U.S. patent application number 09/759459 was filed with the patent office on 2001-07-19 for method for detecting combustion misfires in a multi-cylinder internal combustion engine.
Invention is credited to Buck, Uwe, Lohmann, Andrea, Oertel, Heiko, Schnee, Ralf, Schwabe, Juergen, Viel, Heinz, Wiltsch, Peter.
Application Number | 20010008082 09/759459 |
Document ID | / |
Family ID | 7627477 |
Filed Date | 2001-07-19 |
United States Patent
Application |
20010008082 |
Kind Code |
A1 |
Oertel, Heiko ; et
al. |
July 19, 2001 |
Method for detecting combustion misfires in a multi-cylinder
internal combustion engine
Abstract
The invention relates to a method for detecting combustion
misfires in a multi-cylinder internal combustion engine. Combustion
misfires are detected from data for the rough running of individual
cylinders via a comparison with threshold values at operating
points stored in a characteristic field. These data are determined
within the engine. The combustion misfire detection is suppressed
below an rpm-dependent zero-load characteristic line. The zero-load
characteristic line is continuously adapted to the actually present
lowest load at corresponding rpm values during vehicle
operation.
Inventors: |
Oertel, Heiko;
(Stuttgart-Weilimdorf, DE) ; Lohmann, Andrea;
(Stuttgart, DE) ; Schwabe, Juergen;
(Leinfelden-Echterdingen, DE) ; Schnee, Ralf;
(Eberdingen, DE) ; Buck, Uwe; (Esslingen, DE)
; Wiltsch, Peter; (Wimsheim, DE) ; Viel,
Heinz; (Kaisersbach, DE) |
Correspondence
Address: |
Walter Ottesen
Patent Attorney
P. O. Box 4026
Gaithersburg
MD
20885-4026
US
|
Family ID: |
7627477 |
Appl. No.: |
09/759459 |
Filed: |
January 16, 2001 |
Current U.S.
Class: |
73/114.05 |
Current CPC
Class: |
G01M 15/11 20130101 |
Class at
Publication: |
73/117.3 |
International
Class: |
G01M 015/00; G01L
003/26 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 14, 2000 |
DE |
100 01 283 .3 |
Claims
What is claimed is:
1. A method for detecting combustion misfires in a multi-cylinder
internal combustion engine, the method comprising the steps of:
detecting misfires from data, which are determined in the engine,
for the rough running of individual cylinders, by comparing said
data to threshold values at operating points stored in a
characteristic field; suppressing the detection of combustion
misfires below an rpm-dependent zero-load characteristic line; and,
continuously adapting said zero-load characteristic line to the
actually present lowest load at corresponding rpm values during
operation of the vehicle.
2. The method of claim 1, comprising the further steps of:
measuring actual load values (rl) for actual rpm points and
comparing said actual load values to zero-load values (rl.sub.K)
determined from the stored characteristic line; and, effecting an
assumption of said load values (rl) into the characteristic line
values when said load values drop below zero-load values
(rl.sub.K).
3. The method of claim 2, comprising the further steps of: for low
rpms including the idle range, determining a difference
.DELTA.rl=rl-rl.sub.K when comparing the measured load values (rl)
to the zero-load values (rl.sub.K) determined from the
characteristic line; and, with said zero-load value (rl.sub.K),
determining from said difference (.DELTA.rl) for higher rpms a
corrected zero-load value (rl.sub.NEW=rl.sub.K+.DELTA.r- l), which
is taken into said zero-load characteristic line.
4. The method of claim 3, comprising the further step of forming
said corrected zero-load value (rl.sub.NEW) from said
characteristic line zero-load value (rl.sub.K) and a component
quantity of the computed difference (.DELTA.rl).
Description
BACKGROUND OF THE INVENTION
[0001] Methods for detecting combustion misfires in multi-cylinder
internal combustion engines are known from the state of the art
wherein combustion misfires are detected from data for the rough
running of individual cylinders, which are determined in the
engine, via a comparison to threshold values at operating points
stored in a characteristic field. The threshold values are usually
stored in a characteristic field for individual operating points of
the engine. Combustion misfires below an rpm-dependent zero-load
characteristic line are suppressed.
[0002] The methods are essentially based on detecting combustion
misfires from values for the rough running of individual cylinders
of the engine by a comparison to fixed threshold values in that the
determined rough-running values exceed the threshold value. The
values are determined internally in the engine.
[0003] The rough-running values for individual cylinders, which are
decisive for the detection of misfires, are obtained while using
the realization that a combustion within a cylinder of an engine,
which does not take place or does take place only incompletely, is
associated with characteristic changes of the torque trace of the
engine compared to the normal operation. One can distinguish
between normal operation of the engine without misfires and
operation subjected to misfires from the comparison of the torque
traces, that is, the amount which individual cylinders contribute
to the torque. The differences in the torque trace are determined
by determining segment times. Here, consideration is given to the
situation that a torque contribution, which is lower as a
consequence of an occurring misfire, is associated with a
lengthening of the segment times of the crankshaft. The respective
piston movement of individual cylinders during the torque producing
expansion phase corresponds to a crankshaft segment. The
rough-running values of individual cylinders are determined in a
manner known per se from the measured segment times and are
compared to the above-mentioned threshold values in a follow-on
method step. Such methods for detecting combustion misfires have
been proven in principle and are applied in the positive load range
of the engine above a so-called zero-load characteristic line.
Below the zero-load characteristic line, which is individually
fixed for each vehicle engine, the combustion misfires are
suppressed. In the determination of the decisive zero-load
characteristic line, it should be considered that, for specific
engine systems (for example, .lambda.=1 systems), the load data are
dependent upon external conditions. The ambient pressure and
therefore the counterpressure which opposes the exhaust gas are
considered as external conditions.
[0004] Furthermore, it has been shown in practice that in the rpm
region close to idle, the zero-load level can fluctuate slightly
from vehicle to vehicle.
[0005] From these conditions, the problematic results that a
detection of a combustion misfire in the region of the zero
characteristic line is suppressed, under some circumstances, too
early or too late.
SUMMARY OF THE INVENTION
[0006] In view of the problematic referred to above, the method of
the invention affords the advantage that a precise zero-load
characteristic line is determined for all operating states by
adapting the zero-load characteristic line during vehicle operation
continuously to the actually present lowest loads at corresponding
rpm values so that the combustion misfire detection is always
active in the statutorily prescribed regions and an incorrect
detection because of a defective suppression cannot occur.
[0007] Because of the continuous monitoring of the zero-load level,
vehicle specific differences as well as differences in ambient
pressure can also be considered. The differences in ambient
pressure can occur, for example, because of different levels of
elevation.
[0008] A preferred configuration of the method of the invention
provides that actual load values rl are measured for actual rpm
points and are compared to the zero-load values rl.sub.K determined
from the stored characteristic line. A dropping of the load values
rl below the zero-load values rl.sub.K effects an assumption of the
load values rl into the characteristic line values. In this way,
and via simple structural measures within an engine management
system, the zero-load characteristic line can be applied for the
lowest load points. The zero-load values of the characteristic line
can be adapted in the direction of the actually occurring low loads
via corresponding filtering.
[0009] The region of the zero-load characteristic line is seldom
touched at high rpms. For this reason, it has furthermore been
shown to be advantageous that, for low rpms (preferably in the idle
range) a difference .DELTA.rl=(rl-rl.sub.K) is determined from a
comparison of the measured zero-load values rl with the zero-load
values rl.sub.K determined from the characteristic line; and, from
this difference .DELTA.rl, for higher rpms, a corrected zero-load
value rl.sub.NEW=(rl.sub.K+.DELTA.rl) is determined which is taken
into the zero-load characteristic line. In this way, the difference
of the actual load values, which is present in idle, to the
characteristic line load values is considered for the entire rpm
range. However, a condition precedent for the application is that
it must be made certain that additional consumers within a motor
vehicle, which could lead to a higher idle rpm level, are disabled
during the determination of the actual zero-load values rl.
Furthermore, for specific application purposes, it can be
advantageous to utilize the determined difference .DELTA.rl from
the idle level only at a fixed percentage for the new determination
of the zero-load characteristic line.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The invention will now be described with reference to the
drawings wherein:
[0011] FIG. 1 is a block circuit diagram for the method sequence
for checking and adapting the zero-load characteristic line to
actually existing operating conditions; and,
[0012] FIG. 2 is a block circuit diagram of a second embodiment of
the method of the invention with adaptation of the zero-load
characteristic line in idle and the assumption of the results to
higher rpm levels.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
[0013] In FIG. 1, block 1 represents a storage component wherein
the characteristic field of the originally applied zero-load
characteristic line having the characteristic line zero-load values
rl.sub.K is stored in dependence upon rpm. The method of the
invention determines actual zero-load values rl in dependence upon
specific actual rpm points. These actual zero-load values rl are
compared in an evaluation block 2 with the zero-load values
rl.sub.K resulting from the zero-load characteristic line in
dependence upon the actual rpm (u). If this comparison yields that
the actual zero-load values rl are less than the values rl.sub.K
from the characteristic line and if a several-time check also
yields the same result, then, for the corresponding rpm point, the
newly determined actual zero-load value rl is taken over into the
characteristic line. This takes place in a separate unit 4.
[0014] If, in practice, it is shown that, for specific rpm points
(especially in higher rpm ranges), the zero-load region is seldom
touched, then an adaptation of the actual zero-load values to the
originally present zero-load characteristic line can be carried out
via the embodiment shown in FIG. 2 also for this application.
[0015] The starting point of the method is, as in the first
embodiment, a block 1 wherein the zero-load characteristic line is
applied in the context of a characteristic line field. In the same
manner as in the embodiment of FIG. 1, an actual zero-load value rl
is determined in the additional embodiment of the method of the
invention. The determination of this value takes place at idle rpm
of the engine. Simultaneously, it must be ensured that additional
consumers, which increase the idle load level, are disabled. The
actual zero-load values rl are compared to the zero-load value
rl.sub.K in an evaluation component 2 in the same manner as the
method of FIG. 1. The zero-load value rl.sub.K is obtained from the
zero-load characteristic line. Should it occur that the actually
determined zero-load value rl is less than the value rl.sub.K,
which is determined from the characteristic line, then, in an
additional method step, a difference value .DELTA.rl is formed in
computation block 3. The difference value .DELTA.rl results from
the equation:
.DELTA.rl=rl-rl.sub.K.
[0016] If the comparison between the actual zero-load values rl and
the values rl.sub.K, which are determined from the characteristic
line, shows over a certain time span that the actual zero-load
values rl are continuously less than the values rl.sub.K, which are
pregiven by the zero-load characteristic line, then in a unit 4, a
new zero-load value rl.sub.NEW is fixed as the sum of the
characteristic line zero-load value rl and the computed difference
.DELTA.rl as:
rl.sub.NEW=rl+.DELTA.rl.
[0017] This determination of the new zero-load value rl takes place
for all zero-load characteristic values lying above the idle rpm
level so that a corrected zero-load characteristic line results.
For specific cases of application, it can be advantageous not to
utilize the entire difference value .DELTA.rl for the determination
of the new zero-load value rl.sub.NEW but to use only a specific
percentage of the value determined for .DELTA.rl.
[0018] The decision as to which percentage is used for the new
computation is fixed by the engine developer in dependence upon
given conditions.
[0019] It is understood that the foregoing description is that of
the preferred embodiments of the invention and that various changes
and modifications may be made thereto without departing from the
spirit and scope of the invention as defined in the appended
claims.
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