JP4327582B2 - Knocking detection device - Google Patents

Description

  The present invention relates to a detection device for knocking that occurs in an internal combustion engine, and more particularly to a detection device for knocking that accurately detects the presence or absence of occurrence of knocking even with a detection signal including noise.

  In order to suppress the occurrence of knocking in an internal combustion engine, such as an engine of a vehicle, it is well known that it is effective to correct the ignition timing of the engine to be retarded from the basic ignition timing. For this reason, accurately detecting the occurrence of knocking is essential for suppressing knocking. By the way, in the ignition timing control device for suppressing the occurrence of knocking, there is a knocking sensor provided in a cylinder block or the like of an engine, usually a knocking sensor composed of a piezoelectric body or a magnetostrictive body that converts engine vibration into an electric signal. It is used. Various techniques have been proposed in order to improve the determination accuracy in determining the occurrence of knocking based on the detection result of the knocking sensor. For example, it is possible to avoid erroneous determination of knocking due to electric noise generated when a vehicle wiper is operated or when a lighting is turned on, etc., superimposed on the signal line of the knocking sensor, and the determination accuracy of occurrence of knocking is improved. . Even with this ignition timing control device, the occurrence of knocking may be misjudged and the occurrence of knocking may not be effectively suppressed. As this cause, noise that is not caused by electrical noise is generated in the engine, and the occurrence of knocking is erroneously determined based on this noise. One reason for the generation of noise that is not caused by this electrical noise is that the piston collides with the cylinder bore to make a hitting sound, or the cylinder block vibrates due to this collision. This phenomenon becomes more prominent with the retard of the ignition timing, so depending on the degree of the retard, etc., the frequency and timing at which the vibration caused by the piston hitting or collision approximates the vibration at the time of knocking. Get up in. For this reason, the occurrence of knocking is erroneously determined. If the occurrence of knocking is erroneously determined as described above, the ignition timing is retarded based on the erroneous determination, so that there is a problem that the ignition timing is erroneously retarded. In addition, the ignition timing is retarded in spite of the occurrence of knocking in this way, which may lead to a decrease in combustion efficiency and a decrease in engine performance.

  Piston collisions are not uniform because the frequency of occurrence, the degree of impact, etc. vary depending on individual differences in the engine, changes over time, differences in use environment, and the like. For example, even in the same type of engine immediately after completion, its component accuracy and assembly accuracy differ within an allowable range, and individual differences occur in the compression ratio and the like for each engine. For this reason, the frequency at which vibrations resulting from piston hitting and collisions occur as pseudo knocking differs from engine to engine from the beginning of use. In addition, the compression ratio, the accumulation of carbon particles on the combustion chamber wall surface, and the like change over time depending on the period of use, the environment of use, etc., and therefore change even in the same engine. Therefore, the frequency of occurrence of pseudo knocking varies depending on the secular change and the difference in use environment even in the same engine. For this reason, as described above, the above-described problem (decrease in combustion efficiency and engine performance) due to repeated erroneous determination of occurrence of knocking may become more significant.

  In view of such a problem, Japanese Patent Laid-Open No. 6-505805 (Patent Document 1) discloses a knocking detection device for an internal combustion engine that can avoid erroneous determination of mechanical vibration as knocking. The knock detection device for an internal combustion engine includes at least one knock sensor connected to an evaluation device via a filter, and the center frequency of the at least one filter means is controlled depending on an operating parameter of the internal combustion engine. The knock detection device for an internal combustion engine, wherein the operating parameter is a crankshaft angle, and the center frequency is controlled so that a frequency change that occurs as the crankshaft angle increases in a knocking signal that occurs after top dead center is taken into account. It is characterized by that.

According to this knock detection device for an internal combustion engine, the output signal of the object acoustic sensor from the knock sensor is amplified, filtered, rectified and integrated, and then digitized to determine the presence or absence of knocking. The frequency of vibration due to knocking is varied depending on the operating parameters of the internal combustion engine. Therefore, the center frequency of the filter from which knocking vibration is to be filtered out is shifted. By comparing a signal that has passed through a filter with a controlled center frequency with a signal that has passed through a filter with a constant center frequency, if there is a difference between these signals above a certain value, knocking occurs. It is detected that That is, it is possible to determine whether or not knocking has occurred by analyzing the frequency shift of the signal supplied by the knocking sensor.
JP-T 6-505805

  However, in the knocking detection device for an internal combustion engine disclosed in Patent Document 1, in view of the phenomenon that the peak frequency changes when knocking due to the crank angle occurs, a plurality (a large number) of bandpass filters are used. Process the signal. The vibration intensity value of the signal filtered through each filter is analyzed for each frequency band one by one. As a result, it is necessary to analyze how the frequency intensities filtered by the plurality of filters are related in each frequency band. When the mechanical noise approximates the peak value of the knocking frequency in a specific frequency band, the analysis result in that frequency band includes an error. The presence of this error may cause a determination as to whether knocking has occurred or not.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a knocking detection device capable of detecting the presence or absence of knocking with high accuracy even for a detection signal including noise. Is to provide.

  A knocking detection device according to a first aspect of the invention detects knocking that occurs in an internal combustion engine. The detection device detects a signal value representing a cylinder internal pressure or a signal value representing a vibration or sound of a cylinder block, and stores the detected signal value corresponding to a crankshaft angle. Storage means, analysis means for dividing the stored signal value at predetermined time intervals and performing frequency analysis of the signal value at each time interval, and frequency analysis characteristic values at each time interval Determination means for determining the presence or absence of occurrence of knocking based on the change according to the series.

  According to the first aspect of the invention, for example, a signal value representing a cylinder internal pressure or combustion state is detected using a pressure sensor or an ion current sensor, or a signal value representing vibration or sound of a cylinder block using a vibration detection sensor or microphone. Is detected. If knocking occurs, this signal value has a different intensity depending on the frequency. Along with the elapsed time from when the crankshaft angle is at top dead center, the frequency at which the intensity is maximum (hereinafter referred to as peak frequency) shifts to the low frequency region. The storage means stores a signal value corresponding to the crankshaft angle, and the analysis means divides the crankshaft angle at predetermined time intervals from the time at which the crankshaft angle is the top dead center of the compression stroke, The signal value is frequency analyzed at each interval. The frequency analysis for each time interval means that the frequency analysis is performed by shifting the time. When the peak frequency in the time interval gradually becomes low, it can be determined that knocking has occurred. On the other hand, since the frequency of mechanical noise does not change, even if mechanical noise is included in the signal value, if there is a frequency component whose peak frequency gradually shifts to the low frequency region, knocking has occurred. If there is no such frequency component, it can be determined that knocking has not occurred. As a result, it is possible to provide a knocking detection device capable of detecting the presence or absence of knocking with high accuracy even with a detection signal including noise.

  In the knocking detection device according to the second invention, in addition to the configuration of the first invention, the analysis means includes means for calculating, as a characteristic value, a peak frequency at which the intensity of the signal value is maximum. The determination means includes means for determining whether or not knocking has occurred based on the degree of change in peak frequency with respect to time series.

  According to the second invention, when the detected signal value does not include a component representing knocking but includes only a component representing noise, the peak frequency analyzed as the characteristic value is obtained with respect to the time transition. Has no change. On the other hand, when a component representing knocking is included in the detected signal value, the peak frequency analyzed as the characteristic value has a change with respect to the transition of time regardless of the presence or absence of the component representing noise. If the degree of change in peak frequency with this time is large, it can be determined that knocking has occurred.

  In the knocking detection device according to the third aspect of the invention, in addition to the configuration of the second aspect of the invention, the judging means compares the slope of the change in the peak frequency with respect to time series with a predetermined slope, thereby knocking. Means for determining the presence or absence of the occurrence of the occurrence of

  According to the third aspect of the invention, when the detected signal value does not include a component representing knocking but only a component representing noise, the peak frequency analyzed as the characteristic value corresponds to the transition of time. Has no inclination. On the other hand, when a component representing knocking is included in the detected signal value, the peak frequency analyzed as the characteristic value has a slope with respect to the transition of time regardless of the presence or absence of the component representing noise. As a result of frequency analysis by dividing every predetermined time interval, if the slope at which the peak frequency changes due to this time is larger than the predetermined slope (that is, if the change is large), knocking has occurred. Can be determined.

  A knock detection device according to a fourth aspect of the invention detects knocking that occurs in an internal combustion engine. The detection device detects a signal value representing a cylinder internal pressure or a signal value representing a vibration or sound of a cylinder block, and stores the detected signal value corresponding to a crankshaft angle. Using storage means and a plurality of filters that filter only a specific frequency band, an analysis means for analyzing the stored signal value for each frequency band, and a maximum timing of the signal value in each frequency band Determining means for determining the presence or absence of occurrence of knocking based on the time lag.

  According to the fourth invention, for example, a signal value representing a cylinder internal pressure or combustion state is detected using a pressure sensor or an ion current sensor, or a signal value representing vibration or sound of a cylinder block using a vibration detection sensor or microphone. Is detected. If knocking occurs, this signal value has a different intensity depending on the frequency. The peak frequency shifts to the low frequency region with the elapsed time from when the crankshaft angle is the top dead center of the compression stroke. The storage means stores a signal value corresponding to the crankshaft angle, and the analysis means analyzes the signal value using a plurality of types of bandpass filters from the time when the crankshaft angle is at the top dead center. . Analyzing a signal value using a plurality of types of bandpass filters means analyzing whether or not a specific frequency component is included in the signal value. When a signal waveform appears in the bandpass filter on the lower frequency side as time passes, it indicates that the peak frequency has shifted to the low frequency region. For this reason, in such a case, it can be determined that knocking has occurred. On the other hand, since the frequency of mechanical noise does not change, even if mechanical noise is included in the signal value, if there is a frequency component whose peak frequency gradually shifts to the low frequency region, knocking has occurred. If there is no such frequency component, it can be determined that knocking has not occurred. As a result, it is possible to provide a knocking detection device capable of detecting the presence or absence of knocking with high accuracy even with a detection signal including noise.

  In the knock detection device according to the fifth aspect of the invention, in addition to the configuration of the fourth aspect of the invention, the determination means generates the knock based on the slope of the time lag in each frequency band at the maximum timing of the signal value. Means for determining the presence or absence of.

  According to the fifth invention, when the detected signal value does not include a component representing knocking but only a component representing noise, the peak frequency analyzed using a plurality of bandpass filters is There is no change with respect to the transition of time that the appearing waveform is delayed toward the lower frequency side. On the other hand, when a component representing knocking is included in the detected signal value, the peak frequency analyzed as the characteristic value has a change with respect to the transition of time regardless of the presence or absence of the component representing noise. If the degree of change in peak frequency with this time is large, it can be determined that knocking has occurred.

  In the knocking detection device according to the sixth aspect of the invention, in addition to the configuration of the fifth aspect of the invention, the determination means includes a slope of a time lag in each frequency band and a predetermined slope of the maximum timing of the signal value. And a means for determining whether or not knocking has occurred.

  According to the sixth aspect of the invention, when the detected signal value does not include a component representing knocking but includes only a component representing noise, the peak frequency analyzed as the characteristic value is obtained with respect to the time transition. Has no inclination. On the other hand, when a component representing knocking is included in the detected signal value, the peak frequency analyzed as the characteristic value has a slope with respect to the transition of time regardless of the presence or absence of the component representing noise. As a result of frequency analysis using a plurality of bandpass filters, if the slope at which the peak frequency changes with this time is greater than a predetermined slope (that is, if the change is large), it is determined that knocking has occurred. Can do.

  A knocking detection device according to a seventh aspect of the invention detects knocking that occurs in an internal combustion engine. The detection device detects a signal value representing a cylinder internal pressure or a signal value representing a vibration or sound of a cylinder block, and stores the detected signal value corresponding to a crankshaft angle. Storage means, analysis means for frequency analysis of the stored signal value using Fourier transform or wavelet transform, and determination means for determining the presence or absence of occurrence of knocking based on the result of frequency analysis Including.

  According to the seventh invention, the peak value of the frequency distribution is frequency-analyzed using the short-time Fourier transform or wavelet transform for analyzing the waveform of the signal value changing with respect to the time axis. As a result of such frequency analysis, if it has a change component with respect to time, it can be determined that knocking has occurred.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

<First Embodiment>
Hereinafter, an engine system to which a knock control device for an internal combustion engine according to a first embodiment of the present invention is applied will be described. FIG. 1 is a schematic diagram showing the overall configuration of such an engine system. In the following description, it is assumed that the knock sensor that detects knocking is a vibration sensor that detects vibration of the cylinder block. One or a plurality of knock sensors are provided in the engine. Also, instead of the knock sensor that detects the vibration of the cylinder block, the sound generated by the cylinder block may be detected using a microphone, or the knocking is detected using a pressure sensor that detects the cylinder internal pressure. You may make it do. Also in this case, such a pressure sensor is provided for each cylinder or a specific cylinder, and the number is not particularly limited. Furthermore, in order to detect the combustion state in a cylinder, you may make it use the sensor which detects the ion current which flows between electrodes.

  In FIG. 1, this engine system includes a four-cylinder four-cycle engine 100, an intake passage 200 through which intake air passes through an air cleaner and an air flow meter, a throttle valve 300 that adjusts the amount of intake air supplied to the engine 100, Distributor 400 including a reference angle sensor 410 for detecting a reference crank angle of engine 100 (for example, a compression top dead center of each cylinder) and a crank angle sensor 420 for generating an output signal at every constant crank angle of engine 100. Including. Then, an engine speed NE is calculated based on a signal from a crank angle sensor 420 by an ECU (Electronic Control Unit) 1000 described later.

  The engine system further includes a knock sensor 500 that detects vibration of the cylinder block corresponding to a knock occurrence phenomenon of the engine 100 by a piezoelectric element type (piezo element type), an electromagnetic type (magnet, coil), and the like, and a cooling water temperature of the engine 100 In the cylinder of the engine 100 by a high voltage distributed from the distributor 400, a water temperature sensor 600 that generates a signal corresponding to the engine temperature, an injector (fuel injection valve) 700 that supplies fuel to the intake manifold based on a control signal from the ECU 1000, An ignition device 800 that sparks and ignites an air-fuel mixture, and a digital signal processor (DSP) 900 that digitally processes an output signal (knock sensor signal) from the knock sensor 500 and determines whether knocking has occurred or not.

ECU 1000 includes a CPU (Central Processing Unit) as a central processing unit that executes various known arithmetic processes, a ROM (Read Only Memory) that stores a control program, a RAM (Random Access Memory) that stores various data, and the like. When the ECU 1000 determines that knocking has occurred by the DSP 900, the ECU 1000 shifts the ignition timing by the ignition device 800 in the engine 100 to the retard side in order to suppress the occurrence of knocking. The ECU 1000 delays the ignition timing. When the ECU 900 shifts to the corner side and knocking is no longer detected by the DSP 900, the ECU 1000 shifts the ignition timing to the advance side. By such a KCS (Knock Control System), the ignition timing is controlled to be optimum.

  A signal waveform input from knock sensor 500 to DSP 900 will be described with reference to FIG. The signal waveform shown in FIG. 2 is a waveform while the crank angle advances from the top dead center (TDC) in the compression stroke to about 90 degrees with the horizontal axis as the crank angle. Such a waveform of the crank angle and the vibration intensity is divided into time intervals of T (1), T (2), T (3), and T (4) that are minute times. The length of this time interval is a very short time, and depends on the frequency (sample rate) at which the DSP 900 takes in the signal from the knock sensor 500. The length of this time section is about 128 points (= about 1 ms) at 100 kHz sampling. This is sufficient even when frequency analysis is performed because the number of analysis points is insufficient if this time interval (T (1), T (2), T (3) and T (4)) is too short. The frequency resolution cannot be obtained. On the other hand, if the time interval is too long, the frequency resolution is improved but the time resolution is deteriorated. For this reason, it is determined by the sample rate of knock sensor 500 in DSP 900 so that the frequency resolution and the time resolution are matched. Of course, the number of divisions of such sections is not limited.

  As shown in FIG. 2, depending on the waveform of the knock sensor 500 input from the knock sensor 500 to the DSP 900, vibration caused by knocking cannot be clearly distinguished from vibration caused by mechanical vibration. The knocking detection apparatus according to the present invention is realized by the DSP 900. The DSP 900 accurately detects the presence or absence of knocking even when mechanical vibration is superimposed on the vibration due to knocking. Can do.

  FIG. 3 shows a control block diagram including a DSP 910 which is a specific example of the DSP 900. As shown in FIG. 3, the DSP 910 that realizes the knocking detection device according to the present embodiment includes an A / D conversion unit that converts an analog signal from the knock sensor 500 into a digital signal, and an FFT (Fast (Fast Fourier Transform)) that performs a fast Fourier transform. (Fourier Transform) calculation unit, a peak detection unit that detects a peak frequency based on the result of fast Fourier transform, a slope calculation unit that calculates the slope of the peak frequency, and a frequency based on the result calculated by the slope calculation unit And a frequency transition presence / absence determination unit that determines whether or not there is a transition.

  The frequency transition presence / absence determination unit determines presence / absence of knocking. The result of the presence / absence of knocking determined by the frequency transition presence / absence determination unit is transmitted to ECU 1000, and ECU 1000 controls ignition device 800. The manner in which ECU 1000 controls ignition device 800 is as described above.

  A control structure of a program executed by the DSP 910 in FIG. 3 will be described with reference to FIG.

  In step (hereinafter, step is abbreviated as S) 100, DSP 910 performs fast Fourier transform on time zones T (1) to T (4). In S110, DSP 910 detects the peak frequency in each time domain. In S120, DSP 910 calculates the slope of the peak frequency in each time domain. In S130, DSP 910 determines the occurrence of knocking based on the presence or absence of a peak frequency slope. At this time, the DSP 910 determines that knocking has occurred when it has an inclination that changes more than a predetermined inclination.

  An operation of the knocking detection device according to the present embodiment based on the above-described structure and flowchart will be described.

  When engine 100 is started and ignition device 800 is controlled by ECU 1000, the vibration of the cylinder block is detected by knock sensor 500 and input to DSP 910. The analog signal input from the knock sensor 500 to the DSP 910 is converted into a digital signal by the A / D converter, and fast Fourier transform is executed (S100). At this time, fast Fourier transform is performed by dividing into short time regions T (1) to T (4).

  Based on the result of the fast Fourier transform, the peak frequency in each time domain is detected (S110). The slope of the detected peak frequency is calculated (S120). At this time, when knocking occurs as shown in FIG. 5A, the passage of time passes as shown in the time regions T (1), T (2), T (3), and T (4). Accordingly, the peak frequency shifts to the low frequency side. What is indicated by a dotted arrow in FIG. That is, as shown in FIG. 5A, when knocking occurs, the frequency component of the knock peak decreases as the crank angle advances from the top dead center as a result of frequency analysis by fast Fourier transform. Transition to the frequency domain side. This transition state is calculated as the slope of the knock peak frequency.

  On the other hand, as shown in FIG. 5B, when knocking has not occurred and mechanical noise has occurred, the frequency of the noise peak frequency component changes in any time domain. There is nothing to do. That is, as shown in FIG. 5B, when knocking is not generated and mechanical vibration noise is generated, the top dead center is shown as indicated by the slope (dotted arrow in FIG. 5B). As the crankshaft angle advances, the frequency does not change. That is, the inclination is zero.

  As shown in FIG. 5A, when the knock peak frequency component has an inclination toward the low frequency region with time, it is determined that knocking has occurred (S130).

  As described above, according to the knocking detection device according to the present embodiment, the signal value input from the knocking sensor is divided into a plurality of very short time regions on the basis of the top dead center in the compression stroke. A fast Fourier transform is performed for each divided time domain, and a knock peak frequency component at which the signal value of the knock sensor becomes a maximum value is extracted. When the frequency component of this knock peak has a slope that changes more than a predetermined slope on the low frequency side as time passes (in the process of rotating the crankshaft from 0 degrees to 90 degrees). Determines that knocking has occurred. On the other hand, when there is no such inclination or when no peak has occurred, it is determined that knocking has not occurred.

  As described above, the reason why the knocking peak frequency shifts to the low frequency region side while the crank angle advances from the top dead center in the compression stroke to about 90 degrees is mainly due to the decrease in the gas temperature due to the piston lowering. This is due to a decrease in temperature. That is, in the explosion stroke, the gas temperature in the combustion chamber becomes maximum near the top dead center, and the temperature decreases due to expansion as the piston descends. Since the sound velocity of gas decreases with a decrease in temperature, the gas resonance frequency in the tower when knocking occurs shifts to the low frequency side. On the other hand, noise vibration typified by mechanical vibration has nothing to do with vibration due to resonance of gas in the tower, and therefore does not cause frequency transition. As a result, the presence or absence of knocking can be accurately determined even when vibration due to noise other than knocking occurs.

<Second Embodiment>
Hereinafter, a knocking detection device according to a second embodiment of the present invention will be described. The knocking detection apparatus according to the present embodiment includes a DSP 920 having a configuration different from that of the DSP 910 according to the first embodiment described above, and a control structure of a program executed in the DSP 920 is different. Other hardware configurations are the same as those in the first embodiment (FIG. 1). Therefore, detailed description thereof will not be repeated here.

  FIG. 6 shows a control block diagram of DSP 910 that realizes the knocking detection device according to the present embodiment. As illustrated in FIG. 6, the DSP 920 includes an A / D conversion unit that converts an analog signal from the knock sensor 500 into a digital signal, and a plurality of bandpass filters BPF (1) to BPF (1) to each connected to the A / D conversion unit. BPF (3)..., A time shift calculation unit, and a frequency transition presence / absence determination unit are included.

  The bandpass filter BPF (2) passes a signal component in a lower frequency region than the BPF (1). The band pass filter BPF (3) passes a signal component in a lower frequency region than the band pass filter BPF (2).

  That is, it is configured to pass a signal in a lower frequency region in the order of BPF (1), BPF (2), BPF (3),.

  The time shift calculation unit calculates the time shift of the waveform that has passed through each bandpass filter. The frequency transition presence / absence determining unit determines whether knocking has occurred. At this time, if it is determined that the time lag calculated by the time lag calculator has occurred, it is determined that knocking has occurred.

  A control structure of a program executed in the DSP 920 in FIG. 6 will be described with reference to FIG.

  In S200, DSP 920 extracts and analyzes a plurality of frequency bands (at least three frequency bands) with a band pass filter from the signal waveform input from knock sensor 500 and converted by the A / D converter. In S210, DSP 920 calculates the time lag of the waveform. In S220, DSP 920 calculates the slope of the peak frequency based on the time lag of the waveform. In S230, the DSP 920 determines whether or not knocking has occurred based on the presence or absence of the slope of the peak frequency.

  An operation of the knocking detection device according to the present embodiment based on the above-described structure and flowchart will be described.

  During the operation of the engine 100, a detection signal is input from the knock sensor 500 to the DSP 920 and converted into a digital signal by the A / D converter. A plurality of frequency bands are extracted from the signal waveform converted into the digital signal by a plurality of bandpass filters BPF (1), BPF (2), BPF (3),.

  At this time, as shown in FIGS. 8A and 8B, the waveform of the signal passing through each bandpass filter is obtained with the horizontal axis as the time axis and the vertical axis as the signal intensity. FIG. 8A shows a case where knocking has occurred and mechanical vibration has occurred, and FIG. 8B shows a case where only mechanical vibration has been detected.

  The peak frequency is calculated for each waveform divided into a plurality of frequency bands, and the time lag is calculated (S210). The slope of the peak frequency is calculated from the time lag (S220). This inclination is indicated by a dotted arrow in FIG. The waveform of the bandpass filter BPF (2) in FIG. 8A is the same as that of the bandpass filter BPF (2) in FIG. The waveform shifted to the right is superimposed. That is, in the band pass filter BPF (2) of FIG. 8A, the vibration signal due to knocking and the vibration signal due to noise are superimposed.

  However, in the frequency bands of BPF (1) and BPF (3) in FIG. 8 (A), since the noise peak frequency does not pass, the noise waveform is not superimposed on the knocking waveform, and as shown in FIG. 8 (A). The slope of a simple arrow can be calculated.

  On the other hand, when mechanical noise occurs without knocking, as shown in FIG. 8B, a frequency that passes through a specific frequency band (here, the bandpass filter BPF (2)). A waveform is generated only in a frequency band of noise). There is no waveform in the frequency band of the bandpass filters BPF (1) and BPF (3) in FIG. Therefore, the inclination cannot be calculated. When the inclination is calculated, it is determined that knocking has occurred, and when there is no inclination, it is determined that knocking has not occurred.

  As described above, according to the knocking detection device according to the present embodiment, noise is generated using a plurality of bandpass filters without using the fast Fourier transform as in the above-described embodiment. Even in this case, the presence or absence of knocking can be accurately determined.

<Third Embodiment>
Hereinafter, a knocking detection device according to a third embodiment of the present invention will be described. The knocking detection apparatus according to the present embodiment has a DSP 930 different from the DSP 900 of the first embodiment, and the control structure of a program executed by the DSP 930 is different, as in the second embodiment. The point is a feature. Since the other hardware configuration is the same as that of the first embodiment (FIG. 1), detailed description thereof will not be repeated here.

  FIG. 9 shows a control block diagram of DSP 930 of the knocking detection device according to the present embodiment. As shown in FIG. 9, the DSP 930 includes an A / D conversion unit that converts an analog signal input from the knock sensor 500 into a digital signal, and a short-time Fourier analysis unit or wavelet that performs a short-time Fourier analysis on the converted digital signal. A wavelet analysis unit to analyze and a frequency transition presence / absence determination unit are included.

  The frequency presence / absence determination unit determines the presence / absence of knocking. Note that the short-time Fourier analysis and the wavelet analysis executed in the short-time Fourier analysis unit or the wavelet analysis unit use known techniques, and detailed description thereof will not be repeated here.

  With reference to FIG. 10, a control structure of a program executed by DSP 930 of the knocking detection device according to the present embodiment will be described.

  In S300, DSP 930 executes short-time Fourier analysis or wavelet analysis. In S310, DSP 930 calculates the slope of the peak frequency. In S320, DSP 930 determines the presence or absence of knocking from the presence or absence of tilt.

  An operation of the knocking detection device according to the present embodiment based on the above-described structure and flowchart will be described.

  During operation of engine 100, a detection signal from knock sensor 500 is input to DSP 930. The DSP 930 performs short-time Fourier analysis or wavelet analysis (S300), and the slope of the peak frequency is calculated (S310).

  At this time, the result of wavelet transform is shown in FIGS. FIG. 11A shows a change in frequency with respect to the time axis after wavelet transform in the case where knocking occurs. FIG. 11B shows a frequency change with respect to the time axis after wavelet transformation in the case where knocking has not occurred but mechanical vibration has occurred.

  As shown in FIG. 11A, when knocking occurs, a change in frequency appears with a certain slope with respect to the time axis. On the other hand, as shown in FIG. 11B, when knocking has not occurred and mechanical vibration has occurred, no frequency change occurs with respect to the time axis. In this way, if there is an inclination, it is determined that knocking has occurred. If no knocking has occurred, it is determined that knocking has not occurred because no inclination has occurred even if noise has occurred.

  As described above, according to the knocking detection device according to the present embodiment, the presence or absence of knocking can be accurately determined using the result of frequency analysis using short-time Fourier transform or wavelet transform.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a schematic configuration diagram of an engine system having a knock detection device according to an embodiment of the present invention. It is a figure which shows the waveform of the signal input into a DSP from a knock sensor. It is a control block diagram of the knock detection apparatus according to the first embodiment of the present invention. It is a control structure of a program executed by the DSP of the knock detection device according to the first embodiment of the present invention. It is a figure which shows the analysis result in DSP of the knock detection apparatus which concerns on the 1st Embodiment of this invention. It is a control block diagram of the knock detection apparatus which concerns on the 2nd Embodiment of this invention. It is a control structure of the program run by DSP of the knock detection apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the analysis result in DSP of the knock detection apparatus which concerns on the 2nd Embodiment of this invention. It is a control block diagram of the knock detection apparatus which concerns on the 3rd Embodiment of this invention. It is a control structure of the program run by DSP of the knock detection apparatus which concerns on the 3rd Embodiment of this invention. It is a figure which shows the analysis result in DSP of the knock detection apparatus which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

  100 Engine, 200 Air intake passage, 300 Throttle valve, 400 Distributor, 410 Reference angle sensor, 420 Crank angle sensor, 500 Knock sensor, 600 Water temperature sensor, 700 Injector, 800 Ignition system, 900, 910, 920, 930 DSP, 1000 ECU .

Claims (7)

A detection device for detecting knocking occurring in an internal combustion engine,
Detection means for detecting a signal value representing cylinder internal pressure or detecting a signal value representing vibration or sound of the cylinder block;
Storage means for storing the detected signal value in correspondence with the crankshaft angle;
Analyzing means for dividing the stored signal value at predetermined time intervals and performing frequency analysis of the signal value at each time interval;
Based on a change in accordance with time series of frequency analysis characteristic values at each said time interval, and determining means for determining the presence or absence of occurrence of knocking seen including,
The analysis means includes means for calculating a peak frequency at which the intensity of the signal value is a maximum as a characteristic value ,
The determination means includes a knocking detection apparatus including means for determining whether or not knocking has occurred based on a degree of change in peak frequency with respect to time series . 2. The knocking detection according to claim 1 , wherein the determination unit includes a unit for determining whether or not knocking has occurred by comparing a slope of a change in peak frequency with respect to a time series with a predetermined slope. apparatus. A detection device for detecting knocking occurring in an internal combustion engine,
Detection means for detecting a signal value representing cylinder internal pressure or detecting a signal value representing vibration or sound of the cylinder block;
Storage means for storing the detected signal value in correspondence with the crankshaft angle;
Analysis means for analyzing the stored signal value for each frequency band using a plurality of filters that filter only a specific frequency band;
A knocking detection device comprising: determination means for determining whether or not knocking has occurred based on a time lag in the respective frequency bands at the maximum timing of the signal value. The knocking detection according to claim 3 , wherein the determination unit includes a unit for determining whether or not knocking has occurred based on a slope of a time lag in each frequency region at the maximum timing of the signal value. apparatus. The determination means includes means for determining whether or not knocking has occurred by comparing a slope of a time lag in the respective frequency domain with a predetermined slope at the maximum timing of the signal value. The knock detection device according to claim 4 , further comprising: A detection device for detecting knocking occurring in an internal combustion engine,
Detection means for detecting a signal value representing cylinder internal pressure or detecting a signal value representing vibration or sound of the cylinder block;
Storage means for storing the detected signal value in correspondence with the crankshaft angle;
Analysis means for frequency analysis of the stored signal value using Fourier transform or wavelet transform;
A knocking detection device comprising: a determination unit for determining whether knocking has occurred or not based on a slope of a peak frequency at which the intensity of the signal value with respect to time series is a maximum obtained by the analysis unit . The determination means includes means for determining the presence or absence of occurrence of knocking by comparing the inclination of the change in peak frequency with respect to the time series obtained by the analysis means and a predetermined inclination. The knock detection device according to claim 6 .

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