DE102021102260A1 - Determination of knocking in a cylinder of an internal combustion engine - Google Patents

Abstract

The invention relates to a real-time method for determining knocking in a cylinder of an internal combustion engine, comprising the steps: selecting a cylinder to be diagnosed, determining a diagnostic time window that includes a focal point of combustion in a power stroke of the selected cylinder, determining a speed development of the internal combustion engine during the diagnostic time window, determining a detonation characteristic in the identified cylinder. The invention also relates to an engine control unit and an internal combustion engine.

Description

The invention relates to a method for determining knocking in a cylinder of an internal combustion engine, an engine control unit for an internal combustion engine, and an internal combustion engine with one or more cylinders and an engine control unit.

Rough engine running and irregular combustion are a fundamental problem in internal combustion engines, which can lead in particular to an incorrect build-up of the propulsion torque. The fact that there is a faulty torque build-up can be regularly read from the output variable of the engine speed - i.e. the speed development of the crankshaft.

However, the mere knowledge of the existence of an error is usually not enough to remedy the situation. A clear diagnosis of the malfunction is necessary to rectify the error, whereby the causes of irregular combustion and/or uneven engine running can be very different.

An accurate diagnosis is very complex with current diagnostic systems and requires various information from different subsystems of the combustion engine. Even distinguishing between mechanical problems in the cylinder (e.g. in the sliding pair) on the one hand and problems in the gas filling (charge exchange) or in the air path on the other hand is difficult when the customer visits the workshop with the functionally impaired engine without dismantling.

A visit to the workshop with a poorly running engine can therefore be unpleasant for the customer with regard to the probability of a correct initial diagnosis being successful.

In order to avoid such things better and better, options for predictive maintenance (also known as “health functions”) for combustion engines are becoming increasingly important. These should quantify and better localize the current performance status - and thus the maintenance requirement - in particular with regard to the required scope of maintenance and with regard to an advantageous timeline.

Against the background of the problems described, it is an object of the invention to enable improved identification of a fault cause for rough engine running and/or combustion misfires, and in particular to provide improved determination of knocking in a cylinder of an internal combustion engine.

This object is achieved by a method having the features of claim 1, an engine control device for an internal combustion engine having the features of claim 8, and an internal combustion engine having the features of claim 10. The dependent claims relate to advantageous developments of the invention.

1. (i) Auswahl eines zu diagnostizierenden Zylinders.
2. (ii) Bestimmen eines Diagnose-Zeitfensters, das eine Schwerpunktlage einer Verbrennung in einem Arbeitstakt des ausgewählten Zylinders beinhaltet.
3. (iii) Ermitteln einer Drehzahlentwicklung des Verbrennungsmotors während des Diagnose-Zeitfensters, insbesondere mit einer echtzeitfähigen Samplingqualität.
4. (iv) Ermitteln eines Klopfbetriebskennwerts im identifizierten Zylinder in Abhängigkeit von der ermittelten Drehzahlentwicklung.

According to one aspect, a method for determining knocking in a cylinder of an internal combustion engine, in particular in a motor vehicle, is disclosed. The method has at least the following method steps, which can be carried out in the order given below or in another order that makes sense for the person skilled in the art:

1. (i) Selection of a cylinder to be diagnosed.
2. (ii) Determination of a diagnostic time window that includes a center of gravity of combustion in a power stroke of the selected cylinder.
3. (iii) determining a speed development of the internal combustion engine during the diagnosis time window, in particular with a real-time capable sampling quality.
4. (iv) determining a knocking operation parameter in the identified cylinder as a function of the determined speed development.

As a result, knocking can be detected and/or quantitatively determined while the motor vehicle is being driven. A high probability of imminent knocking operation, ie a tendency to knocking, can also be predicted using the knocking operation parameter, in particular under certain boundary conditions. This is an advantage of the invention compared to detection using one or more knocking sensors: knocking combustion does not have to be detected using the knocking operation parameter Sufficient to make a diagnostic statement, unlike detection with a seismic knock sensor.

The diagnosis time window extends in particular at least essentially between a (real or, for simplification, assumed across the board for several operating states) ignition crank angle position at an ignition time of the identified cylinder and a burn-end crank angle position at a defined burn end of the selected cylinder. The diagnosis time window can also have a crank angle range at each of its two edges, in which the speed development is relevant for determining a pressure index for an original edge point of the diagnosis time window, for example the ignition point or the end of combustion.

In the present case, a knocking operation is to be understood in particular as a so-called knocking combustion in the diagnosed cylinder. In the case of knocking combustion, uncontrolled rapid combustion takes place in the combustion chamber with correspondingly high energy peaks in a short period of time. One reason for knocking combustion can be, for example, parallel ignition of the mixture in the combustion chamber away from the spark plug, for example if there are smoldering residues there. The knocking noise that characterizes knocking operation arises in particular from the fact that different combustion fronts in the combustion chamber meet at supersonic speeds.

1. (a) an eine Diagnosekomponente des Motorsteuergeräts für weitere Onboard-Diagnosefunktionen, und/oder
2. (b) an eine Steuerkomponente des Motorsteuergeräts für eine Echtzeitregelung von Funktionen des Verbrennungsmotors in Abhängigkeit von dem ermittelten Klopfbetriebskennwert.

According to a further aspect, an engine control unit for an internal combustion engine is disclosed, which is set up to transfer knocking operation characteristic values (KB) determined and/or stored in the memory, in particular by means of a method according to an embodiment of the invention

1. (a) to a diagnostic component of the engine control unit for further onboard diagnostic functions, and/or
2. (b) to a control component of the engine control unit for real-time regulation of functions of the internal combustion engine as a function of the knocking operating parameter determined.

According to one embodiment, the engine control unit has a non-volatile memory and is set up to store one or more manifestations of the knock operating characteristic value, in particular determined at one or different diagnosis times, in the non-volatile memory.

According to one embodiment, the engine control unit is set up to transfer forms of the knock operation parameter stored in the memory to an off-board computer for offline diagnostic functions. In particular, the process function in the engine control unit is also enabled for the transfer of the knocking operation parameter to cloud storage, which enables remote diagnosis of fleet vehicles without them having to be in the workshop environment.

According to a further aspect, an internal combustion engine with multiple cylinders is disclosed, comprising an engine control device according to an embodiment of the invention.

The invention is based, among other things, on the consideration that more and more “health functions” are being developed for the drives in modern passenger cars. These should quantify the current performance status. Since the tendency to knock in combustion engines is an elementary but not directly measurable parameter for combustion efficiency and component stress, it must be recorded while driving if you want to continuously monitor the performance of the combustion engine. From a technical point of view, there is a gap here so far.

In general, the combustion chamber of a cylinder contains a mass of air and a mass of fuel for combustion, the two masses being present as a mixture. The tendency to knock characterizes the pressure rise rates and pressure amplitudes of irregular combustion, particularly in Otto engines. In order to protect the mechanical components, such knocking combustion cycles require the knocking intensity to be limited by means of a controller intervention.

The knock intensity input signal used by the controller strongly influences the dynamics and strength of the knock controller and, in turn, combustion efficiency, torque output, exhaust gas temperature and emissions. The length of the combustion delay determines the combustion quality, consumption, driving comfort and emissions to a very large extent. Knocking work cycles cannot currently be measured directly during the first work cycle, not even with a knock sensor. This means that there is no dynamic controller which would be able to regulate, in particular to minimize, the tendency towards knocking operation from work cycle to work cycle (i.e. within a work cycle).

The invention is now based, among other things, on the idea of determining a characteristic number for a cylinder pressure at specific crankshaft positions from the crankshaft speed, which is already determined with high temporal resolution in modern internal combustion engines, and from this in turn deriving a characteristic value for whether knocking operation - i.e. knocking combustion - present in the cylinder.

Due to the short intervals between the individual speed measurements (in the range of a few milliseconds), it is possible with the invention to estimate the pressure build-up in the cylinder during combustion after ignition in detail and to evaluate the energy release in the cylinder using a pressure-based analysis.

The required determination of the pressure in the cylinder from the crankshaft speed can, for example, according to an in WO 2019/238338 A1 described method or with another known method, in particular at least three previously defined crankshaft positions (e.g.: first position: ignition; second position: shortly after a center of gravity - ie 50% combustion conversion - the combustion; third position, in particular in half the crank angle width between the first and second position).

A knock pressure energy integral for the knock intensity can then be evaluated based on the determined values for the cylinder pressure. If necessary, simplifying assumptions can be made for the evaluation in order to carry out an analysis that is still sufficiently accurate and capable of real-time on an otherwise known, typical engine control unit of a motor vehicle. Possible simplifying assumptions of this type are described here for an exemplary embodiment.

A knocking work cycle can be detected with the invention by comparing the determined value of the established knock pressure energy integral with a predetermined reference value, or by exceeding it.

The event detected in this way (i.e. the single-cycle knocking operation determined in this way) can be transferred to a data acquisition module in the vehicle for later use; Additionally or alternatively, when the event is detected, a controller intervention by the engine control unit can be triggered to prevent further knocking.

This can accelerate the identification of knocking: Together with the built-in knock sensors (e.g. seismic vibration sensors), the knock event in the cylinder can be detected after just one or a few cycles, and thus much faster than with the knock sensor alone. The knock sensor alone typically requires a number of work cycles until knocking is reliably detected on the basis of the frequency spectra in the sensor signal.

In this way, the controller intervention can also be accelerated and the mechanical component stress can be lowered earlier and permanently.

In addition, data collection can be supported: In the area of the “health functions” of drives, a simple, additional parameter can be collected with the invention: the limit load operation. It can be answered in the customer's onboard operation for later evaluation how often the engine was exposed to knocking, some of which was harmful. In the case of known engine control devices, only the controller interventions (later ignition angles to avoid them) are usually made available for this purpose.

Furthermore, a reduction in the manufacturing costs of the vehicle drive can be achieved with the invention: With sufficiently precise application of a control unit function within the meaning of the invention, it is conceivable that the knock sensor system could be omitted in engines that are operated in a quasi-stationary manner for a longer period of time.

According to one embodiment, the knock operation parameter is determined as a function of a pressure curve and/or a pressure gradient and/or a knock pressure energy in the selected cylinder during the specific diagnosis time window.

This enables knocking operation to be determined on the basis of the energy introduced into the combustion chamber of the cylinder by the combustion.

In particular, the pressure curve and/or the pressure gradient is determined as a function of the speed curve.

According to one embodiment, the knock operation characteristic is determined by evaluating a knock pressure energy integral over the diagnosis time window. In particular, knocking pressure energy is to be understood as meaning energy that is released in addition to typical combustion energy due to the even higher pressure gradients in knocking combustion. The knocking pressure energy integral can therefore represent, in particular, combustion energy released specifically by knocking operation.

This enables the energy input into the combustion chamber of the cylinder to be analyzed as a function of the torque variation of the crankshaft during the diagnosis time window, in particular via the intermediate step of a pressure evaluation.

In particular, an amount of the knocking pressure energy integral over the diagnosis time window is the knocking operating characteristic.

According to one embodiment, the knocking pressure energy, in particular the knocking pressure energy integral, is determined as a function of at least three characteristics of a pressure index, which is determined at least at three time intervals in the diagnosis time window.

This enables a diagnosis of the knocking behavior of the cylinder as a function of a high-frequency, continuously determined rotational speed of the crankshaft.

According to one embodiment, knocking is determined when an evaluation of the knock pressure energy integral results in an energy value that corresponds to at least one knock energy limit value, in particular for this cylinder, or is higher than this.

In this way, when the vehicle is being driven, knocking can be detected immediately for each working step of a cylinder, which, among other things, can enable direct control intervention to avoid knocking and/or possibly improved “predictive maintenance”.

For typical cylinders of modern internal combustion engines in motor vehicles, the knocking energy limit is in particular between 0.06 bar ² /KW ³ and 0.105 bar ² /KW ³ when operating under full load and at low speeds.

According to one embodiment, in addition to knocking operation, a risk of knocking operation can also be determined, in particular if the evaluation of the knocking pressure energy integral results in an energy value that is just below the knocking energy limit value and/or a time derivation/development of the energy value shows that the knocking energy limit value soon - i.e. in particular within a few working cycles of the internal combustion engine.

According to one embodiment, to determine the speed development, a continuous speed curve is recorded during the diagnosis time window and the recorded values are provided with a resolution of at least on the order of ten milliseconds, in particular in a control unit.

As a result, the knocking operation parameter can be determined while driving and/or can be determined as a function of the determined speed development.

• 1 a-c zeigt in schematischen Ansichten einen Verbrennungsmotor mit einer Motorsteuerung nach einer beispielhaften Ausführung der Erfindung, wobei in 1a die Einbauumgebung des Verbrennungsmotors, in 1b relevante Parameter sowie in 1c Drehmomentbeiträge an dem Kurbeltrieb des Verbrennungsmotors über die Zeit dargestellt sind.
• 2 zeigt ein Schaubild mit einem Diagramm einer Drehzahlentwicklung eines Arbeitszyklus des Verbrennungsmotors nach 1 und einer Darstellung der Takte der einzelnen Zylinder.
• 3 zeigt ein vergrößertes Detail aus dem Diagramm nach 2.
• 4 zeigt ein Schaubild mit einem Diagramm einer Druckentwicklung und einem Brennverlauf in einem Brennraum eines Zylinders aus 1, wobei aus dem Schaubild ein Klopfdruckenergie-Integral ersichtlich ist.
• 5 zeigt ein Ablaufdiagramm von Verfahrensschritten einer beispielhaften Ausführung eines erfindungsgemäßen Verfahrens.

Further advantages and application possibilities of the invention result from the following description in connection with the figures.

• 1ac shows in schematic views an internal combustion engine with an engine controller according to an exemplary embodiment of the invention, wherein in 1a the installation environment of the internal combustion engine, in 1b relevant parameters as well as in 1c Torque contributions to the crank mechanism of the internal combustion engine are shown over time.
• 2 shows a diagram with a diagram of a speed development of a working cycle of the internal combustion engine 1 and a representation of the strokes of the individual cylinders.
• 3 shows an enlarged detail from the diagram 2 .
• 4 shows a diagram with a diagram of a pressure development and a combustion process in a combustion chamber of a cylinder 1 , where a knocking pressure energy integral can be seen from the graph.
• 5 shows a flowchart of method steps of an exemplary embodiment of a method according to the invention.

In 1a an internal combustion engine 1 is shown in its installation environment, the internal combustion engine 1 in the exemplary embodiment being a four-stroke gasoline engine with four cylinders Z1, Z2, Z3 and Z4.

In the representation of 1a shows the installation environment, in particular the intake system 9 with the air filter LF at the air inlet, the exhaust gas turbocharger ATL and an intercooler and the air collector LS towards the cylinders Z.

In 1b the internal combustion engine 1 is shown in a more detailed schematic view. The internal combustion engine 1 has the cylinders Z1, Z2, Z3 and Z4, with all cylinders Z providing their torque contribution M to the crank mechanism KT detection unit 6 and a cylinder pressure determination unit 7 for the reference pressures from the environment and air collector or crankcase, as well as for determining cylinder pressures p1, p2, p3 (or p13, p32) as a function of speeds n and detected by means of the speed detection unit 6 a rotational speed development 101 of the crankshaft KT in the diagnosis time window 112 determined by the computing unit 4 from the detected rotational speeds n.

Of the 1b It can be seen, among other things, that depending on the respective cylinder pressure p, each cylinder Z can cyclically apply a torque contribution M to the crank mechanism KT. The totality of the torque contributions results in a rotational speed n of a crankshaft of the crank mechanism KT that varies over time.

A reference pressure p can be used by the pressure detection unit 7 , the instantaneous speed n can be used by the speed detection unit 6 and the arithmetic unit 4 by the engine controller 2 .

In 1c a diagram of a torque development 100 with an exemplary torque curve 10 on the crank drive KT during normal operation over the crank angle KW is shown. It can be seen that the torque contribution M comes from different cylinders Z in alternation.

In 2 is a sketch of an exemplary diagram 100 of a speed development 101 of a four-stroke cycle (= one working cycle (ASP): top dead center gas exchange (LOT) → intake → bottom dead center (UT) → valve closure and compression → top dead center ignition (ZOT) → expanding → UT → outlet) of the internal combustion engine 1 shown.

Flowchart 100 shows curve 101 of engine speed n over one working cycle (ASP) of a 4-cylinder gasoline engine. The ignition times (ZZP) and an exemplary possible diagnosis time window 112 for the cylinder Z1 to be diagnosed are marked. The associated working strokes of the cylinders Z1 - Z4 are shown below.

The example shown of a four-cylinder gasoline engine shows which area 112 of the crank angle scale can be used for knock diagnosis. The limits of the diagnosis time window 112 for the cylinder Z1 to be diagnosed are before and after the center of combustion 113, for example from the ignition of the mixture to a crankshaft position after the center of gravity.

Accordingly, three points in time P1, P3, P2 are determined within the diagnosis time window 112 in order to be able to carry out the exemplary method in a time-discrete manner, for example P1 at φ ₁ =690° CA, P3 at φ ₃ =715° CA and P2 at φ ₂ = 740° CA, with P3 lying in the middle between P1 and P2.

A diagnostic cylinder pressure value p1=p _diag.1 , p2=p _diag.2 and p3=p _diag.3 is determined for each of the points P1, P2 and P3 by means of mechanical calculation. For the calculation need different Difference values are formed, which are applied for each of the points P _k starting from the associated crank angle φ _k at the times (ie crank angles) φ k −x and φ k +x. The interval width for the respective differential value calculations is therefore 2x.

• Die 2 bis 4 erläutern ein Ausführungsbeispiel erfindungsgemäßer Verfahren zur Bestimmung eines Klopfbetriebs eines Zylinders Z im Fahrbetrieb mit Hilfe der Kurbelwellendrehzahl n des Kurbelwellentriebs KT. Im folgenden Absatz ist das im Ausführungsbeispiel durchgeführte Verfahren zunächst zusammenfassend beschrieben.

How the diagnostic cylinder pressure values p _diag,1 , p _diag,2 and p _diag,3 can be determined from the measured speed development 101 in the diagnosed cylinder Z is described below in the statements on equations (6) - (21):

• the 2 until 4 explain an exemplary embodiment of the method according to the invention for determining a knocking operation of a cylinder Z while driving with the aid of the crankshaft speed n of the crankshaft drive KT. The method carried out in the exemplary embodiment is initially described in summary in the following paragraph.

In the exemplary embodiment, the vehicle is being driven, in particular full-load operation of the internal combustion engine 1 at a comparatively low speed. For example, under such conditions, knocking combustion, ie knocking operation KB, can occur in the cylinders.

A live engine control function continuously reads speed values n for the crankshaft KT during driving operation (due to friction delay, an increased speed drop from one point in time to a directly subsequent point in time is to be expected in a compression phase of a cylinder) and uses this to determine a speed development 101 - cf. 1-3 . At specific crank angles φ ₁ , φ ₃ , φ ₂ (corresponds to points in time P1, P3, P2), diagnostic cylinder pressures p _diag,1 , p _diag,3 and p _diag,2 are calculated as a function of the speed development.

With the help of the determined values for the diagnostic cylinder pressures p _diag , a knock pressure energy integral E can be evaluated in real time using certain assumptions explained below.

A comparison of the value of the integral E calculated in this way with predetermined values then allows a direct conclusion to be drawn during driving operation as to whether knocking operation KB is present.

An exemplary method with method steps described in detail and associated, simplifying assumptions for a real-time capable evaluation is shown below for a cylinder Z1 by way of example.

First, a diagnosis time window 112 is defined for cylinder Z1. Since the development of pressure in the combustion chamber around the ignition times is the determining factor for detecting knocking combustion (i.e. cylinder knocking), at least according to the invention, the diagnostic time window 112 is defined by the subsequent crank angle positions in the exemplary embodiment.

The starting point P1 of the diagnosis time window 112 is established at the crank angle position φ ₀ =φ ₁ =690° CA for the diagnosed cylinder Z1. It is a virtual ignition point ZZP1 that spans all operating states.

The end point P2, the diagnosis time offset 112, is established at the crank angle position φ _E =φ ₂ =740° CA for the diagnosed cylinder Z1. At this crank angle position, a focal point of the combustion - which typically occurs at approx. 8° crank angle (non-knocking) - has already clearly passed through.

A center point P3 with respect to the crank angle is set at φ ₃ =715° CA.

The above-described selection of the crankshaft positions φ ₁ , φ ₃ , φ ₂ for determining the diagnostic cylinder pressures p _diag,1 , p _diag,3 and p _diag,2 is based on the considerations described below.

With the help of the knock integral function according to Franzke (Franzke, D.: Contribution to the determination of a knock criterion in gasoline engine combustion and to the precalculation of the knock limit, dissertation, Technical University of Munich, 1981), meaningful edge points of the diagnosis time window 112 are determined.

The direct application of the Franzke approach has the disadvantage that the unburned temperature T _u must also be constantly balanced. This is unsuitable for a real-time application on an engine control unit 2, but well suited for deriving computing premises.

The Franke boundary condition for a test engine examined by the applicant for the context of the invention is: $$C=\frac{{\phi }_{klOpf}-{\phi }_{SOC}}{BD}\approx 0.53$$

Knocking combustion and thus knocking operation KB therefore occurs at the center of combustion in cylinder 1—ie at approximately the 50% conversion point in the combustion cycle.

Therefore, for the purposes of the invention, in the exemplary embodiment, the adapted integral value is calculated from equation (5) until shortly after the position of the center of gravity. Knock-intensive areas at full load have their center of gravity later than 8° CA after TDC. For this reason, P2 is set at φ ₂ = 20° CA after TDC (corresponds to 740° CA). The corresponding associated cylinder pressure is then also evaluated.

Furthermore, the Franzke integral shows itself to be comparatively tolerant with regard to its concrete start of evaluation. For this reason and for reasons of practicality of real-time evaluation in engine control unit 2, an evaluation start at virtual ignition point ZZP1 or P1 of constant φ ₁ =30° CA before ZOT (corresponds to 690° CA) is selected. The corresponding associated cylinder pressure is then also evaluated.

P3 is set at a crank angle position in the middle between φ ₂ and φ ₁ , resulting in φ ₃ = 5° CA before ITDC (corresponds to 715° CA).

Based 4 shows how a knock pressure energy integral E can be used using some simplifying assumptions to determine knock operation KB of cylinder Z1.

In 4 a pressure curve p (solid line) and a curve of the combustion A (a combustion curve integral is representative of the curve of the combustion as a dashed line in the diagram) are plotted in the combustion chamber of the cylinder Z1 over the crankshaft position KW. A combustion center 113 is defined as that crank angle KW at which a center of combustion occurs, ie 50% of the mixture quantity in the cylinder has been converted by the combustion.

A knock pressure energy integral E is determined by the area delimited at the edge points φ ₁ and φ ₃ of the diagnosis time window 112 under the pressure curve p.

The knock pressure energy integral E is generally defined as follows, where p _HPF represents a high-pass filtered pressure signal in the combustion chamber of the cylinder: $$E_p\left({\phi }_E\right)={\displaystyle \int {}_{{\mathrm{<figure-callout\; id="0"\; label="\phi "\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_0}^{{\phi }_E}{\left(\frac{\mathrm{i.e}{p}_{HPf}}{\mathrm{i.e}\phi }\right)}^2}$$

To simplify the real-time application on an exemplary engine control unit 2, multiple application of the multiplication rule for integration on equation (1) and neglecting higher-order derivatives (quadratic and cubic) results in: $$E_p^{*}\left({\phi }_E\right)=p_{HPf}\cdot \frac{\mathrm{i.e}{p}_{HPf}}{\mathrm{i.e}\phi }$$

A simplifying assumption A1 is that a high-pass filter and the first derivative of a signal below a cut-off frequency have the same transfer function. The present application of the invention moves below the cut-off frequency since the pressure signal p used is calculated and is not itself jittered. Accordingly, the following applies approximately: $$p_{HPf}\approx \frac{\mathrm{i.e}p}{\mathrm{i.e}\phi }$$

Substituting equation (3) twice into equation (2) enables a calculation with a mean modeled pressure signal p: $$E_p^{**}\left({\phi }_E\right)=\frac{\mathrm{i.e}p}{\mathrm{i.e}\phi }\cdot \frac{{\mathrm{i.e}}^{2}p}{\mathrm{i.e}\phi }$$

A conversion of equation (4) into difference quotients and a linear approximation result in: $$\begin{array}{l}{E}_p^{***}\left({\phi }_E\right)=\frac{\Delta p}{\Delta \phi }\cdot \frac{{\Delta }^2\mathrm{<figure-callout\; id="2"\; label="p\; \Delta \; \phi "\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">p</figure-callout>}}{\Delta {\phi }^{}}\approx \frac{{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">p</figure-callout>}}_2-{\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">p</figure-callout>}}_1}{{\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_2-{\mathrm{<figure-callout\; id="1"\; label="\phi "\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_1}\cdot \left(\frac{{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">p</figure-callout>}}_2-2<figure-callout\; id="3"\; label="\cdot \; p"\; filenames="DE102021102260A1\_0033.png"\; state="\{\{state\}\}">\cdot </figure-callout>p_{}{}_3+p_1}{{\left({\mathrm{\phi }}_2-{\mathrm{\phi }}_1\right)}^2}\right)\\ =\frac{{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">p</figure-callout>}}_2^2-{\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">p</figure-callout>}}_1^2-2<figure-callout\; id="3"\; label="\cdot \; p"\; filenames="DE102021102260A1\_0033.png"\; state="\{\{state\}\}">\cdot </figure-callout>p_{}{}_3\cdot \left({\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">p</figure-callout>}}_2-p_1\right)}{{\left({\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_2-{\mathrm{\phi }}_1\right)}^3}\end{array}$$

Equation (5) can be evaluated with respect to a calculation of E using the pressure values p ₁ =p _diag,1 , p ₃ =p _diag,3 and p ₂ =p _diag,2 introduced above.

The following is the determination of a pressure value p _{zyl,diag described in detail} as an example and representative for the determination of the pressure values p _diag,1 , p _diag,3 and p _diag,2 :

Formelzeichen Bedeutung J₀, J Allg. / anteiliges Massenträgheitsmoment φ Winkelstellung der Kurbelwelle ω Winkelgeschwindigkeit M_tan Moment durch Gaskraft im Zylinder und oszillierender Massenkraft M_R Moment durch Reibungsverluste M_L Moment durch Lastanforderung M_M Anteiliges Moment durch rotatorische Massenträgheit n_mot Aktuell anliegende Motordrehzahl A power balance should - based on a measured speed difference - allow a comparison between a target cylinder pressure and an actual state: $$\frac{\mathrm{i.e}}{\mathrm{i.e}t}\left(\frac{1}{2}\cdot {\mathrm{<figure-callout\; id="0"\; label="J"\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">J</figure-callout>}}_0\cdot {\omega }^2\right)=\left(M_{tan}-M_R-M_L\right)\cdot \omega$$

symbol meaning J ₀ , J General / proportional mass moment of inertia φ Angular position of the crankshaft ω angular velocity M _tan Moment due to gas force in the cylinder and oscillating mass force _MR moment due to friction losses M _L moment by load request M _M Partial moment due to rotational mass inertia n _engine Current engine speed

Differentiation, substitution and introduction of a moment of inertia (division of the inertia components) results in the equation: $$J\cdot \dot{\omega }={\displaystyle \sum _i{M}_i=M_{tan}-M_R-M_L-M_M}$$

• „Gleichanteil“: $$\overline{M_{tan}}=\overline{M_R}-\overline{M_L}$$
  
  Die Bilanzierung des Gleichanteils geht von einem stationären Betriebspunkt aus. Das mittlere bereitgestellte Moment hält die mittlere Drehzahl konstant, weil es korrespondiert mit den Momentenforderungen aus Last und Reibung.
• „Wechselanteil“: $$J\cdot \dot{\omega }=\widetilde{M_{tan}}-\widetilde{M_R}-\widetilde{M_M}$$
  

If the equation is meaningfully divided into a "direct component" and an "alternating component", the following sub-equations are obtained:

• "Constant proportion": $$\overline{M_{tan}}=\overline{M_R}-\overline{M_L}$$
  
  The balancing of the direct component is based on a stationary operating point. The average torque provided keeps the average speed constant because it corresponds to the torque requirements from load and friction.
• “Change share”: $$J\cdot \dot{\omega }=\widetilde{M_{tan}}-\widetilde{M_R}-\widetilde{M_M}$$
  

$$\dot{\omega }\approx {\left(\frac{\pi }{30}\right)}^2\cdot nmot\cdot \frac{\Delta nmot}{\Delta \phi }$$

A conversion from time-based derivation to crank angle-based difference formation takes place with the help of the relationship $$\omega =\frac{\mathrm{i.e}\phi }{\mathrm{i.e}t}=\pi \cdot \frac{n_{m\mathrm{<figure-callout\; id="30"\; label="O\; t"\; filenames="DE102021102260A1\_0035.png"\; state="\{\{state\}\}">O</figure-callout>}t}}{30}\text{by}$$

$$\dot{\omega }\approx {\left(\frac{\pi }{30}\right)}^2\cdot nmOt\cdot \frac{\Delta nmOt}{\Delta \phi }$$

Formelzeichen Bedeutung A_K Kolbendeckfläche = const. r_K Wirkradius der Kurbelwelle entspricht halben Hub = const. l_Pl Pleuellänge = const. m_osz Oszillatorische Massenteil entspricht Kolbenbaugruppe und anteiliger Pleuelmasse = const. p_zyl Im Zylinder vorherrschender Druck p₀ Referenzdruck, Kurbelgehäusedruck β(φ) Pleuelschwenkwinkel in Abhängigkeit der Kurbelwinkelstellung s̈(φ) Kolbenbeschleunigung in Abhängigkeit von der Kolbenstellung The decisive quantities from equation (6) are further detailed for the evaluation. The relationship for the resulting moment from the inner-cylindrical gas force and results in: $$\widetilde{M_{tan}}=\left[A_K\cdot \left[p_{\mathrm{e.g}yt}\left(\phi \right)-p_0\right]-m_{Os\mathrm{e.g}}\cdot \ddot{s}\left(\phi \right)\right]\cdot {\mathrm{right}}_k\cdot \frac{\text{sin}\left(\phi +\beta \right)}{\text{cos}\beta }$$

symbol meaning A _K Piston top area = const. r _K Effective radius of the crankshaft corresponds to half the stroke = const. l _pl connecting rod length = const. m _osc Oscillatory mass part corresponds to piston assembly and proportionate connecting rod mass = const. p _cyl Pressure prevailing in the cylinder _p0 Reference pressure, crankcase pressure β(φ) Connecting rod swivel angle depending on the crank angle position s̈(φ) Piston acceleration as a function of piston position

Further detailing the variable factors from Equation (8) yields: $$\ddot{s}\left(\phi ,\dot{\phi },\ddot{\phi }\right)={\mathrm{right}}_k\cdot \ddot{\phi }\cdot \text{sin}\phi +{\mathrm{right}}_k\cdot {\dot{\phi }}^2\cdot \text{cos}\phi +\raisebox{1ex}{${\mathrm{<figure-callout\; id="2"\; label="right\; k"\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">right</figure-callout>}}_k$}\!\left/ \!\raisebox{-1ex}{$2$}\right.\cdot \ddot{\phi }\cdot {\lambda }_{pl}\cdot \text{sin}\left(2\cdot \phi \right)+{\mathrm{right}}_k\cdot {\dot{\phi }}^2\cdot {\lambda }_{pl}\cdot \text{cos}\left(2\cdot \phi \right)$$

Assuming a constant mean speed nmot, the relationship for the piston acceleration is simplified to: $${\ddot{s}}_{\mathrm{right}ea}\left(\phi ,\dot{\phi }\right)={\mathrm{right}}_k\cdot {\dot{\phi }}^2\cdot \left(\text{cos}\phi +{\mathrm{\lambda }}_{\text{Pl}}\cdot \text{cos}\left(2\phi \right)\right)$$

The assumption leads to an error that can be neglected. The influence of the angular acceleration results in a negligibly small deviation over the entire map. $$\beta \left(\phi =\right)\text{arcsin}\left({\lambda }_{pl}\cdot \text{sin}\phi \right)$$

$$p_{zyi}={\overline{p}}_{zyi}$$

push rod ratio $${\lambda }_{pl}=\raisebox{1ex}{${\mathrm{right}}_k$}\!\left/ \!\raisebox{-1ex}{$l_{pi}$}\right.$$

$$p_{\mathrm{e.g}yi}={\overline{p}}_{\mathrm{e.g}yi}$$

oder wie im weiteren auch genutzt der
Bezug zum Kurbelgehäusedruck $$p_0=p_{KurbGeh}=p_{umg}=DPS$$

wobei DPS für den Unterdruck im Saugrohr steht.relation to the ambient pressure $$p_{}$$$${}_0=p_{\mathrm{and}mG}$$

or as further also used the
relation to crankcase pressure $$p_{}$$$${}_0=p_{K\mathrm{and}\mathrm{right}bGeH}=p_{\mathrm{and}mG}=DPS$$

where DPS stands for the vacuum in the intake manifold.

The friction torque from Equation (6) can be represented in different ways. Either a model can be introduced which reflects measurement data for a specific operating point of the diagnosis. A goal-oriented approach here would be a functional linking of the term with the speed, the load and the oil temperature.

In the following, however, it is assumed that the diagnosis is carried out at firmly defined steady-state load points. As a result, the friction torque for this load point can be assumed to be constant. $$\widetilde{M_R}=cOnst.$$

$$J=const.$$

The same approach is also used for the proportional moment due to rotational mass inertia and the mass moment of inertia. $$\widetilde{M_M}=cOnst.$$

$$J=cOnst.$$

A suitable choice of diagnosis constants in the stationary operating point allows a simple application of the parameters afterwards.

Solving equation (6) for the gas moment gives: $$\widetilde{M_{tan}}=J\cdot \dot{\omega }+\widetilde{M_R}+\widetilde{M_M}$$

After inserting the relationships from equations (14) to (16), one can conclude the following simplification with the application constant KRM: $$\widetilde{M_{tan}}=J\cdot \dot{\omega }+K_{RM}$$

Application of the diagnosis:

In 3 the detail X is off 2 , ie the speed development 101 via the crank angle KW during the diagnosis time window 112 with the speed measuring points around P1, P3 and P2 of cylinder Z1. The speed is measured for the point P1 at the crank angles φ ₁ -x and φ ₁ +x to enable a difference value formation according to equation (18) below. This measuring point offset of 2x by φ ₃ or φ ₂ also applies to the speed measurement around points P3 and P2.

The angular velocity gradient from equation (17) is expanded. The speed to be determined must be averaged and constants are marked again. $$\begin{array}{l}\dot{\omega }\approx {\left(\frac{\pi }{30}\right)}^2\cdot \overline{n_{mOt}}\cdot \frac{\Delta n_{mOt}}{\Delta \phi }\\ \dot{\omega }\approx {\left(\frac{\pi }{30}\right)}^2\cdot \frac{n_{mOt}{}_{{}_{\mathrm{\phi +}\text{x}}}+n_{mOt}{}_{{}_{\mathrm{\phi -}\text{x}}}}{2}\cdot \frac{n_{mOt}{}_{{}_{\mathrm{\phi +}\text{x}}}+n_{mOt}{}_{{}_{\mathrm{\phi -}\text{x}}}}{2\text{x}}\\ \dot{\omega }\approx \frac{1}{2}\cdot {\left(\frac{\pi }{30}\right)}^2\cdot \frac{n_{mOt}{{}_{{}_{\mathrm{\phi +}\text{x}}}}^2+n_{mOt}{{}_{{}_{\mathrm{\phi -}\text{x}}}}^2}{2\text{x}}\\ \dot{\omega }\approx K_{\omega }\cdot \frac{n_{mOt}{{}_{{}_{\mathrm{\phi +}\text{x}}}}^2+n_{mOt}{{}_{{}_{\mathrm{\phi -}\text{x}}}}^2}{2\text{x}}\end{array}$$

mit einer Kinematikkonstanten für den Stationärpunkt, in welchem die Diagnose stattfindet $$K_K=r_k\cdot \frac{\text{sin}\left(\phi +\beta \right)}{\text{cos}\beta }$$

The term for the tangential moment from equation (8) is subsequently expanded to include the relationships from equations (9) to (13) and constants are identified. $$\begin{array}{l}\widetilde{M_{tan}}=\left[\frac{\left({\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">p</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">p</figure-callout>}}_2-2\cdot p_{\mathrm{and}mG}+2\cdot DPS\right)}{2}\cdot A_K-m_{Os\mathrm{e.g}}\cdot \ddot{s}\left(\phi \right)\right]\cdot {\mathrm{right}}_k\frac{\text{sin}\left(\phi +\beta \right)}{\text{cos}\beta }\\ \widetilde{M_{tan}}=\left[\frac{\left({\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">p</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">p</figure-callout>}}_2-2\cdot p_{\mathrm{and}mG}+2\cdot DPS\right)}{2}\cdot A_K-m_{Os\mathrm{e.g}}\cdot \ddot{s}\left(\phi \right)\right]\cdot K_K\end{array}$$

with a kinematic constant for the stationary point in which the diagnosis takes place $$K_K={\mathrm{right}}_k\cdot \frac{\text{sin}\left(\phi +\beta \right)}{\text{cos}\beta }$$

After inserting equations (19) and (18) into equation (17), solving for the cylinder pressures and combining all constants, we get: $$\begin{array}{l}\left[\frac{\left({\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">p</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">p</figure-callout>}}_2-2\cdot p_{\mathrm{and}mG}+2\cdot DPS\right)}{2}\cdot A_K-m_{Os\mathrm{e.g}}\cdot \ddot{s}\left(\phi \right)\right]\cdot K_K\\ =J\cdot K_{\omega }\cdot \frac{n_{mOt}{{}_{{}_{\mathrm{\phi +}\text{x}}}}^2+n_{mOt}{{}_{{}_{\mathrm{\phi -}\text{x}}}}^2}{2\text{x}}+K_{\mathrm{<figure-callout\; id="1"\; label="R\; M\; p"\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">R</figure-callout>}M}& \\ \frac{p_{}}{}\frac{{}_1+{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">p</figure-callout>}}_2}{2}=\frac{J\cdot K_{\omega }}{K_K\cdot A_K}\cdot \frac{n_{mOt}{{}_{{}_{\mathrm{\phi +}\text{x}}}}^2+n_{mOt}{{}_{{}_{\mathrm{\phi -}\text{x}}}}^2}{2\text{x}}+\frac{K_{RM}}{K_K\cdot A_K}+\frac{m_{Os\mathrm{e.g}}\cdot \ddot{s}\left(\phi \right)}{A_K}+p_{\mathrm{and}mG}-DPS\\ \cdot \frac{p_{\mathrm{\phi +}\text{x}}+p_{\mathrm{\phi -}\text{x}}}{2}=K_1\frac{n_{mOt}{{}_{{}_{\mathrm{\phi +}\text{<figure-callout id="2" label="x" filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png" state="{{state}}">x</figure-callout>}}}}^2-n_{mOt}{{}_{{}_{\mathrm{\phi -}\text{x}}}}^2}{2\text{x}}+{\mathrm{<figure-callout\; id="2"\; label="K"\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">K</figure-callout>}}_2+\frac{m_{Os\mathrm{e.g}}\cdot \ddot{s}\left(\phi \right)}{\Delta k}+p_{\mathrm{and}mG}-DPS\end{array}$$

All pressure variables and speeds in equation (20) can be measured at points in time P1 and P2. A suitable indicator measurement technique known per se resolves the necessary physical variables based on the crank angle or at least averaged over several working cycles. In addition or as an alternative to the indication measurement technology, data from a suitable operating model, for example the engine control, can be accessed. The kinematic constant K _K can be tabulated and used depending on the piston position.

The influence of the speed nmot with regard to the oscillatory masses can, for example, be calculated in real time or stored on the control unit in the form of a lookup table of a suitably stored operating model with regard to speed and load.

The reduced piston acceleration (9) can be formulated for the two discrete points: $${\ddot{s}}_{\mathrm{right}ea}\left(\phi ,\dot{\phi }\right)={\mathrm{right}}_k\cdot {\left[\frac{\frac{\pi }{30}\left(n_{mOt}{}_{{}_{\mathrm{\phi -}\text{x}}}+n_{mOt}{}_{{}_{\mathrm{\phi +}\text{x}}}\right)}{2}\right]}^2\cdot \left[\text{cos}\left(\phi \right)+\text{cos}\left({\mathrm{<figure-callout\; id="1"\; label="\phi "\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_1+{\phi }_2\right)\right]$$

The constants K ₁ and K ₂ can be determined using reference measurements (engine function or gas exchange OK).

Diagnosis process:

After determining the application constants K ₁ and K ₂ , Equation (15) can be used to determine the diagnostic cylinder pressure from the speed change in compression: $${\overline{p}}_{\mathrm{e.g}yi,\mathrm{i.e}iaG}={\mathrm{<figure-callout\; id="1"\; label="K"\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">K</figure-callout>}}_1\cdot \frac{n_{mOt}{{}_{{}_{\mathrm{\phi +}\text{x}}}}^2+n_{mOt}{{}_{{}_{\mathrm{\phi -}\text{x}}}}^2}{2\text{x}}+{\mathrm{<figure-callout\; id="2"\; label="K"\; filenames="DE102021102260A1\_0032.png,DE102021102260A1\_0033.png"\; state="\{\{state\}\}">K</figure-callout>}}_2+\frac{m_{Os\mathrm{e.g}}\cdot {\ddot{s}}_{\mathrm{right}ea}\left(\phi ,n_{mOt}\right)}{A_K}+p_{\mathrm{and}mG}-DPS$$

The diagnostic cylinder pressure p _zyl,diag is an indication of the pressure curve during compression of the cylinder.

In this way, the diagnostic cylinder pressures p ₁ =p _diag,1 , P ₃ =P _diag,3 and p ₂ =p _diag,2 can be determined during driving operation for the diagnostic time window 112 of the diagnosed cylinder Z1.

Equation (5) can be filled with the pressure values p ₁ , p ₂ and p ₃ and evaluated.

The result of the evaluation of the knocking pressure energy integral E is compared with a limit value Eg, which is set at Eg=0.05 bar ² /KW ³ in the exemplary embodiment. If the determined value of E exceeds the limit value, knocking operation KB is recognized or determined in the exemplary method.

In the exemplary embodiment, various options are provided for using the specific knocking operation KB for onboard diagnosis 204 and/or offboard diagnosis 208 and/or control tasks 206 using engine control 2 (cf. 5 ).

For this purpose, the determined values E of the knocking pressure energy integral and/or the statement derived therefrom by comparison with the limit value Eg as to whether knocking is present are continuously stored in a non-volatile memory 202 of the engine control unit 2 or stored for further use while the motor vehicle is being driven. If, for example, the associated knock pressure energy integral E is evaluated for each cylinder Z for each ignition, a new value KB is stored in memory 202 for each ignition—in particular with a time stamp and/or initial values for determining and/or specifying the diagnosed cylinder. for example Z1.

The stored values KB can be made available in real time, i.e. in particular immediately during driving operation, for example to an online diagnostic component 204 and/or an engine control system 206 of the engine controller 2. The values KB can also be made available to an offboard diagnostic computer 208 at a later point in time, for example in the workshop.

• Verfahrensschritt S10: Auswahl eines zu diagnostizierenden Zylinders Z1.
• Verfahrensschritt S20: Bestimmen eines Diagnose-Zeitfensters 112, das eine Schwerpunktlage 113 einer Verbrennung A in einem Arbeitstakt des ausgewählten Zylinders Z1 beinhaltet.

In 5 process steps of the process are shown in a flowchart:

• Method step S10: selection of a cylinder Z1 to be diagnosed.
• Method step S20: Determination of a diagnosis time window 112, which contains a center position 113 of a combustion A in a power stroke of the selected cylinder Z1.

Method step S30: determining a speed development 101 of the internal combustion engine, in this case the crankshaft of the crank mechanism KT, during the diagnosis time window with a real-time capable sampling quality.

Method step S40: Determining the knocking pressure energy in the diagnosis time window 112, present in the form of the knocking pressure energy integral E, as a function of at least three characteristics p ₁ , p ₃ and p ₂ of a pressure index p _diag , which is associated with the respective points P1, P3 and P2 is determined in the diagnosis time window 112 .

Method step S50: Determination of the knock operation characteristic by evaluating a knock pressure energy integral E over the diagnostic time window.

Method step S61: Determination of a knocking operation KB if an evaluation of the knocking pressure energy integral results in an energy value E which corresponds to a knocking energy limit value Eg or is higher than this.

Method step S62: Determination of a regular operation RB determines if the evaluation shows that the energy value E is lower than the energy limit value Eg.

Method step S63: determining a distance margin Δ(RB;KB) between knocking mode KB and the present control mode RB. From the evaluation of the energy value E, in particular from its absolute or relative distance from the energy limit value Eg, a conclusion is drawn as to how much knock reserve there is in the selected cylinder. The values determined for this or a corresponding time series can also be stored in memory 202 and/or used for diagnosis and/or control.

Reference List

1

combustion engine

2

Engine control / engine control unit

4

unit of account

6

Crankshaft speed acquisition unit

7

Cylinder pressure determination unit

9

intake system

10

Torque curve of the combustion engine over one engine cycle

12

torque holes

14

predetermined limit for relevant torque contribution

16

Cylinder temperature determination unit

18

lambda probe

101

speed curve

112

diagnostic time window

113

focus of combustion

150

Speed development diagram

202

Storage

204

Engine control diagnostic component

206

Engine management control component

208

Offboard diagnostic calculator

(Sxx)

process steps

A

Combustion (represented by the course of combustion, represented by a combustion course integral)

ATL

exhaust gas turbocharger

E

Knock Pressure Energy Integral

eg

Limit value for the knock pressure energy integral

KB

Detonation mode, representative of knocking combustion in the cylinder

KT

Crank mechanism, in particular crankshaft

week

crank angle

LF

air filter

LS

air collector

M

Torque of a cylinder in 1

n

rotational speed

p

cylinder pressure

pdiag

Pressure index, here diagnostic cylinder pressure

P

Measurement times, at the beginning, middle, end of the diagnosis time window

t

Time interval in the diagnosis time window

x

half the interval width to form the difference value, starting from P

Z

cylinder

ZZP

ignition timing of a cylinder

φ1

Crank angle position to P1

φ2

Crank angle position to P2

φ3

Crank angle position to P3 (middle between P1 and P2)

QUOTES INCLUDED IN DESCRIPTION

This list of the documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• WO 2019/238338 A1 [0022]

Claims (10)

Method for determining knocking in a cylinder (Z1, Z2, Z3, Z4) of an internal combustion engine (1), comprising the steps: - selecting a cylinder (Z1) to be diagnosed, - determining a diagnostic time window (112) which has a center of gravity (113) of a combustion (A) in a working stroke of the selected cylinder, - determining a speed development (101) of the internal combustion engine (1) during the diagnostic time window, in particular with a real-time capable sampling quality, characterized by the step: - determining a knock operation characteristic ( KB) in the identified cylinder depending on the determined speed development. procedure according to claim 1 , characterized in that the knock operation parameter is determined as a function of a pressure curve (p) and/or a pressure gradient (dp) and/or a knock pressure energy in the selected cylinder during the specific diagnosis time window. Method according to one of the preceding claims, characterized in that the knock operation parameter is determined by evaluating a knock pressure energy integral (E) over the diagnosis time window. procedure according to claim 3 or 4 , characterized in that the knocking pressure energy, in particular the knocking pressure energy integral, is determined as a function of at least three characteristics (p1, p3, p2) of a pressure index (p _diag ), which is determined at a time interval (2x) in the diagnosis time window . Method according to one of the preceding claims, characterized in that knocking operation (KB) is determined if an evaluation of the knocking pressure energy integral results in an energy value which corresponds to a knocking energy limit value (Eg) or is higher than this. Method according to one of the preceding claims, characterized in that to determine the speed development, a continuous course of a speed (N) of a crank mechanism is recorded during the diagnosis time window and the recorded values with a resolution of at least in the order of ten milliseconds, in particular in one Engine control unit (2) are provided. Engine control unit (2) for an internal combustion engine, set up to transfer knocking operation characteristic values (KB) determined and/or stored in a memory, in particular by means of a method according to one of the preceding claims - to a diagnostic component (204) of the engine control unit for further onboard diagnostic functions, and/or - To a control component (206) of the engine control unit for real-time regulation of functions of the internal combustion engine as a function of the determined knocking operation parameter (KB). according to the engine control unit claim 7 , having a non-volatile memory (202), characterized in that the engine control unit is set up to store one or more manifestations of the knock operation parameter (KB) determined at one or different diagnosis times, in particular, in the memory. according to the engine control unit claim 8 , set up to transfer forms of the knocking operation parameter stored in the memory to an offboard computer (208) for offline diagnostic functions. Internal combustion engine (1) with several cylinders (Z), characterized by an engine control unit (2) according to one of Claims 7 until 9 .

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