Abstract: Provided is a knocking detection apparatus capable of reducing erroneous determination of knocking during transition, and improving knocking detection accuracy regardless of whether an engine is in steady operation or transient operation. A knocking detection apparatus according to the present invention estimates a background level based on an operating state of an internal combustion engine, and calculates a knocking determination index by using the estimated value.

Abstract: A control device for controlling an engine including an injector that supplies fuel into a cylinder and an in-cylinder pressure sensor that detects an in-cylinder pressure being a pressure inside the cylinder, is provided. The device includes a processor configured to execute an abnormal combustion determining module to determine whether combustion of a mixture gas inside the cylinder is abnormal based on a detection value of the in-cylinder pressure sensor. The abnormal combustion determining module determines that an abnormal combustion has occurred in which progress of the combustion of the mixture gas is excessively fast, when an in-cylinder pressure intensity that is a spectrum value of a frequency component of an in-cylinder pressure waveform less than a given reference frequency is greater than or equal to a given determination intensity, the in-cylinder pressure waveform being detected by the in-cylinder pressure sensor.

Abstract: A method and a device are provided for knock recognition of an internal combustion engine, which device Fourier-transforms, weights in frequency-dependent fashion, and sums a signal of a knock sensor in order to produce a first knock signal. Here, from a multiplicity of first knock signals, a concentration point of the multiplicity of the first knock signals is determined, and a first offset value is subtracted from the first knock signal in order to form a second knock signal, the first offset value being ascertained from the concentration point of the multiplicity of the first knock signals, and a second knock signal that has a value below zero being set to the value zero. The further-processed second knock signal is then evaluated as knocking or non-knocking.

Abstract: For signal processing of solid-borne or structure-borne sound signals, in particular in motor vehicles, and a corresponding occupant protection system, a first-order high-pass filter is provided as a filter, wherein the ?3 dB cut-off frequency thereof lies between the upper and lower operating frequency of the signal evaluation. The signal delay in the filter becomes significantly lower. Damping of the frequencies in the operating range becomes non-uniform, wherein components below the cut-off frequency are damped more heavily. Not only can triggering cases be detected earlier, but also non-triggering cases can be reliably detected.

Abstract: A sensor signal processing device includes an AD conversion section, a filter section, a timing signal generation section, and an arithmetic section. The timing signal generation section generates a signal synchronized with a crank angle of an engine based on a signal indicating the crank angle and generates a data acquisition timing signal by compensating the signal synchronized with the crank angle with a delay time of the filter. The arithmetic section acquires a plurality of sensor signals, which is transmitted from a sensor, converted from an analog signal to a digital signal by the AD conversion section, and filtered by the filter section, in a term before and after receiving the data acquisition timing signal and generates a data synchronized with the data acquisition timing signal.

Abstract: Systems and methods for monitoring health of one or more subsystems of a vehicle system are disclosed. At least one sensor can be operatively coupled to a vehicle subsystem having an operational signature and a control system is coupled to the at least one sensor. Using information provided by the at least one sensor, the control system is structured to generate a reference signature of the subsystem during a learning phase and an operational signature of the subsystem subsequent to the learning phase. Systems and methods for identifying the particular subsystem exhibiting degraded performance are also disclosed.

Abstract: In a knock control device of an internal combustion engine equipped with a control unit which updates a background level based on an output signal from a knock sensor and detects the generation of a knock by comparing a variation of the background level with a knock determination value, a determination as to whether the knock is generated is performed by ((variation of first filter value of peak hold value)>((1?filter coefficient)/(1+filter coefficient)×(predetermined value larger than maximum value of variation of peak hold value in case where knock is not generated))).

Abstract: A method and a system is disclosed for determining RON and/or MON values from constant volume combustion chamber apparatuses capable of producing pressure versus time combustion profiles having a fast combustion region and a slow combustion region, where data from the two regions is used to compute RON and/or MON values for light distillate fluid samples using a series expansion equation.

Abstract: A method comprises steps for reconstructing in-cylinder pressure data from a vibration signal collected from a vibration sensor mounted on an engine component where it can generate a signal with a high signal-to-noise ratio, and correcting the vibration signal for errors introduced by vibration signal charge decay and sensor sensitivity. The correction factors are determined as a function of estimated motoring pressure and the measured vibration signal itself with each of these being associated with the same engine cycle. Accordingly, the method corrects for charge decay and changes in sensor sensitivity responsive to different engine conditions to allow greater accuracy in the reconstructed in-cylinder pressure data.

Abstract: Provided is a control apparatus for an internal combustion engine with which temporal and frequency resolutions necessary for analysis of a frequency of knock by digital signal processing are ensured with limited amounts of processing and memory. The control apparatus includes a lowpass filter for eliminating a high frequency component of an output signal from a knock sensor or a cylinder internal pressure sensor, an A/D conversion unit for performing A/D conversion on the output signal from the filter, and DFT processing units for performing digital signal processing on data obtained by the A/D conversion as knock detection units, each of the DFT processing units includes observation interval setting units for dividing the A/D-converted data to set observation intervals each containing a predetermined number of samples, and a multi-frequency simultaneous analysis unit for simultaneously analyzing multiple frequencies by a discrete Fourier transform for each of the set observation intervals.

Abstract: The duration of a knock detection window over which a filtered knock signal is single-point DFT-processed for engine knock detection is user adjustable. The knock detection window is defined by at least two overlapping identical duration sub-windows, and the extent of the sub-window overlap is changed to adjust the duration of the knock detection window. The DFT processing is performed over each sub-window and the processing results are combined for knock detection.

Abstract: The present invention relates to a knocking detecting device for an internal combustion engine, for controlling a timing at which an ignition coil is actuated according to a knocking occurrence intensity, the knocking detecting device including the signal processing module for processing a signal attributable to knocking occurring in the operation of the internal combustion engine to determine a knocking occurrence intensity, in which the signal processing module includes: signal detecting means for detecting a signal attributable to knocking; frequency intensity calculating means for selecting a plurality of frequencies extracted from an output of the signal detecting means to calculate a frequency intensity; and knocking intensity determining means for finally determining that knocking occurs in a case where it is determined that at least two primary determination results of among a plurality of primary knocking determination results based on the outputs of the frequency intensity calculating means.

Abstract: Provided is a control apparatus for an internal combustion engine with which temporal and frequency resolutions necessary for analysis of a frequency of knock by digital signal processing are ensured with limited amounts of processing and memory. The control apparatus includes a lowpass filter for eliminating a high frequency component of an output signal from a knock sensor or a cylinder internal pressure sensor, an A/D conversion unit for performing A/D conversion on the output signal from the filter, and DFT processing units for performing digital signal processing on data obtained by the A/D conversion as knock detection units, each of the DFT processing units includes observation interval setting units for dividing the A/D-converted data to set observation intervals each containing a predetermined number of samples, and a multi-frequency simultaneous analysis unit for simultaneously analyzing multiple frequencies by a discrete Fourier transform for each of the set observation intervals.

Abstract: When detecting the combustion noise on a combustion engine (10) by using a knock sensor (14), the problem arises in that prior art methods cannot determine with sufficient accuracy how much fuel reaches the cylinder (11) of the combustion engine (10) during a specified injection pulse. For different reasons, e.g. for minimizing the fuel consumption or for optimizing exhaust emissions, a multiple injection with, in part, the smallest quantities of fuel is commonly used in today's combustion engines (10) that require a precise fuel metering. To this end, the measuring window (M) for detecting the combustion noises of an individual injection pulse with regard to its starting and/or ending position is variably formed according to operating parameters so that only the combustion noises taken into consideration are detected that serve as a measure for the injected quantity of fuel.

Abstract: A method for determining fuel volatility and consequently performing cold starting of an internal combustion engine; in the event of cold starting, the method provides for the determination of an enrichment percentage as a function of a stored value for fuel volatility; the determination of a predicted value for starting quality before performing starting; the starting of the engine using the previously determined enrichment percentage; the determination of a measured value for starting quality; the determination of a correction value of the stored value for fuel volatility as a function of the comparison between the measured value for starting quality and the predicted value for starting quality; and the updating of the stored value for fuel volatility by applying the correction value to said stored value, so consequently modifying the amount of enrichment in force.

Abstract: An engine ECU executes a program including a step of calculating intensity values LOG(V), a step of detecting vibration waveforms, a step of calculating a correlation coefficient K based on vibration waveforms, a step of preparing frequency distribution of intensity values LOG(V) smaller than a threshold V(1) and intensity values LOG(V) in an ignition cycle where correlation coefficient K is larger than a threshold K(1), a step of calculating a knock determination level V(KD) based on a median V(50) and a standard deviation ? of intensity values LOG(V), and a step of counting the number of intensity values LOG(V) larger than knock determination level V(KD) as the number of times that knocking has occurred.

Abstract: The invention concerns a method to determine the fuel composition of a fuel mixture from a first fuel and a second fuel for the operation of an internal combustion engine, wherein the first and the second fuel have different combustion rates and/or different specific energy contents and wherein the internal combustion engine has at least one pressure sensor in at least one combustion chamber, with which a temporal pressure curve and/or a pressure curve under conditions of angular synchronism is determined. Provision is made according to the invention for the composition of a fuel mixture to be determined from the temporal pressure curve and/or the pressure curve under conditions of angular synchronism of the gas pressure in the combustion chamber, of which there is at least one. A fuel mixture from fuels with different combustion rates exists, for example, in an alcohol-gasoline mixture. Alcohol has a faster combustion process than gasoline.

Abstract: The duration of a knock detection window over which a filtered knock signal is single-point DFT-processed for engine knock detection is user adjustable. The knock detection window is defined by at least two overlapping identical duration sub-windows, and the extent of the sub-window overlap is changed to adjust the duration of the knock detection window. The DFT processing is performed over each sub-window and the processing results are combined for knock detection.

Abstract: An engine ECU executes a program including a step of calculating intensity values LOG(V) based on signals transmitted from a knock sensor; a step of deciding a maximum value V(MAX) in frequency distribution of intensity values LOG(V) for N cycles (N is a natural number); a step of calculating a knock determination level V(KD) based on the frequency distribution; a step of, when the knock determination level V(KD) is smaller than the maximum value V(MAX), removing V(MAX) from the frequency distribution; and a step of counting the total frequency of removed maximum values V(MAX) as knock occupancy KC. Maximum values V(MAX) are removed until the knock determination level V(KD) and the maximum value V(MAX) coincide, and the knock determination level V(KD) is recalculated.

Abstract: A method of statistically characterizing combustion knock events includes receiving signals from a sensing device such as an accelerometer, estimating at least one parameter of a probability distribution function based on the received signals, and calculating a value indicative of an nth percentile based on the parameter to predict upcoming combustion knock events.

Abstract: A method of statistically characterizing combustion knock events includes receiving signals from a sensing device such as an accelerometer, estimating at least one parameter of a probability distribution function based on the received signals, and calculating a value indicative of an nth percentile based on the parameter to predict upcoming combustion knock events.

Abstract: An in-cylinder pressure sensor for outputting a signal corresponding to an internal cylinder pressure of an engine is provided. A first signal and a second signal are extracted from the output signal of the in-cylinder pressure sensor. The first signal has a frequency band corresponding to knocking of the engine. The second signal has a frequency band used for detecting a peak of the internal cylinder pressure. A knocking detection period is set based on the second signal. The first signal in the knocking detection period is examined to determine whether or not knocking has occurred.

Abstract: A knocking determining apparatus of an internal combustion engine that includes an in-cylinder injector and an intake port injector and that determines knocking based on an output signal of a knock sensor. The knocking determining apparatus includes a knocking determination prohibition unit prohibiting, when a ratio of fuel injection from the in-cylinder injector and the intake port injector is changed, knocking determination for a prescribed period after that change, or a knocking determination level change unit changing a knocking determination level for a prescribed period after that change.

Abstract: The invention relates to a method for determining the energy (KNKE) of the knock of an internal combustion engine, using an analog signal supplied by a sensor fixed to the engine. The inventive method includes the following steps: a) the analog signal is shaped, b) the analog signal is converted into a sequence of digital samples, c) the signal is subjected to digital filtering, and d) the signal is adjusted and e) integrated. According to the method: i) the shaping of the analog signal includes combining the signal with a continuous component (Vcnf) adapted to render the shaped signal a positive signal or a zero signal, and ii) the digital filtering is carried out by a band-pass filter with an infinite impulse response, the transfer function thereof including a zero for the zero frequencies.

Abstract: Misfire of an engine is detected by extracting a pressure component of combustion from an output of a pressure sensor disposed in a cylinder. An engine misfire detection apparatus obtains a combustion parameter Cr that is a correlation between a reference signal Fc synchronous with the combustion cycle of the engine and cylinder pressure Pc obtained from an output of a pressure sensor disposed in the cylinder. The apparatus detects a misfire of the engine based on the combustion parameter. A misfire can be accurately detected even under a low load condition because the combustion parameter indicating the combustion component is extracted from the cylinder pressure as a correlation between the reference signal synchronous with the combustion cycle of the engine and the cylinder pressure obtained from the sensor output.

Abstract: In a knock sensor signal processing apparatus, a first apparatus which receives an engine knock sensor signal performs A/D conversions of the signal with a predetermined period and transmits successive pluralities of A/D values in parallel, by serial data communication, to a second apparatus in response to respective commands received from the second apparatus. The number of communication lines provided for transmitting the A/D values is made greater than those for transmitting commands from the second apparatus to the first apparatus, so that a high A/D conversion frequency together with low data rate of transmitting the A/D values can be achieved, thereby reducing communication-generated noise.

Abstract: An engine ECU executes a program including a step of calculating a knock intensity N as based on comparing a waveform detected as a waveform of a vibration attributed to knocking with a knock waveform model stored in a memory as a waveform of a vibration attributed to knocking for crank angles except for crank angles where a magnitude of a vibration not attributed to knocking is greater than a predetermined magnitude, a step of determining that the engine knocks if knock intensity N is larger than a predetermined reference value, and a step of determining that the engine does not knock if knock intensity N is not larger than a predetermined reference value.

Abstract: A method for processing an accelerometer signal associated with the combustion process in an operating internal combustion engine, the method comprising the steps of measuring an accelerometer signal across a window of selected crank angle degrees during a cycle of the engine, the measured accelerometer signal including a combustion acceleration component and a motored acceleration components; and applying a shape function to the measured accelerometer signal to reduce the motored acceleration component.

Abstract: A combustion state detecting apparatus is provided for an engine having internal pressure sensor for detecting an internal pressure of a combustion chamber of the engine and crank angle detector for detecting a crank angle of the engine. The apparatus calculates a volume of the combustion chamber based on the crank angle detected by the crank angle detector and estimator for estimating a motoring pressure of the engine in accordance with a calculation equation using the calculated volume. The apparatus adjusts either of the pressure detected by the internal pressure sensor and the pressure estimated by the estimator during a compression stroke of the engine to minimize the error between the detected pressure and the estimated pressure. The apparatus determines a combustion state during a combustion stroke of the engine based on a relation between the pressure adjusted and the other pressure.

Abstract: Devices and methods for knock detection and knock control are described, in which, in addition to the customary component parts, the knock-detection circuit has a filter with switchable filter characteristic. The switchover of the filter characteristic, i.e. the shift, for example, of the mid-frequency of the filter, is carried out taking into consideration specifiable quantities or parameters, for instance, as a function of rotational speed. During the switchover of the filter characteristic, i.e. the shift of the mid-frequency, problems could occur in the knock detection; that is why measures are proposed which carry out the knock detection according to a special knock-detection algorithm during a switchover phase lasting a specifiable time.

Abstract: A device for signal evaluation is described, in particular for knock recognition in an internal combustion engine, in which the signals forwarded by sensors are evaluated digitally and error recognition is carried out that performs two different test functions, whereby a first test function supplies a test pulse at a specifiable location, and the second test function clears the sensor signals, and the reaction of both the analog and digital parts of the circuit are monitored.

Abstract: The method for knock detection includes establishing that knock is occurring in the internal combustion engine when the amplified knock signal exceeds a predetermined reference level in a predetermined manner. The reference level is determined on the basis of individual cylinders and the increase in the reference level is limited when a new reference level leaves a predetermined reference level range or the gradient of the sound increase exceeds a predetermined threshold value. For determination of the reference level range and/or the threshold for the gradient average values of the signals originating from the sound of other cylinders are considered.

Abstract: A knock detection device that can not only detect knock accurately, but can also detect heavy knock quickly. Cylinder pressure is detected by a pressure sensor installed in each cylinder in an internal combustion engine. AS the occurrence or non-occurrence of heavy knock is determined based on the ratio between the maximum value of cylinder pressure fluctuation and the maximum value of cylinder pressure divided by a prescribed value, it becomes possible to detect the occurrence of heavy knock quickly. If it is determined that heavy knock has occurred, a knock suppression measure involving, for example, reducing the spark advance angle, is immediately applied, thus preventing damage to the internal combustion engine.

Abstract: Method for processing a sensor signal of a knocking sensor for an internal combustion engine, having the following steps: a time window is defined for the evaluation of the sensor signal as a function of the operating state and/or the operating behavior of the internal combustion engine, a plurality of sampled values of the sensor signal are sampled within the predefined time window with a predefined sampling frequency, and an output signal which represents the knocking behavior of the internal combustion engine is determined from the sampled values, the Fourier transform of the sampled values being calculated in order to determine the output signal.

Abstract: A knock detection device that can not only detect knock accurately, but can also detect heavy knock quickly. Cylinder pressure is detected by a pressure sensor installed in each cylinder in an internal combustion engine. AS the occurrence or non-occurrence of heavy knock is determined based on the ratio between the maximum value of cylinder pressure fluctuation and the maximum value of cylinder pressure divided by a prescribed value, it becomes possible to detect the occurrence of heavy knock quickly. If it is determined that heavy knock has occurred, a knock suppression measure involving, for example, reducing the spark advance angle, is immediately applied, thus preventing damage to the internal combustion engine.

Abstract: Devices and methods for knock detection and knock control are described, in which, in addition to the customary component parts, the knock-detection circuit has a filter with switchable filter characteristic. The switchover of the filter characteristic, i.e. the shift, for example, of the mid-frequency of the filter, is carried out taking into consideration specifiable quantities or parameters, for instance, as a function of rotational speed. During the switchover of the filter characteristic, i.e. the shift of the mid-frequency, problems could occur in the knock detection; that is why measures are proposed which carry out the knock detection according to a special knock-detection algorithm during a switchover phase lasting a specifiable time.

Abstract: In a method for detecting knocking combustion during the operation of an internal combustion engine with a device for measuring the ionic current, the raw ionic current signal or the evaluated value of the knocking intensity are normalized. This enables the value of the knocking intensity to be reliably compared with a threshold value. The normalization avoids the falsifying influence of large intensity fluctuations of the raw ionic current signal from one combustion cycle to the next without any relation to the true knocking intensity.

Abstract: A method for error detection during an evaluation of sensor signals, in particular during an evaluation of output signals of knock sensors in an internal combustion engine, with at least one sensor and an evaluating device connected therewith, the method includes the steps of forming at least one variable reference level from output signals of a sensor or sensors; comparing the variable reference level for error detection with upper and/or limiting values; making a conclusion about an error in the case of a predeterminable exceeding of the upper and/or exceeding of the lower limiting value by the actual reference level; and forming at least one limiting value in dependence on preceding reference values.

Abstract: The apparatus detects knock in an internal combustion engine with at least one knock sensor associated with a cylinder of the internal combustion engine. The apparatus initially processes the analog knock sensor output signals in an analog signal preparing device (18), which can include a multiplexer and analog/digital converter, but the actual knock detection occurs only in a purely digital signal analysis device (19), which processes the prepared and digitized knock sensor output signals. The digital signal analysis device (19) extracts at least one knock index and compares it with predetermined threshold values for knock detection, preferably considering a reference value for knock-free operation. A method of detecting knock is also described which is based on the use of this apparatus.

Abstract: A spectral method, and corresponding system, for knock detection includes acquiring (603) spectral energy associated with vibration caused by a knocking condition from a running engine. Preferably, a sampled data system (105) acquires the spectral energy by converting an output from an accelerometer (101) into data samples (103) in a digital form. Then from the acquired spectral energy, a knock variable is derived from magnitudes of spectral components, representing a characteristic of a combustion chamber located within the running engine. In a preferred embodiment the knock variable is derived from magnitudes of spectral components related by ratios corresponding to Bessel function coefficients. The preferred embodiment includes a Digital Signal Processor (109) applying a Fast Fourier Transform method (503) to estimate a spectral content used to determine the knock variable. Then, a knock indication is provided (509) when the knock variable exceeds a magnitude of a predetermined threshold (507).

Abstract: A method of detecting and controlling detonation, including the steps of: generating (10) a vibration signal (D) proportional to the intensity of vibration on the crankcase; wide-band-filtering (11) the vibration signal (D) to generate a first intermediate signal; rectifying (12) the first intermediate signal to generate a second intermediate signal; integrating (13) the second intermediate signal to generate a first numeric value; calculating (14) a logarithm of the first numeric value to obtain a second numeric value (Xi); calculating (16) a difference between the second numeric value (Xi) and the mean value (&mgr;i) to obtain a third numeric value (&dgr;i) with a predetermined threshold value (&dgr;o); determining (18) the presence of detonation in the event the third numeric value (&dgr;i) has a first predetermined relationship with the predetermined threshold value (&dgr;o); forming (19, 21) a detonation index (Ii) indicating the behavior of the engine in terms of detonation; and obtaining (22) a spark l

Abstract: A method for knock control during KC emergency operation with which, given low application expenditure, a torque gain can be attained, while the application reliability increases. The method for knock control of multi-cylinder internal combustion engines having 2n cylinders, a cylinder counter, at least one knock sensor and an evaluation unit for evaluating the knock-sensor signal with the aid of an individual knock-recognition characteristic for each cylinder, is characterized in that during KC emergency operation, cylinder pairs are formed from the cylinders operating offset in each case by 360°, and the minimal value of the two knock-recognition characteristics of the cylinder pair is assumed in each case as the knock-recognition threshold for the cylinders of the cylinder pair affected by the malfunction of the phase recognition.

Abstract: To obtain a knock detection apparatus which may obtain a good knock pulse S/N even if an ionic current generation amount is changed by the change of a kind of fuel or plugs, a knock detection apparatus for detecting a knock generated, in an internal combustion engine, in which a vibratory component superimposed on an ionic current generated by combustion of fuel is extracted, the component that is equal to or more than a knock detection threshold value is shaped in waveform into a pulse waveform, a knock strength is calculated through counting and calculation process of the number of pulses of the pulse waveform by an engine controlling unit, an ignition timing is controlled on the basis of the knock strength, comprises a knock detection threshold value adjusting unit for changing the knock detection threshold value on the basis of information of an ionic current.

Abstract: To obtain a knock detection apparatus for an internal combustion engine which may obtain a good knock pulse S/N even if an ionic current generation amount is changed by the change of a kind of fuel or plugs, a vibratory component superimposed on an ionic current generated by combustion of fuel is extracted and shaped in waveform into a pulse waveform by comparison with a threshold value, the number of the pulses in the pulse waveform is calculated by a calculation unit, and a control of an ignition timing is performed on the basis of an output result of the calculation unit. The knock detection apparatus for an internal combustion engine comprises an integration circuit for integrating (charging) the vibratory component superimposed on the ionic current and a discharge circuit for discharging a predetermined amount of charge from the integrated charge. The threshold value is self-adjusted by a balance of charge/discharge between the integration circuit and the discharge circuit.

Abstract: A knock suppression control apparatus for an internal combustion engine which can avoid erroneous knock detection and hence the erroneous knock suppression control, to thereby ensure knock suppression control with high reliability.

Abstract: A method for error detection during an evaluation of sensor signals, in particular during an evaluation of output signals of knock sensors in an internal combustion engine, with at least one sensor and an evaluating device connected therewith, the method includes the steps of forming at least one variable reference level from output signals of a sensor or sensors; comparing the variable reference level for error detection with upper and/or limiting values; making a conclusion about an error in the case of a predeterminable exceeding of the upper and/or exceeding of the lower limiting value by the actual reference level; and forming at least one limiting value in dependence on preceding reference values.

Abstract: A control system and method for obtaining combustion stability in an internal combustion engine including an accelerometer mounted on the engine for detecting engine block vibrations and an engine controller for processing an accelerometer output signal indicating engine block vibration intensity to measure cylinder combustion energy, the energy measurement being correlated to other combustion parameters including indicated mean effective pressure (IMEP), the controller developing a control signal that may be used in a closed loop fashion to adjust engine variables including exhaust gas recirculation, air/fuel ratio, and spark advance, thereby adjusting the engine operating characteristics to achieve optimum combustion energy.

Abstract: The apparatus detects knock in an internal combustion engine with at least one knock sensor associated with a cylinder of the internal combustion engine. The apparatus initially processes the analog knock sensor output signals in an analog signal preparing device (18), which can include a multiplexer and analog/digital converter, but the actual knock detection occurs only in a purely digital signal analysis device (19), which processes the prepared and digitized knock sensor output signals. The digital signal analysis device (19) extracts at least one knock index and compares it with predetermined threshold values for knock detection, preferably considering a reference value for knock-free operation. A method of detecting knock is also described which is based on the use of this apparatus.