EP1520091B1 - Method and device for the control of an internal combustion engine - Google Patents

Abstract

A device and a method for the control of an internal combustion engine, in particular a diesel internal combustion engine are disclosed. Characteristic parameters are determined from a structural noise sensor which are used for control of the internal combustion engine. At least one parameter is determined by means of an analysis with a filtration which selects at least two angular ranges.

Description

State of the art

The invention relates to a method and a device for controlling an internal combustion engine according to the preambles of the independent claims.

A method and a device for controlling an internal combustion engine, in particular a diesel internal combustion engine is known from US 6,390,068 known. This document describes a method for monitoring an injection system. The output signal of a structure-borne sound sensor is integrated via a measuring window and filtered with a predetermined frequency band. In this case, the signal is checked via two crank angle windows F 1 and F 2 to the effect at which crank angle the signal reaches a predetermined amplitude value. Furthermore, starting from the structure-borne sound signal, the amount of fuel that is metered in the pre-injection or main injection is calculated. The quantities thus derived from the structure-borne noise signal are checked to see if they are outside a permissible value range. If this is the case, the device recognizes errors

The DE 196 12 179 C describes a method for controlling the combustion process of an internal combustion engine. By means of a structure-borne sound sensor, the start of combustion in the cylinders is determined and, if necessary, changed in such a way that an uneven torque output of the cylinders is equalized. Here, a filtering of the signal in a measuring window (MF) per injection is provided. Based on the filtered signal only one parameter is determined.

A method and a device for controlling an internal combustion engine, in particular a diesel internal combustion engine is known from DE 195 36 110 known. There, based on the signal of a structure-borne sound sensor, quantities are determined which are used to control the internal combustion engine.

According to the invention, at least two parameters are determined based on the signal of a structure-borne sound sensor. These are used to control the internal combustion engine. The evaluation of the structure-borne sound signal includes at least one filtering which selects at least two angular ranges. Based on the correspondingly processed signal, the characteristics result. The fact that several angular ranges are evaluated, a reliable determination of the events to be evaluated is possible.

It is advantageous that at least two parameters are determined. Preferably, a parameter is determined for each angular range in which an evaluation takes place.

In a particularly advantageous embodiment, new characteristics are determined by dividing the characteristics among each other. In this case, by way of example, two parameters K 1 and K 2 are determined by filtering in at least one angular range and the quotient is formed. By dividing the two parameters that characterize the intensity of the sound emission in the two sub-areas, the actual parameter is then determined by ratio formation, which is independent of absolute signal values and thus of sensor tolerances and drifts.

In an advantageous embodiment, the characteristics are compared with setpoints. Depending on this comparison, manipulated variables can be predetermined which influence the injection and / or the position of the inlet valves and / or the outlet valves. The determined characteristics characterize certain events and / or times. The parameter preferably characterizes the noises determined in the corresponding measurement window. In a pre-injection there is a simple relationship between the noise emission and the injected fuel quantity.

It is advantageous if a correlation coefficient is determined as a parameter by means of a cross-correlation which characterizes the deviation of the measured signal from a reference signal.

The reference signal preferably corresponds to the structure-borne sound signal in preferred states. For example, the reference signal corresponds to the structure-borne sound signal at a desired pre-injection.

drawing

The invention will be explained below with reference to the embodiments (embodiments) shown in the drawing.

FIG. 1 shows a block diagram of the procedure according to the invention and FIGS. 2 to 4 show various configurations of the evaluation according to the invention of the structure-borne sound signal.

FIG. 1 shows the method according to the invention for measuring and evaluating the structure-borne sound signal as a block diagram. With 0 is a structure-borne sound sensor, with 1 an anti-aliasing filter, with 2 is a windowing, with 3a, 3b, 3c are three parallel FIR filters, with 4a, 4b and 4c are three parallel magnitude formations and with 5a, 5b, and 5 c are called three integrators. In the FIR filters, the amount of education and the Integrators each have multiple branches. In the exemplary embodiment, 3 parallel branches are shown. In other embodiments, other numbers of parallel branches may be provided.

The parallel FIR filters can be freely parameterized. Different frequency ranges can be considered simultaneously. This is advantageous because interference signals in the vehicle, which are caused for example by the connection of a pump, by valve noise of another cylinder, superimpose the actual useful signal in certain frequency ranges interference signals. By filtering one and / or several frequency ranges are selected in which the useful signal can be measured as possible without interference. The combination of several selected frequency ranges allows a more reliable detection of the useful signal.

The output signals of the individual branches reach a control 6. In this case, an output signal is forwarded for each considered angular range and each considered frequency range. In the illustrated embodiment, a signal of a first split injection filtered by a first filtering method is designated In1F1. A signal of a first split injection filtered by a second filtering method is designated In1F2, and a signal of a second split injection filtered by the first filtering method is designated In2. Signals associated with at least one angular range are filtered by at least one filtering method. Preferably, signals are filtered multiple angular ranges with multiple filtering methods. An angular range is assigned in particular to a partial injection of a combustion process.

Preferably, 3 filters are used which are spread over the entire evaluation range, i. for all injections. Due to the window formation, angle ranges are excluded which do not contain any signal component and / or in which disturbances occur.

In one embodiment, the controller 6 can be connected directly to the structure-borne sound sensor 0 via a first connection 7 and / or directly to the windowing 2 via the connection 8. With Outa is a manipulated variable for valve control, with Outb a manipulated variable for controlling the actuation starts of pre-, main, post-injections and with Outc a manipulated variable for controlling the actuation time of pre-, main, Called post-injections. These variables are chosen only by way of example, so only some of these sizes or all of these variables can be output.

As shown in FIG. 1, the structure-borne sound signal is measured in one or more measurement windows. Preferably, two to three measuring windows per injection are provided. A measuring window is defined by the window position and the window length. The window position corresponds to the angular position of the camshaft and / or the crankshaft, at which the detected size is likely to occur. The window length corresponds to the angle range around which the detected size can change. The window position and window length, is variably adjustable to capture different sizes. The windowing selects the angular range to be evaluated within which the structure-borne sound signal is evaluated. Depending on which size is to be obtained as the output variable, different measurement windows are specified. Preferably, a partial injection is assigned to each window. The individual partial injections are assigned at least one measuring window.

There follow preferably three parallel paths, each with a so-called FIR filter 3a, 3b and 3c, in each case an amount formation 4a, 4b and 4c and an integrator 5a, 5b and 5c. In addition, the unprocessed structure-borne sound signal Inb via the connection 7 and / or the output signal of the fenestration 2 Inb via the connections 8 to the controller 6 passed. The abbreviation FIR stands for Finite Impulse Response. The time signal is transformed into the frequency domain and defined frequency components are selected. Advantages over conventional filters are that a linear phase response is feasible and that greater freedom in filter design is possible. In improved embodiments, more paths may be provided.

As an alternative to the FIR filter, other filters with different transmission characteristics may also be provided. Preferably bandpasses, lowpasses, highpasses, bandstop filters and / or nonlinear filters are used. Preferably, filters are used which select certain frequency ranges.

As an alternative to the amount formation, a square or similar functions can also be used. It is essential that a quantity is formed which characterizes the signal power, which depends quadratically on the signal amplitude.

Alternatively, any averaging can be implemented in these angular ranges for integration over certain angular ranges if a relative consideration of different characteristic values relative to one another is carried out by quotient formation or a similar mathematical method.

The controller 6 acts on a valve control unit, not shown, with a first manipulated variable Outa. This is preferably a variable that influences the opening and / or closing times of the intake valves and / or the exhaust valves. The controller 6 also acts on control elements, not shown, which influence the fuel metering with a second signal Outb, which influences the start of control of one or more pilot, main and post-injections. Furthermore, the controller 6 acts on illustrated adjusting elements, which influence the fuel metering with a third signal Outc, which determines the driving time and thus the amount of one or more pilot, main and post injections.

FIG. 2 shows the signal processing in the controller 6 in more detail using the example of an input variable Inb. 21 denotes a time-of-flight correction, 22 a malfunction compensation, 23 an averaging, 24 a statistical value calculation and 25 an interference-level switching between control / regulation.

Preferably, a structure-borne noise sensor is used for a plurality of cylinders of the internal combustion engine. The sound wave created in the combustion chamber takes a running time to reach the sensor. Therefore, the signals from cylinders farther from the sensor reach the sensor later than from the closer cylinders. This runtime or the necessary correction is a defined quantity, which depends on the installation location of the sensor. It is first applied to the test stand or vehicle in order to take it into account in the signal processing. For block 21, this means that there is a time shift of the signals with the previously applied quantities.

The useful signals are interference signals superimposed by background noise. For example, the valve stroke of another cylinder causes a characteristic vibration in the cylinder Waveform. These disturbances are determined beforehand on the test engine. These interference signals are compensated in noise compensation 22.

For this purpose, certain characteristic oscillations are subtracted in certain time ranges from the measured signal. For interfering signals with characteristic frequency components, these are subtracted in the frequency spectrum.

In block 22, therefore, the occurring, previously determined on the experimental engine noise, subtracted from the input signal in the time and / or frequency domain.

The averaging 23 determines an average over several variables. The calculation 24 determines various statistical quantities, such as the variance. The rating 25 causes, based on the level of the noise level of the signal, a switching between map controlled and controlled operation. If the interference level does not exceed a threshold value, the corresponding output variable is regulated. The output variable is determined as a function of the comparison of a measured value or a variable calculated from one or more measured values with a desired value.

FIG. 3 shows the evaluation of the structure-borne sound signals transmitted via the connection 7 and / or 8 in the controller 6. With Inc is a reference signal and Inb the structure-borne noise signal is called, which is transmitted via the connection 7 and / or via the connection 8. 31 is an integrator and 32 is an evaluation method.

The integrator 31, the structure-borne sound signal is fed. The analysis method 32, the structure-borne sound signal and the reference signal is supplied. Further, thresholding at 33 and weighting and / or combination of features at 34 are indicated. The thresholding 33 is supplied to the output signal of the integrator 31 and the structure-borne sound signal. The weighting and / or combination of the features 34 are fed to the output signal of the threshold value formation 33 and that of the evaluation method 32. The weighting and / or combination of the features is preferably designed as Kalman filtering.

The output signal of the evaluation method 32 is designated as parameter Ka. These are preferably the times at which certain signals occur and / or information about the similarity of the input signals, which are also referred to as the correlation coefficient. The output of thresholding 33 is also referred to as characteristic Kb. These characterize the times at which certain signals occur. The output variables of the weighting 34 correspond to the output variables of the controller 6.

The evaluation of the processed structure-borne noise signals, which reach the controller 6 via connection 7 or 8, takes place via the block 32 and / or the block 33. Both in the block 32 and in the threshold value formation 33, reference signals are used. As reference signals structure-borne sound signals are used, which were measured under defined operating conditions. Thus, for example structure-borne noise signals that occur in overrun mode and / or structure-borne sound signals that occur with only one pre- or main or post-injection can be used as a reference signal. Preferably, the reference signals are detected in the corresponding operating states and stored in suitable memory means.

The evaluation method used is preferably a KKF and / or a wavelet analysis and / or an FIR filtering.

One way to evaluate the signals is spectral analysis. The goal here is to describe the signal power in the frequency domain. The following tools are provided individually or in combination:

In the KKF, which is also referred to as the cross-correlation function, the signals are convoluted in the time domain. With this method, a measured signal is evaluated. The KKF evaluates the similarity of the signal with reference signals. The correlation coefficient describes the agreement. The value 1 denotes an identical course of the signal and the reference signal. As a further result of the KKF, the time of occurrence of a specific event in the signal can be detected.

By calculating the cross-correlation function between the reference signals and the measured signals, the absolute points in time and / or the angular positions of the occurring signal oscillations are determined.

The FIR is used to reduce noise and select relevant frequency ranges. This can be used to calculate the power of certain frequency components. By windowing the signals can also be determined in which measurement window and thus when an event occurs in the measurement signal.

The wavelet analysis, in which the signal is convoluted with a reference signal, corresponds to a simple FIR filtering. Advantageous is their simple implementation in software and hardware.

The evaluation in block 32 contains at least 2 possibilities with which the parameters can be calculated and the control can be realized. In order to increase the accuracy and the reliability, in advantageous embodiments, the calculated features are combined and weighted by mathematical methods, in particular by the use of a so-called Kalman filtering.

This evaluation of the occurring signal vibrations and the parameters calculated from them allow the following procedure. Various events trigger characteristic sound waves that cause vibrations in the structure-borne sound signal. With the described procedures it is recognized when this oscillation occurs and / or with which of the reference signals there is a great similarity. In the former, the temporal position and / or the angular position is determined in the second method, we determined a correlation coefficient.

The block 33 includes the evaluation of the measured structure-borne sound signals and / or the integral values. In this case, a start time in the signal is detected by the exceeding of a defined, operating point-dependent threshold value. Based on the parameters calculated using this method, the times at which an inlet valve and / or an outlet valve closes and / or opens, the top dead center occurs, the individual partial injection start or end and / or the combustion begins or ends are detected. Preferably, a corresponding time is detected when the corresponding filtered signal exceeds certain thresholds. It is provided that the filtering of the structure-borne sound signal and the reference values for the different sizes are selected differently.

In addition to pressure changes due to combustion, sound waves through engine attachments and / or ancillary components influence the structure-borne sound signal. The actuation of the intake valves and / or the exhaust valves causes mechanical vibrations, which are recognized by the structure-borne sound sensor as a characteristic oscillation in the waveform. According to the invention, the angular ranges of the structure-borne noise signals in which these vibrations preferably occur are filtered out by means of the fenestration 2 and / or the FIR filter. By evaluating the correspondingly filtered signal, the angular positions are determined at which the inlet and / or outlet valves open and / or close. According to the invention, the variables determined in this way are fed as actual value to a control, which, starting from a comparison of these actual variables with a desired value, determines a corresponding manipulated variable which is used to act on an actuating element which actuates the inlet and / or outlet valves. In this case, the time position and / or the angular position can be determined directly. Further, by associating the measured signal with the reference signals, the occurring vibration is assigned to a particular event or condition. Thus, it is recognized that a measured vibration correlates with the closing or opening of the valve.

In the region of top dead center, a characteristic oscillation occurs at fixed angular positions in the signal curve. This is recognized by the evaluation 32 detected and used for example for OT detection and calibration.

The onset of combustion causes a vibration in the structure-borne sound signal. The detection of the beginning of the combustion and thus of the ignition delay makes it possible to control the start times of the injection.

Furthermore, it can be concluded by the detection of the start of combustion of the main injection to the pilot injection, since the pilot injection significantly affects the ignition delay of the main combustion. According to the invention, the variables determined in this way are fed as actual value to a control, which, starting from a comparison of these actual variables with a desired value, controls a corresponding manipulated variable which controls an actuating element which controls the start and / or drive duration of pilot, main and post-injections.

The analysis of the structure-borne sound signals by means of the blocks 1, 2, 3, 4 and 5 provides a number of characteristics, which is determined by the number of measurement windows times the number of injections per injection cycle. The processing of these parameters is shown in FIG.

The evaluation of the structure-borne sound signals shown in FIG. 4 is carried out in the controller 6. The variables In1 to Inx correspond to the output signals of the blocks 5a, 5b and 5c. Inc denotes the reference signal or reference signal. The number x of the input variables In1 to Inx preferably corresponds to the number of partial injections times the number of measuring windows per partial injection.

It can thus be provided that an averaging takes place via a plurality of characteristic variables in the same injection, an averaging via the injection into a plurality of cylinders and / or an averaging over a plurality of partial injections. In addition to averaging, other statistical quantities, such as the variance, can be determined.

Furthermore, it can be provided that a comparison and / or an evaluation of the parameters different windows within a cycle with each other.

Also, comparing and / or evaluating the characteristics of the various windows from cycle to cycle is advantageous.

It is particularly advantageous if a comparison and / or an evaluation of the characteristics of the various windows takes place with reference signals Inc which were measured under defined conditions.

The pre-injection drastically influences the noise and exhaust emissions due to the strong influences on the combustion process. This affects the ignition delay as well as the gradient of the cylinder pressure curve. The structure-borne sound signal is a direct measure of the changes occurring in the cylinder pressure. The parameters calculated from the structure-borne sound signal for the pre-combustion and / or the main combustion show a clear dependence on the pre-injection quantity. The effects of the pilot injection on the structure-borne noise signal can be used for an optimization of the pre-injection. Optimization means a reduction or increase of the Pre-injection quantity while maintaining defined ignition delays and cylinder pressure gradients.

For the comparison and the evaluation, the relationship is used that the turnover speed or the injected fuel quantity influence the parameters. Larger amounts of fuel or faster conversion speeds affect the signal intensity in different frequency ranges. Filtering, amount formation and integration identify these influences. The comparison of the signals with each other or with parameters that were determined under reference conditions provide the connection sought to the injected fuel quantity and the times of the individual injections and thus allow their regulation.

The evaluation according to path 1-2-3-4-5 from Fig.1 subdivides both the main injection and the pilot injection into different measurement windows, in each of which the evaluation takes place. The result, in particular the signal value integrated via the measuring window, corresponds to a combination of integrator values which is characteristic for this operating point. An increase in the pilot injection quantity leads to a stronger pre-combustion, a previous and slower main combustion. This has the effect on the integrator values of the pilot injection that generally higher values occur. In the case of the main combustion, the integrator values of the earlier measurement windows increase because the main combustion takes place earlier. The values of the mean measured values decrease because the burning speed is lower. According to the invention, the times and injection quantities are concluded by comparing the measured pattern with the patterns determined under reference conditions.

According to the invention, at least one of the parameters In is determined. This characteristic is fed as actual value to a control. The setpoint used is the corresponding characteristic variable Inc, which occurs when a pre-injection takes place with an optimum pre-injection quantity. If the parameters measured during operation deviate from the parameter with optimum pre-injection, the controller influences the pre-injection quantity via the manipulated variable Out in such a way that the difference between the setpoint and the actual value is reduced.

A particularly advantageous embodiment is shown in FIG. At least two filtered signals In1 and In2, through appropriate filtering and signal processing By means of blocks 1 to 5, a quotient formation 50 is obtained. The output signal Ka, which represents a parameter, arrives at a controller 52 at whose second input the reference signal Inc is present. This reference signal Inc is provided by a setpoint input 54.

In the following, the procedure of the embodiment of Figure 5 will be described using the example of a pilot injection and a main injection. The procedure is not limited to this combination. It can be used in any combination of partial injections, that is, a first partial injection and at least a second partial injection (see above). Instead of the output signal of blocks 1 to 5, a parameter Ka determined from this can also be used. This means that a variable calculated from several sizes In can also be used.

By filtering, a first value In1, which characterizes the noise emission of the pilot injection, and a second value In2, which characterizes the noise emission of the main injection, are determined. This results in a division of the characteristic Ka. This corresponds to the ratio between the parameter for the pilot injection and the characteristic for the main injection. Based on this parameter, which corresponds to the ratio between pilot injection and main injection, then the specification of the manipulated variable Outc. That is, the duration of the pilot injection is set depending on the ratio of the noise emission in the pilot injection and the noise emission in the main injection. This means that a third parameter is determined by dividing two parameters.

In this particularly advantageous embodiment, new characteristics are determined by dividing the characteristics among each other. Two characteristic quantities K1 and K2 are in particular determined by filtering in at least one angular range and the quotient K3 = g * K1 / K2 is formed, where g represents an additional weighting factor. By dividing the two characteristics that characterize the intensity of the sound emission in the two sub-areas, the actual parameter is then determined by ratio formation, which is independent of absolute signal values and thus of sensor tolerances and sensor drifts.

These angular ranges are, for example, areas a, which are characteristic of certain partial injections, such as the pre-injection and the main injection are areas b which are characteristic of certain partial injections under certain process conditions, areas c where no combustion takes place and / or areas d where characteristic disturbances like valve rattling take place.

Preferably, the quotients of the characteristics between the regions which are characteristic for the pre-injection and the regions which are characteristic of the main injection are considered. Alternatively or additionally, the quotients of the parameters are formed between regions with injection and regions without injection. Furthermore, the characteristics of areas between which the weight of the partial burns shifts depending on the process conditions can be considered.

It is particularly advantageous if the manipulated variable is determined by means of a control. For this purpose, the parameter Ka is compared with a nominal value Inc. Depending on the comparison, the manipulated variable will then be specified. In this case, a constant setpoint or a setpoint dependent on the operating state can be specified.

As an alternative to regulation, an addaptive control can also be provided. In certain operating states, the parameter Ka is compared with the setpoint Inc. Based on the comparison, a correction variable is determined and stored. With the stored correction value, the manipulated variable is corrected in the other operating states.

Claims (7)

1. Method for controlling an internal combustion engine, in which characteristic variables which are used to perform open-loop control of the internal combustion engine are obtained on the basis of the signal of a solid-borne sound sensor, wherein at least one characteristic variable is obtained by an evaluation which includes filtering which selects at least two angular ranges per injection, characterized in that at least two characteristic variables are obtained for the at least two angular ranges, in that a third characteristic variable is determined by dividing two characteristic variables, and in that the third characteristic variable is compared with a setpoint value and a manipulated variable is predefined or corrected on the basis of the comparison.
2. Method according to Claim 1, characterized in that the manipulated variables influence the injection and/or the position of the inlet and/or of the outlet valves.
3. Method according to one of the preceding claims, characterized in that a correlation coefficient is obtained as a characteristic variable by means of a cross correlation, said correlation coefficient characterizing the deviation of the measured signal from a reference signal.
4. Method according to Claim 1, characterized in that the reference signal corresponds to the solid-borne sound signal in preferred states.
5. Method according to one of the preceding claims, characterized in that the angular position of the crankshaft and/or of the camshaft at which specific events occur serves as a characteristic variable.
6. Method according to one of the preceding claims, characterized in that the characteristic variable characterizes the intensity of the signal in specific angular ranges.
7. Device for controlling an internal combustion engine, in which characteristic variables which are used to perform closed-loop, control of the internal combustion engine are obtained on the basis of the signal of a solid-borne sound sensor, in that filtering which selects at least two angular ranges per injection, and having means which determine at least one characteristic variable on the basis of the filtered signals, characterized in that means are provided which determine at least two characteristic variables for the at least two angular ranges, which determine a third characteristic variable by dividing two characteristic variables and compare the third characteristic variable with a setpoint value and predefine or correct a manipulated variable on the basis of the comparison.

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