a second cutoff frequency, while allowing
frequencies below the second cutoff frequency to pass, to produce
the voltage signal.
18. The machine of claim 14, wherein the voltage signal is received
by a voltage detector operatively coupled to the sensor package,
and the voltage detector is set with at least one of a high voltage
level, indicative of the particulate filter being clean, and a low
voltage level, indicative of the particulate filter being
loaded.
19. The machine of claim 18, wherein the voltage detector is
configured to automatically trigger regeneration of the particulate
filter when the voltage signal falls below the low voltage
level.
20. The machine of claim 18, wherein at least one of the high
voltage level and the low voltage level is selectively adjusted
based at least in part on the intensity of the sound waves produced
by the internal combustion engine.
Description
TECHNICAL FIELD
[0001] The present disclosure relates generally to filter
monitoring, and more particularly to a system and method for
monitoring the state of a filter.
BACKGROUND
[0002] Engines, including diesel engines, gasoline engines, natural
gas engines, and other engines known in the art, may exhaust a
complex mixture of air pollutants. The air pollutants may be
composed of gaseous and solid materials, including, for example,
particulate matter. Particulate matter may include unburned carbon
particles, such as soot. Particulate matter may be generated during
operation of an engine as fuel is supplied to the engine and is
combusted in one or more combustion chambers within the engine. The
engine may expel this particulate matter along with other engine
exhaust from the one or more combustion chambers through an exhaust
line. If this particulate matter is not filtered or otherwise
removed from the engine exhaust, these particulates may be vented
to the environment. Due to increased attention on the environment,
exhaust emission standards have become more stringent. The amount
of particulates emitted from an engine may be regulated depending
on the type of engine, size of engine, and/or class of engine.
[0003] In order to remove particulate matter from engine exhaust,
an exhaust filtration system may be disposed within the exhaust
line. The exhaust filtration system may include a particulate
filter or trap that may remove particulate matter from the engine
exhaust. Particulate filters may typically include a wire mesh
medium through which the engine exhaust may be passed. The wire
mesh medium may filter or trap particulate matter from the engine
exhaust. Use of the particulate filter for extended periods of time
may cause particulate matter to build up in the wire mesh medium,
thereby causing the functionality of the filter and engine
performance to decrease. To avoid this decrease, a heating element
may be used to increase the temperature of the trapped particulate
matter above the combustion temperature of the trapped particulate
matter, thereby burning away the trapped particulate matter and
regenerating the filter system. Although regeneration may reduce
the buildup of particulate matter in the filter, repeated
regeneration of the filter may result in a buildup of ash in the
components of the filter over time, or may cause damage to the
filter, possibly resulting in a deterioration of filter
performance.
[0004] At least one system has been developed for diesel
particulate filter monitoring. For example, U.S. Pat. No. 6,964,694
to Rauchfuss et al. ("Rauchfuss") discloses incorporating one or
more acoustic sensors into an exhaust system of an engine for
detecting one or more frequencies. For example, the one or more
acoustic sensors may be fluidly or mechanically coupled to portions
of the exhaust system to determine the frequency caused by the
exhaust flow through the filter. The acoustic emissions from the
filter may be compared to a known filter state to determine the
present filter state. However, in Rauchfuss, the proximity of the
acoustic sensors to the upstream and downstream sides of the filter
may present problems. For example, the relatively high temperature
of the exhaust at the upstream and downstream sides of the filter
may damage the acoustic sensors. Furthermore, Rauchfuss does not
disclose an efficient way to focus on specific frequencies that are
most relevant with respect to determining the filter state.
[0005] The disclosed system is directed to overcoming one or more
of the problems set forth above.
SUMMARY OF THE INVENTION
[0006] In one aspect, the present disclosure is directed to an
engine assembly. The engine assembly may include an internal
combustion engine configured to combust fuel. The combustion of
fuel may produce exhaust and sound waves that may be directed into
an exhaust line. The engine assembly may also include a particulate
filter operatively coupled to the exhaust line, the particulate
filter being configured to filter the exhaust. The engine assembly
may further include a sensor package operatively coupled to the
exhaust line, wherein at least a portion of the sensor package
extends into the exhaust line at a location downstream from the
particulate filter. The sensor package may be configured to monitor
the sound waves passing through the particulate filter and to
produce an electrical signal indicative of the intensity of the
sound waves.
[0007] In another aspect, the present disclosure is directed to a
method of monitoring a particulate filter. The method may include
producing exhaust and sound waves by combusting fuel with an
internal combustion engine. The method may also include directing
the exhaust and sound waves through the particulate filter. The
method may further include converting the sound waves into an
electrical signal with a sensor package. The sensor package may be
operatively coupled to an exhaust line of the internal combustion
engine at a location downstream from the particulate filter, and at
least a portion of the sensor package may extend into the exhaust
line. The method may further include regenerating the particulate
filter if the electrical signal falls outside a predetermined
range.
[0008] In yet another aspect, the present disclosure is directed to
a machine including an internal combustion engine configured to
combust fuel. The combustion of fuel may produce exhaust and sound
waves that may be directed into an exhaust line. The machine may
also include a particulate filter operatively coupled to the
exhaust line. The particulate filter may be configured to filter
the exhaust. The machine may further include a sensor package
operatively coupled to the exhaust line. At least a portion of the
sensor package may extend into the exhaust line at a location
downstream from the particulate filter. The sensor package may be
configured to convert the sound waves passing through the
particulate filter into a voltage signal indicative of the
intensity of the sound waves.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a diagrammatic illustration of a combustion
chamber of an engine according to an exemplary disclosed embodiment
of the present disclosure.
[0010] FIG. 2 is a diagrammatic illustration of an engine having a
particulate filter assembly according to an exemplary embodiment of
the present disclosure.
[0011] FIG. 3A is a block diagram of a monitoring assembly
according to an exemplary disclosed embodiment of the present
disclosure.
[0012] FIGS. 3B-3E are graphs of signals from the monitoring
assembly of FIG. 3A, according to an exemplary disclosed embodiment
of the present disclosure.
[0013] FIG. 4 is a flow diagram of a method for monitoring the
state of a particulate filter according to an exemplary embodiment
of the present disclosure.
DETAILED DESCRIPTION
[0014] Exemplary embodiments of the present disclosure are
illustrated in the accompanying drawings. Wherever possible, the
same reference numbers will be used throughout the drawings to
refer to the same or like parts.
[0015] FIG. 1 shows a combustion chamber 16 from an internal
combustion engine 10 of a machine (not shown), including an intake
line 12 and an exhaust line 14. Intake line 12 may provide an
intake path for air, fuel, recirculated exhaust gases, or any
suitable combination thereof. The air, fuel, and/or gases from
intake line 12 may be directed into combustion chamber 16 through
an intake port 18. The air, fuel, and/or gases may be combusted
within combustion chamber 16, which may produce heat, sound energy,
and exhaust. In order to evacuate the exhaust from within
combustion chamber 16, an exhaust valve 20 may be opened to place
combustion chamber 16 into fluid communication with exhaust line 14
via an exhaust port 22. When exhaust valve 20 is opened, the sound
energy produced by combustion, in the form of sound waves, may also
escape from combustion chamber 16 into exhaust line 14.
[0016] In the embodiment shown in FIG. 2, exhaust line 14 is shown
as being coupled to four separate combustion chambers (not shown).
However, any number of combustion chambers may be used.
Furthermore, internal combustion engine 10 may include diesel
engines, gasoline engines, natural gas engines, and other engines
known in the art.
[0017] Exhaust line 14 may be operatively connected to a
particulate filter assembly 24. The exhaust and sound waves exiting
from combustion chamber 16 may flow downstream through exhaust line
14 into particulate filter assembly 24. Particulate filter assembly
24 may be configured to filter or trap particulate matter in the
exhaust. Particulate filter assembly 24 may include, for example,
an inlet 26 for receiving the exhaust stream, an outlet 28 allowing
filtered exhaust to exit from particulate filter assembly 24, a
filter element 34 located between inlet 26 and outlet 28, and a
particulate filter regeneration device 32.
[0018] In one embodiment, filter element 34 may be located within a
filter housing 30. Filter element 34 may be constructed of any
material useful in removing pollutants and/or particulates from the
exhaust stream, such as, for example, foam cordierite, sintered
metal, ceramic, or silicon carbide. It is contemplated that filter
element 34 may also include catalyst materials capable of
collecting soot, NOx, sulfur compounds, particulate matter, and/or
other pollutants known in the art. Such catalyst materials may
include, for example, alumina, platinum, rhodium, barium, cerium,
and/or alkali metals, alkaline-earth metals, rare-earth metals or
combinations thereof. Filter element 34 may be situated
horizontally, vertically, radially, or helically. Additionally or
alternatively, filter element 34 may be arranged in a honeycomb,
mesh, or any other suitable configuration so as to maximize the
available surface area for filtration.
[0019] Particulate filter regeneration device 32 may be configured
to increase the temperature of the exhaust stream produced by
internal combustion engine 10 to a predetermined temperature. The
predetermined temperature may include, for example, a regeneration
temperature of filter element 34. As the temperature of the exhaust
stream increases, the temperature of the trapped particulate matter
in filter element 34 may also increase. When the trapped
particulate matter reaches the predetermined temperature, it may
burn away, and thus, filter element 34 may be regenerated. In one
embodiment, particulate filter regeneration device 32 may be
operatively coupled to exhaust line 14 at a location upstream from
filter element 34. It is also contemplated that particulate filter
regeneration device 32 may be operatively coupled to filter housing
30 and/or filter element 34. Particulate filter regeneration device
32 may include, for example, a fuel injector and an igniter, heat
coils, electrical conductors, and/or other heat sources known in
the art. Such heat sources may be configured to assist in
increasing the temperature of the exhaust stream by convection,
combustion, and/or other methods of heat transfer.
[0020] A filter monitoring assembly 36 may be operatively connected
to internal combustion engine 10. Filter monitoring assembly 36 may
be configured to determine the state of filter element 34, and in
particular, the degree of loading (amount of trapped particulate
matter) in filter element 34. Upon making a determination about the
state of filter element 34, filter monitoring assembly 36 may
selectively help trigger the activation of particulate filter
regeneration device 32 to regenerate filter element 34 when such
action is deemed appropriate. Filter monitoring assembly 36 is
shown in FIG. 3A, and may include, for example, a sensor package
38, a control box 40, and/or an alert assembly 42, and may be
mounted near, on, or in exhaust line 14. In one embodiment, at
least a portion of filter monitoring assembly 36 may be inserted
into exhaust line 14, and may rest therein at any suitable location
downstream from filter element 34. In another embodiment, where the
portion of filter monitoring assembly 36 is inserted into a
tailpipe section 60 of exhaust line 14, it should be understood
that the portion may be configured to create little to no
backpressure in exhaust line 14 and allow the free flow of exhaust
therethrough.
[0021] Sensor package 38 may be configured to receive an input,
such as, for example, sound waves that have traveled out of
combustion chamber 16, through filter element 34, and into exhaust
line 14. Sensor package 38 may convert the sound waves into an
electrical (e.g. voltage) signal, and may include a microphone 44,
a high-pass filter 46, and an envelope detector 48. It is
understood that sensor package 38 may include fewer or additional
components and may, in certain embodiments, constitute a single
component. Filter monitoring assembly 36 may also include another
sensor package (not shown) located upstream of filter element 34,
which may be used for comparing and contrasting the upstream and
downstream sound waves.
[0022] Microphone 44 may include a piezoelectric microphone having
ceramic or quartz crystals linked with a diaphragm exposed to the
sound waves in exhaust line 14. Additionally or alternatively, the
ceramic or quartz crystals may be directly exposed to the sound
waves. The impact of the sound waves may cause stress in the
ceramic or quartz crystals, causing them to generate a microphone
signal proportional to the acoustic pressure of the sound waves.
FIG. 3B is an exemplary illustration of the microphone signal in
the form of a microphone voltage waveform.
[0023] The microphone signal may be directed into high-pass filter
46. High-pass filter 46 may include a resistor-capacitor circuit
configured to block or filter out frequencies that are lower than a
predetermined cutoff frequency, while allowing frequencies higher
than the cutoff frequency to pass. Additionally or alternatively,
high-pass filter 46 may include components in place of or in
addition to the resistor-capacitor circuit, and it should be
understood that suitable high-pass filter constructions known in
the art may be employed. In one embodiment, high-pass filter 46 may
be set to block frequencies below 2,000 Hz, because generally,
sound waves having such frequencies may pass through filter element
34 relatively unattenuated regardless of the loading of filter
element 34, and thus, provide little information about the state of
filter element 34. It should be understood that the cutoff
frequency may be selectively adjusted to suit a particular
application. FIG. 3C is an exemplary illustration of a high-pass
filter signal, generated after the microphone signal has passed
through high-pass filter 46. With the low frequencies having been
removed, the remaining frequencies may form a high-pass filter
voltage waveform having a lesser amplitude than the microphone
voltage waveform.
[0024] The high-pass filter signal may enter envelope detector 48,
which may be configured to convert the high-pass filter signal into
the voltage signal, an example of a voltage signal waveform being
shown in FIG. 3E. Envelope detector 48 may include a rectifier 50
and a low-pass filter 52. Rectifier 50 may include a full wave
rectifier, configured to convert an alternating current waveform,
such as, for example, high-pass filter voltage waveform, into a
direct current waveform by reversing the negative (or positive)
portions of the alternating current waveform. Accordingly, an
entirely positive (or negative) direct current waveform, such as
the full wave rectifier waveform shown in FIG. 3D, may be produced.
The full wave rectifier waveform may then be passed through
low-pass filter 52. Low-pass filter 52 may include a
resistor-capacitor circuit configured to block or filter out
frequencies higher than a predetermined cutoff frequency, while
allowing frequencies lower than the predetermined cutoff frequency
to pass. As the full wave rectifier waveform passes through
low-pass filter 52, it may be converted into the voltage signal
waveform.
[0025] A signal detector, such as, for example, a voltage detector
54, may be operatively connected to sensor package 38 in order to
receive the electrical signal. A low signal (e.g. voltage) level
may be set for voltage detector 54. The low voltage level may be
indicative of a point at which filter element 34 is clogged and
should be regenerated. When the voltage signal approaches or falls
below the low voltage level, voltage detector 54 may send out an
output signal to initiate a function. In one embodiment, voltage
detector 54 may send the output signal to a regeneration signal
device 58 and/or regeneration device 32 to trigger regeneration of
filter element 34. Additionally or alternatively, voltage detector
54 may activate an alert assembly 42, such as, for example, a light
in a cab of the machine, thus telling the operator that
regeneration of filter element 34 may be required. It is also
contemplated that the voltage signal from low-pass filter 52 may be
directly connected to the light in the cab, and the light may turn
off when the voltage signal becomes too low or weak to continue
powering the light.
[0026] Control box 40 may be provided to monitor and maintain
engine firing sequences and events associated therewith, such as,
for example, when to inject fuel, when to open valves, and other
variables to ensure that internal combustion engine 10 is running
efficiently. In one embodiment, voltage detector 54 may be included
in control box 40. Sensor package 38 may be operatively connected
to control box 40 using an analog-to-digital converter 56.
Analog-to-digital converter 56 may be configured to convert the
voltage signal into a discrete digital number that may be
relatively easily analyzed and/or monitored by voltage detector
54.
[0027] Sensor package 38 and/or control box 40 may be calibrated
when filter element 34 is clean by taking a reading of the sound
waves passing through filter element 34 when it is clean to provide
a reference or baseline voltage signal. As filter element 34
becomes increasingly loaded with particulate matter, the actual
voltage signal from sensor package 38 may decrease with respect to
the baseline voltage signal, due to the attenuating effect of the
particulate matter in filter element 34. When the actual voltage
signal falls below the low voltage level, it may indicate that
regeneration of filter element 34 is required. It is contemplated
that the low voltage level may be set by, for example, using design
data, historical performance data, and/or taking a reading of sound
waves passing through a clogged filter element with sensor package
38 and control box 40 to produce another reference voltage signal,
such as the low voltage level.
[0028] As long as internal combustion engine 10 continually
operates in the same condition under which the reference voltage
signals were taken, then the reference voltage signals may
accurately reflect the state of filter element 34. However,
internal combustion engine 10 may not always operate in the same
condition, but rather, may operate differently as the load on
internal combustion engine 10 changes. For example, when internal
combustion engine 10 is subjected to a low load condition, internal
combustion engine 10 may produce a first level of horsepower that
has associated with it a particular level of sound energy. If the
reference voltage signals are taken during the low load condition,
then the reference voltage signals may accurately indicate the
state of filter element 34 as long as the internal combustion
engine 10 continues to operate in the same low load condition.
However, machines may often be used in dynamic environments, where
they may not operate under the exact same load conditions at all
times, but rather, may be subject to changing load conditions as
the machine travels up and down inclines, or when the machine lifts
and lowers objects. If internal combustion engine 10 is subjected
to a high load condition, it may respond by producing an increase
in horsepower and may generate a level of sound energy greater than
that generated during the low load condition. The increase in the
level of sound energy may produce a corresponding increase in the
value of the actual voltage signal produced by sensor package 38.
If voltage detector 54 compares the actual voltage signal produced
in the high load condition to the reference voltage signals
produced when internal combustion engine 10 is operating under the
low load condition, then an inaccuracy may result. For example,
suppose that the baseline voltage signal is taken during the low
load condition. If internal combustion engine 10 is then
subsequently subjected to the high load condition, the increased
level of sound energy may produce an actual voltage signal greater
than the baseline voltage signal. As internal combustion engine 10
continues to operate in the high load condition, filter element 34
may become clogged. However, the actual voltage signal may not fall
far enough below the baseline voltage signal to trigger
regeneration, because the level of sound energy in the high load
condition may compensate for the attenuation caused by clogging of
filter element 34. Thus, regeneration of filter element 34 may not
be performed although it may be necessary.
[0029] A solution to the problem may include providing control box
40 with a mechanism configured to associate the reference voltage
signals with engine horsepower, thus allowing control box 40 to
adjust these signals as the engine horsepower changes. For example,
control box 40 may include one or more electronic databases (not
shown) configured to store one or more engine maps. An engine map
may include, for example, a table associating particular reference
voltage signals, such as, for example, baseline voltage signals and
low voltage levels, with engine horsepower values. Control box 40
may monitor engine horsepower, and, based at least in part on the
table in the engine map, may selectively adjust the reference
voltage signals for voltage detector 54 to reflect changes in the
sound energy that may occur as a result of changes in engine
horsepower. This adjustment may serve to ensure that the state of
filter element 34 may be accurately determined regardless of the
changing sound energy levels created by internal combustion engine
10. It should be understood that the one or more databases may
include a plurality of engine maps accessible by control box 40.
Each engine map may apply to a particular machine, specific engine
model, and/or work site environment. The engine maps may be created
by using design data, historical performance data, experimental
data, and/or any other information that may be suitable for
associating engine horsepower with sound energy levels.
[0030] An exemplary method of monitoring filter element 34 will now
be described in greater detail. To start (step 62), sensor package
38 may be installed on exhaust line 14 (step 64). In one
embodiment, sensor package 38 may be attached to the outside wall
of exhaust line 14 at any suitable location downstream from filter
element 34. In another embodiment, at least microphone 44 may
extend into exhaust line 14 at any suitable location downstream
from filter element 34. In yet another embodiment, sensor package
38 may be inserted into exhaust line 14 through an opening 61 at or
near tailpipe section 60 proximate the furthermost downstream end
of exhaust line 14. These installation locations are exemplary
only, and it should be understood that sensor package 38 may be
installed on, in, or near exhaust line 14 at any location suitable
for receiving sound waves from combustion chamber 16 after they
have passed through filter element 34 and into exhaust line 14
[0031] The process of converting the sound waves into the voltage
signal may begin when the sound waves reach microphone 44.
Microphone 44 may convert the sound waves into a microphone signal
(step 66). The microphone signal may enter high-pass filter 46 to
filter out frequencies of the microphone signal lower than a first
predetermined cutoff frequency to create the high-pass filter
signal (step 68). The high-pass filter signal may enter full wave
rectifier 50, and full wave rectifier 50 may convert the high-pass
filter signal into the rectified voltage signal, having a direct
current waveform, by reversing the negative portions of the
high-pass filter signal waveform (step 70). The rectified voltage
signal may then be passed through low-pass filter 52. Low-pass
filter 52 may block or filter out frequencies of the direct current
waveform higher than a second predetermined cutoff frequency, while
allowing frequencies lower than the second predetermined cutoff
frequency to pass (step 72). The voltage signal may emerge from
low-pass filter 52 and enter voltage detector 54. The reference
voltage signal may be pre-set in voltage detector 54 using the
engine map as a guide. The voltage signal may be compared to the
reference voltage signal to determine the degree of loading of
filter element 34 (step 74). The voltage detector may continually
monitor the voltage signal. If the voltage signal falls outside of
a predetermined acceptable range (step 76: YES), such as the range
of values between the baseline voltage signal and the low voltage
level, then regeneration of filter element 34 may be initiated
(step 78). If the voltage signal falls within a predetermined
acceptable range (step 76: NO), then the process returns to step
66. The process may end (step 80) when internal combustion engine
10 is shut off.
[0032] In the mode of operation described above, the sound waves
received by sensor package 38 may be converted by sensor package 38
into the voltage signal indicative of the state of filter element
34. The voltage signal may be received by control box 40. Control
box 40 may signal for the activation of particulate filter
regeneration device 32 based on the strength or value of the
voltage signal. In another mode of operation, the voltage signal
may directly control a light in the cab of the machine, to inform
the machine operator when regeneration of filter element 34 is
required.
INDUSTRIAL APPLICABILITY
[0033] The disclosed monitoring assembly may have applicability in
internal combustion engines, such as diesel engine assemblies.
Monitoring assembly 36 may have particular applicability in
monitoring the state of a filter element 34 of a diesel engine.
[0034] Monitoring assembly 36 may assist filter element 34 by
controlling the timing, number, and/or duration of regenerations
performed on filter element 34. By using monitoring assembly 36 to
determine the state of filter element 34, clogging of filter
element 34 may be directly measured without relying on back
pressure sensor readings and similar devices that may not provide
accurate indications of the actual state of filter element 34.
Using the analysis performed by monitoring assembly 36 as the basis
for triggering regeneration can help to ensure that regeneration
may take place when necessary, which may result in increased filter
efficiency, cleaner exhaust, and improved engine efficiency. Also,
unnecessary regenerations may be avoided, which may help to extend
the working life of filter element 34, because repeated
regeneration of filter element 34 may cause cracking and/or other
forms of damage.
[0035] Further, monitoring assembly 36 may be properly
characterized as a passive monitoring system. In contrast, an
active monitoring system may inject sound energy into one side of
filter element 34 and may read the sound energy as it emerges from
the other side. Accordingly, active monitoring systems may include
sound wave generation devices and other components for broadcasting
signals. These device and components may be costly, and may be too
delicate for harsh engine environments. In contrast, monitoring
assembly 36 may operate using the sound energy from an internal
combustion engine 10, and may not require the use of sound wave
generation devices. Thus, monitoring assembly 36 may monitor filter
element 34 using fewer components than active monitoring systems.
As long as internal combustion engine 10 is running, monitoring
assembly 36 may monitor filter element 34, and may automatically
initiate regeneration of filter element 34 or alert a machine
operator that regeneration may be required.
[0036] Furthermore, monitoring assembly 36 may be configured to
monitor and analyze types of sound energy that may be more helpful
for determining the state of filter element 34 than other types of
sound energy. For example, low frequency sound waves, such as, for
example, those under 2,000 Hz, may pass through a clogged
particulate filter relatively unattenuated. Thus, monitoring low
frequency sound waves may provide little assistance in determining
the state of filter element 34. A high-pass filter 46 in monitoring
assembly 36 may filter or block out the low frequency sound waves.
High frequency sound waves may experience greater attenuation than
low frequency sound waves when they pass through a clogged
particulate filter. For example, sound waves having frequencies
between 2,000 Hz and 7,000 Hz may experience a 5 dB or higher drop
in intensity when passing through a clogged particulate filter.
Thus, high-pass filter 46 may allow monitoring assembly 36 to focus
on the high frequency sound waves that may convey more information
about the state of filter element 34. Monitoring assembly 36 may
also include a full wave rectifier 50 and a low-pass filter. Full
wave rectifier 50 may create an easily filtered output for
filtering by low-pass filter 52, allowing low-pass filter 52 to
output a relatively steady signal to a low voltage detector 54.
This configuration may help to improve the accuracy and precision
of monitoring assembly 36.
[0037] It will be apparent to those skilled in the art that various
modifications and variations can be made in the disclosed system
and method without departing from the scope of the disclosure.
Additionally, other embodiments of the disclosed system and method
will be apparent to those skilled in the art from consideration of
the specification. It is intended that the specification and
examples be considered as exemplary only, with a true scope of the
disclosure being indicated by the following claims and their
equivalents.
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