U.S. patent application number 09/750209 was filed with the patent office on 2001-06-07 for method for the cylinder-selective knock control of an internal combustion engine.
Invention is credited to Cianciara, Wojciech, Fischer, Gerhard, Haug, Thomas.
Application Number | 20010002590 09/750209 |
Document ID | / |
Family ID | 7871615 |
Filed Date | 2001-06-07 |
United States Patent
Application |
20010002590 |
Kind Code |
A1 |
Cianciara, Wojciech ; et
al. |
June 7, 2001 |
Method for the cylinder-selective knock control of an internal
combustion engine
Abstract
The total ignition angle ZW(z) of each cylinder z is composed of
cylinder-selective values basic ignition angle GZ(z) {determined by
engine speed n and load L}, knock adjustment angle KNK(z), in
addition to a first adaptation value AD1(z) and a second adaptation
value AD2 common to all cylinders. ADl(z) is increased when KNK(z)
is greater than a threshold DEC and is reduced when KNK(z) is lower
than a threshold INC. The second adaptation value AD2 is formed as
a function of the average value {overscore (AD1)} of the adaptation
values of all cylinders.
Inventors: |
Cianciara, Wojciech;
(Grunthal, DE) ; Fischer, Gerhard;
(Maxhutte-Deglhof, DE) ; Haug, Thomas; (Straubing,
DE) |
Correspondence
Address: |
LERNER AND GREENBERG, P.A.
Post Office Box 2480
Hollywood
FL
33022-2480
US
|
Family ID: |
7871615 |
Appl. No.: |
09/750209 |
Filed: |
December 22, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09750209 |
Dec 22, 2000 |
|
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PCT/DE99/01787 |
Jun 17, 1999 |
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Current U.S.
Class: |
123/406.2 |
Current CPC
Class: |
F02P 5/1522 20130101;
F02P 5/1523 20130101; Y02T 10/40 20130101 |
Class at
Publication: |
123/406.2 |
International
Class: |
F02P 005/152 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 22, 1998 |
DE |
198 27 704.0 |
Claims
We claim:
1. A cylinder-selective knock control method for an internal
combustion engine, which comprises: defining, in association with a
respective operating point that depends on a load and an engine
speed, a cylinder-selective ignition angle from a predetermined
cylinder-selective basic ignition angle associated with knock-free
operation and a cylinder-selective knock adjustment angle that
increases stepwise with a predetermined step size in a retarded
direction each time a knock occurs and decreases stepwise with a
predetermined step size in an advanced direction after each engine
cycle during knock-free operation; determining a cylinder-selective
first adaptation value of a first adaptation circuit from a
comparison of the knock adjustment angle with a first and a second
threshold value; wherein the first threshold value is greater than
the step size, specified in the retarded direction, of the
cylinder-selective knock adjustment angle, and the second threshold
value is less than the step size, specified in the retarded
direction, of the cylinder-selective knock adjustment angle;
modifying the cylinder-selective adaptation value of the first
adaptation circuit in the retarded direction with a predetermined
first adaptation step size after each engine cycle for as long as
the knock adjustment angle is greater in terms of an absolute value
thereof than the first threshold value; holding the
cylinder-selective adaptation value of the first adaptation circuit
constant for as long as the knock adjustment angle is less than the
first threshold value and greater than the second threshold value
in terms of the absolute value; and modifying the
cylinder-selective adaptation value of the first adaptation circuit
in the advanced direction with a predetermined second adaptation
step size for as long as the knock adjustment angle is less in
terms of the absolute value than the second threshold value;
determining a second adaptation value, associated with all the
cylinders, of a second adaptation circuit from a comparison of the
average value of all the cylinder-selective adaptation values of
the current operating point with a predetermined threshold; and
using the cylinder-selective first adaptation value and the second
adaptation value associated with all the cylinders to form a
cylinder-selective total ignition angle in accordance with the
formula ZW(z)=GZ(z)-KNK(z)-AD1(z)-AD2 where z is a number of the
cylinder, ZW is the total ignition angle, GZ is the basic ignition
angle, KNK is the knock adjustment angle, AD1 is the first
adaptation value, and AD2 is the second adaptation value.
2. The method according to claim 1, which comprises: modifying the
second adaptation value of the second adaptation circuit in the
retarded direction by a predetermined decrement after each engine
cycle if the average value of all the cylinder-selective adaptation
values of the current operating point has a negative sign and is
greater in terms of its absolute value than the threshold; and
modifying the second adaptation value of the second adaptation
circuit in the advanced direction by a predetermined increment
after each engine cycle if the average value is less in terms of
its absolute value than the threshold.
3. The method according to claim 1, which comprises storing at
least one quantity selected from the group consisting of the first
step size, the second step size, the first adaptation step size,
the second adaptation step size, the first threshold value, and the
second threshold value, as a function of the operating point in a
map assigned to the quantity.
4. The method according to claim 1, which comprises blocking an
adaptation of the first or second adaptation circuit for
predetermined operating point ranges.
5. The method according to claim 1, which comprises specifying
maximum values in the advanced direction or minimum values in the
retarded direction, the values being applicable to all the
cylinders, for the adaptation values.
6. The method according to claim 1, which comprises incrementing a
sum of the knock adjustment angle and the first adaptation value
with the step size if operation is knock-free in a range in which
the knock adjustment angle is greater than the first threshold
value.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a continuation of copending International
Application PCT/DE99/01787, filed Jun. 17, 1999, which designated
the United States.
BACKGROUND OF THE INVENTION
[0002] Field of the Invention
[0003] The invention relates to a method for the cylinder-selective
knock control of an internal combustion engine, in which a
predetermined cylinder-selective basic ignition angle associated
with knock-free operation and a cylinder-selective knock adjustment
angle that increases stepwise with a predetermined step size in the
retarded direction each time a knock occurs and decreases stepwise
with a predetermined step size in the advanced direction after each
engine cycle during knock-free operation form a cylinder-selective
ignition angle in association with the respective operating point,
which is dependent on load and engine speed. A method of that kind
is known from German published patent application DE 29 25 770
Al.
[0004] When engine knock occurs in a cylinder z of the internal
combustion engine, the ignition angle for this cylinder is retarded
by a certain amount--step size SK.sub.dec--thereby reducing the
probability that knocking combustion will occur in this cylinder.
If the engine then operates without knock, the ignition angle is
slowly advanced again by a predetermined amount SK.sub.inc.
[0005] The known total ignition angle ZW(z) for a cylinder z at a
particular operating point is made up of a basic ignition angle
GZ(z) for knock-free operation, which is dependent on the load L
and the engine speed n, is stored in a map and--in the case of a
four-cylinder engine--is updated every 180.degree.of crank angle
(hence the term "cylinder-selective"), this basic angle being
calculated from the ignition dead center position ZOT(z) closest to
ignition, and of an additional knock adjustment angle KNK(z) for
this cylinder z owing to engine knock: ZW(z)=GZ(z)-KNK(z). It
should be noted here that the knock adjustment angle KNK(z) can
assume only negative values, in line with the recognition that a
positive sign signifies "advance", while a negative sign signifies
"retardation".
[0006] The respective knock adjustment angles KNK(z) are entered in
one load- and engine-speed-dependent map per cylinder. As the
change from one operating point to the next occurs, the last knock
adjustment angle KNK(z) entered is stored at the old operating
point. When the engine re-enters this operating point, this value
is reused as the knock adjustment angle KNK(z) for knock control.
This method has the disadvantage that a relatively random knock
adjustment angle will be stored, depending on the time at which the
change in the operating point occurs.
[0007] This results in the following disadvantages:
[0008] the knock limit is not adapted accurately;
[0009] the ignition-angle profile in the case of transitions
between the adaptation ranges is nonuniform, and the torque profile
is therefore not continuous either;
[0010] the internal combustion engine is not operated exactly at
the knock limit; as a result, optimum torque and optimum specific
fuel consumption are not assured.
SUMMARY OF THE INVENTION
[0011] The object of the invention is to provide a method for
cylinder-selective knock control of an internal combustion engine
which overcomes the above-noted deficiencies and disadvantages of
the prior art devices and methods of this kind, and which is
improved such that the knock limit is adapted as accurately as
possible, that a uniform ignition-angle profile and hence also a
continuous torque profile is obtained in the case of transitions
between the adaptation ranges, and that optimum torque and optimum
specific fuel consumption are established.
[0012] With the above and other objects in view there is provided,
in accordance with the invention, a cylinder-selective knock
control method for an internal combustion engine, in which there is
formed, in association with a respective operating point that
depends on a load and an engine speed, a cylinder-selective
ignition angle from a predetermined cylinder-selective basic
ignition angle associated with knock-free operation and a
cylinder-selective knock adjustment angle that increases stepwise
with a predetermined step size in a retarded direction each time a
knock occurs and decreases stepwise with a predetermined step size
in an advanced direction after each engine cycle during knock-free
operation. The novel method is characterized by the following
method steps:
[0013] determining a cylinder-selective first adaptation value of a
first adaptation circuit from a comparison of the knock adjustment
angle with a first and a second threshold value;
[0014] wherein the first threshold value is greater than the step
size, specified in the retarded direction, of the
cylinder-selective knock adjustment angle, and the second threshold
value is less than the step size, specified in the retarded
direction, of the cylinder-selective knock adjustment angle;
[0015] modifying the cylinder-selective adaptation value of the
first adaptation circuit in the retarded direction with a
predetermined first adaptation step size after each engine cycle
for as long as the knock adjustment angle is greater in terms of an
absolute value thereof than the first threshold value;
[0016] holding the cylinder-selective adaptation value of the first
adaptation circuit constant for as long as the knock adjustment
angle is less than the first threshold value and greater than the
second threshold value in terms of the absolute value; and
[0017] modifying the cylinder-selective adaptation value of the
first adaptation circuit in the advanced direction with a
predetermined second adaptation step size for as long as the knock
adjustment angle is less in terms of the absolute value than the
second threshold value;
[0018] determining a second adaptation value, associated with all
the cylinders, of a second adaptation circuit from a comparison of
the average value of all the cylinder-selective adaptation values
of the current operating point with a predetermined threshold;
and
[0019] using the cylinder-selective first adaptation value and the
second adaptation value associated with all the cylinders to form a
cylinder-selective total ignition angle in accordance with the
formula
ZW(z)=GZ(z)-KNK(z)-AD1(z)-AD2
[0020] where z is a number of the cylinder, ZW is the total
ignition angle, GZ is the basic ignition angle, KNK is the knock
adjustment angle, AD1 is the first adaptation value, and AD2 is the
second adaptation value.
[0021] In accordance with an added feature of the invention, the
second adaptation value of the second adaptation circuit:
[0022] is modified in the retarded direction by a predetermined
decrement after each engine cycle if the average value of all the
cylinder-selective adaptation values of the current operating point
has a negative sign and is greater in terms of its absolute value
than the threshold; and
[0023] is modified in the advanced direction by a predetermined
increment after each engine cycle if the average value is less in
terms of its absolute value than the threshold.
[0024] In accordance with an additional feature of the invention,
at least one quantity of the group consisting of the first step
size, the second step size, the first adaptation step size, the
second adaptation step size, the first threshold value, and the
second threshold value, is stored in dependence on the operating
point in a map assigned to the quantity.
[0025] In accordance with another feature of the invention, an
adaptation of the first or second adaptation circuit is blocked for
predetermined operating point ranges.
[0026] In accordance with a further feature of the invention, there
are specified maximum values in the advanced direction or minimum
values in the retarded direction for the adaptation values; the
values are thereby applicable to all the cylinders.
[0027] In accordance with a concomitant feature of the invention,
the sum of the knock adjustment angle and the first adaptation
value is incremented with the step size if operation is knock-free
in a range in which the knock adjustment angle is greater than the
first threshold value.
[0028] In sum, the invention adds to the known cylinder-selective
knock adjustment angle KNK(z) a first adaptation value AD1 of a
first adaptation circuit and a second adaptation value AD2 of a
second adaptation circuit common to all the cylinders. The
generation of the adaptation values will become clear from the
explanation in greater detail below with reference to the schematic
drawing figure.
[0029] Although the invention is illustrated and described herein
as embodied in a method for cylinder-selective knock control of an
internal combustion engine, it is nevertheless not intended to be
limited to the details shown, since various modifications and
structural changes may be made therein without departing from the
spirit of the invention and within the scope and range of
equivalents of the claims.
[0030] The construction of the invention, however, together with
additional objects and advantages thereof will be best understood
from the following description of the specific embodiment when read
in connection with the accompanying drawing figure.
BRIEF DESCRIPTION OF THE DRAWING
[0031] FIG. 1 is a graphical timing chart showing the setting of a
cylinder-selective ignition angle along a time line.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] Referring now to the schematic figure of the drawing in
detail, the total ignition angle ZW(z) for a cylinder z is made up
as follows in accordance with the formula below:
ZW(z)=GZ(z)-KNK(z)-AD1(z)-AD2.
[0033] The signs of these values are significant: GZ(z), AD1(z) and
AD2 can have positive or negative signs (signifying advance or
retardation), while KNK(z) can have only a negative sign
(retardation).
[0034] The drawing shows the basic ignition angle GZ(z) in relation
to the ignition dead center position ZOT(z), the variation of the
cylinder-selective knock adjustment angle KNK(z) in relation to the
basic ignition angle GZ(z), and the variation of the first and
second adaptation values AD1 and AD2 plotted for a particular
operating point of the internal combustion engine, which is
dependent on the load L and the engine speed n.
[0035] The basic ignition angles GZ(z), which are also represented
as arrows in the drawing, are entered in a map for each cylinder z
as degrees of crank angle .degree.KW for example, calculated from
the ignition top dead center position ZOT(z)=0.degree.KW of the
cylinder z (plotted as a horizontal broken line right at the bottom
of the drawing)--with a positive sign to indicate advance and a
negative sign to indicate retardation--as a function at least of
the engine speed n and the load L and, as mentioned above, they are
read out from this map and updated.
[0036] This basic ignition angle is used for ignition in cylinder z
if there is no engine knock: ZW(z)=GW(z).
[0037] If engine knock K occurs in cylinder z, however, the total
ignition angle ZW(z) is retarded by a knock adjustment angle KNK(z)
(decremented), with the step size in each case being S.sub.Kdec. In
the drawing, knocks K are shown after three successive ignitions,
shifting the total ignition angle ZW(z) by a value
KNK(z)=3*S.sub.Kdec in the retarded direction to
ZW(z)=GZ(z)-KNK(z)=GZ(z)-3*S.sub.Kdec.
[0038] If, subsequently, engine knock no longer occurs, the
absolute value of the knock adjustment angle KNK(z) is reduced by a
predetermined step S.sub.Kinc after each engine cycle
(720.degree.of crank angle) or after several engine cycles (or at
predetermined time intervals), as illustrated in enlarged form
within a broken-lined circle in the drawing, and the total ignition
angle ZW(z) is hence also advanced again (incremented). The step
sizes S.sub.Kdec and/or S.sub.Kinc can be constants or vary as a
function of the operating point.
[0039] In the drawing, two predetermined threshold values, a first
threshold value DEC and a second threshold value INC, which are
retarded relative to the basic ignition angle GZ(z), have been
entered as chain-dotted lines, these values being significant for
the first adaptation value AD1(z) of the first adaptation
circuit:
[0040] as long as the knock adjustment angle KNK(z) is greater in
terms of its absolute value than the first threshold value DEC, t2
to t3 in the drawing, a cylinder-selective first adaptation value
AD1(z) should be increased with a predetermined step size
S.sub.ADdec, (thereby retarding, i.e. decrementing, the total
ignition angle ZW(z));
[0041] as long as the knock adjustment angle KNK(z) is less in
terms of its absolute value than the first threshold value DEC and
greater in terms of its absolute value than the second threshold
value INC, t3 to t4 in the drawing, the cylinder-selective first
adaptation value AD1(z) should be constant; and
[0042] as soon as the knock adjustment angle KNK(z) is less in
terms of its absolute value than the second threshold value INC,
from t4 in the drawing, the absolute value of the
cylinder-selective first adaptation value AD1(z) should be reduced
with a predetermined step size S.sub.ADinc.
[0043] In a preferred exemplary embodiment, the sum of the knock
adjustment angle KNK(z) and the first adaptation value AD1 (broken
line between t2 and t3 in the drawing) should be incremented with
the step size S.sub.kinc for as long as the knock adjustment angle
KNK(z) is greater in terms of its absolute value than the first
threshold value DEC, in order to avoid slowing the rate at which
the total ignition angle ZW(z) is incremented.
[0044] The step size S.sub.Kdec is chosen so that, as illustrated
in the drawing, the predetermined first threshold value DEC is not
exceeded by the knock adjustment angle KNK(z) at the very first
knock but, for example, only at the second knock at time t1, e.g.
S.sub.Kdec=3.degree.of crank angle and DEC=3.5.degree.of crank
angle. This has a damping effect on the knock control system. The
first adaptation values AD1(z), which are stored in a map as a
function of the operating point for each cylinder, and second
adaptation values AD2, described below, are illustrated in separate
diagrams in the drawing, the upper diagram representing the sum of
GZ(z)-KNK(z)-AD1(z) as a broken line.
[0045] In the first adaptation circuit, cylinder-selective knock
adaptation is performed to adapt the ignition angle differences as
a function of the load L and the engine speed n on the basis of the
differences in compression between the cylinders. The map in which
the first adaptation values AD1(z) are stored contains the
cylinder-specific adaptation components used for knock control,
these having been determined at the respective operating point.
[0046] The knock limits are generally adjusted for a defined engine
and a defined fuel. In normal operation, engines, components and
fuels have certain tolerances, which can have a considerable effect
on the knock limit. These deviations apply to all the cylinders;
with the exception of the fuel grade, they generally change only
slowly.
[0047] To compensate effectively for such effects, a second
adaptation value AD2 of a second adaptation circuit common to all
the cylinders is formed by calculating the average value {overscore
(AD1)} of the first adaptation values AD1(z) of the first
adaptation circuit of all the cylinders at the respective operating
point and comparing it with a predetermined threshold S2. If the
average value {overscore (AD1)} is greater in terms of its absolute
value than S2, AD2 is retarded by a predetermined decrement D (with
a negative sign) after each engine cycle; otherwise, it is advanced
by a predetermined increment I (with a positive sign). In the case
of a change of operating point, the average value {overscore (AD1)}
is calculated from the first adaptation values AD1(z) of the new
operating point and compared with the threshold S2, and AD2 is
increased or reduced in accordance with the result of
comparison.
[0048] In the drawing, the bold continuous line ZW(z) shows the
variation of the total ignition angle ZW(z) for a cylinder (z),
comprising the basic ignition angle GZ(z), the knock adjustment
angle KNK(z), the first adaptation value AD1(z) and the second
adaptation value AD2, which is common to all the cylinders:
ZW(z)=GZ(z)-KNK(z)-AD1(z)-AD2,
[0049] where the values KNK(z), AD1(z) and AD2 each bring about a
retardation of the ignition angle.
[0050] The instantaneously valid quantities for ZW(z), KNK(z),
AD1(z) and AD2 are represented as arrows.
[0051] Normally, the total ignition angle ZW(z) is not advanced
beyond the predetermined basic ignition angle GZ(z). When changing
to a fuel with a higher octane rating, for example, it may however
be appropriate to take account of this fact and to permit positive
values for the first and second adaptation circuit, which can mean
the total ignition angle being advanced beyond the basic ignition
angle GZ(z) . It is therefore worthwhile to specify valid maximum
values (+AD1.sub.max, +AD2.sub.max) in the advanced direction or
even minimum values (-AD1.sub.min, -AD2.sub.min) in the retarded
direction for the adaptation values (AD1(z)) or (AD2) for all the
cylinders (z).
[0052] In this case, however, it is necessary for physical reasons
to determine operating point ranges in which such an advance beyond
the basic ignition angle GZ(z) should be permitted and to define
limiting values (if necessary dependent on the operating point) for
such an advance in order to avoid engine damage.
[0053] After each engine cycle (every 720.degree.of crank angle),
the instantaneous values KNK(z) and AD1(z) are stored in the
corresponding maps as a function of the operating point, the common
second adaptation value AD2 also being stored, and the operating
point is re-determined as a function of the load L and the engine
speed n.
[0054] When the internal combustion engine is switched off, all the
first adaptation values AD1(z) of the first adaptation circuit are
stored in cylinder-selective maps, and the second adaptation value
AD2 of the second adaptation circuit is stored in non-volatile
memory (in an EEPROM) and read back when operation starts
again.
[0055] Because the adaptation rates (step sizes S.sub.ADdec,
S.sub.ADinc) for decrementing and implementing the adaptation
values AD1 of the first adaptation circuit are separate, the
average position of the ignition angle at the knock limit can be
determined quite accurately.
[0056] Defining ranges of the knock adjustment angle KNK(z) in
which no adaptation is performed (by means of the threshold values
DEC and INC) ensures that minor knock control activity does
not-trigger changes to the adaptation values; this calms the first
adaptation circuit and leads to uniform ignition angles.
[0057] The knock control component is made up of the knock
adjustment angle KNK(z) and the two adaptation values AD1(z) and
AD2. The characteristic of each individual circuit can
advantageously be adjusted independently of those of the other
circuits. This makes it possible to adapt the knock control system
in an optimum manner to each internal combustion engine.
[0058] Owing to the fact that the threshold values DEC and INC for
the activation of the first adaptation circuit are linked with the
step sizes S.sub.Kdec, S.sub.Kinc of the knock adjustment angles
KNK(z), the adaptation characteristic is not affected if the knock
control parameters are changed.
[0059] The input variables for the second adaptation circuit are
the first adaptation values AD1(z) of the first adaptation circuit,
thereby allowing the damping effect of the latter to be exploited;
the only ignition angle corrections that occur in the second
adaptation circuit are those caused by the effects of aging or by
changes in the fuel grade.
* * * * *