Method for robust knock identification in an internal combustion engine, controller and motor vehicle

Abstract

The invention relates to a method for automatically recognizing knock in an internal combustion engine having a plurality of cylinders, variable intake valve lift and knock sensors. The invention further relates to a corresponding controller and a motor vehicle equipped with the controller. In the method, the internal combustion engine is operated in such a way that the intake valves are closed while still in the intake stroke. Here, the sensor signals of the knock sensors are received in a predefined measurement time window and are analyzed in terms of criteria for detecting knock. Here, a predefined base threshold for knock recognition is modified by means of a predefined variable disturbance factor, which depends on the relative timing of the intake valve closure of at least one of the cylinders relative to a predefined reference point. A knock is only recognized when the signal based on the sensor signal at least reaches the modified base threshold.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for automatically recognizing knock in an internal combustion engine, a correspondingly designed controller and a motor vehicle equipped with the controller. BACKGROUND

[0002] Internal combustion engines have been known for a long time, but there is always an interest and a demand for further improvements, for example, in terms of efficiency and reliability. A known problem is the so-called knock, which can occur under certain conditions due to irregular or uncontrolled combustion in the cylinder volume at correspondingly high pressures and temperatures by means of an additional igniter. Such a knock can lead to knock damage, which can range from damage to the piston to significant engine damage, i.e. to a corresponding failure of the internal combustion engine. Therefore, there have been approaches for automatically recognizing knock by means of a corresponding knock sensor, which can detect, for example, acoustic signals caused by a knock. If a knock is detected, the ignition angle or the ignition time can then be adapted, for example, in order to avoid further knocks. However, it can be problematic here that the knock sensor can not only detect signals caused by an actual knock, but also a large number of foreign signals or control signals from other sources and thus make reliable recognition of a knock difficult.

[0003] A method for adjusting knock in an internal combustion engine having at least one cylinder is described, for example, in AT 517396 B1. Here, the at least one cylinder is equipped with an intake valve, wherein, when a knock occurs in the at least one cylinder, the knock in the cylinder is reduced by actuating the intake valve belonging to the cylinder recognized as a knock in such a way that the temperature of the charge in the cylinder is reduced. When the intake valve belonging to the cylinder recognized as a knock is actuated in this way, cylinder-specific and / or global measures are taken to compensate for the power of the internal combustion engine. Here, for example, the corresponding intake valve can be closed earlier in the intake stroke by means of a variable valve train. Likewise, the temperature of the cylinder charge can be reduced to avoid a knock by delivering an increased amount of cooled exhaust gas to the cylinder in question. Therefore, in particular, an efficiency loss should be avoided in the knock adjustment range.

[0004] A valve fault detection is addressed in DE 112 01 0 004 825 B4. For this purpose a method is described in which an engine having a plurality of cylinders is operated in a cylinder cut-off mode. There the expected useful torque during an operating window is estimated by means of a torque model. In addition, parameters are measured which are indicative of the actual engine torque during the operating window. Then, based on a comparison of the measured parameters with expected parameter values based on the expected useful torque, it is determined whether a valve actuation fault occurred within an engine cycle. Within the scope of this method an accelerometer can also be used as knock sensor. A knock causes a corresponding vibration pattern of the engine and thus a feature in the output signal of the accelerometer which is related to the knock. Thus, by searching for the knock feature in the corresponding frequency range the engine knock can be detected.

[0005] In DE 112 01 0 004 825 B4 a control device for an internal combustion engine is described which comprises an intake pipe temperature transition characteristic calculation device for evaluating a transition characteristic of an intake pipe temperature based on a flow rate of gas flowing into the intake pipe, a flow rate of gas flowing out of the intake pipe, an intake pipe pressure, and a time change rate of the intake pipe pressure. Thus, a control device for an internal combustion engine should be provided which is able to accurately evaluate the characteristic of the intake pipe temperature during a transition time even in an internal combustion engine having a variable valve or a turbocharger. Thus, for example, a brief knock can be appropriately prevented by a calculation of a time of day during a transition time of the internal combustion engine based on the evaluated transition characteristic of the intake pipe. Thus, the problem should be avoided that a correction amount is determined empirically in order to appropriately prevent a brief knock is too cost-intensive because in a typical internal combustion engine a large number of actuators are working which can lead to an innumerable number of superimposed acceleration patterns. SUMMARY

[0006] It is the task of the present invention to enable a particularly reliable or robust knock recognition of an internal combustion engine.

[0007] For this purpose the present invention proposes a method for automatically recognizing a knock in an internal combustion engine having a plurality of cylinders, a variable intake valve lift and a knock sensor, in which method

[0008] - the internal combustion engine is operated in a manner that the intake valve is closed before the end of the intake stroke,

[0009] - a sensor signal received by the knock sensor in a predefined measurement time window is analyzed in terms of predefined criteria for detecting a knock, based on which a signal of the sensor signal must reach at least one predefined base threshold in order to be recognized as a knock,

[0010] - modifying the base threshold value by means of a predefined variable disturbance factor, which depends on the relative timing of the closing of the intake valve of at least one of the cylinders relative to a predefined reference point, and

[0011] - identifying the signal as a knock only if it at least reaches the modified base threshold value,

[0012] wherein the disturbance factor is modified by means of a predefined operating time factor, which increases with increasing operating time of the internal combustion engine and accordingly reduces the disturbance factor.

[0013] The application further proposes a controller for an internal combustion engine for automatically detecting knocks, wherein the controller comprises an input interface for detecting a sensor signal of a knock sensor, a data memory and a processor device connected to the data memory for processing the sensor signal and an output interface for outputting a detection signal indicating a detection of a knock, and is designed to implement the method according to the application.

[0014] The application further proposes a motor vehicle having an internal combustion engine having a plurality of cylinders, a variable intake valve lift, a knock sensor and a controller according to the application.

[0015] The method according to the application serves to automatically identify a knock in an internal combustion engine having a plurality of cylinders, a variable intake valve lift and at least one knock sensor. The internal combustion engine can be, for example, a drive engine of a motor vehicle. In the method, the internal combustion engine is operated in such a way that the intake valves of the cylinders are closed already during the respective intake stroke, i.e. before the end of the intake stroke. Here, the intake valves of the cylinders are closed before the respective bottom dead center or reversal point of the respective piston or of the respective connecting rod and crankshaft connected thereto. Thus, in the operation, the compression in the cylinders is less than the respective expansion in the following working stroke. For example, the internal combustion engine can thus be operated in the manner of a so-called Miller cycle or Miller operation. Further, in the method according to the application, the sensor signal received by the knock sensor in a predefined measurement time window is analyzed in terms of predefined criteria for detecting a knock. Here, the measurement time window is shorter than the respective period or cycle time of the internal combustion engine. For example, the measurement time window can cover an angular range of between 30° and 60° with respect to the rotational movement of the crankshaft of the internal combustion engine.

[0016] It is also possible to predefine, i.e. define, a plurality of measurement time windows, for example an early injection measurement time window and a main measurement time window, which can partially overlap or adjoin one another. The predefined measurement time windows can for example start at a crank angle or crank motion of approximately 20° after the respective top dead center of the cylinder. The measurement time windows of the plurality of cylinders can thus be considered relatively, i.e. at the same time, absolutely, but at different times, with respect to their respective top dead center. Since only the sensor signals received in the respective measurement time window are analyzed for detecting or recognizing knock, a particularly efficient and effective knock recognition can be achieved, since for example the data processing effort is limited and extraneous signals or interference signals outside the respective measurement time window in which knock can occur are automatically disregarded. For recognizing knock, the sensor signals or signals based on the sensor signals or the output of the knock sensor must reach or exceed at least one predefined base threshold. As a result, most of the unavoidable external noise or interference noise and hum, which can for example originate from the operation of the internal combustion engine, if necessary the operation of the surrounding components and / or from other external influences, can already be effectively filtered out.

[0017] It has however proven that, due to the phase-shifted movement of the cylinders relative to one another, in particular when the internal combustion engine is operated with the described early intake valve closure or in or with a Miller cycle, the intake valve closure, i.e. the time of the intake valve closure, of one cylinder can fall into the measurement time window for knock recognition of another cylinder. It is therefore provided in the method according to the application that the base threshold for knock recognition is modified by means of a predefined variable disturbance factor, which depends on the relative time of the intake valve closure of at least one of the cylinders relative to a predefined reference point. The reference point can for example be a defined reference time or a reference event or the time of a reference event, for example the respective top dead center. The relative time of the intake valve closure can then for example be given by a defined crank angle after the predefined reference point, wherein the respective current rotational speed of the internal combustion engine can also be taken into account. The reference point can for example indicate when the maximum stroke or the zero position is reached in the respective cylinder, i.e. generally the position or the position state of the crankshaft or the respective piston. For detecting the reference point, a respective sensor, for example a sensor wheel or the like, can be provided.

[0018] In order to modify the base threshold value, this base threshold value can be multiplied, for example, by a corresponding interference factor, wherein the interference factor can be greater than 1, in particular. The resulting modified base threshold value can thus be greater than the initially predefined base threshold value, in particular. Here, it can be taken into account by means of the interference factor that the closing of the intake valve can generate a signal, for example an acoustic signal or a vibration signal, which can be detected by the knock sensor in at least a portion of the internal combustion engine, and that the closing of the intake valve of one cylinder can fall into the measurement time window for the normal knock recognition of another cylinder in the Miller operation of the internal combustion engine. The closing of the intake valve of one cylinder can thus interfere with or influence the knock recognition of another cylinder. Since the intake valve lift of the internal combustion engine is variable and the closing of the intake valve can be carried out accordingly depending on the actuation at different relative times, a particularly accurate, reliable and robust knock recognition can ultimately be achieved by means of the corresponding variability of the interference factor. Since the closing of the intake valve is controlled, its corresponding time is here at least essentially known, i.e. used or taken into account without problems in the context of the knock recognition, for example by means of a correspondingly designed controller.

[0019] Furthermore, in the method according to the application, a sensor signal or a signal based on the sensor signal is only recognized as a knock, i.e. as a signal caused by uncontrolled combustion in the corresponding cylinder, when it reaches or exceeds at least the corresponding modified base threshold value.

[0020] The application is based, in particular, on the recognition that in the described operating mode or the described operating mode, by means of the correspondingly early closing of the intake valve and since the closing of the intake valve can be achieved at different relative times by means of variable intake valve lift, i.e. corresponding valve train control, the normal knock recognition can be disturbed or influenced in a correspondingly different degree or in different ways. In correspondence therewith, the conventional use of a constant base threshold value can lead to a false recognition of a knock or a signal or an event, or, if the base threshold value is chosen to be too high, to an undetected real knock. By means of the corresponding control of the internal combustion engine, a false recognition of a knock can thus lead to unreasonable Zündwinkelrückzügen and thus to an ultimately unnecessary increase in consumption, emissions and component loads due to the increased exhaust gas temperature and to an adverse effect on the driving behavior of a motor vehicle equipped with the internal combustion engine. The undetected recognition of a real knock can lead to an intensification of the knock damage, i.e. for example to piston damage or to a complete failure of the internal combustion engine. These problems can be avoided or mitigated by means of the application.

[0021] For detecting the signal, the knock sensor can comprise, for example, a piezoelectric element which outputs an electrical voltage, i.e. an electrical voltage signal, as a sensor signal. The electrical voltage varies with the sound waves or vibrations impinging on the knock sensor or the piezoelectric element. Although the application is described here for simplicity's sake only with reference to one single knock sensor, a plurality of knock sensors can be arranged spatially distributed on the internal combustion engine and their signals used, i.e. evaluated, in a corresponding manner. For example, one respective knock sensor can be provided for each cylinder or, for example, for each two adjacent cylinders.

[0022] The evaluation of the sensor signal and thus the knock identification described here can be carried out in each cycle, i.e. in each working cycle of the engine or of the respective cylinder.

[0023] In a possible design of the application, for the evaluation, the sensor signal is filtered by means of a predefined bandpass filter. The filtered sensor signal thus derived is then integrated over a measurement time window, i.e. in terms of its time or duration. The integral value thus produced is then compared with a modified base threshold value. This is a practical and possible solution for relatively simply implementing a signal-based knock identification. Here, too, the measurement time window can be divided into a plurality of sections or segments, for which the method is used separately. Depending on the relative timing of the intake valve closure, a modified base threshold value can then be used for one or more of the sections or segments and the originally predefined base threshold value for the remaining sections or segments as a comparison variable for the knock identification. In this way, it can be taken into account in particular simply and effectively that the intake valve closure and thus the disturbance signal caused by the intake valve closure does not necessarily occur over the entire measurement time window. In this way, a further improved, i.e. more accurate or more reliable, knock identification can be achieved if necessary.

[0024] In another possible design of the application, an individual disturbance factor is predefined for each cylinder and used for the evaluation. It can be taken into account in this way that different cylinders can have different acoustic or vibration characteristics, for example due to microscopic differences in the region of the intake valves, material differences, manufacturing tolerances, the relative arrangement of the knock sensors and / or more similar reasons. Each cylinder can thus have an individual signal characteristic which can be taken into account by a correspondingly matched individual disturbance factor. For example, a standard disturbance factor can first be predefined for all cylinders, which can be individually matched to each of the cylinders from the measured values or sensor signals of the knock sensors. Overall, in this way, the knock identification can be further improved.

[0025] In another possible design of the application, for the recognition of signals as knock, an adaptive mechanism is used which is designed to learn over time that extraneous signals (i.e. external noise or interference noise) which are not produced by actual knock (i.e. not by uncontrolled combustion in the cylinder) and which are not to be considered for the recognition of knock. The mechanism for the recognition of knock can for example recognize extraneous signals on the basis of their time of occurrence or the corresponding time interval of their occurrence by means of peak values or signal shapes and / or the like, which are not related to the relative time position of the measurement time window or the corresponding change. For example, extraneous signals with a constant frequency can also occur with respect to the varying rotational speed of the internal combustion engine or always in the exact same time interval from a determined, predefined reference point, which is not in agreement with the case of knock as the cause. The recognized extraneous signals can for example be filtered out of the sensor signals automatically before a further analysis process, i.e. the actual recognition of knock, is carried out on the basis of the thus remaining residual signal. The adaptive mechanism can for example be implemented as a self-learning algorithm or by means of a machine learning device. In this way, the recognition of knock can be improved automatically, especially in the background that a corresponding manual programming of the recognition of knock with all actually or potentially occurring extraneous signals is not practical.

[0026] In a possible further development of the application, the disturbance factor is reduced in a predefined manner, especially gradually or stepwise, as the adaptability of the mechanism increases. In other words, the disturbance factor or its application on the underlying threshold is gradually faded out over the operating time of the internal combustion engine during which the mechanism learns to recognize external signals. This can for example be implemented according to a predefined ramp function or the like. Thereby, it can be taken into account that the adaptive mechanism will also learn, i.e. recognize, the disturbance or the disturbance signal caused by the intake valve closing as an extraneous signal. By means of the correspondingly trained adaptive mechanism, false recognitions of knock can then be avoided or reduced. At the same time, by gradually or progressively reducing the disturbance factor, the modified underlying threshold can be reduced to the initially predefined underlying threshold, whereby the risk of not recognizing a relatively weak, apparent deflagration can be reduced.

[0027] In a possible further development of the application, the reduction rate of the disturbance factor or the application of the disturbance factor or the influence on the base threshold is changed in dependence on the rotational speed of the internal combustion engine. Thus, the reduction of the disturbance factor can be accelerated or slowed down in the respective reduction phase. For example, in the case of a lower rotational speed, in particular in the case of a simultaneously relatively high load, the reduction, i.e. the drop, of the disturbance factor can be slowed down. The design proposed here is based on the knowledge that the disturbance of the knock recognition caused by the intake valve closure can be more severe or more important in this operating state of the internal combustion engine than in the case of a higher rotational speed and / or a smaller load.

[0028] In a further possible design of the application, the disturbance factor is modified by a predefined operating time factor which increases with increasing operating time of the internal combustion engine or with increasing number of work cycles carried out or experienced by the internal combustion engine and reduces the disturbance factor accordingly. In other words, the disturbance factor is reduced to an increasingly greater extent with increasing operating time of the internal combustion engine or with increasing number of work cycles carried out or experienced. Thereby, it can be taken into account that the impact of the intake valve into its valve seat changes over time, burrs, unevennesses or mismatches change over time, i.e. an adaptation or aging process of the intake valve usually occurs. This leads to a reduction of the disturbance effect of the intake valve closure on the knock recognition with increasing operating time. By the here predefined modification of the disturbance factor based on the operating time or the running time, it is thus possible to maintain a reliable and robust knock recognition over time, although the respective characteristics of the internal combustion engine can change here.

[0029] In another possible design of the application, for the analysis processing a variable hysteresis factor is predefined, which takes into account an interference signal coverage caused by the intake valve closure of one of the cylinders, which influences the sensor signal received by the knock sensor, for a disturbance time period, which is movable, i.e. can be shifted in time, with respect to the measurement time window for the knock identification. Here, the hysteresis factor defines for which part range of the measurement time window the interference factor is used or to what extent it is used. In other words, the intake valve closure does not produce or does not always produce a clearly defined single peak, but can be characterized, i.e. described, by a broadened, if necessary, including multiple peak or envelope signal shape. This can be caused, for example, by the intake valve gradually seating on its respective valve seat or the vibrations occurring here after the first contact with the valve seat and / or after the intake valve has seated on the valve seat. Since the seating of the intake valve on its respective valve seat does not always take place in exactly the same way, the signal shape resulting therefrom can be shifted completely or partially into or out of the measurement time window. This can also be determined or influenced by the relative timing of the intake valve closure, i.e. the respective spread. By means of the hysteresis factor, this can be taken into account and thus make the knock identification even more accurate, more reliable and more robust.

[0030] Another aspect of the application is a controller for an internal combustion engine, in particular of a motor vehicle, for automatically detecting, i.e. identifying, knock in the internal combustion engine or in at least one cylinder of the internal combustion engine. Here, the controller comprises an input interface for detecting a sensor signal of a knock sensor, a data memory and a processor device connected to the data memory for processing the sensor signal and an output interface for outputting a detection signal indicating the detection of knock. Here, the controller is designed to automatically implement at least one variant or embodiment of the method according to the application. For this purpose, a corresponding program code or a corresponding computer program representing, i.e. encoding or implementing, the method steps, processes or measures of the respective method can be stored on the data memory. The computer program can then be executed by the processor device in order to cause the implementation or execution of the respective method.

[0031] Another aspect of the application is a motor vehicle having an internal combustion engine with a plurality of cylinders, a variable intake valve lift, at least one knock sensor and a controller according to the application. In other words, the motor vehicle according to the application can thus be designed to implement or apply the method according to the application. In particular, the motor vehicle according to the application can be the motor vehicle described in connection with the remaining aspects of the application.

[0032] Correspondingly, the components or parts mentioned in connection with the different aspects of the application, i.e. the method according to the application, the controller according to the application and the motor vehicle according to the application, can also be respectively the same or identical components or parts or refer to the same or identical components or parts, respectively.

[0033] Further features of the application can be gathered from the figures and the figure description. The features and feature combinations mentioned in the above description and in the figures and / or only shown in the figures, can be essential for the application either alone or in the respective combination, and are therefore claimed in the claims. BRIEF DESCRIPTION OF DRAWINGS

[0034] The figures show a schematic view of a motor vehicle with knock recognition in a single figure. DETAILED DESCRIPTION

[0035] Figure 1 A schematic view of a motor vehicle 10 with an internal combustion engine 12, which can be a gasoline engine, in particular, is shown, which is operated or operable with an intake valve closure at the end of the intake stroke in each working cycle, that is to say, in particular, with a Miller cycle or Miller operation. The internal combustion engine 12 comprises a plurality of, for example, four or six, cylinders 14, of which two are shown here by way of example. In particular, this is a first cylinder 16 with a first piston 18 and a second cylinder 20 with a second piston 22. The pistons 18, 22 are here connected to a schematically shown crankshaft 24. By way of example, the first piston 18 is here in the vicinity of the firing position, while the second piston 22 is on its path toward its bottom dead center.

[0036] The cylinders 14 each have an intake valve 26 with a controlled variable valve mechanism 28. The variable valve mechanism 28 is connected to a controller 30 for control purposes.

[0037] The controller 30 has here a data memory 32 and a processor 34 connected thereto for executing an operating or control program stored on the data memory 32, which is shown here schematically. The processor 34 can be, for example, a microchip, a microprocessor, a microcontroller, a hardware circuit and / or comprise such a microchip, microprocessor, microcontroller, hardware circuit, etc. Furthermore, the controller 30 has an input interface 36 via which a knock sensor 38 of the internal combustion engine 12 is connected. Thus, via the input interface 36, the controller 30 can detect a sensor signal received or provided by the knock sensor 38 for processing by means of the processor 34 and the data memory 32.

[0038] Here, the controller 30 is designed to recognize knock on the basis of the detected sensor signal of the knock sensor 38. If knock is recognized, the controller 30 can actuate the intake valve 26 or rather its variable valve train 28 by means of the output interface 40, for example, in order to avoid or reduce further knock.

[0039] Especially in supercharged gasoline engines, significant disturbances can occur in the knock recognition or detection of gasoline engines in connection with the Miller cycle, i.e. in the Miller combustion method, due to the early intake valve closing occurring here. The intake valve closing, in the present case for example of the intake valve 26 of the second cylinder 20, can cause a solid sound. Said solid sound, which is caused by the intake valve 26 seating into its valve seat and / or by the mechanical relaxation of the variable valve train 28 upon closing of the intake valve 26, can lead to a corresponding disturbance signal in the sensor signal of the knock sensor 38, since the solid sound or the acoustic signal originating from the intake valve 26 can reach the knock sensor 38, for example by a corresponding propagation or transmission in the housing or component of the internal combustion engine 12 in which the knock sensor 38 is arranged. Such a disturbance signal has a significant negative effect on the knock recognition, so that for an accurate, reliable and robust knock recognition, such a disturbance signal should be largely eliminated or filtered out. This is achieved in the present case by means of the automatic processing of the sensor signal of the knock sensor 38 by the correspondingly designed controller 30.

[0040] In the present case, for this purpose a reference variable can be predefined, which outputs the respective time of the intake valve closing of the intake valve 26 by means of the course of the camshaft of the internal combustion engine 12 and the respective current extension (which defines the base position of the camshaft). This can be achieved for example by means of the current angular position of the crankshaft 24 relative to the respective top dead center. From said reference variable, i.e. the respective time of the intake valve closing, a cylinder-specific disturbance factor can be applied to the predefined base threshold value, i.e. to the knock threshold value for the knock recognition in the predefined measurement time window, for example in the main time window and in the pre-ignition measurement time window. For this purpose, for example a respective family of characteristic curves can be predefined with respect to the relative cylinder charge and the rotational speed of the internal combustion engine 12, for example stored in the data memory 32. Said pre-ignition measurement time window can for example start at a crankshaft angle of 0° at the top dead center and extend for example over a crankshaft movement of 20°. Subsequently or overlappingly, said main measurement time window can extend for example up to a crankshaft angle of 60° to 70°.

[0041] By means of the hysteresis value it is possible to take into account the respective point in time of the intake valve closure or the shift of the disturbance signal due to the intake valve closure with respect to the measurement time window. The hysteresis value can be understood as a characteristic value with respect to the angular position of the crankshaft 24 which defines or takes into account at which point the disturbance signal extends or how the disturbance signal occurs or moves in time with respect to the measurement time window. In this way it is possible to take into account that the intake valve closure is not completely constant, but finally only the region defined by the predefined measurement time window should be taken into account for the knock identification.

[0042] Especially when using an adaptive or learnable mechanism for the knock identification, the initially used cylinder-specific disturbance factor can be reduced in time, i.e. be reduced again in the signal processing. Such a mechanism can learn over time and filter out or disregard for the actual knock identification noises and disturbance noises which are not caused by actual knockings or actual unavoidable background noises (Grundrauschen) in the operation of the internal combustion engine 12. This reduction, i.e. the stepwise or gradual reduction, can be achieved for example over several hundred working cycles of the internal combustion engine 12. Here, the reduction of the disturbance factor can be varied in relation to the respective current rotational speed of the internal combustion engine 12, i.e. slowed down or accelerated. For this purpose, for example a respective characteristic curve with respect to the rotational speed can be predefined, in particular stored in the data memory 32.

[0043] Likewise, the disturbance factor can be modified, for example multiplied, by means of a predefined operating time factor which takes into account aging, i.e. a change over time, and with increasing operating time or aging of the internal combustion engine 12 the disturbance factor is reduced more and more. Here, the actual operating time of the internal combustion engine 12 or the number of actually experienced working cycles is not related to the operating time of the motor vehicle 10 for example. That is to say, the operating time factor can be reset for example when replacing the internal combustion engine 12 or when replacing the intake valve 26 for the motor vehicle 10.

[0044] Overall, the described examples show how it is possible to reduce the influence of mechanical disturbance quantities (here: intake valve closure) on the knock identification when analyzing the combustion of a gasoline engine.

[0045] List of reference signs

[0046] 10 motor vehicle

[0047] 12 internal combustion engine

[0048] 14 cylinder

[0049] 16 first cylinder

[0050] 18 first piston

[0051] 20 second cylinder

[0052] 22 second piston

[0053] 24 crankshaft

[0054] 26 intake valve

[0055] 28 variable valve mechanism

[0056] 30 controller

[0057] 32 data storage

[0058] 34 processor

[0059] 36 input interface

[0060] 38 knock sensor

[0061] 40 output interface

Claims

1. A method for automatically identifying knock in an internal combustion engine (12) having multiple cylinders (14), variable intake valve lift, and a knock sensor, wherein in the method, - The internal combustion engine (12) is operated in such a manner that the intake valve is closed before the end of the intake stroke. - The sensor signal received by the detonation sensor (38) within a predetermined measurement time window is analyzed and processed according to a predetermined standard for detecting detonation. The signal based on the sensor signal must reach at least one predetermined basic threshold in order to be identified as detonation. - The base threshold is modified by means of a pre-given variable disturbance factor, which depends on the relative time of the closing of the intake valve (26) of at least one of the cylinders (14) with respect to a pre-given reference point, and - The signal is identified as detonation only if it reaches at least the modified base threshold. in, The interference factor is modified by a pre-given operating time factor, which increases as the operating time of the internal combustion engine (12) increases and the interference factor decreases accordingly.

2. The method according to claim 1, characterized in that, For analysis and processing, the sensor signal is filtered using a pre-defined bandpass filter. The resulting filtered sensor signal is integrated over a measurement time window, and the resulting integrated value is compared with a modified base threshold.

3. The method according to claim 1 or 2, characterized in that, Each cylinder (14) is given a separate interference factor in advance and the separate interference factor is used for the analysis process.

4. The method according to claim 1 or 2, characterized in that, An adaptive mechanism is used to identify signals as detonation. This adaptive mechanism is designed to learn over time that the signals are not generated by detonation and does not take into account the foreign signals for detonation identification.

5. The method according to claim 4, characterized in that, As the adaptability of the mechanism increases, the interfering factors are reduced in a pre-defined manner.

6. The method according to claim 5, characterized in that, The reduction rate of the disturbance factor is changed according to the rotational speed of the internal combustion engine (12).

7. The method according to claim 1 or 2, characterized in that, For the purpose of the analysis, a hysteresis factor is given in advance, which takes into account the interference signal covering the interference period caused by closing the intake valve (26) of one of the cylinders (14) and affecting the sensor signal received by the knock sensor (38). The interference period is movable relative to the measurement time window used for knock identification, and the hysteresis factor defines which part of the measurement time window to use the interference factor.

8. A controller (30) for automatically detecting knock in an internal combustion engine (12), wherein, The controller (30) includes an input interface (36) for detecting sensor signals from the detonation sensor (38), a data storage (32), a processor device (34) connected to the data storage for processing the sensor signals, and an output interface (40) for outputting and displaying the detection signal of the detonation detection, and is designed to implement the method according to any one of claims 1 to 7.

9. A motor vehicle (10) having an internal combustion engine (12) having a plurality of cylinders (14), a variable intake valve lift, a knock sensor (38) and a controller (30) according to claim 8.

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