U.S. patent application number 10/363306 was filed with the patent office on 2004-01-22 for method for heating a catalyst used in internal combustion engine with direct fuel injection.
Invention is credited to Bellmannn, Holger, Heinrich, Detlef, Roth, Andreas, Wagner, Jens, Winkler, Klaus.
Application Number | 20040011029 10/363306 |
Document ID | / |
Family ID | 7654818 |
Filed Date | 2004-01-22 |
United States Patent
Application |
20040011029 |
Kind Code |
A1 |
Wagner, Jens ; et
al. |
January 22, 2004 |
Method for heating a catalyst used in internal combustion engine
with direct fuel injection
Abstract
A method for heating a catalytic converter in internal
combustion engines is introduced wherein: an index for the
temperature of the catalytic converter is formed; below a
predetermined temperature of the catalytic converter, a first
heating measure takes place wherein the temperature of the exhaust
gas is increased; and, above the predetermined temperature,
alternatively or supplementary to the first heating measure, a
second heating measure takes place wherein a reaction-capable
mixture is supplied to the catalytic converter in addition to the
exhaust gas and the reaction of this mixture releases heat in the
catalytic converter.
Inventors: |
Wagner, Jens; (Stuttgarg,
DE) ; Roth, Andreas; (Muelacker-Lomersheim, DE)
; Bellmannn, Holger; (Ludwigsburg, DE) ; Heinrich,
Detlef; (Ludwigsburg, DE) ; Winkler, Klaus;
(Rutesheim, DE) |
Correspondence
Address: |
Walter Ottesen
Patent Attorney
P O Box 4026
Gaithersburg
MD
20885-4026
US
|
Family ID: |
7654818 |
Appl. No.: |
10/363306 |
Filed: |
March 3, 2003 |
PCT Filed: |
August 29, 2001 |
PCT NO: |
PCT/DE01/03214 |
Current U.S.
Class: |
60/295 ; 123/295;
60/284; 60/286; 60/301 |
Current CPC
Class: |
F02D 2200/0802 20130101;
F02D 41/405 20130101; Y02T 10/44 20130101; F02D 41/0245 20130101;
Y02T 10/26 20130101; F02D 41/025 20130101; Y02T 10/40 20130101;
F02D 41/1446 20130101; Y02T 10/12 20130101; F02D 2041/389 20130101;
F02D 37/02 20130101 |
Class at
Publication: |
60/295 ; 123/295;
60/284; 60/286; 60/301 |
International
Class: |
F01N 003/00; F02B
017/00; F01N 003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 2, 2000 |
DE |
100 43 375.8 |
Claims
1. Method for heating up a catalytic converter in internal
combustion engines, characterized in that: an index for the
temperature of the exhaust-gas system is formed; a first heating
measure takes place below a predetermined temperature of the
exhaust-gas system at which the temperature of the exhaust gas is
increased; and, above a predetermined temperature, alternatively or
supplementary to the first heating measure, a second heating
measure takes place for which a reaction-capable mixture is
supplied to the catalytic converter in addition to the exhaust gas
and the reaction of this mixture releases heat in the catalytic
converter.
2. Method of claim 1, characterized in that, as a first measure, a
deterioration of the efficiency of the engine combustion takes
place via a change of the ignition angle.
3. Method of claim 1, characterized in that, as a second measure
for an engine having gasoline-direct injection, a fuel
after-injection takes place after the combustion.
4. Method of claim 3, characterized in that the after-injection is
combined with stratified operation.
5. Method of claim 4, characterized in that the air quantity, which
is inducted by the internal combustion engine, is throttled to the
extent that the needed heat flow is achieved for a requested higher
temperature.
6. Method of claim 1, characterized in that an exhaust-gas
composition is adjusted for a heating of an NOx-storage catalytic
converter in homogeneous operation, the exhaust-gas composition
deviating from the stoichiometric exhaust-gas composition.
7. Electronic control arrangement for carrying out the method of
the claims 1 to 6.
Description
[0001] It is already known to heat up the catalytic converter
because of the consequences of a deterioration of the efficiency of
the engine combustion. A deterioration of efficiency of the engine
combustion can, for example, be caused by a deviation of the
ignition time point from the optimal time point. The optimal time
point is defined by the maximum efficiency. With a loss of
efficiency, the exhaust gas is hotter in comparison to the
operation without a loss of efficiency. Accordingly, the exhaust
gas develops an increased heating operation in the catalytic
converter.
[0002] In gasoline-direct injection engines, the possibility is
present to inject fuel in a targeted manner into the cylinder after
the engine combustion in the expansion stroke when operating with
air excess. Here, the subsequently injected fuel reacts with the
excess air of the engine combustion partially in the combustion
chamber and partially in the exhaust-gas system. The heat, which is
released in the exothermal reaction, heats the catalytic
converter.
[0003] An efficiency can be assigned also to the catalytic
converter heating measures. The efficiency of the after-injection
is at a maximum when the chemical energy, which is introduced
additionally into the catalytic converter as air/fuel mixture, is
completely converted into heat in the catalytic converter. Up to
now, both of the above-mentioned measures were utilized
alternatively. Here, losses in the heat effect were observed. The
losses are referred to the heating action which is achieved with
the maximum efficiency of the catalytic converter heating
measure.
[0004] The invention is directed to improving the efficiency of the
catalytic converter heating measures.
[0005] This improvement is achieved with the features of claim
1.
[0006] In detail, the method of the invention relates to the
heating of a catalytic converter in internal combustion engines
with the steps:
[0007] forming an index for the temperature in the exhaust-gas
system;
[0008] triggering a first heating measure wherein the temperature
of the exhaust gas is increased below a predetermined temperature
of the exhaust-gas system;
[0009] triggering a second heating measure above the predetermined
temperature wherein a reactionable mixture is supplied to the
catalytic converter in addition to the exhaust gas and the reaction
in the exhaust gas and catalytic converter releases heat there and
this takes place alternatively or as a supplement to the first
heating measure.
[0010] A further embodiment of the invention provides that, as a
first measure, a deterioration of the efficiency of the engine
combustion takes place via a change of the ignition angle.
[0011] Another embodiment provides that, as a second measure, in an
engine having gasoline-direct injection, a fuel after-injection
takes place after the combustion.
[0012] A further embodiment provides that the after-injection is
combined with stratified operation.
[0013] A further embodiment provides that the air quantity, which
is inducted by the internal combustion engine, is throttled to the
extent that the needed heat flow is achieved for a requested higher
temperature. A throttling of this kind improves the after-reaction
in the catalytic converter (only slightly lean lambda improves the
conversion in the catalytic converter), the exhaust-gas temperature
is higher and the spatial velocity of the exhaust gas is less which
leads to a longer dwell time of the exhaust gas in the catalytic
converter.
[0014] A further embodiment provides that an exhaust-gas
composition is adjusted which departs from the stoichiometric
exhaust-gas composition for heating an NOx-storage catalytic
converter in homogeneous operation.
[0015] The invention also relates to an electronic control
arrangement for carrying out the method.
[0016] In the context of one embodiment, a deterioration of the
efficiency of the engine combustion via a change of the ignition
angle takes place as a first measure.
[0017] As a second measure, a fuel after-injection can take place
after the combustion in an engine having gasoline-direct
injection.
[0018] The above-mentioned after-injection can, for example, be
especially combined with stratified operation.
[0019] An engine control program is known from DE 198 50 586 which
controls the switchover between stratified operation and
homogeneous operation.
[0020] In stratified operation, the engine is operated with an
intensely stratified cylinder charge and high air excess in order
to achieve the lowest possible fuel consumption. The stratified
charge is achieved via a late fuel injection which, in the ideal
case, leads to a partitioning of the combustion chamber into two
zones: the first zone contains a combustible air/fuel mixture cloud
at the spark plug. The first zone is surrounded by the second zone
and this second zone comprises an insulating layer of air and
residual gas. The potential for optimizing consumption results from
the possibility of operating the engine substantially unthrottled
while avoiding charge exchange losses. The stratified operation is
preferred at comparatively low loads.
[0021] At higher load, when the power optimization is primary, the
engine is operated with a homogeneous cylinder charge. The
homogeneous cylinder charge results from an early fuel injection
during the induction operation. As a consequence, a longer time is
available for mixture formation up to the combustion. The potential
of this operating mode for power optimization results, for example,
from utilizing the entire combustion chamber volume for filling
with a combustible mixture.
[0022] In a further embodiment of the invention, an after-injection
takes place after a combustion with air excess in combination with
a throttling of the air quantity inducted by the internal
combustion engine. The after-injected fuel quantity determines the
heat amount which is to be released. The throttling of the air
supply effects a metering of the air quantity for this purpose.
This air quantity can, for example, be designed so that a
stoichiometric air/fuel ratio results in the exhaust gas from the
sum of the regularly injected fuel and the after-injected fuel.
This makes possible an exhaust-gas decontamination with a three-way
catalytic converter. The air supply is thereby throttled to the
extent that the necessary heat flow is reached for a requested
temperature.
[0023] An exhaust-gas composition can be adjusted for heating an
NOx-storage catalytic converter during homogeneous operation which
deviates from the stoichiometric exhaust-gas composition.
[0024] This invention is based upon the fact that the reaction of
the after-injected fuel requires an air excess in the combustion
chamber. This takes place substantially during stratified operation
for internal combustion engines having gasoline-direct injection.
Increased raw emissions occur because the additionally injected
fuel is not completely combusted in the combustion chamber.
Furthermore, the exhaust-gas temperatures are rather colder in
stratified operation. For this reason, the increased emissions
cannot be converted exothermally in the catalytic converters which
are too cold. In this way, the heat energy of the fuel, which is
not combusted in the combustion chamber, is lost.
[0025] In the procedure of the invention, first hot exhaust gas is
generated during homogeneous operation with retarded ignition. In
this way, the temperature of the catalytic converters is raised
with clearly less raw emissions. If minimum temperatures for the
catalytic converter are reached, then the increased raw emissions
which occur for after-injection, can be better converted in the
catalytic converters. In this way, the advantage of a significant
reduction of the emissions and the advantage of an increased
efficiency of the release of heat in the catalytic converter is
achieved.
[0026] An exhaust-gas composition close to lambda equals one is
achieved with throttling during the injection of additional fuel.
Additionally, the exhaust gas has a higher temperature and a lower
spatial velocity for the same fuel conversion. In this way, the
emissions are further reduced because the conversion of the
catalytic converters is again improved.
[0027] An exhaust-gas composition is adjusted in the case of a
heating of an NOx-storage catalytic converter with this exhaust-gas
composition departing from the stoichiometric exhaust-gas
composition.
[0028] In this way, the stored NOx can be reduced when there is a
rich exhaust gas.
[0029] For lean exhaust gas, the NOx discharge is prevented which
would occur for exhaust gas having lambda equal one and increased
temperature. In this way, an NOx peak in the exhaust gas is
advantageously avoided.
[0030] In the following, an embodiment of the invention is
explained with reference to the figures.
[0031] FIG. 1 shows the technical background of the invention;
and,
[0032] FIG. 2 shows a flow diagram as an embodiment of the method
of the invention.
[0033] In FIG. 1, 1 represents the combustion chamber of a cylinder
of an internal combustion engine. The flow of air to the combustion
chamber is controlled via an inlet valve 2. The air is drawn in by
suction via an intake manifold 3. The intake air quantity can be
varied via a throttle flap 4 which is driven by a control apparatus
5. The control apparatus 5 defines an embodiment of the electronic
control arrangement of the invention in combination with the given
method. The following are supplied to the control apparatus:
signals as to the torque command of the driver (for example, via
the position of an accelerator pedal 6); a signal as to the engine
rpm n from an rpm transducer 7; a signal as to the quantity ml of
the inducted air by an air quantity sensor 8; and, a signal US as
to the exhaust-gas composition and/or exhaust-gas temperature from
an exhaust-gas sensor 12. Additionally, a separate exhaust-gas
temperature sensor or catalytic converter temperature sensor can be
provided. The exhaust-gas temperature and/or catalytic converter
temperature can, however, also be computed from the remaining
operating parameters. This is known, for example, from U.S. Pat.
No. 5,590,521. The exhaust-gas sensor 12 can, for example, be a
lambda probe whose Nernst voltage indicates the oxygen content in
the exhaust gas and whose internal resistance can be applied as an
index for the probe temperature, exhaust-gas temperature and/or
catalytic converter temperature. The exhaust gas is conducted
through at least one catalytic converter 15 wherein toxic
substances of the exhaust gas are converted (for example, a
three-way catalytic converter) and/or are temporarily stored
(NOx-storage catalytic converter).
[0034] In this technical background, the catalytic converter
temperature can be measured (sensors 16 and 17) or can be modeled
from operating variables of the engine. The modeling of
temperatures in the exhaust-gas system of internal combustion
engines is known, for example, from U.S. Pat. No. 5,590,521.
Compared to the position in or ahead of the catalytic converter,
the position after a pre-catalytic converter but ahead of an
NOx-storage catalytic converter is to be preferred for BDE systems.
The position of the temperature sensors is therefore not limited to
the illustrated positions in or ahead of a catalytic converter.
Also, a position after the catalytic converter can be
considered.
[0035] The control apparatus 5 forms output signals for adjusting
the throttle flap angle (.alpha.) via an actuating member 9 and for
driving a fuel injection valve 10 via which the fuel is metered
into the combustion chamber. The control apparatus 5 forms these
output signals from the above, and, if required, additional input
signals as to other parameters of the internal combustion engine
such as intake air temperature and coolant temperature, et cetera.
Furthermore, a triggering of the ignition via an ignition device 11
is controlled by the control apparatus.
[0036] The throttle flap angle (.alpha.) and the injection
pulse-width (ti) are essential actuating variables, which are to be
matched to each other, for realizing the desired torque, the
exhaust-gas composition and the exhaust-gas temperature. A further
significant actuating variable for influencing these variables is
the angular position of the ignition relative to the piston
movement. The determination of the actuating variables for
adjusting the torque is the subject matter of DE 198 51 990 which
is to be incorporated into the disclosure.
[0037] Furthermore, the control apparatus controls additional
functions for achieving an efficient combustion of the air/fuel
mixture in the combustion chamber, for example, an exhaust-gas
recirculation (not shown) and/or tank venting. The gas force, which
results from the combustion, is converted into a torque by the
piston 13 and the crankshaft 14.
[0038] FIG. 2 shows a flow diagram of an embodiment of the method
of the invention. For heating by means of after-injection, the
engine control according to the invention requires minimum
temperatures in the exhaust-gas system. Until these temperatures
are reached, homogeneous operation with retarded ignition is
required and adjusted, for example, as a first measure. This is
realized via the step sequence 2.1, 2.2 and 2.3 in FIG. 2 and these
steps are reached from a higher order engine control program. When
the necessary temperatures are reached, the after-injection is
permitted as a possible alternative (or as a second measure). A
switchover to stratified operation takes place with after-injection
in order to generate a higher heat flow. This is realized by the
sequence of steps 2.1, 2.2 and 2.4 in FIG. 2. Here, the air flow is
throttled to the extent that the necessary heat flow is achieved
with a required temperature.
[0039] The throttling takes place in a first embodiment via a
controlled closure of the throttle flap by a predetermined angle or
to a predetermined opening angle. Stated otherwise, the throttling
takes place uncontrolled in this example. The mixture composition
should be close to lambda equal one for a maximum release of heat.
Temporary mixture enrichment toward lambda values less than one can
occur because of a dynamic driving operation with changing torque
requests. In this way, the exhaust-gas emissions are deteriorated
in an unwanted manner.
[0040] The after-injection is advantageously controlled with the
aid of an available exhaust-gas probe to avoid a deterioration of
the exhaust gas. In this way, a breakthrough of rich exhaust gas
can be prevented. The term "breakthrough" is the occurrence of HC
emissions rearward of the catalytic converter. As a further
advantage, the exothermal energy released is maximally utilized at
lambda equals one.
[0041] Because of the heat request, a necessary fuel quantity for
the after-injection is determined for maximum possible throttling.
In addition to the heat request, also the air requirement of the
after-injection and the temperature increase because of the
throttling must be considered. The latter is especially important
in order to prevent overheating of components in the exhaust-gas
system.
[0042] Alternatively to the control of the after-injected fuel
quantity via the measured exhaust-gas lambda, the throttling can be
controlled via the measured exhaust-gas lambda.
[0043] For reasons of safety, the control is so designed that the
control intervention operates only to reduce but not to increase
the after-injected fuel quantity. For exhaust gas which is
continuously too lean, the throttling can be increased in lieu of
an increase of the after-injected fuel quantity. A minimum value
may not be exceeded in order to protect components.
* * * * *