U.S. patent application number 12/365356 was filed with the patent office on 2009-08-06 for method for the regeneration of a particle filter installed in the exhaust gas train of a vehicular diesel engine.
This patent application is currently assigned to MAN Nutzfahrzeuge Oesterreich AG. Invention is credited to Gottfried Raab, Klaus Richter.
Application Number | 20090193790 12/365356 |
Document ID | / |
Family ID | 40627139 |
Filed Date | 2009-08-06 |
United States Patent
Application |
20090193790 |
Kind Code |
A1 |
Richter; Klaus ; et
al. |
August 6, 2009 |
Method For The Regeneration Of A Particle Filter Installed In The
Exhaust Gas Train Of A Vehicular Diesel Engine
Abstract
A method for regenerating a soot-laden particle filter in the
exhaust gas train of a diesel engine in a vehicle, wherein the
engine is equipped with a fuel injection system having an injection
valve for each cylinder and an exhaust braking device including a
butterfly valve in the exhaust gas train upstream of the particle
filter. An exhaust braking phase is initiated by closing the
butterfly valve, thereby causing hot exhaust gas to be compressed
upstream of the butterfly valve. Regeneration of the particle
filter is then initiated by injecting diesel fuel into the
cylinders substantially after the respective pistons pass top dead
center, and allowing the hot exhaust gas mixture containing
unburned fuel and air to flow past the butterfly valve so that the
mixture ignites the soot and then supports combustion of the soot,
thereby regenerating the particle filter.
Inventors: |
Richter; Klaus; (Steyr,
AT) ; Raab; Gottfried; (Perg, AT) |
Correspondence
Address: |
COHEN, PONTANI, LIEBERMAN & PAVANE LLP
551 FIFTH AVENUE, SUITE 1210
NEW YORK
NY
10176
US
|
Assignee: |
MAN Nutzfahrzeuge Oesterreich
AG
Steyr
AT
|
Family ID: |
40627139 |
Appl. No.: |
12/365356 |
Filed: |
February 4, 2009 |
Current U.S.
Class: |
60/274 ; 60/287;
60/295 |
Current CPC
Class: |
F02D 41/025 20130101;
F02D 41/12 20130101; F02D 41/1448 20130101; F02D 41/029 20130101;
Y02T 10/40 20130101; F02D 41/405 20130101; F02D 9/06 20130101; Y02T
10/44 20130101; Y02T 10/12 20130101; F02D 41/40 20130101; F01N
3/023 20130101; F01N 3/0235 20130101; Y02T 10/26 20130101; F02D
2200/0802 20130101 |
Class at
Publication: |
60/274 ; 60/295;
60/287 |
International
Class: |
F01N 9/00 20060101
F01N009/00; F01N 3/023 20060101 F01N003/023 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 4, 2008 |
AT |
A 166/2008 |
Claims
1. A method for regenerating a particle filter installed in an
exhaust gas train of a diesel engine in a vehicle and partially
loaded with separated soot particles, wherein the engine is
equipped with a fuel injection system comprising an injection valve
for each cylinder and an exhaust braking device comprising a
butterfly valve in the exhaust gas train upstream of the particle
filter, the method comprising: initiating an exhaust braking phase
by closing the butterfly valve, thereby causing hot exhaust gas to
be compressed upstream of the butterfly valve; initiating
regeneration of the particle filter during an exhaust braking phase
by injecting diesel fuel into the cylinders substantially after the
respective pistons pass top dead center, thereby creating a hot gas
mixture containing unburned fuel and air; and allowing the hot gas
mixture to flow past the butterfly valve so that the mixture
ignites the soot and then supports combustion of the soot, thereby
regenerating the particle filter.
2. The method of claim 1 wherein regeneration is initiated when the
diesel engine is in an RPM range which is significantly lower than
a nominal RPM value of the diesel engine.
3. The method of claim 1 further comprising: detecting actual
pressure values in the exhaust gas train at a time before or
immediately after initiating an exhaust braking phase; and
determining the degree of soot loading of the particle filter based
on the actual pressure values.
4. The method of claim 3 comprising: predefining a nominal pressure
value range, determining the degree of soot loading of the particle
filter by comparing the actual pressure values to the nominal
pressure value range; and determining when the particle filter
should be regenerated based on the location of the actual pressure
values in the nominal pressure value range.
5. The method of claim 1 comprising: detecting the temperature
value of the particle filter during regeneration; injecting the
diesel fuel during regeneration with a timing that is set within a
range between a minimum and a maximum after top dead center; and
injecting the diesel fuel during regeneration in a quantity which
is set as a function of the detected temperature values of the
particle filter, wherein the quantity of fuel injected is inversely
proportional to the temperature.
6. The method of claim 5 wherein the injection timing is between a
minimum of 5 crankshaft degrees after TDC and a maximum of 120
crankshaft degrees after TDC.
7. The method of claim 1 further comprising: detecting operating
values relevant to regeneration during regeneration, the operating
values comprising exhaust gas backpressure between the butterfly
valve and the particle filter; and terminating the regeneration
when the detected operating values indicate a satisfactory degree
of regeneration.
8. The method of claim 1 wherein the regeneration is controlled by
a computer-based electronic control unit, the method comprising:
storing nominal value data in the electronic control unit;
transmitting actual operating values to the electronic control
unit; evaluating the actual operating values based on the stored
nominal value data; and based on the evaluation, generating control
commands for elements including the butterfly valve, the injection
valves, and an exhaust bypass around the butterfly valve.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a method for the regeneration of a
particle filter installed in the exhaust gas train of a vehicular
diesel engine and partially loaded with separated soot particles,
where the diesel engine is equipped with an exhaust brake device,
to which a butterfly valve in the exhaust gas train upstream of the
regeneration site belongs, and with a fuel injection system with an
injection valve for each cylinder.
[0003] 2. Description of the Related Art
[0004] In utility vehicles with diesel engines, particle filters
are provided in the exhaust gas trains to satisfy the legally
imposed exhaust gas regulations. Oxidation catalysts are installed
upstream of the particle filters to increase the concentration of
NO.sub.x in the exhaust gas, and in some cases SCR catalysts can be
installed downstream. These particle filters are loaded to a
greater or lesser extent with the soot separated from the exhaust
gas. At sufficiently high exhaust gas temperatures (>350.degree.
C.), the soot is oxidized almost continuously. If the exhaust gas
temperatures are not high enough, it is known that thermal
regeneration can be initiated and supported by the injection of a
certain amount of fuel into the exhaust gas train upstream of the
particle filter to be regenerated. The diesel fuel, serving as an
HC carrier, is injected here by means of specially provided fuel
metering devices. The heat released during the oxidation of the
vaporized hydrocarbons (HC) in the exhaust gas train heats the
particle filter to the ignition temperature of the collected soot.
An open and closed-loop electronic control system, which is usually
very complex, ensures that suitable starting conditions are
provided for this type of regeneration. Especially in the case of
vehicles like route buses and delivery trucks, which are operating
under non-steady-state conditions most of the time, this known
method of initiating the regeneration of soot-loaded particle
filters usually results in the consumption of comparatively large
amounts of fuel, which, as a result of increasing fuel prices, is
strongly reflected in vehicle operating costs.
SUMMARY OF THE INVENTION
[0005] It is therefore an object of the invention to improve the
regeneration method of the general type in question so that it can
be implemented more simply in terms of design and apparatus and
also so that, upon its application, the extra amount of fuel
consumed is less than that of the previously mentioned known
regeneration methods.
[0006] According to the invention, the particle filter is
regenerated during an exhaust braking phase by injecting diesel
fuel into the cylinders substantially after the respective pistons
pass top dead center, thereby creating a hot gas mixture containing
unburned fuel and air. The hot gas mixture is allowed to flow past
the butterfly valve so that the mixture ignites the soot and then
supports combustion of the soot, thereby regenerating the particle
filter.
[0007] In contrast to conventional methods, the inventive method
allows the soot particle-loaded particle filter to be regenerated
only during the times that the exhaust brake is operating. This
means that the inventive method can be applied only in conjunction
with diesel engines which have an exhaust brake device, to which a
butterfly valve installed in the exhaust gas train upstream of the
particle filter and either upstream or downstream of the turbine of
an exhaust gas turbocharger also belongs. The butterfly valve is
usually in the pass-through position, but it is switched into its
blocking position during a normal exhaust braking phase, as a
result of which the gas backed up in the blocked-off area of the
exhaust gas line cooperates with the pistons in the individual
engine cylinders to increase the braking power. So that the engine
does not stall out during the braking process, however, the
butterfly valve is not completely closed, or a small bypass
channel, located in the area of the butterfly valve and passing
around it, is opened by a valve, so that a small amount of the gas
can flow from the backed-up area into the following section of the
exhaust gas line. Since the butterfly valve is closed when the
driver releases the fuel throttle, almost no fuel is admitted for
combustion. As a result, the exhaust gas is little more than the
air ingested during the intake stroke.
[0008] The previously described specific relationships which are
present during an exhaust braking phase, in conjunction with the
fuel injection system inside the engine, can be used especially
effectively to regenerate a particle filter partially loaded with
soot particles. The inventive type of regeneration can be realized
with the use of the existing technical devices already on the
engine; that is, there is no need in practice for any additional
design measures or apparatus; on the contrary, the only additional
step required is increase the "depth" of the open and closed-loop
control system to handle the regeneration function with the
existing devices. In general, therefore, according to the
invention, a particle filter partially loaded with soot particles
will never be regenerated except during exhaust braking phases of
the engine: it will be started after the exhaust braking phase has
been initiated, and it will continue during the rest of the exhaust
braking phase. During such an exhaust braking phase, the speed of
the diesel engine is decelerated to a lower-to-medium rpm range
significantly below the nominal rpm's, and a certain quantity of
diesel fuel is injected via the engine's own injection valves into
the cylinders of the exhaust-braked diesel engine, namely, at a
time which is significantly after top dead center (TDC). In
addition, technical control measures are taken to ensure that part
of the hot gas mixture which then is present in the backpressure
area of the blocked-off exhaust gas line and which contains a
certain amount of unburned fuel and the air which has become highly
compressed during the exhaust braking process can flow through the
butterfly valve or bypass it. During the regeneration of the
partially soot-loaded particle filter, this hot gas mixture which
has passed through or by the butterfly valve acts during the
exhaust braking phase as a highly efficient oxidizing agent, which,
at the beginning of the regeneration phase, brings about the
initial ignition of the soot and then supports its accelerated
oxidation/combustion.
[0009] Because every regeneration of the particle filter according
to the inventive method leads to the consumption of a certain
amount of fuel, it is advisable, before the initiation of a
regeneration phase, to question, i.e., to determine, the necessity
of a particle filter regeneration. This is done, for example, by
detecting the pressure values representative of the degree to which
the filter is loaded with soot particles, such as the exhaust gas
backpressure in the exhaust gas train. It is also possible to
specify in advance a value range for the degree of soot loading and
either to set the regeneration process in motion immediately
whenever the actual soot load lies within the specified value
range, or, depending on the situation, to initiate it after a
certain time delay. In this case, a certain nominal range will be
predefined for the evaluation of the detected pressure values
representative of the soot particle load. By comparing the
transmitted actual pressure values with the pressure values of the
nominal range, it is then possible, depending on the position of
the actual pressure values within this range, to determine whether
a regeneration is necessary at once or whether it can instead be
started at a later time. In this way, it is possible to avoid the
unnecessary consumption of fuel.
[0010] The quantity of fuel needed to regenerate the particle
filter can also be limited by adjusting it within a regeneration
phase as a function of detected actual temperature values of the
particle filter, namely, by adjusting it to comparatively large
injection quantities at low particle filter temperatures and to
smaller injection quantities at higher particle filter
temperatures. The start of a fuel injection or of a fuel injection
sequence can, in terms of technical control measures involved, lie
within in a range between "minimally after TDC", e.g., 5 crankshaft
degrees after TDC, and "maximally after TDC", e.g., 120 crankshaft
degrees after TDC, and the quantity of fuel to be injected can also
be adjusted variably to suit the circumstances.
[0011] To limit the consumption of fuel required for particle
filter regeneration even more, it is also effective to determine
the actual regeneration state of the particle filter within a
regeneration phase. Once again, this can be done by detecting
operating values representative of this state such as the exhaust
gas backpressure in the exhaust gas train. The regeneration phase
is terminated as soon as an operating value representative of a
sufficient degree of regeneration has been obtained.
[0012] It is known in the case of certain diesel engines installed
in MAN trucks and busses that, to avoid the coking which might
occur as a result of the overheating of the injection nozzle heads
projecting into the combustion chambers during an exhaust braking
phase when the exhaust braking rpm's are in the range of the
nominal rpm's and the compressed air takes on extremely high
temperatures, fuel can be injected into the cylinders for a brief
period of time to cool the injection nozzle bores. See the diagram
in FIG. 2, which illustrates these relationships. In the
load-versus-rpm diagram according to FIG. 2, DM designates the
torque curve of the diesel engine at full load, BK the brake power
curve obtained when the diesel engine is operating in exhaust
braking mode, and an the fuel injection map for nozzle cooling
during exhaust braking mode. As can be seen, the nozzle-cooling
injection map an lies in the area of the nominal rpm value nm of
the diesel engine. The nominal rpm line is designated nN. When the
braking rpm value of the diesel engine is in this heat-critical rpm
range, fuel is injected briefly to cool the injection nozzles. The
injection of fuel to cool the injection nozzles, however, is not
related in any way to the inventive particle filter regeneration
method.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a torque vs. RPM diagram, showing the fuel
injection map, according to the invention;
[0014] FIG. 2 is a torque vs. RPM diagram, showing the fuel
injection map, according to the prior art; and
[0015] FIG. 3 is a schematic diagram of a diesel engine for
practicing the inventive method.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0016] In the following, the inventive method is explained in
greater detail on the basis of the diagram of FIG. 1 and a
schematic diagram of a diesel engine according to FIG. 3.
[0017] FIG. 3 shows a schematic diagram of a diesel engine 1
installed in a vehicle such as a truck, bus, or other utility
vehicle. Each of six cylinders 2 has two outlet valves, each of
which communicates with an exhaust gas-collecting manifold 4 by way
of an outlet channel 3. In the case shown here, the cylinders 2 are
divided into two banks of three each, and each bank is connected to
one manifold 4. Both manifolds 4 lead to the turbine 5 of an
exhaust gas turbocharger 6 and are components of the exhaust gas
train of the diesel engine 1, which, on the outlet side of the
turbine 5, is connected to a section 7, in which a particle filter
8 is installed. In the example shown here, an oxidation catalyst 9
is installed upstream of the particle filter 8. This catalyst is
responsible for producing a significant increase in the quantity of
NO.sub.x present in the exhaust gas, whereas the particle filter 8
serves the primary purpose of separating/filtering out and of
oxidizing the soot particles present in the exhaust gas.
[0018] A compressor 10 is connected to the turbine 5 of the exhaust
gas turbocharger 8. This compressor compresses the charge air and
sends it through a charge air line 11 and the intake channels 12
branching off from it into the cylinders 2, which receive the
charge air in a controlled manner through the intake valves, two
per cylinder.
[0019] The diesel engine 1 is equipped with a common rail injection
system, the main components of which are a high-pressure delivery
pump 13, a high-pressure distribution rail 14, and six injection
valves 16, each of which is connected to the rail 14 by a
high-pressure connecting line 15. So that they can be actuated, the
injection valves 16 have electromagnetic-electronic control heads,
which receive their injection control commands via electrical
control lines 17 from a computer-based electronic control unit 18.
This unit 18 includes as its main components a CPU (Central
Processing Unit), a data storage unit, and input/output interface
devices.
[0020] The diesel engine 1 is also equipped with an internal
exhaust pressure braking device, e.g., one like that which is known
in professional circles as the MAN-EVB.RTM., over a million of
which have already been installed in MAN engines. This exhaust
braking device includes a butterfly valve 19, which can be located
in the exhaust gas train of the diesel engine either upstream or
downstream of the turbine 5 of the exhaust gas turbocharger 6. In
the example according to FIG. 3, the butterfly valve 19 is
installed directly upstream of the inlet to the turbine 5, i.e.,
between the turbine and the manifold 4. The valve 19 can be
switched between its normal position (=full pass-through) and a
blocking position (=exhaust braking mode position) by a servomotor
20, which preferably also receives control commands from the
control unit 18. The blocking position can be such that the gas in
the blocked-off section of the exhaust gas train, i.e., the gas in
the area of the manifold 4, is indeed backed up, but nevertheless a
small amount of this backed-up gas is still allowed to pass
through. The possibility is also available of using the butterfly
valve 19 to block off the exhaust gas train completely and to allow
a small amount of the backed-up gas to flow through a bypass line
22, which can be opened and closed by a valve or butterfly valve
21. This version is shown in dotted line in FIG. 3. The servomotor
21' of the valve or butterfly valve 21 also receives its control
commands from the control unit 18.
[0021] Pressure sensors 23 and 24, installed upstream and
downstream of the particle filter 8, detect the pressures
prevailing in the exhaust gas train 7 at the measurement sites in
question and transmit them as actual pressure values to the control
unit 18 via measurement lines 25, 26. A temperature sensor 28
detects the temperature in the particle filter 8, and a temperature
sensor 28 detects the temperature in the oxidation catalyst 9. The
actual temperature values thus detected are also transmitted to the
control unit 18, in this case via measurement lines 29, 30.
[0022] In the following, the inventive method for regenerating the
particle filter 8 is explained in greater detail on the basis of
the diagram of FIG. 1 in conjunction with a diesel engine 1 of the
type illustrated in FIG. 3 and described above. This method is
characterized in that a particle filter 8 partially loaded with
separated soot particles is never regenerated except during exhaust
braking mode. In the diagram according to FIG. 1, M.sub.d stands
for the torque, and n.sub.M stands for the rpm's of the diesel
engine 1. The nominal rpm value of the diesel engine 1 is indicated
in the diagram by the line nm. The full-load torque curve is
indicated in the diagram by DM. The course of the exhaust braking
power which occurs during exhaust braking is indicated in the
diagram by the curve BK. A regeneration phase for the particle
filter 8 is started when the driver of the vehicle initiates an
exhaust braking phase; the control unit 18 receives this control
input via the signal line 31 and transmits the commands by means of
which the butterfly valve 19 and, if present, the valve or
butterfly 21 are moved into their exhaust braking mode positions.
The control unit 18 knows the exhaust gas backpressure in the
exhaust gas train 7 on the basis of the pressure values which are
being transmitted continuously to it by the pressure sensors 23, 24
or which it accepts from them at regular intervals.
[0023] This exhaust gas backpressure, which the control unit 18
either already knows prior to an exhaust braking phase or which,
alternatively, it knows only after the start of an exhaust braking
phase by requesting the pressure values from the pressure sensors
23, 24, is representative of the degree to which the particle
filter 8 is loaded with soot particles. Because the inventive
regeneration method causes a certain amount of fuel to be consumed,
it is advisable to determine the necessity for regenerating the
particle filter 8 beforehand, e.g., on the basis of the detected
exhaust gas backpressure, and then, as a function of that
determination, to initiate the regeneration by means of the
additional inventive measures only if necessary. As part of the
process for determining the necessity for regeneration, a certain
nominal range can be predefined for the evaluation, to be conducted
by the control unit 18, of the detected pressure values
representative of the soot particle loading of the particle filter
8. By comparison of the detected actual pressure values with the
pressure values of the nominal range in the control unit 18, it is
determined on the basis of the location of the actual pressure
values within the latter whether it is necessary to regenerate the
particle filter immediately or whether the regeneration can be
started at some later time. As a result, it is possible to limit
the amount of fuel which must be consumed for regeneration.
[0024] The regeneration measures themselves are specified by the
control unit 18. If an exhaust braking phase has been initiated and
if it has been found that it is necessary to regenerate the
particle filter, the particle filter regeneration process is
started and then executed within this exhaust braking phase. Via
the engine's own injection valves 16, a certain quantity of diesel
fuel is injected into the cylinders 2 of the exhaust
pressure-braked diesel engine at a time which is, in each case,
significantly after the top dead center (TDC) point. In addition,
the control unit 18 initiates control measures by which some of the
hot gas mixture now present in the blocked-off part 4 of the
exhaust gas train, consisting of a certain amount of vaporized,
unburned fuel and a certain amount of air, which has become highly
compressed during the exhaust braking mode, can pass through or
bypass the butterfly valve 19. This hot gas mixture then arrives in
the downstream particle filter 8, in which, acting as a highly
efficient oxidizing agent, it produces an initial ignition of the
soot deposited there and then supports its accelerated
oxidation.
[0025] In the diagram of FIG. 1, the area in which the fuel is
injected for the regeneration of the particle filter 8 is shown by
the injection map c. It size, designated by the boundary line b, is
defined by the injection times and injection quantities used during
a regeneration phase. From the diagram according to FIG. 1, it can
be seen from the injection map c that the regeneration of the
particle filter 8 during an exhaust braking phase occurs within an
rpm range of the decelerated diesel engine 1 which is significantly
below the nominal rpm value nm of the diesel engine 1, i.e., in its
lower-to-medium rpm range. Within an activated regeneration phase
controlled by the control unit 18 during an exhaust braking phase,
the timing of the start of the fuel injection into each cylinder 2
is fixed in a range between minimally after TDC, e.g.,
approximately 5 crankshaft degrees after TDC, and maximally after
TDC, e.g., 120 crankshaft degrees after TDC, and the quantity of
fuel to be injected, defined on the basis of the length of the
injection time, is fixed as a function of the detected actual
temperature value of the particle filter 18, so that comparatively
long injection times with large injection quantities are used at
lower particle filter temperatures, whereas shorter injection
periods with smaller injection quantities are used at higher
particle filter temperatures. It is also possible, however, to
divide the injection period into several shorter timed
injections.
[0026] During a regeneration phase activated within an exhaust
braking phase, it is advisable to determine the actual degree to
which the particle filter 8 has been regenerated so as not to cause
the consumption of an unnecessary amount of fuel. This is
accomplished again by detection of operating values relevant to the
purpose, such as the exhaust gas backpressure in the exhaust gas
train 7 by means of the pressure sensors 23, 24 and their
evaluation by the control unit 18. The control unit 18 takes care
of terminating a regeneration phase as soon as it detects an
operating value representative of a satisfactory degree of
regeneration.
[0027] The invention provides a highly efficient method for the
regeneration of particle filters, especially of the type installed
in vehicles in which, as a result of their intended uses, a high
particle filter temperature sufficient for continuous, independent
regeneration is not or only seldom reached.
[0028] The various features of novelty which characterize the
invention are pointed out with particularity in the claims annexed
to and forming a part of the disclosure. For a better understanding
of the invention, its operating advantages, and specific objects
attained by its use, reference should be had to the drawing and
descriptive matter in which there are illustrated and described
preferred embodiments of the invention.
* * * * *