WO1999046571A1 - Method for evaluating knock signals of internal combustion engines - Google Patents

Method for evaluating knock signals of internal combustion engines Download PDF

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Publication number
WO1999046571A1
WO1999046571A1 PCT/DE1999/000532 DE9900532W WO9946571A1 WO 1999046571 A1 WO1999046571 A1 WO 1999046571A1 DE 9900532 W DE9900532 W DE 9900532W WO 9946571 A1 WO9946571 A1 WO 9946571A1
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Prior art keywords
knock
signal
signals
correlation
internal combustion
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PCT/DE1999/000532
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German (de)
French (fr)
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Stefan Hermann
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Siemens Aktiengesellschaft
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L23/00—Devices or apparatus for measuring or indicating or recording rapid changes, such as oscillations, in the pressure of steam, gas, or liquid; Indicators for determining work or energy of steam, internal-combustion, or other fluid-pressure engines from the condition of the working fluid
    • G01L23/22—Devices or apparatus for measuring or indicating or recording rapid changes, such as oscillations, in the pressure of steam, gas, or liquid; Indicators for determining work or energy of steam, internal-combustion, or other fluid-pressure engines from the condition of the working fluid for detecting or indicating knocks in internal-combustion engines; Units comprising pressure-sensitive members combined with ignitors for firing internal-combustion engines
    • G01L23/221—Devices or apparatus for measuring or indicating or recording rapid changes, such as oscillations, in the pressure of steam, gas, or liquid; Indicators for determining work or energy of steam, internal-combustion, or other fluid-pressure engines from the condition of the working fluid for detecting or indicating knocks in internal-combustion engines; Units comprising pressure-sensitive members combined with ignitors for firing internal-combustion engines for detecting or indicating knocks in internal combustion engines
    • G01L23/225—Devices or apparatus for measuring or indicating or recording rapid changes, such as oscillations, in the pressure of steam, gas, or liquid; Indicators for determining work or energy of steam, internal-combustion, or other fluid-pressure engines from the condition of the working fluid for detecting or indicating knocks in internal-combustion engines; Units comprising pressure-sensitive members combined with ignitors for firing internal-combustion engines for detecting or indicating knocks in internal combustion engines circuit arrangements therefor

Definitions

  • the invention relates to a method for evaluating knock signals in internal combustion engines according to the preamble of claim 1.
  • the knock signal is a frequency-modulated sine signal that runs synchronously with the motocycle and is only generated during the expansion phase.
  • the carrier frequency is approximately a motor-dependent variable.
  • the signal coming from the knock sensor is filtered with a bandpass filter and then rectified.
  • This method is sensitive to interference, since all noise signals that are in the evaluated spectral or time range in which no knock signal occurs affect the output signal.
  • a knock filter as a bandpass filter and a comparator, which is followed by a correlation filter.
  • the correlation filter is tuned to the center frequency of an expected knock signal, so that interference pulses arriving in a statistical sequence are not used for knock detection.
  • DE 40 08 284 AI describes a circuit arrangement for knock detection by means of correlation filtering, in which two correlation signals phase-shifted by 90 ° have the frequency of the expected knock signals.
  • the present invention has for its object to provide a method for evaluating knock signals by correlation filtering, which has a large signal-to-noise ratio, which can be carried out with a simply designed circuit and which without modification of the hardware by changing less parametric sizes is adaptable to any type of internal combustion engine.
  • the method according to the invention has the significant advantage that the signal-to-noise ratio is relatively high and only the software has to be changed to adapt to different types of internal combustion engines, while the hardware can remain unchanged.
  • Fig. 2b the first correlation signal U2
  • Fig. 2d the second correlation signal U3.
  • the block diagram according to FIG. 1 shows a device for evaluating knock signals of an internal combustion engine, with a knock sensor 1, the output signal of which, the knock signal U1 (corresponding to FIG. 2b), is fed to an evaluation device 2.
  • the output signal Ul consists of the knock component 3 UK, which is filtered out of the knock signal U1 by the correlation filtering according to the invention, and a noise component UR.
  • the correlation filtering is carried out by means of two predetermined correlation signals U2 and U3 according to FIG. 2c, d - starting at the instant of the maximum combustion chamber pressure in the upper piston dead center of a cylinder (FIG. 2a) - in the expansion phase.
  • a DC voltage signal Uout is present at the output of the evaluation device 2, the level of which is a measure of the size of the knock component UK.
  • the first correlation signal U2 preferably has the same phase position as the knock component UK and the second correlation signal U3 is preferably 90 ° out of phase with the correlation signal U2.
  • the two correlation signals U2, U3 are preferably digital, frequency-modulated signals with a constant frequency swing and variable wobble time.
  • Wobbling times are stored in a map memory of a microcontroller uC as a function of parameters such as speed, ignition timing and knocking frequency, as is their frequency deviation, and are read out by means of a software program and "fed to the evaluation device 2.
  • the evaluation device 2 consists of a first M1 and a second multiplier M2.
  • the knock signal U1 and the first correlation signal U2 are fed to the first multiplier M1 at its two inputs.
  • the second multiplier is knocked off at its two inputs. 4 gnal Ul and the second correlation signal U3 supplied.
  • the two multipliers M1, M2 multiply the respective input signals in such a way that there are correlated signals at the output of the multipliers M1, M2, which are rectified via subsequent rectifiers G1, G2, preferably two-way rectifiers.
  • the output signals of the rectifiers G1, G2 are added via an adder Add.
  • the output signal of the adder Add is filtered via a low-pass filter TP, the sum signal Uout, a DC voltage signal, being present at the output of the low-pass filter TP for further processing in a control or / and regulating circuit, the level of which is a measure of the size of the knock component UK, ie , for the intensity of the knock.

Abstract

The invention relates to a method for evaluating the knock signals of an internal combustion engine, comprising at least one knock sensor (1). The knock part (UK) of the output signal (U1) is filtered out of the knock signal (U1) by correlation filtering using two predetermined correlation signals (U2, U3), synchronously with the production of the knock which starts in the upper dead centre of the piston. In correlation signals (U2, U3) are digital, frequency-modulated signals with a constant frequency deviation and a variable sweep time. A direct voltage signal (Uout) appears at the output of an evaluation device (2), the level of this signal being a measure of the size of the knock part (UK).

Description

1 Beschreibung 1 description
Verfahren zur Auswertung von KlopfSignalen bei BrennkraftmaschinenProcess for evaluating knock signals in internal combustion engines
Die Erfindung betrifft ein Verfahren zur Auswertung von KlopfSignalen bei Brennkraftmaschinen nach dem Oberbegriff des Anspruchs 1.The invention relates to a method for evaluating knock signals in internal combustion engines according to the preamble of claim 1.
Das Klopfsignal ist ein mit dem Motozyklus synchron verlaufendes, frequenzmoduliertes Sinussignal und entsteht nur während der Expansionsphase. Die Trägerfrequenz ist annähernd eine motorabhängige Größe.The knock signal is a frequency-modulated sine signal that runs synchronously with the motocycle and is only generated during the expansion phase. The carrier frequency is approximately a motor-dependent variable.
Bei nahezu allen bekannten Klopferkennungseinrichtungen wird das aus dem Klopfsensor kommende Signal mit einem Bandpaß gefiltert und anschließend gleichgerichtet.In almost all known knock detection devices, the signal coming from the knock sensor is filtered with a bandpass filter and then rectified.
Diese Methode ist störempfindlich, da alle Rauschsignale, die im ausgewerteten Spektral- oder Zeitbereich liegen, in dem kein Klopfsignal auftritt, das Ausgangssignal beeinflussen.This method is sensitive to interference, since all noise signals that are in the evaluated spectral or time range in which no knock signal occurs affect the output signal.
Aus der DE 34 30 000 AI ist eine Vorrichtung zur Auswertung von KlopfSignalen bekannt, mit einem Klopffilter als Bandpaß und einem Vergleicher, dem ein Korrelationsfilter nachgeschaltet ist. Das Korrelationsfilter ist dabei auf die Mittenfrequenz eines zu erwartenden Klopfsignals abgestimmt, so daß in statistischer Folge eintreffende Störimpulse nicht zur Klopferkennung herangezogen werden.From DE 34 30 000 AI an apparatus for evaluating knock signals is known, with a knock filter as a bandpass filter and a comparator, which is followed by a correlation filter. The correlation filter is tuned to the center frequency of an expected knock signal, so that interference pulses arriving in a statistical sequence are not used for knock detection.
In DE 40 08 284 AI ist eine Schaltungsanordnung zur Klopferkennung mittels Korrelationsfilterung beschrieben, bei welcher zwei um 90° phasenverschobene Korrelationssignale die Frequenz der zu erwartenden KlopfSignale aufweisen. 2 Der vorliegenden Erfindung liegt die Aufgabe zugrunde, ein Verfahren zur Auswertung von Klopfsignalen durch Korrelationsfilterung anzugeben, welches ein großes Signal-/Rausch- Verhältnis aufweist, welches mit einer einfach ausgestalteten Schaltung durchgeführt werden kann und welches ohne Modifikationen der Hardware durch Änderung weniger parametrischer Größen an jeden Typ einer Brennkraftmaschine anpaßbar ist.DE 40 08 284 AI describes a circuit arrangement for knock detection by means of correlation filtering, in which two correlation signals phase-shifted by 90 ° have the frequency of the expected knock signals. 2 The present invention has for its object to provide a method for evaluating knock signals by correlation filtering, which has a large signal-to-noise ratio, which can be carried out with a simply designed circuit and which without modification of the hardware by changing less parametric sizes is adaptable to any type of internal combustion engine.
Diese Aufgabe wird durch die Merkmale des Anspruchs 1 gelöst.This object is solved by the features of claim 1.
Das erfindungsgemäße Verfahren hat den wesentlichen Vorteil, daß das Signal-/Rausch-Verhältnis relativ hoch ist und in der Anpassung an unterschiedliche Typen von Brennkraftmaschinen nur die Software geändert werden muß, während die Hardware unverändert bleiben kann.The method according to the invention has the significant advantage that the signal-to-noise ratio is relatively high and only the software has to be changed to adapt to different types of internal combustion engines, while the hardware can remain unchanged.
Weitere vorteilhafte Ausgestaltungen der Erfindung ergeben sich aus den Unteransprüchen.Further advantageous embodiments of the invention result from the subclaims.
Ein Ausführungsbeispiel der Erfindung ist in der Zeichnung dargestellt.An embodiment of the invention is shown in the drawing.
Es zeigen:Show it:
Fig. 1: Ein Blockschaltbild einer Einrichtung zur Durchführung des erfindungsgemäßen Verfahrens,1: A block diagram of a device for performing the method according to the invention,
Fig . 2a den Verlauf der Verdichtung über der Zeit,Fig. 2a the course of the compression over time,
Fig . 2b das erste Korrelationssignal U2, und
Figure imgf000004_0001
Fig . 2d das zweite Korrelationssignal U3.Fig. 2b the first correlation signal U2, and
Figure imgf000004_0001
Fig. 2d the second correlation signal U3.
Das Blockschaltbild nach Figur 1 zeigt eine Einrichtung zur Auswertung von Klopfsignalen einer Brennkraftmaschine, mit einen Klopfsensor 1, dessen Ausgangssignal, das Klopfsignal Ul (entsprechend Figur 2b) einer Auswerteeinrichtung 2 zuge- führt wird. Das Ausgangssignal Ul besteht aus dem Klopfanteil 3 UK, welcher durch die erfindungsgemäße Korrelationsfilterung aus dem Klopfsignal Ul herausgefiltert wird, und einem Rauschanteil UR. Zur Detektion des Klopfanteils UK erfolgt die Korrelationsfilterung mittels zweier vorgegebener Korre- lationssignale U2 und U3 gemäß Figur 2c, d - beginnend im Augenblick des maximalen Brennraumdrucks im oberen Kolbentotpunkt eines Zylinders (Fig. 2a) - in der Expansionsphase.The block diagram according to FIG. 1 shows a device for evaluating knock signals of an internal combustion engine, with a knock sensor 1, the output signal of which, the knock signal U1 (corresponding to FIG. 2b), is fed to an evaluation device 2. The output signal Ul consists of the knock component 3 UK, which is filtered out of the knock signal U1 by the correlation filtering according to the invention, and a noise component UR. To detect the knock component UK, the correlation filtering is carried out by means of two predetermined correlation signals U2 and U3 according to FIG. 2c, d - starting at the instant of the maximum combustion chamber pressure in the upper piston dead center of a cylinder (FIG. 2a) - in the expansion phase.
Am Ausgang der Auswerteeinrichtung 2 steht ein Gleichspan- nungssignal Uout an, dessen Pegel ein Maß für die Größe des Klopfanteils UK ist. Das erste Korrelationssignal U2 hat vorzugsweise die gleiche Phasenlage wie der Klopfanteil UK und das zweite Korrelationssignal U3 ist um vorzugsweise 90° gegenüber dem Korrelationssignal U2 phasenverschoben.A DC voltage signal Uout is present at the output of the evaluation device 2, the level of which is a measure of the size of the knock component UK. The first correlation signal U2 preferably has the same phase position as the knock component UK and the second correlation signal U3 is preferably 90 ° out of phase with the correlation signal U2.
Die beiden Korrelationssignale U2,U3 sind vorzugsweise digitale, frequenzmodulierte Signale mit konstantem Frequenzhub und variabler Wobbelzeit.The two correlation signals U2, U3 are preferably digital, frequency-modulated signals with a constant frequency swing and variable wobble time.
Die unterschiedlichen Korrelationssignale U2,U3 und derenThe different correlation signals U2, U3 and their
Wobbeizeiten sind in einem Kennfeld-Speicher eines Microcontrollers uC in Abhängigkeit von Parametern wie Drehzahl, Zündzeitpunkt und Klopffrequenz abgelegt, ebenso deren Frequenzhub, und werden mittels eines Software-Programms ausge- lesen, und" der Auswerteeinrichtung 2 zugeführt.Wobbling times are stored in a map memory of a microcontroller uC as a function of parameters such as speed, ignition timing and knocking frequency, as is their frequency deviation, and are read out by means of a software program and "fed to the evaluation device 2.
Durch diese Maßnahme brauchen die Hardware-Komponenten bei unterschiedlichen Brennkraftmaschinen nicht verändert zu werden. Die Anpassung an verschiedene Typen von Brennkraft a- schinen erfolgt durch eine Anpassung der Software. Zu diesem Zweck besteht die Auswerteeinrichtung 2 aus einem ersten Ml und einem zweiten Multiplizierer M2. Dem ersten Multiplizierer Ml werden an seinen beiden Eingängen das Klopfsignal Ul und das erste Korrelationssignal U2 zugeführt. Dem zweiten Multiplizierer werden an seinen beiden Eingängen das Klopfsi- 4 gnal Ul und das zweite Korrelationssignal U3 zugeführt. Über die beiden Multiplizierer Ml, M2 erfolgt eine multiplikative Verknüpfung der jeweiligen Eingangssignale derart, daß am Ausgang der Multiplizierer Ml, M2 korrelierte Signale anste- hen, die über nachfolgende Gleichrichter G1,G2, vorzugsweise Zweiweggleichrichter, gleichgerichtet werden. Die Ausgangssignale der Gleichrichter Gl, G2 werden über einen Addierer Add addiert. Über einen Tiefpaß TP wird das Ausgangssignal des Addierers Add gefiltert, wobei am Ausgang des Tiefpasses TP das Summensignal Uout, ein Gleichspannungssignal, zur weiteren Verarbeitung in einem Steuer- oder/und Regelkreis ansteht, dessen Pegel ein Maß für die Größe des Klopfanteils UK, d.h., für die Intensität des Klopfens ist. This measure means that the hardware components in different internal combustion engines do not have to be changed. The software is adapted to different types of internal combustion engines. For this purpose, the evaluation device 2 consists of a first M1 and a second multiplier M2. The knock signal U1 and the first correlation signal U2 are fed to the first multiplier M1 at its two inputs. The second multiplier is knocked off at its two inputs. 4 gnal Ul and the second correlation signal U3 supplied. The two multipliers M1, M2 multiply the respective input signals in such a way that there are correlated signals at the output of the multipliers M1, M2, which are rectified via subsequent rectifiers G1, G2, preferably two-way rectifiers. The output signals of the rectifiers G1, G2 are added via an adder Add. The output signal of the adder Add is filtered via a low-pass filter TP, the sum signal Uout, a DC voltage signal, being present at the output of the low-pass filter TP for further processing in a control or / and regulating circuit, the level of which is a measure of the size of the knock component UK, ie , for the intensity of the knock.

Claims

Patentansprüche claims
1. Verfahren zur Auswertung von KlopfSignalen (Ul) wenigstens eines an einer Brennkraftmaschine angeordneten Klopfsensors (1) durch Korrelationsfilterung in einer Auswerteschaltung (2), wobei jedes Klopfsignal (Ul) in einem ersten Multiplizierer (Ml) mit einem ersten Korrelationssignal (U2) und in einem zweiten Multiplizierer (M2) mit einem zweiten, zu dem ersten um 90° phasenverschobenen Korrelationssignal (U3) mul- tipliziert wird, wobei die Ausgangssignale beider Multiplizierer (M1,M2) gleichgerichtet und addiert werden und das Summensignal tiefpaßgefiltert wird, und wobei der Pegel des tiefpaßgefilterten Summensignals (Uout) ein Maß für die Größe des Klopfanteils (UK) des Klopfsignals (Ul) ist.1. Method for evaluating knock signals (Ul) of at least one knock sensor (1) arranged on an internal combustion engine by correlation filtering in an evaluation circuit (2), each knock signal (Ul) in a first multiplier (Ml) with a first correlation signal (U2) and is multiplied in a second multiplier (M2) by a second correlation signal (U3) which is phase-shifted by 90 °, the output signals of both multipliers (M1, M2) being rectified and added and the sum signal being low-pass filtered, and the Level of the low-pass filtered sum signal (Uout) is a measure of the size of the knock component (UK) of the knock signal (Ul).
d a d u r c h g e k e n n z e i c h n e tcharacterized
daß die Korrelationssignale (U2,U3) digitale, frequenzmodulierte Signale mit konstantem Frequenzhub und variabler Wob- belzeit sind.that the correlation signals (U2, U3) are digital, frequency-modulated signals with a constant frequency swing and variable sweep time.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die Korrelationssignale (U2,U3) als Funktionen von Parametern wie Motordrehzahl, Zündzeitpunkt und Klopffrequenz sowie deren Frequenzhub in Kennfeldern eines Microcontrollers (μC) gespeichert sind und mittels eines Software-Programms ausgelesen und den beiden Multiplizierern (M1,M2) zugeführt werden.2. The method according to claim 1, characterized in that the correlation signals (U2, U3) are stored as functions of parameters such as engine speed, ignition timing and knock frequency and their frequency swing in maps of a microcontroller (μC) and read out by means of a software program and the two Multipliers (M1, M2) are supplied.
3. Verfahren nach Anspruch 1 oder 2 , dadurch gekennzeichnet, daß die Korrelationssignale (U2,U3) der Auswerteschaltung [ 2 ab dem Zeitpunkt des maximalen Brennraumdrucks in einem Zylinder der Brennkraftmaschine zugeführt werden. 3. The method according to claim 1 or 2, characterized in that the correlation signals (U2, U3) of the evaluation circuit [2 are supplied from the time of the maximum combustion chamber pressure in a cylinder of the internal combustion engine.
PCT/DE1999/000532 1998-03-11 1999-02-26 Method for evaluating knock signals of internal combustion engines WO1999046571A1 (en)

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DE19810526 1998-03-11

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3430000A1 (en) * 1984-08-16 1986-02-27 Robert Bosch Gmbh, 7000 Stuttgart DEVICE FOR EVALUATING KNOCKING SIGNALS
DE4008284A1 (en) * 1990-03-15 1991-09-19 Bosch Gmbh Robert KNOCK DETECTION CIRCUIT ARRANGEMENT
EP0529786A2 (en) * 1991-08-30 1993-03-03 Loral Aerospace Corporation Apparatus and method for detecting vibration patterns
US5469479A (en) * 1992-02-27 1995-11-21 Texas Instruments Incorporated Digital chirp synthesizer

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3430000A1 (en) * 1984-08-16 1986-02-27 Robert Bosch Gmbh, 7000 Stuttgart DEVICE FOR EVALUATING KNOCKING SIGNALS
DE4008284A1 (en) * 1990-03-15 1991-09-19 Bosch Gmbh Robert KNOCK DETECTION CIRCUIT ARRANGEMENT
EP0529786A2 (en) * 1991-08-30 1993-03-03 Loral Aerospace Corporation Apparatus and method for detecting vibration patterns
US5469479A (en) * 1992-02-27 1995-11-21 Texas Instruments Incorporated Digital chirp synthesizer

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
U. TIETZE, CH. SCHENK: "Halbleiter-Schaltungstechnik", 1980, SPRINGER-VERLAG, BERLIN HEIDELBERG NEW YORK, XP002108444 *

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