Measuring and testing – Engine detonation – Specific type of detonation sensor
Reexamination Certificate
2002-11-05
2004-11-09
Lefkowitz, Edward (Department: 2855)
Measuring and testing
Engine detonation
Specific type of detonation sensor
C123S644000
Reexamination Certificate
active
06813933
ABSTRACT:
BACKGROUND INFORMATION
The present invention relates to the positioning of a measurement window in time for the analysis of ionic current signals detected on internal combustion engines via the electrodes of a spark plug.
It has long been the practice to use features extracted from the measured ionic current characteristic for monitoring and controlling the combustion process in engines, e.g., internal combustion engines. Examples of this include detection of misfiring, knock detection or regulation of the combustion position.
The measurement window is restricted if the ionic current measurement is performed on an engine via the spark gap of a spark plug. This restriction results from the fact that no ionization current is measurable during the ignition operation due to the superimposed spark current. Methods and devices for ionic current measurement in combination with ignition systems in engines are known from German Patent 196 49 278 and German Patent 197 00 179. Because of the superimposed spark current, the test signal resulting during the ignition operation is not suitable for extraction of combustion information. To prevent incorrect classifications (e.g., in detection of misfiring), the ionic current signal in most known systems is analyzed only within measurement window ranges that explicitly do not include the ignition operation because they are outside the time or angle ranges in which the ignition sparks burn.
There are two known methods for positioning measurement windows, as described in European Patent 0 188 180 B1, for example:
Positioning the measurement window with regard to a fixed crank angle range, which corresponds to a certain piston motion of the cylinder in question.
Positioning the measurement window with regard to the ignition point in time, there being a delay by an applicable period of time to take into account the spark duration and the die-down process.
These methods have in common the fact that the measurement window is positioned in a purely controlled manner. The spark duration varies as a function of physical and engine-related properties. In both methods of positioning the beginning of the measurement window, this requires a complicated application, which must take into account such operating parameters as the rotational speed, load, processing of the mixture, etc. Because of the control of the positioning of the measurement window, the application must be implemented in the sense of a “worst case estimate.” In other words, the beginning of the measurement window is placed very late to ensure that the ignition influences will die down in all cases.
However, a worst case application runs counter to the requirements of an ionic current measurement because the earliest possible beginning of the measurement window is to be desired. This is true to a particular extent for operating points having a low load and a high rotational speed, or in engines having a high flow rate of gases in the cylinder, e.g., in engines with direct injection of gasoline, in which there is a targeted charge movement through valves or butterfly valves to adjust a certain inhomogeneous distribution of the mixture in the cylinder.
ADVANTAGES OF THE INVENTION
The core of the present invention is the determination of the actual spark duration through measurement technology and the use of this information for positioning the measurement window. This procedure offers the advantage that not all engine-related and physical influencing factors on the spark duration are taken into account in the application for positioning the measurement window.
The present invention may be used to particular advantage in combination with an ignition system having ignition transformer, e.g., a.c. ignition according to German Patent 197 00 179 or a capacitor ignition system or an inductive transistor ignition or an inductive coil ignition or an inductive coil ignition having a limited spark duration, as described in German Patent Application 196 49 278 A1. The ignition system for an internal combustion engine according to the latter patent specification is combined with a measurement device for ionic current on the secondary winding on the ground side, each spark plug being allocated one ignition transformer.
According to the present invention, the end of the spark is detected and the measurement window is opened for the ionic current signal as a function of the end of the spark. Detection of the spark current and the ionic current in separate branch circuits is particularly advantageous for separation of ignition spark current influences and the actual ionic current signal. To reduce the equipment complexity, however, it is also possible to detect the spark current and the ionic current in the same branch circuit. In the latter embodiment, the distinction between ionic current and spark current is made on the basis of a threshold value for detecting the end of the spark. In systems having alternating spark current, it is advantageous for the signal to undergo rectification and low-pass filtering before being compared with the end-of-spark detection threshold. It is also advantageous for a measurement window for the ionic current to be opened only after an applicable lag time, which depends on the ignition system, with respect to the end of the spark detected. This lag time is determined essentially by the system. It is subject to only minor statistical variation in comparison with the spark duration. Thus, the procedure according to the present invention always guarantees a maximally early beginning of the measurement window. Switching an amplifier stage after the end of the spark has the advantageous effect that the full signal stroke is again available for the ionic current measurement. The period of time during which the signal exceeds the threshold for detection of the spark current permits a conclusion regarding faults in the ignition system. In the case of inductive ignition systems, the information regarding the spark burning period is used to advantage to adapt the ignition energy adaptively to the actual demand. To reduce circuit complexity, it is advantageous to combine a number of ignition coils on the ground-side end of the secondary winding.
This method is needed in ignition systems in which the spark duration is not defined precisely. This is mainly the case in inductive ignition, but information about the actual end of the spark may also be of interest in ignition systems in which the spark duration may be varied, because the required information is generated locally.
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Foerster Juergen
Guenther Achim
Ketterer Markus
Davis Octavia
Kenyon & Kenyon
Lefkowitz Edward
Robert & Bosch GmbH
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