U.S. patent application number 10/908265 was filed with the patent office on 2007-01-11 for method for cleaning a particle filter and a vehicle for utilizing said method.
This patent application is currently assigned to VOLVO LASTVAGNAR AB. Invention is credited to Christer ALM, Per PERSSON, Bo SVENSSON.
Application Number | 20070006576 10/908265 |
Document ID | / |
Family ID | 20289456 |
Filed Date | 2007-01-11 |
United States Patent
Application |
20070006576 |
Kind Code |
A1 |
PERSSON; Per ; et
al. |
January 11, 2007 |
METHOD FOR CLEANING A PARTICLE FILTER AND A VEHICLE FOR UTILIZING
SAID METHOD
Abstract
Method and arrangement for regenerating a particle filter (15)
arranged in thermal proximity to a catalyst unit (16) in an exhaust
duct (10) connected to an internal combustion engine (2). The
particle filter is located downstream of an adjustable exhaust
pressure regulator (20) for regulating an exhaust flow through the
exhaust duct. When the internal combustion engine is driven at low
engine load, the exhaust pressure regulator (20) is activated with
a predetermined regulating pressure. Fuel is then supplied to the
exhaust duct (10) by means of an injection unit, the catalyst unit
(16) being exposed to the fuel, which is oxidized, and the particle
filter (15) being heated to such a temperature that soot particles
are converted into carbon dioxide in reaction with oxygen contained
in the exhaust flow.
Inventors: |
PERSSON; Per; (Partille,
SE) ; SVENSSON; Bo; (Hisings Backa, SE) ; ALM;
Christer; (Goteborg, SE) |
Correspondence
Address: |
NOVAK DRUCE & QUIGG, LLP
1300 EYE STREET NW
400 EAST TOWER
WASHINGTON
DC
20005
US
|
Assignee: |
VOLVO LASTVAGNAR AB
S-405 08
Goteborg
SE
|
Family ID: |
20289456 |
Appl. No.: |
10/908265 |
Filed: |
May 4, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/SE03/01621 |
Oct 20, 2003 |
|
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|
10908265 |
May 4, 2005 |
|
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Current U.S.
Class: |
60/295 ; 60/286;
60/297 |
Current CPC
Class: |
Y02T 10/146 20130101;
Y02T 10/144 20130101; F02D 41/405 20130101; Y02T 10/40 20130101;
F01N 3/0253 20130101; Y02T 10/12 20130101; F02B 37/22 20130101;
F01N 3/035 20130101; F02B 29/04 20130101; F01N 13/0097 20140603;
Y02T 10/26 20130101; F02D 41/025 20130101; Y02T 10/16 20130101;
F02D 41/029 20130101; F02B 37/00 20130101; Y02T 10/44 20130101 |
Class at
Publication: |
060/295 ;
060/286; 060/297 |
International
Class: |
F01N 3/00 20060101
F01N003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 5, 2002 |
SE |
0203250-6 |
Claims
1. A method for regenerating a particle filter (15) arranged in
thermal proximity to a catalyst unit (16) in an exhaust duct (10)
connected to an internal combustion engine (2), said particle
filter being located downstream of an adjustable exhaust pressure
regulator (20) for regulating an exhaust flow through the exhaust
duct, said method comprising: establishing by means of a control
unit (24) that the internal combustion engine is being driven at
low engine load; activating the exhaust pressure regulator (20)
with a predetermined regulating pressure; and supplying fuel to the
exhaust duct (10) by means of an injection unit, the catalyst unit
(16) being exposed to said fuel, which is oxidized, and the
particle filter (15) being heated to a temperature at which soot
particles are converted into carbon dioxide in reaction with oxygen
contained in the exhaust flow.
2. The regenerating method as recited in claim 1, wherein said
injection unit supplies fuel to a combustion chamber arranged in
the internal combustion engine (2) at such a stage of the working
cycle of the internal combustion engine that fuel is allowed to
pass through the combustion chamber into the exhaust duct (10) in a
non-combusted or partly combusted state, said non-combusted or
partly combusted fuel being oxidized on contact with the catalyst
unit (16) and the particle filter (15) being heated to such a
temperature that soot particles are converted into carbon monoxide
in reaction with oxygen contained in said exhaust flow.
3. The regenerating method as recited in claim 2, wherein said fuel
is supplied during one of (1) the expansion stroke and (2) the
exhaust stroke of the internal combustion engine.
4. The regenerating method as recited in claim 1, wherein fuel is
supplied directly to the exhaust duct (10) via an injection unit
assigned to the exhaust duct.
5. The regenerating method as recited in claim 1, wherein fuel is
supplied when the exhaust gas temperature at the particle filter
(15), under low load and with the exhaust pressure regulator
activated, is at least 250.degree. C.
6. A vehicle (1) comprising: an internal combustion engine (2) and
a particle filter (15) in thermal proximity to a catalyst unit (16)
in an exhaust duct (10) connected to the internal combustion
engine, the particle filter being located downstream of an
adjustable exhaust pressure regulator (20) for regulating an
exhaust flow through the exhaust duct; and an injection system
configured so that when regeneration of the particle filter (15) is
necessary, fuel is supplied to the exhaust duct (10) with
simultaneous activation of the exhaust pressure regulator (20), the
catalyst unit (16) is exposed to the fuel which is oxidized, and
the particle filter is heated to such a temperature that soot
particles are converted into carbon dioxide in reaction with oxygen
contained in said exhaust flow.
7. The vehicle as recited in claim 6, wherein the injection system
is configured to supply fuel to combustion chambers arranged in the
internal combustion engine (2) at such a stage of the working cycle
of the internal combustion engine that fuel is allowed to pass
through the combustion chamber into the exhaust duct (10) in a
non-combusted or partly combusted state.
8. The vehicle as recited in claim 7, wherein said injection system
is configured to supply fuel during one of (1) the expansion stroke
and (2) the exhaust stroke of the internal combustion engine.
9. The vehicle as recited in claim 6, wherein the vehicle further
comprises an injection unit assigned to the exhaust duct (10), said
injection unit being arranged to supply fuel directly to the
exhaust duct.
10. The vehicle as recited in claim 6, wherein the exhaust pressure
regulator (20) comprises a pneumatically operated piston (22) that
is connected to a valve disk (23) which, when moved in the
direction of a seat, forms a throttle for the exhaust flow of the
engine.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation patent application
of International Application No. PCT/SE2003/001621 filed 20 Oct.
2003 which was published in English pursuant to Article 21(2) of
the Patent Cooperation Treaty, and which claims priority to Swedish
Application No. 0203250-6 filed 5 Nov. 2002. Said applications are
expressly incorporated herein by reference in their entireties.
TECHNICAL FIELD
[0002] The present invention relates to a method for regenerating a
particle filter arranged in thermal proximity to a catalyst unit in
an exhaust duct connected to an internal combustion engine, such as
is often utilized to power a vehicle.
BACKGROUND OF INVENTION
[0003] In the combustion process in diesel engines, soot particles
are also formed in addition to water vapor, nitrogen oxides and
carbon dioxide. Small quantities of uncombusted hydrocarbons and
carbon monoxide also occur. A diesel engine provided with a
particle filter greatly reduces particle emissions. However, the
particle filter has to be regenerated more or less continuously so
that it does not become full and cause high pressure drops across
the exhaust system. In order for the particle filter to
self-regenerate automatically, an exhaust gas temperature of at
least 250.degree. C. and sulfur-poor fuel<30 ppm are necessary.
When the diesel engine works at low load levels and/or low ambient
temperatures, however, the exhaust gas temperature is usually lower
than 250.degree. C., which leads to soot accumulating in the
particle filter. If such operating states are allowed to continue
for a relatively long time, the soot build-up in the particle
filter can reach a detrimental level. In this context, the
expression detrimental level shall be taken to mean that if the
operating state is subsequently changed and regeneration of the
filter begins, there is an imminent risk of overheating with
permanent damage to the filter as a consequence. Moreover, there is
a risk that the magnitude of the exhaust back-pressure can threaten
the functioning of the engine.
[0004] EP 341 832, for example, describes a system comprising a
filter in which soot particles are caught. The soot particles are
then combusted in a nitrogen dioxide environment. The nitrogen
dioxide is formed from within the exhaust gases from nitrogen
monoxide in an oxidation catalyst arranged upstream of the filter.
One problem with the system described in EP 341 832 is that the
capacity for converting the soot particles into carbon dioxide is
low in operating conditions with low exhaust gas temperatures. In
this connection, the regeneration of the particle filter requires
too much time or, as the case may be, is inadequate, then the
filter gradually becomes blocked with increased pressure drop as a
consequence. This in turn results in the filter having to be
serviced frequently.
SUMMARY OF THE INVENTION
[0005] One object of the invention is therefore to provide a method
which makes possible effective regeneration of particle filters and
is moreover easy to apply to internal combustion engines.
[0006] According to the inventive method, an injection unit
assigned to the internal combustion engine supplies fuel to an
exhaust system connected to the engine at times when the engine is
driven with low engine load, an exhaust pressure regulator arranged
in the exhaust system then being activated. A catalyst unit
arranged in the exhaust duct in thermal proximity to the particle
filter is exposed to the fuel supplied, which is oxidized. In this
connection, the particle filter is heated to such a temperature
that soot particles are converted into carbon dioxide in reaction
with oxygen contained in said exhaust gases. The injection unit can
consist of a separate unit which has an injector located in the
exhaust duct, or of the existing injection system of the internal
combustion engine.
[0007] The invention makes use of the fact that an exhaust pressure
regulator can be used at low load in order to build up a
back-pressure in the exhaust system which increases the temperature
of the exhaust flow.
[0008] In a preferred embodiment, the fuel is supplied by means of
injectors assigned to the combustion chambers of the engine. In
this case, the fuel is supplied as indicated above, when the engine
is driven at low load and the exhaust pressure regulator is
activated, and at such a stage that fuel is allowed to pass through
the combustion chamber into the exhaust duct in a non-combusted or
only partly combusted state. This is achieved by supplying the fuel
at a delayed crank angle position in relation to normal injection;
that is to say, during the expansion or exhaust stroke.
[0009] The invention also relates to a vehicle in which the method
described above is implemented.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The invention will be described in greater detail with
reference to accompanying drawing figures, in which:
[0011] FIG. 1 diagrammatically shows a vehicle comprising an
internal combustion engine equipped with a particle filter which is
regenerated by a method according to the present invention;
[0012] FIG. 2 diagrammatically shows, in greater detail, a
turbocharged diesel engine with a particle filter according to the
arrangement of FIG. 1; and
[0013] FIG. 3 graphically shows the volumetric flow of injected
fuel quantity during normal operation and at low engine load when
regeneration takes place.
DETAILED DESCRIPTION
[0014] FIG. 1 shows a vehicle 1 equipped with an internal
combustion engine 2 and a gearbox 3 coupled to the engine. The
gearbox has an output driving shaft 4 which, via a propeller shaft
5, drives at least one pair of driving wheels 6. In a conventional
way, the vehicle 1 is constructed around a frame 7 which is
supported by the driving wheels 6, and preferably a set of
steerable wheels 8. The vehicle preferably comprises (includes, but
is not necessarily limited to) a cab 9.
[0015] In a conventional way, the internal combustion engine is
equipped with an exhaust system 10 which comprises an exhaust pipe
11 connected to the outlet ports of the engine. A turbine 12 is
preferably arranged in the exhaust system 10 and forms part of a
turbo unit 13 and is thus mechanically coupled to a compressor 14
arranged on the intake side (not shown) of the engine.
[0016] There may also be a turbine mechanically coupled back to the
driving shaft of the internal combustion engine in a turbo compound
system.
[0017] The engine is of the diesel type, which means that soot
particles are formed during the combustion process. The exhaust
system is therefore equipped with a particle filter 15. An
oxidation catalyst 16 is arranged in thermal proximity to the
particle filter. In the present context, thermal proximity shall be
taken to mean that the reaction which takes place in the oxidation
catalyst is capable of heating the particle filter. For this
purpose, the oxidation catalyst is usually mounted upstream of and
in direct proximity to the particle filter, but it is also
conceivable to integrate the particle filter and the oxidation
catalyst on a common bearing structure where catalyst material is
spread over the filtering body.
[0018] The oxidation catalyst and the particle filter can
preferably be designed as described in EP 341 832 or EP 835 684.
Soot particles are caught in the particle filter 13. Under
favorable conditions, a continuous conversion of nitric oxide NO
into nitrogen dioxide NO.sub.2 takes place in the oxidation
catalyst. Oxidation of the soot particles then takes place in a
nitrogen dioxide environment, the soot particles being oxidized to
form carbon dioxide in one, some or all of the processes
NO.sub.2+C=>NO+CO, NO.sub.2+C=>1/2N.sub.2+CO.sub.2 or
2NO.sub.2+C=>2NO+CO.sub.2.
[0019] On account of the relatively low content of NOx, and in
particular NO.sub.2, however, these processes are too slow in order
completely to regenerate the filter at low temperatures and/or low
load on the engine. Disruption of the NO.sub.2 formation, for
example on account of sulfur poisoning, also leads to impaired soot
combustion.
[0020] The soot particles can also react directly with the excess
oxygen O.sub.2 present in diesel exhaust gases, but a prerequisite
for this is that the temperature exceeds approximately 600.degree.
C. This reaction is several powers of ten faster than the reaction
in which NO.sub.2 reacts with the soot because the concentration of
oxygen O.sub.2 remaining in diesel exhaust gases is approximately
three powers of ten greater than the concentrations of NO.sub.2
are. If this temperature is used for regeneration of the soot
filter, the whole regeneration can be limited to a few minutes.
[0021] FIG. 2 shows in greater detail the internal combustion
engine 2 which is arranged for regeneration of a particle filter
according to the invention. The internal combustion engine
preferably forms part of a driving unit for a truck or a bus. The
engine is advantageously of the directly injected diesel engine
type in which a turbo unit 13 with an exhaust-driven turbine 12 and
a compressor 14 arranged on the turbine shaft is used for
compression and supply of combustion air. Intake air is supplied to
the supercharger from an air filter 17 for compression, after which
the compressed air is cooled as it passes through an intercooler 18
before it is supplied to the intake manifold 19 of the engine.
[0022] The exhaust gases of the engine are collected in a
conventional way in an exhaust manifold 11 and are then conducted
to the turbine 12 of the supercharger 13 for driving the compressor
14. The exhaust gases are then conducted onward via an exhaust
pressure regulator 20 to a muffler unit 21 with a particle filter
15.
[0023] The exhaust pressure regulator 20 can be of a kind known per
se and comprises a piston valve with a pneumatically controlled
piston 22 and a valve disk 23 mounted at the opposite end of a rod.
A regulating air pressure acts against the piston 22 via a
compressed-air line (not shown) which is connected to a
compressed-air system contained in the vehicle, which is used for
generating power for auxiliary units in the vehicle.
[0024] A control unit 24, suitably a microprocessor, is connected
to the exhaust pressure regulator 20 via the compressed-air line 25
for controlling the regulating pressure depending on input data.
Such input data is provided via, for example, a line 26 to the
particle filter 15. The exhaust pressure regulator can be activated
by, for example, detection of the particle quantity in the particle
filter 15 having reached a certain level. Alternatively, activation
can take place on detection of the pressure drop in the particle
filter having reached a certain level. Another variant is to detect
whether the engine has worked at low load for a certain time. By
means of the control unit 24, the valve disk can therefore be set
between fully open position and active position, where a given
exhaust pressure is defined by the interaction of the valve with
the gas flowing through.
[0025] The exhaust pressure regulator 20 can be activated to
different degrees depending on how hot the exhaust gases are. In
this connection, the exhaust gas temperature can be measured and
the exhaust pressure regulator can be controlled until its desired
temperature is obtained. Alternatively, the control unit of the
engine can, with a known ambient temperature in combination with
the current operating point, calculate the exhaust gas temperature
and then control the exhaust pressure regulator until the desired
exhaust gas temperature is obtained.
[0026] FIG. 3 shows diagrammatically the volumetric flow of
injected fuel quantity during normal operation and at low engine
load during regeneration. The regulation of injected fuel quantity
and the angle position of the crankshaft when injection takes place
are controlled by the control unit 24 in a manner well-known to the
expert. An example of a control unit for vehicles is given in
SAEJ1939/71,1996. The graph shows the volumetric flow as a function
of the crankshaft angle position, which is indicated with the
bottom and top dead centers of the piston as reference points. The
four strokes of the internal combustion engine are indicated along
the x axis, the intake stroke between 0.degree. and 180.degree.,
the compression stroke between 180.degree. and 360.degree., the
expansion stroke between 360.degree. and 540.degree., and the
exhaust stroke between 540.degree. and 720.degree..
[0027] Curve A shows the fuel quantity supplied for an operating
case when the engine is working under normal load. Fuel is then
supplied at the transition between the compression stroke and the
expansion stroke with a duration of between 3 and 30 crank angle
degrees.
[0028] The curves B.sub.1-B.sub.3 show the fuel quantity supplied
under low engine load for regeneration of a particle filter
arranged downstream of an oxidation catalyst in the exhaust duct.
The fuel is preferably supplied during the expansion stroke or the
exhaust stroke within a range covering 30.degree. to 90.degree.
after top dead center between the compression stroke and the
expansion stroke. A wider range of 0.degree. to 360.degree. after
top dead center between the compression stroke and the expansion
stroke is possible; that is to say, during the expansion stroke and
the exhaust stroke.
[0029] In illustrative embodiments B.sub.1 and B.sub.2, fuel is
supplied between 30.degree. and 180.degree. after top dead center
between the compression stroke and the expansion stroke.
[0030] In illustrative embodiment B.sub.3, fuel is supplied
270.degree. after top dead center.
[0031] The invention is not to be regarded as being limited to the
illustrative embodiments described above, but a number of further
variants and modifications are conceivable and that are within the
scope of the patent claims below.
* * * * *