Method for operating an internal combustion engine having at least one combustion space and internal combustion engine for carrying out such a method
阅读说明：本技术 用于运行具有至少一个燃烧空间的内燃机的方法和用于执行这样的方法的内燃机 (Method for operating an internal combustion engine having at least one combustion space and internal combustion engine for carrying out such a method ) 是由 T.弗兰克 T.康拉德 A.托特 于 2018-11-16 设计创作，主要内容包括：本发明涉及一种用于运行具有至少一个燃烧空间(3)的内燃机(1)的方法,其中,对于所述至少一个燃烧空间(3),在所述内燃机(1)的运行中取决于时间地探测固体声音信号,其中,在预先确定的测量窗口中,从所探测到的固体声音信号中测得至少一个评价参量,其中,将所述至少一个评价参量与至少一个预先确定的比较参量进行比较,由此获得至少一个比较结果,并且其中,借助所述比较结果将在所述燃烧空间(3)中的爆震事件或干扰信号配属于所述固体声音信号。(The invention relates to a method for operating an internal combustion engine (1) having at least one combustion space (3), wherein, for the at least one combustion space (3), a solid-borne sound signal is detected as a function of time during the operation of the internal combustion engine (1), wherein, in a predetermined measurement window, at least one evaluation variable is measured from the detected solid-borne sound signal, wherein the at least one evaluation variable is compared with at least one predetermined comparison variable, thereby obtaining at least one comparison result, and wherein, by means of the comparison result, a knock event or a disturbance signal in the combustion space (3) is assigned to the solid-borne sound signal.)
1. Method for operating an internal combustion engine (1) having at least one combustion space (3), wherein,
-detecting a structure-borne noise signal as a function of time during operation of the internal combustion engine (1) for the at least one combustion space (3), wherein,
measuring at least one evaluation variable from the detected structure-borne sound signal in a predetermined measurement window, wherein,
-comparing the at least one evaluation variable with at least one predetermined comparison variable, thereby obtaining at least one comparison result, and wherein,
-assigning a knock event or a disturbance signal in the combustion space (3) to the structure-borne sound signal by means of the comparison result.
2. The method according to claim 1, characterized in that at least one knock prevention measure is performed when a knock event is assigned to the structure-borne sound signal.
3. Method according to any one of the preceding claims, characterized in that the structure-borne sound signal is detected by means of a knock sensor.
4. Method according to any one of the preceding claims, characterized in that the structure-borne sound signal is measured in the predetermined measurement window
a) An energy parameter, and/or
b) The temporal length of the course of the signal curve, and/or
c) Signal shape parameter
As evaluation parameters.
5. Method according to one of the preceding claims, characterized in that a threshold value is applied as comparison variable, wherein,
assigning a knock event to the structure-borne sound signal when the evaluation variable is greater than the comparison variable, and wherein,
-assigning a disturbance signal to the structure-borne sound signal if the evaluation variable is smaller than the comparison variable.
6. Method according to any one of the preceding claims, characterized in that the energy quantity is measured by squaring the solid-borne sound signal and by integrating the squared solid-borne sound signal over the predetermined measurement window.
7. Method according to one of the preceding claims, characterized in that the temporal length of the signal curve of the solid-sound signal is measured by squaring the solid-sound signal, wherein the squared solid-sound signal is normalized by the maximum value of the squared solid-sound signal in the predetermined measurement window, wherein for the normalized and squared solid-sound signal a first time index value in the case of a first signal threshold value and a second time index value in the case of a second signal threshold value are measured in the measurement window, wherein the temporal length is calculated as the difference between the second time index value and the first time index value.
8. Method according to any one of the preceding claims, wherein the signal shape quantity is measured by squaring the solid-state sound signal, wherein the squared solid-state sound signal is normalized by a maximum value of the squared solid-state sound signal in the predetermined measurement window, and wherein the normalized and squared solid-state sound signal is integrated over the predetermined measurement window.
9. Method according to any of the preceding claims, wherein the structure-borne sound signal is filtered before the squaring.
10. Internal combustion engine (1) configured for carrying out the method according to any one of claims 1 to 9.
Technical Field
The invention relates to a method for operating an internal combustion engine and to an internal combustion engine which is designed to be operated by means of such a method.
Background
From german laid-open patent application DE 102013215924 a1, a method for operating an internal combustion engine is known in which a combustion space of the internal combustion engine is monitored as a function of (auf … hin) a knock event, wherein the start of injection and therefore also the ignition time for a cylinder for which the knock event is determined are adjusted back step by step until no more knock occurs in the cylinder. It is also known in principle to detect (ermitteln) such a knock event from a solid-state sound signal, which can be detected, in particular, by a knock sensor. However, during operation of the internal combustion engine, a disturbing signal in the form of solid-borne sound vibrations is also generated, which do not originate from a knock event. For example, when the pistons are loaded on the one hand by load changes in the connection of the rod pistons and on the other hand by the combustion space pressure, a change in the abutment of the respective piston is caused in the upper ignition dead center of an internal combustion engine designed as a stroke piston motor (angelewechseln). Such a change in the setting leads to a solid-borne sound vibration and thus to a solid-borne sound signal which can be detected, in particular, by a solid-borne sound sensor, such as, for example, a knock sensor, and which lies within a measurement window at the time of knock control. That is, the disturbance signal cannot be separated from the knock event with respect to its occurrence in time. In addition, the interference signal can contain the same frequency components as the structure-borne noise signal generated by the knock event, so that no frequency filtering for distinguishing between different signals is taken into account. If the interference signal exceeds a certain level, it is therefore erroneously interpreted as knocking, wherein measures are then taken to prevent knocking by means of knock control. This has a negative effect on the operation of the internal combustion engine: on the one hand, the efficiency of the internal combustion engine is reduced, and on the other hand, the pairing masses introduced do not reduce the occurring disturbances, so that the final operation is regulated to its limit stop (in ihren Anschlagl ä uft) and the internal combustion engine is switched off by an emergency stop in the worst case, in order to ensure a plausible protection of the internal combustion engine.
Disclosure of Invention
The object of the present invention is to provide a method for operating an internal combustion engine and an internal combustion engine, in which the disadvantages mentioned do not occur.
The object is achieved by the subject matter of the independent claims. Advantageous embodiments emerge from the dependent claims.
The object is achieved, in particular, by a method for operating an internal combustion engine having at least one combustion space, wherein a structure-borne sound signal is detected for the at least one combustion space as a function of time during operation of the internal combustion engine. In a predetermined (in particular temporal) measurement window, at least one evaluation variable (in particular not the signal amplitude of the solid-borne sound signal) is measured, in particular calculated, from the detected solid-borne sound signal, wherein the at least one evaluation variable is compared with at least one predetermined comparison variable, thereby obtaining at least one comparison result. With the aid of the comparison result, either a knock event in the combustion space or a disturbance signal is assigned to the solid-borne sound signal. This type of behavior is based on the recognition that, for example, a disturbance signal generated in the measurement window as a result of a displacement change can be separated from a knock event by introducing a metric which is applied to an evaluation variable measured from the structure-borne sound signal. The comparison of the evaluation variable with the comparison variable provides a measurement that allows a knock event to be distinguished from a disturbance signal. It is thereby possible to significantly reduce the relative share of falsely positively (false-positive) detected knock events or even to avoid falsely positively detected knock events, as a result of which the operation of the internal combustion engine as a whole is more efficient and economical, the efficiency of the internal combustion engine is ultimately increased, and emergency stop events are avoided.
The time-dependent detection of the structure-borne sound signal involves the structure-borne sound signal being detected unambiguously time-dependent. Additionally or alternatively, it is also possible for the structure-borne sound signal to be detected as a function of the crankshaft angle, i.e., in degrees of the crankshaft angle (° KW). It is also possible that the structure-borne sound signal is first detected with a defined time dependence (in particular with a certain resolution) and then converted or converted into a structure-borne sound signal dependent on the crankshaft angle as a function of the rotational speed. In this case, there is a clear dependency between time on the one hand and the crankshaft angle on the other hand with respect to the current rotational speed.
It is possible to detect the structure-borne sound signal only in a predetermined measurement window. It is also possible, however, for the structure-borne sound signal to be detected continuously and evaluated only within a predetermined measurement window (in any case with regard to possible knock events).
Preferably, the predetermined measurement window is delimited by a crankshaft angle range, which preferably comprises top dead center ignition (ignition OT). It is particularly feasible that, when the ignition OT is determined to 0 ° KW according to the regulations (perKonvention), a predetermined measurement window (stated in degrees crank angle) extends from 25 ° KW before the ignition OT to 55 ° KW after the ignition OT, that is to say from-25 ° KW to +55 ° KW, wherein the predetermined measurement window preferably extends from-20 ° KW to +50 ° KW, preferably from-15 ° KW to +45 ° KW, preferably from-10 ° KW to +40 ° KW, preferably from-5 ° KW to +35 ° KW, preferably from-2 ° KW to +30 ° KW, preferably from-1 ° KW to +25 ° KW.
Preferably, the at least one evaluation variable is measured from the detected solid-borne sound signal only if the maximum value of the detected solid-borne sound signal within the predetermined measurement window exceeds a predetermined limit amplitude maximum value and therefore exceeds a predetermined level. The maximum limit amplitude value is preferably selected such that knock events can be excluded at least with high reliability when the maximum limit amplitude value is not exceeded. No further evaluation of the structure-borne sound signal is then necessary, so that the computing time and thus also the corresponding costs associated therewith can be saved. In other words, it is preferably first tested whether the structure-borne sound signal exceeds a predetermined limit amplitude value within a predetermined measurement window, wherein the further method step is only carried out if this is in fact the case. In this connection, it has also been shown that the predetermined limiting amplitude value is not sufficient by itself to reliably separate the knock event from the interference signal.
It is possible to measure a plurality of evaluation variables from the detected structure-borne sound signal. In this case, the first and second evaluation variables are then used to distinguish between a knock event and a disturbance signal, wherein a predetermined comparison variable is particularly preferably provided for each evaluation variable, wherein each evaluation variable is compared with the predetermined comparison variable associated therewith. Then as many comparison results as the application evaluation parameters were obtained. The decision whether a knock event is present or a disturbance signal is present is then preferably taken in the sense of a majority decision. Thus, a knock event is identified when a majority of the comparison results point to this, where a minority of the comparison results represent a disturbance signal. Conversely, the disturbance signal is identified when a majority of the comparison results are directed toward the disturbance signal, wherein a minority of the comparison results are representative of the knock event. In this way, the reliability of the differentiation between knock events on the one hand and disturbance signals on the other hand can be further increased, wherein in particular the proportion of falsely and positively detected knock signals is also reduced.
According to a further development of the invention, at least one knock prevention measure is implemented when a knock event is assigned to the structure-borne sound signal. In contrast, when the disturbance signal is assigned to the structure-borne sound signal, the knock prevention measure is preferably not performed. In this way, when the interference signal is assigned to the solid-borne sound signal, the introduction of an unnecessary knock prevention measure and detrimental to the efficiency of the internal combustion engine is prohibited. Preferably, as a knock prevention measure, the ignition point in time, in particular the injection point in time and/or the ignition point in time, is adjusted to the rear, i.e. closer to the upper ignition point, for at least one combustion space. In this way, knocking can be reduced in at least one combustion space, whereby the internal combustion engine is taken care of. The ignition time can be adjusted forward again when no more knocking events occur.
According to a further development of the invention, the structure-borne sound signal is detected by means of a knock sensor. Knock sensors have proven to be extremely robust and durable and furthermore cost-effective. It is possible to assign a separate knock sensor to each combustion space of the internal combustion engine (as long as the internal combustion engine has a plurality of combustion spaces). It is also possible to assign a common knock sensor to several combustion spaces of the internal combustion engine, wherein this is possible without any problem because different predetermined measurement windows are temporally distributed for different combustion spaces (autoinnenderfallen). In particular, it is possible for the internal combustion engine to have only one knock sensor for all combustion spaces on the whole, or for the internal combustion engine to have separate knock sensors for different groups of combustion spaces, for example a knock sensor for each bank (zylindbank).
Alternatively, it is also possible for the structure-borne sound signal to be detected by means of a combustion space pressure sensor. In particular when the internal combustion engine is generally equipped with a combustion space pressure sensor (for example for pressure indication in at least one combustion space), the combustion space pressure sensor can advantageously be used together to detect a structure-borne noise signal.
In a further development of the invention, the energy quantity of the structure-borne sound signal is measured in a predetermined measurement window as the evaluation quantity. An energy quantity is understood here to mean a quantity which is representative of the energy contained in the structure-borne sound signal within a predetermined measurement window. In this connection, it has been found that the knocking events on the one hand and the interference signals on the other hand (in particular the interference signals generated by the change in the setting of the piston) are separated from one another anyway on the energy scale (engieskala) to such an extent that a differentiation by means of the energy variables is possible. In this case, the structure-borne sound signal originating from a knock event typically has a higher energy than the interference signal. If the statistical frequency of the knock events on the one hand and the interference signals on the other hand is modeled on an energy scale, it is shown that the maxima of the two profiles are in any case significantly separated from one another. In this way, it is possible to determine the value of the energy variable above which the solid-borne sound signal is caused by a knock event with a high probability as the predetermined comparison variable, wherein below this value the disturbance signal can be assigned to the solid-borne sound signal with a high probability. By means of this method of operation, the proportion of falsely and positively detected knock events can be significantly reduced from the comparison state without the method being carried out.
In addition or alternatively, the temporal length of the signal profile of the structure-borne sound signal is preferably measured in a predetermined measurement window as the evaluation variable.
In this case, a signal profile of the solid-borne sound signal is understood to mean a profile of the solid-borne sound signal within a predetermined measurement window from a certain starting value to a certain end value, wherein the certain starting value and the certain end value are selected such that a tip or peak of the solid-borne sound signal lies in an interval between the certain starting value and the certain end value. The signal profile is observed, in particular, starting from a first signal threshold value of the structure-borne sound signal up to a second signal threshold value, wherein the temporal length is calculated between a time index value assigned to the first signal threshold value and a time index value assigned to the second signal threshold value. In this connection, it has been found that the structure-borne sound signals caused by knock events on the one hand and the interference signals on the other hand are also significantly separated from one another on a time-length scale, wherein the structure-borne sound signals which can be attributed to knock events have a significantly longer signal profile than the interference signals. If the respective frequency distributions on the length scale are observed, it is also shown that the maximum frequency distributions for the solid-borne sound signal originating from knock events on the one hand and the interference signal on the other hand are significantly separated from one another. It is thus also possible to select a suitable length in time value as the predetermined comparison variable, wherein a knock event can be detected with high reliability if the length in time of the signal curve is longer than the predetermined length value, and wherein a disturbance signal is detected if the length in time is shorter than the predetermined length value. In this way, the proportion of the falsely and positively detected knock signal can be significantly reduced from the comparison state without the method being carried out.
Alternatively or additionally, it is provided that a signal shape variable of the structure-borne sound signal is measured in a predetermined measurement window as the evaluation variable. The signal shape parameter is representative in particular of the shape of the signal profile of the structure-borne sound signal. It has proven to be possible to distinguish between knocking and disturbance signals by means of a good signal shape.
In particular, at least two of the evaluation variables, for example the energy variables on the one hand and the temporal length of the signal profile on the other hand, are preferably used cumulatively. In this case, a knock event is particularly preferably detected when the comparison result assigned to the two evaluation variables represents a knock event, wherein a disturbance signal is detected when only one or none of the two comparison results represents a knock event. It is also possible to apply all evaluation variables cumulatively. The accuracy of the method can thus be further increased by evaluating the combination of parameters (Verknufung).
According to a further development of the method, a threshold value is used as the comparison variable, wherein knock events in the combustion space are assigned to the solid-borne sound signal when the evaluation variable is greater than the threshold value, and wherein a disturbance signal is assigned to the solid-borne sound signal when the evaluation variable is less than the threshold value. In particular, in this way, at least one unambiguous measure can be provided for evaluating the structure-borne sound signal. As already explained above, different measures are preferably used, which are used cumulatively for the discrimination of knock events on the one hand and of interference signals on the other hand.
Preferably, the comparison variable is determined in a test bench test. In this case, in a test-bed test it is possible to differentiate knock combustion from the disturbance signal in different ways, so that it is possible to formulate a frequency distribution, in particular in the form of a histogram, of the knock events on the one hand and of the disturbance signal on the other hand for the evaluation variable, wherein, if the frequency distribution of the disturbance signal on the one hand and the knock events on the other hand for the evaluation variable is clearly separated, a suitable comparison variable can be determined on the scale of the evaluation variable in order to ensure a differentiation that is as reliable as possible.
In a further development of the invention, the energy quantity is measured by squaring the solid-borne sound signal (possibly only in a predetermined measurement window), the squared solid-borne sound signal being integrated over the predetermined measurement window. In this way, a measurement quantity is obtained which is in any case representative for the energy contained in the structure-borne sound signal.
The temporal length of the signal profile is preferably measured in the following manner: the solid-borne sound signal is squared (if appropriate only within the measurement window), wherein the squared solid-borne sound signal is normalized to a maximum (peak value) of the squared solid-borne sound signal within a predetermined measurement window. This takes place in particular in that the maximum of the squared structure-borne sound signal is measured within a predetermined measurement window, and then the squared structure-borne sound signal is divided over the whole, i.e. at each point of the signal curve, by the measured maximum of the squared structure-borne sound signal. Thereby, all squared structure-borne sound signals are normalized to a maximum value of 1. For the normalized, squared structure-borne sound signal, a first time index value is measured in the case of a first signal threshold value in a measurement window, wherein a second (temporally subsequent) time index value is measured in the case of a second signal threshold value. The first signal threshold and the second signal threshold are preferably defined as thresholds that are a percentage of the maximum of the squared signal curve trend. It is possible that the first signal threshold and the second signal threshold are selected identically. It is also possible that different values are applied to the first signal threshold value on the one hand and the second signal threshold value on the other hand.
A time point or a crankshaft angle at which a first signal threshold value (before the maximum value is passed) is reached for the first time is used as the first time index value, wherein a time point or a crankshaft angle at which a second signal threshold value (after the maximum value is passed) is reached is measured as the second time index value. The difference between the second time index value and the first time index value is calculated as a length in time.
The length in time is preferably calculated in ° KW. If the time indicator value is detected as the point in time (since the structure-borne sound signal is also detected in a clearly time-dependent manner), the temporal length is preferably calculated by multiplying the difference in time indicator value by the temporal resolution of the detection of the structure-borne sound signal at ° KW (in particular depending on the current rotational speed of the internal combustion engine).
The signal shape parameter is preferably measured as follows: the structure-borne sound signal is squared (if necessary only in a predetermined measurement window). The squared solid-sound signal is normalized with the maximum (peak value) of the squared solid-sound signal within a predetermined measurement window. Here, the normalization is carried out as explained for the length in time measured. The normalized, squared structure-borne sound signal is integrated over a predetermined measurement window. In this way, the signal shape parameters are obtained as a measurement number that is representative for the signal shape. In this case, the signal shape variable is formed analogously to the energy variable, except for the normalization.
In accordance with a further development of the invention, the structure-borne sound signal (in particular both in the case of the measured energy quantity and in the case of the temporal length of the course of the measured signal curve and also in the case of the measured signal shape quantity) is filtered before the square. In particular, disturbances which occur in the frequency band in which the solid-borne sound signal attributable to knock events occurs can be removed in this case, which disturbances can be separated from the frequency band.
The object is also achieved by a combustion engine which is designed to carry out the method according to the invention or the method according to one of the embodiments described above. In this case, the advantages which have already been explained in connection with the method are achieved in particular in connection with internal combustion engines.
The internal combustion engine has, in particular, a control device, which is designed to carry out the method. In this case, it is possible to provide a separate control device for carrying out the method. Particularly preferably, the method is implemented in a central control unit, in particular a motor control unit (ECU), of the internal combustion engine. In the control unit, the comparison variable, which is preferably predetermined, is stored as a threshold value, which is measured, in particular, in a test stand test.
Preferably, the internal combustion engine has at least one knock sensor, which is designed to detect a solid-borne sound signal, wherein the knock sensor is also operatively connected to the control unit for transmitting the solid-borne sound signal detected by the knock sensor to the control unit.
The internal combustion engine is preferably designed as a stroke piston motor. It is possible that the internal combustion engine is designed for driving a passenger car, a utility vehicle or a commercial vehicle. In a preferred embodiment, the internal combustion engine is used for driving, in particular, heavy land or water vehicles, such as mining vehicles, trains (wherein the internal combustion engine is used in locomotives (Lokomotive) or in motor vehicles (Triebwagen)), or ships. It is also possible to use the internal combustion engine for driving a vehicle for defence, for example an armoured vehicle. An embodiment of the internal combustion engine is preferably also used fixedly, for example, for a fixed energy supply in a backup power supply operation, a permanent load operation or a top load operation, wherein the internal combustion engine in this case preferably drives a generator. Also possible is the stationary use of the internal combustion engine for driving auxiliary units, for example fire extinguishing pumps on offshore drilling platforms. Furthermore, the use of the internal combustion engine in the field of the transport of fossil raw materials and in particular fuels, such as oil and/or gas, is possible. The use of the internal combustion engine in the industrial field or in the construction field, for example in construction or construction machines, for example in cranes or excavators, is also possible. The internal combustion engine is preferably designed as a gasoline motor, as a gas motor for operation with natural gas, biogas, specialty gas or other suitable gases, or as a two-component motor, in particular as a dual-fuel motor, in particular for operation with gasoline and diesel and/or with gas and diesel. In particular, when the internal combustion engine is designed as a gas motor, the internal combustion engine is suitable for use in a combined heat and power plant for stationary energy generation.
The invention also relates to a computer program product having instructions on the basis of which the method according to the invention or the method according to one of the embodiments described above is carried out when the computer program product is operated on a control device of a computing means, in particular of an internal combustion engine.
Furthermore, a data carrier with such a computer program product or on which such a computer program product is stored is also encompassed by the present invention.
The description of the method on the one hand and the internal combustion engine on the other hand should be understood complementary to one another. The features of the internal combustion engine explained explicitly or implicitly in connection with the method are preferably features of an embodiment of the internal combustion engine, individually or in combination with one another. The method steps explained explicitly or implicitly in connection with the internal combustion engine are preferably steps of an embodiment of the method, individually or in combination with one another. The method is preferably characterized by at least one step which is determined by at least one feature of the internal combustion engine according to the invention or the preferred embodiment. The internal combustion engine is preferably characterized by at least one feature which is determined by at least one step of the method according to the invention or the preferred embodiment.
Drawings
The invention is explained in more detail below with the aid of the figures. In this case, the amount of the solvent to be used,
the sole figure shows a schematic illustration of an exemplary embodiment of an internal combustion engine which is designed to carry out an embodiment of the method for operating the internal combustion engine.
Detailed Description
The sole figure shows a schematic illustration of an embodiment of an internal combustion engine 1 which is designed to carry out the method for its operation described in more detail below. The internal combustion engine 1 has at least one
Preferably, the internal combustion engine has a plurality of
In this case, a knock sensor 9 is assigned to the
The knock sensor 9 is operatively connected to a
The solid-borne sound signal is detected by the knock sensor 9, wherein it is evaluated with respect to the occurrence of knock events in a predetermined, temporal measurement window associated with the
In order to still be able to reliably distinguish knock events from disturbance signals, within the scope of a preferred method for operating the internal combustion engine 1, it is provided that, for the
Preferably, a plurality of evaluation variables are measured, wherein each evaluation variable is compared in each case with a predetermined comparison variable associated therewith. In this way a plurality of comparison results is obtained. The decision whether a knock event is present or a disturbance signal is then preferably taken in the sense of a majority decision, wherein a knock event is identified in particular when the majority of the comparison results points to this. Conversely, if the majority of the comparison results are directed towards the disturbance signal, or if there are as many comparison results favorable for knock events as favorable for the disturbance signal, the decision is preferably made on the basis of the disturbance signal.
If a knock event is assigned to the structure-borne sound signal, at least one knock prevention measure is preferably carried out, in particular by the
Preferably, the energy quantity and/or the signal shape quantity and/or the temporal length of the signal profile of the structure-borne sound signal are measured in a predetermined measurement window as evaluation variables.
Preferably, a threshold value is used as the comparison variable, wherein a knock event is assigned to the solid-borne sound signal if the evaluation variable is greater than the comparison variable, and wherein an interference signal is assigned to the solid-borne sound signal if the evaluation variable is less than the comparison variable.
The energy quantity is preferably measured by squaring the solid-borne sound signal, the squared solid-borne sound signal being integrated over a predetermined measurement window.
The temporal length of the signal profile is preferably measured by squaring the solid-borne sound signal, the squared solid-borne sound signal being normalized to a maximum of the squared solid-borne sound signal within a predetermined measurement window. For the normalized and squared structure-borne sound signal, a first time index value in the case of a first signal threshold and a second time index value in the case of a second signal threshold are measured in a measurement window, wherein the length in time is then calculated as the difference between the second time index value and the first time index value.
The signal shape variable is preferably measured by squaring the solid-borne sound signal, the squared solid-borne sound signal being normalized to the maximum of the squared solid-borne sound signal in a predetermined measurement window, and the normalized and squared solid-borne sound signal being integrated over the predetermined measurement window.
Preferably, the structure-borne sound signal is filtered before being squared.
With the method and internal combustion engine 1 proposed here, it is possible to prevent unnecessary reductions in the efficiency and power of the internal combustion engine and emergency stops due to a plurality of falsely and positively detected knock events.
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