DE102021130562A1 - Determination of a temperature drop in the cylinder resulting from an injection - Google Patents

Abstract

The invention relates to a method for determining a reduction in a temperature level in a cylinder of an internal combustion engine, the reduction being achieved by injecting fuel close to ignition, having the steps: selecting a cylinder to be diagnosed, determining a diagnostic time window, determining a speed development of the internal combustion engine during the diagnostic window.

Description

The invention relates to a method for determining a reduction in a temperature level in a cylinder of an internal combustion engine, a control device for an internal combustion engine, and an internal combustion engine with a plurality of cylinders and a control device.

The combustion quality (e.g. in terms of torque, degree of conversion, burning rate, raw exhaust emissions, etc.) is crucial for the operation of internal combustion engines. Under certain conditions, the combustion quality can be read from the output variable of the engine speed - i.e. from the speed development of the crankshaft.

However, just knowing that combustion is not optimal is usually not enough to remedy the situation. Correcting a deviation requires a clear diagnosis, although the causes of suboptimal combustion 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.

For example, the control task of operating an internal combustion engine without knocking, but not unnecessarily throttling power even in low-speed, high-load operation, is very complex. In order to provide a satisfactorily precise regulation for this function or other functions, known motor vehicles lack a sufficiently precise picture of the temperature development in the combustion chambers of the cylinders.

In addition, the possibilities of predictive maintenance (also known as “health functions”) for combustion engines are becoming increasingly important. These are intended to quantify the current performance status - and thus, among other things, the need for maintenance - 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 combustion quality and/or to improve regulation of the combustion in a cylinder.

This object is achieved by a method having the features of claim 1, a control means for an internal combustion engine having the features of claim 7, 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, insbesondere desjenigen Zylinders, in dessen Brennraum als nächstes Kraftstoff eingespritzt wird.
2. (ii) Bestimmen eines Diagnose-Zeitfensters, das insbesondere vor der zweiten Einspritzung, beispielsweise zwischen der ersten und der zweiten Einspritzung von Kraftstoff in den ausgewählten Zylinder liegt, alternativ aber auch eine oder beide der zwei Einspritzungen beinhalten kann.
3. (iii) Ermitteln einer Drehzahlentwicklung des Verbrennungsmotors während des Diagnose-Zeitfensters, insbesondere mit einer echtzeitfähigen Samplingqualität. Unter einem Diagnose-Zeitfenster ist insbesondere ein zusammenhängender Zeitraum als Anteil eines oder mehrerer Takte des Verbrennungsmotors zu verstehen. Unter einem Diagnose-Zeitpunkt ist insbesondere ein Zeitpunkt innerhalb des Diagnose-Zeitfensters zu verstehen, für welchen eine, mehrere oder alle Bestimmungsgrößen einer zu ermittelnden Zielgröße ermittelt werden.
4. (iv) Ermitteln der Absenkung des Temperaturniveaus im ausgewählten Zylinder in Abhängigkeit von der ermittelten Drehzahlentwicklung.

According to one aspect, a method for determining a, in particular relative, reduction in a temperature level in a cylinder of an internal combustion engine is disclosed, the reduction being able to be achieved by means of a second injection of fuel close to ignition, but also by means of a first or single main injection. 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, in particular that cylinder into whose combustion chamber fuel is injected next.
2. (ii) Determination of a diagnosis time window, which lies in particular before the second injection, for example between the first and the second injection of fuel into the selected cylinder, but alternatively can also contain one or both of the two injections.
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. A diagnosis time window is to be understood in particular as a continuous period of time as a proportion of one or more cycles of the internal combustion engine. A diagnosis point in time is to be understood in particular as a point in time within the diagnosis time window for which one, several or all parameters of a target variable to be determined are determined.
4. (iv) Determination of the lowering of the temperature level in the selected cylinder as a function of the determined speed development.

• Der ermittelte Wert kann als Input für einen Regler zum Vermeiden einer klopfenden Verbrennung dienen, und diesen Regler insbesondere dahingehend verbessern, dass aufgrund der verbesserten Regelungsgüte ein Sicherheitsabstand zur Klopfgrenze verringert werden kann.

If it is determined to what extent the second or, if applicable, the first/single injection lowers the mixture temperature in the cylinder, the value determined can improve various regulations for the operation of the internal combustion engine:

• The determined value can be used as an input for a controller to avoid knocking combustion, and improve this controller in particular to the effect that a safety margin to the knock limit can be reduced due to the improved control quality.

The determined value can also be used as an input for a temperature model when controlling the peak combustion temperatures. As a result, NOx emissions can be avoided, especially since the temperature peaks are lower due to the improved control.

The invention is applicable per se to any injection of fuel into the cylinder, i.e. to a second or one of possibly several further injections that are more or less close to ignition, as well as to a first or only main injection.

In the following, however, the invention is described and explained exclusively in the context of a second, near-ignition injection to make it easier to understand.

In the present case, a reduction, in particular a relative reduction, is to be understood in particular as a reduction compared to a case in which no second injection would take place. For example, in particular at a later crank angle position, when combustion has progressed further, there can be a higher absolute temperature value in the cylinder than at the second injection. Nevertheless, at this point in time the absolute temperature value is relatively lower than it would have been if no second injection had taken place.

The diagnosis time window extends in particular from a crank angle position after a first injection and before the second injection to a crank angle position after an ignition point of the selected cylinder.

1. (a) an eine Steuerkomponente des Steuermittels für eine Echtzeitregelung von Funktionen des Verbrennungsmotors in Abhängigkeit von der übergebenen Werten der Absenkung des Temperaturniveaus, und/oder
2. (b) an eine Diagnosekomponente des Steuermittels für weitere Onboard-Diagnosefunktionen.

According to a further aspect, a control means for determining a, in particular relative, reduction in a temperature level in a cylinder of an internal combustion engine is disclosed, which is designed in particular in and/or as part of an engine control unit for an internal combustion engine of a passenger car. The control means is set up to transfer values of a lowering of a temperature level that are determined and/or stored in a memory, in particular by means of a method according to an embodiment of the invention

1. (a) to a control component of the control means for real-time regulation of functions of the internal combustion engine as a function of the transmitted values of the lowering of the temperature level, and/or
2. (b) to a diagnostic component of the control means for further onboard diagnostic functions.

According to one embodiment, the control means has a non-volatile memory and is set up to store one or more characteristics of the lowering of the temperature level determined at one or different diagnosis times, in particular, in the memory.

According to one embodiment, the control means is set up to transfer characteristics of the lowering of the temperature level stored in the memory to an off-board computer for offline diagnostic functions.

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

The invention is based, among other things, on the consideration that the combustion chamber in the cylinder contains an air mass and a fuel mass for combustion. The temperature curve in the combustion chamber indicates how quickly the mixture is converted, which and how many raw emissions are produced and how far away from the irregular combustion limit is operated in a certain operating state (e.g. in petrol engines, in particular knocking phenomena).

There is a conflict of goals: high temperatures for efficient mass conversion and high pressure gradients, low temperatures for low NOx emissions and "optimal" temperatures for an operation close to knocking. The conflict of objectives results in a requirement for live regulation for a variable that cannot be quantified in the engine without the invention. Temperatures in the combustion chamber cannot be measured directly in the car or on the test bench using known methods. Therefore, no diagnosis can be made based on temperature values. Likewise, regulations based on a setpoint temperature profile cannot be implemented.

The invention is now based, among other things, on the idea of balancing the gas mass composition in the combustion chamber with the aid of a pressure estimate, which in turn uses a high-resolution sensed speed development on the crankshaft. In particular, with the help of the mass balance, which according to one embodiment can be set up before a second injection close to ignition, a "starting temperature" (i.e. reference temperature) before an injection close to ignition, i.e. without the associated temperature reduction, can be determined.

Then, in particular, an energy balance for the second injection can be set up close to the ignition point. With an optional setting of premises for simplified injection balancing, a temperature difference resulting from the injection is then calculated.

The knowledge obtained from this with regard to injection cooling achieved with the second injection can then be used as an adjustment parameter for controlling a crank angle position of the injection and/or an injection quantity, and/or for health monitoring of the cylinder.

• (v) Ermitteln einer Referenztemperatur im identifizierten Zylinder zum Zeitpunkt oder unmittelbar vor der zweiten Einspritzung, insbesondere ohne Berücksichtigung der Auswirkung der zweiten Einspritzung auf die Temperaturentwicklung, und
• (vi) Ermitteln der Absenkung des Temperaturniveaus in Abhängigkeit von der ermittelten Referenztemperatur.

According to one embodiment, the method additionally has the steps:

• (v) determining a reference temperature in the identified cylinder at the time or immediately before the second injection, in particular without taking into account the effect of the second injection on the temperature development, and
• (vi) Determining the lowering of the temperature level as a function of the determined reference temperature.

As a result, the lowering of the temperature level can be determined specifically during different operating states of the internal combustion engine or the cylinder. On the other hand, by determining a reference temperature as an absolute value, it is possible to specify the lowering of the temperature level also in an absolute (delta) temperature value, and from this - based on the reference temperature - also to specify an absolute value of the lowered temperature, at least for a specific one crank angle.

According to one embodiment, the reference temperature in the identified cylinder is determined as a function of a pressure index for the cylinder in the diagnosis time window, which depends on the speed development in the diagnosis time window.

The lowering of the temperature level can be determined particularly easily via the intermediate step of a pressure index derived from the speed development, in particular because the lowering of the temperature level can thus be determined as a function of variables already determined or provided on engine control units of the applicant.

According to one embodiment, the reference temperature is determined as a function of a cylinder volume at a diagnosis point in time in the diagnosis time window (in particular at the point in time of the second injection), and/or a residual gas content, and/or a combustion air ratio, in particular in each case in the identified cylinder at the point in time or immediately before the second Injection.

The lowering of the level can thus be determined as a function of variables that are already stored in known engine control units for internal combustion engines in passenger cars, for example in lookup tables, and/or are available to the engine control unit in every operating state in the form of current values.

According to one embodiment, the residual gas content and/or the combustion air ratio is (1) predetermined as a constant for one, several or all operating cases of the internal combustion engine, and/or (2) is read out from a pre-filled characteristic diagram as a function of an engine load and the engine speed, and/or (3) calculated from other engine and/or operating and/or environmental variables, and/or (4) measured using a suitable sensor.

The desired application of the invention can be taken into account by a suitable selection of the values used or the source of the values: If, for example, a real-time evaluation is desired during driving operation, a source or values is used that entails the lowest possible computational effort , such as a constant that affects the accuracy of the determination result only to a tolerable extent. If, on the other hand, a precise evaluation is sought in the design process or in the workshop, for example, sensor values or more precise but more computationally intensive calculation methods can be used.

• (vii) Aufstellen einer Energiebilanz im Zylinder für die zweite Einspritzung, insbesondere unmittelbar, nach der zweiten Einspritzung, wobei für die Energiebilanz insbesondere ein Energiegehalt eines, insbesondere ungezündeten, Gasgemischs nach der zweiten Einspritzung gegenübergestellt wird einer Summe eines Energiegehalts vor der zweiten Einspritzung und einer Verdampfungswärme des bei der zweiten Einspritzung eingespritzten Kraftstoffs, und/oder
• (viii) Ermitteln einer Nacheinspritztemperatur aus der aufgestellten Energiebilanz, insbesondere in Abhängigkeit von der ermittelten Referenztemperatur, und/oder
• (ix) Ermitteln der Absenkung des Temperaturniveaus in Abhängigkeit von der ermittelten Referenztemperatur und der ermittelten Nacheinspritztemperatur, insbesondere als Temperaturdifferenz der ermittelten Referenztemperatur und der ermittelten Nacheinspritztemperatur.

According to one embodiment, the method has one, several or all of the following method steps:

• (vii) Establishing an energy balance in the cylinder for the second injection, in particular immediately after the second injection, wherein for the energy balance in particular an energy content of a, in particular unignited, gas mixture after the second injection is compared with a sum of an energy content before the second injection and a Heat of vaporization of the fuel injected during the second injection, and/or
• (viii) determining a post-injection temperature from the energy balance established, in particular as a function of the reference temperature determined, and/or
• (ix) determining the lowering of the temperature level as a function of the determined reference temperature and the determined post-injection temperature, in particular as a temperature difference between the determined reference temperature and the determined post-injection temperature.

The establishment of an energy balance makes it possible to make a statement about a temperature change in the cylinder depending on the reference temperature from the energy input of the fuel injected during the second injection. Knowing the reference temperature, this enables both a determination of the lowering of the temperature level and a determination of the absolute temperature level to be expected after the second injection.

According to one embodiment, the speed development is determined with a real-time capable sampling quality. In particular, in the present case we are talking about a real-time capable sampling quality if the variable—in this case the speed—is determined with a sampling time of approximately 10 ms or less, in particular continuously and/or without a break. In particular, the combustion air ratio is determined with a lower sampling quality, in particular with a sampling time of 0.1 or 1 second or longer, because lambda probes do not allow a significantly higher resolution sampling quality due to their measuring principle (comparison of combustion gas with reference residual air content).

• 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 schematisches Diagramm der Temperaturentwicklung im ausgewählten Zylinder mit und ohne zweite Einspritzung.
• 5 zeigt in 5a ein Schaubild einer Massenbilanzierung und in 5b ein Schaubild einer Energiebilanzierung im ausgewählten Zylinder.
• 6 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 schematic diagram of the temperature development in the selected cylinder with and without a second injection.
• 5 shows in 5a a diagram of a mass balance and in 5b a diagram of an energy balance in the selected cylinder.
• 6 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 with the air filter at the air inlet, the exhaust gas turbocharger and an intercooler and the air collector towards the cylinders Z.

In 1b the internal combustion engine 1 is shown in a more detailed schematic view. Internal combustion engine 1 has cylinders Z1, Z2, Z3 and Z4, with all cylinders Z providing their torque contribution M to a crankshaft of a crank mechanism KT. The internal combustion engine 1 additionally has a control means 2 according to an exemplary embodiment of the invention, which optionally has a computing unit 4 if the control means 2 is not designed as part of an engine control unit. The control means 2 also has a rotational speed detection unit 6 and a cylinder pressure determination unit 7 for the reference pressures from the environment and air collector or crankcase. The control means 2 also has a cylinder volume determination unit and can access measured values from all lambda probes of the internal combustion engine 1 .

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 the crankshaft of the crank mechanism KT that varies over time.

A reference pressure p in the environment can be detected by means of the pressure detection unit 7, the instantaneous speed n can be detected by means of the speed detection unit 6 and used by the control means 2.

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

In the representation of 1 c slightly different torque curves result from the combustion of the mixture in the different cylinders.

A diagnosis time window 112 for carrying out a method according to an exemplary embodiment of the invention is provided for each cylinder Z. The respective diagnosis time window includes a crank angle range starting from a position between a first and a second injection E2 close to ignition.

In 2 is a sketch of an exemplary diagram 150 of a speed development 101 of a four-stroke cycle (= one cylinder working cycle: top dead center gas exchange (LOT) → intake → bottom dead center (UT) → compression → top dead center ignition (ZOT) → expand → UT → outlet ) of the internal combustion engine 1 is shown.

Diagram 150 shows curve 101 of engine speed n over one working cycle 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 in the compression are marked. A point in time or a crank angle position at the second injection E2 close to ignition is also marked. The associated working strokes of the cylinders Z1-Z4 are shown below.

In the exemplary embodiment, the diagnosis time window 112 for the cylinder Z1 is defined by way of example from 20° CA before the start of the second injection E2 to 2° CA before the start of the second injection E2. The limits depend on an existing engine operating point and can be flexibly adapted to this, so that the point in time or a crank angle position for the second, near-ignition injection E2 is included in the diagnosis time window. The dynamic adjustment of the limits of the diagnosis time window 112 is also possible for dynamic driving depending on boundary conditions such as an ignition angle and the cylinder pressure profile.

In the exemplary embodiment with an injection E2 close to ignition at 675° CA, the diagnostic time window 112 is therefore set at: 655° CA-673° CA, based on a crank angle specification for cylinder Z1. In the representation of 1c and 2 - which relates to the entire internal combustion engine with four cylinders, this crank angle value corresponds to -65° to -47° with respect to top dead center of ignition (TDC).

A diagnosis point in time KW _ΔT within the diagnosis time window 112 is determined at a crank angle position at which the temperature reduction through the second injection E2 is fully implemented. In practice, in the implementation with the control means 2, the crank angle position of E2 coincides with the crank angle position KW _ΔT , in particular due to corresponding simplifying assumptions 4 are further elaborated.

In 3 the detail X is off 2 , ie the speed development 101 over the crank angle KW during the diagnosis time window 112 with the limit points P1 and P2 of the diagnosis time window of cylinder Z1 are entered. For cylinder pressure P ₁ in cylinder Z1, p ₁ (t ₁ , n ₁ ) applies at measuring point P1, and p ₂ (t ₂ , n ₂ ) for cylinder pressure p ₂ at measuring point P2. Shortly before the ignition ZZP1, the ignition-close injection E2 takes place in order to lower the temperature in the cylinder Z1.

the 2 until 6 explain an exemplary embodiment of the method according to the invention for determining a reduction ΔT in a temperature level Tz in the cylinder Z1 while driving using the crankshaft speed n of the crankshaft drive KT.

4 shows a schematic diagram of the temperature level (i.e. a temperature development) Tz in the selected cylinder Z1 over the rotation of the crankshaft in °KW, with second injection E2 (dashed line T _E2 (KW)) and for comparison without second injection (solid line T(KW) ). For the sake of clarity, the diagram only shows dragged curves without combustion influences on the temperature development.

The classic course of a temperature curve over °CA is illustrated with the solid line. Without a second injection close to ignition, a classic temperature curve T(KW) that is essentially symmetrical around the ignition top dead center (ZOT) occurs, with the absolute value of T̅ changing with the position of the crankshaft.

In the case of an "ignition injection" - i.e. a second injection E2 close to ignition - a small quantity of fuel is injected close to the ignition point ZZP1. As soon as the fuel begins to evaporate, heat is extracted from the other gas mass in the combustion chamber, which causes the mean cylinder temperature Tz to decrease over the further course, analogous to the dashed curve _TE2 (KW), with the absolute value of _TE2 with the KW position is changeable.

This decrease in the mean temperature Tz also influences the beginning of combustion from mixture ignition at ZZP1. Since the gas mass is converted at a lower starting temperature, the peak temperature in the expansion phase is reduced with the second injection close to ignition. The extent to which this effect occurs depends on the cooling ΔT of the temperature level Tz that follows injection E2.

The extent of the cooling ΔT can be used as an input for a controller for knock advance, by means of which more efficient ignition angles can be adjusted; So a distance to the knock limit can be reduced by improved (pre-) control. The extent of the cooling ΔT can also serve as an input for a temperature model in the peak temperature control in the combustion to avoid raw NOx emissions in the combustion by lowering the temperature peaks.

5 shows a diagram of a mass balance ( 5a) and a diagram of an energy balance ( 5b) in the selected cylinder Z1.

In 5a a mass balance in the combustion chamber of the cylinder is shown as a starting point for determining the reduction ΔT in the temperature level Tz: $$m=m_{tOt}=m_{L\mathrm{and}ft}+m_{K\mathrm{right}aftstOff}+m_{RestGas}$$

The relationship between the air mass and the fuel mass is as follows: $$m_{K\mathrm{right}aftstOff}=\frac{m_{tOt}}{\lambda \cdot L_{st}}$$

λ

gemessenes Verbrennungsluftverhältnis (<1 = „fett“, 1 = stöchiometrisch, >1 = „mager“)

Lst

kraftstoffabhängige chemische Konstante, sog. stöchiometrische Kraftstoff-Luft-Verhältnis, typisch zwischen 14-16kg/kg z.B. für häufige Ottokraftstoffe

symbol meaning

λ

Measured combustion air ratio (<1 = "rich", 1 = stoichiometric, >1 = "lean")

Lst

Fuel-dependent chemical constant, so-called stoichiometric fuel-air ratio, typically between 14-16kg/kg, for example for common petrols

Equation (2) in (1) results $$m_{tOt}=m_{L\mathrm{and}ft}\cdot \left(1+\frac{1}{\lambda \cdot L_{st}}\right)+m_{RestGas}$$

In the exemplary embodiment, the air mass is substituted using typical engine control variables: the current air mass in the cylinder is estimated in the engine control for the purpose of the correct fuel admixture. The existing function for this is the so-called load detection. It estimates a relative filling "rf" in percent. The filling rf is defined as 100% if the max. cylinder volume were completely filled with air under standard conditions. $$m_{L\mathrm{and}ft}=\mathrm{right}f\cdot \frac{{\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">p</figure-callout>}}_0\cdot V_{max}}{R\cdot {\mathrm{<figure-callout\; id="0"\; label="T"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">T</figure-callout>}}_0}$$

rf

relative Luftfüllung des Zylinders in %

p0

Atmosphärendruck unter Normbedingungen (1013hPa)

Vmax

maximales Zylindervolumen im unteren Totpunkt der Kurbelwelle

R

ideale Gaskonstante

T0

Umgebungstemperatur unter Normbedingungen (293K)

symbol meaning

rf

relative air filling of the cylinder in %

p0

Atmospheric pressure under standard conditions (1013hPa)

V max

maximum cylinder volume at bottom dead center of the crankshaft

R

ideal gas constant

T0

Ambient temperature under standard conditions (293K)

Equation (4) in (3) results $$m_{tOt}-\mathrm{right}f\cdot \frac{{\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">p</figure-callout>}}_0\cdot V_{max}}{R\cdot {\mathrm{<figure-callout\; id="0"\; label="T"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">T</figure-callout>}}_0}\cdot \left(1+\frac{1}{\lambda \cdot L_{st}}\right)+m_{RestGas}$$

The residual gas fraction results proportionately from the total mass $$m_{RestGas}=m_{tOt}\cdot x\mathrm{right}G$$

Substituting (6) into (5) and applying the ideal gas equation for the total mass in equation (5) yields $$\frac{p\cdot V}{R\cdot T}\cdot \left(1-x\mathrm{right}G\right)=\mathrm{right}f\cdot \frac{{\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">p</figure-callout>}}_0\cdot V_{max}}{R\cdot {\mathrm{<figure-callout\; id="0"\; label="T"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">T</figure-callout>}}_0}\cdot \left(1+\frac{1}{\lambda \cdot L_{st}}\right)$$

Solving the equation for the temperature T by reducing R yields $$T=\frac{p\cdot V\cdot {\mathrm{<figure-callout\; id="0"\; label="T"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">T</figure-callout>}}_0\cdot \left(1-x\mathrm{right}G\right)}{{\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">p</figure-callout>}}_0\cdot V_{max}\cdot \mathrm{right}f\cdot \left(1+\frac{1}{\lambda \cdot L_{st}}\right)}$$

Introducing the constant K ₀ for all appropriate values, the equations can be simplified as follows: $$K_0\left(a\right)=\frac{V\left(a\right)\cdot T_0}{{\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">p</figure-callout>}}_0\cdot V_{max}}\sim 290\cdot \frac{V\left(a\right)}{V_{max}}\left[\frac{K}{ba\mathrm{right}}\right]$$

V(α)

Zylinder-Volumenwert zum Zeitpunkt der Temperaturermittlung

symbol meaning

V(α)

Cylinder volume value at the time of temperature determination

If one now inserts equation (9) into (8), one obtains for the temperature: $$T\left(a\right)=\overline{T}=p\cdot K_0\left(a\right)\cdot \frac{1}{\mathrm{right}f}\cdot \frac{1-x\mathrm{<figure-callout\; id="1"\; label="right\; G"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">right</figure-callout>}G}{1+\frac{1}{\lambda \cdot L_{st}}}$$

Equation (10) can be used to determine cylinder temperature T̅̅ before the ignition injection E2. The inherent quantities are determined as follows: size directly from the engine control unit determination p no p= p _diag (determination based on the speed signal of the combustion engine, for example as below or in DE10 2018 209 252 A1 described) K ₀ Yes Cylinder volume of the current °CA from the lookup table stored in the engine control unit xrg Yes No Either a value from the engine control unit or a constant assumption, e.g. xrg=0.12 rf Yes Motor load value in % from load sensing function λ Yes Combustion air ratio from lambda probe

If it is desired to save further computing time online, the right-hand fraction in equation (10) can also be further simplified. This occurs with an acceptable reduction in the calculation accuracy that can otherwise be achieved.

upper bookend 0.05 0.7 14 0.8620 lower bookend 0.25 1 16 0.7059 Bio-Ethanol 0.1 1 9 0.8100 Magerbrennverfahren 0.1 1.4 16 0.8615 For this purpose, the interplay of the parameters for a corresponding engine operation is estimated in its extremes. An example number set looks as follows in the example: Description of K ₁ behavior xrg [-] λ [-] L _st [-] $K_1:=\frac{1-x\mathrm{<figure-callout\; id="1"\; label="right\; G"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">right</figure-callout>}G}{1+\frac{1}{\lambda \cdot L_{st}}}$

upper booking 0.05 0.7 14 0.8620 lower booking 0.25 1 16 0.7059 bio ethanol 0.1 1 9 0.8100 lean burn process 0.1 1.4 16 0.8615

In the case of a constant assumption for K ₁ , K ₁ ~0.8 is appropriate; Equation (10) therefore simplifies to: $$T\left(a\right)=\overline{T}=K_0\left(a\right)\cdot K_1\cdot \frac{p_{\mathrm{e.g}yl,\mathrm{i.e}iaG\left(a\right)}}{\mathrm{right}f}$$

Equation (11) can be analogous to equation (10) for determining cylinder temperature T̅̅ be used directly in front of the near-ignition injection E2.

In the following, the determination of the cooling .DELTA.T in driving operation by the near-ignition injection E2 by means of the control means 2 with the help of in 5b exemplarily illustrated energy balances in the control unit are explained.

• Annahme 1: Schlagartige Einspritzung - der SOI und der EOI werden aus Gründen der Vereinfachung instantan gemeinsam angenommen. Diese Prämisse ist aufgrund der klassischen Mengenaufteilung (große Einspritzung im Saugtakt, kleine Einspritzung in Zündungsnähe) realitätsnah. Es kann für einen modellierten instantanen Einspritzzeitpunkt E2 angenommen werden, dass sich dieser in der Hälfte zwischen SOI und EOI befindet.
• Annahme 2: Schlagartige Verdampfung - es wird angenommen, dass der Verdampfungsvorgang für die gesamte Masse ohne Zeitdauer ist, sondern instantan erfolgt. Tendenziell werden die ermittelten Temperaturdeltas damit leicht überschätzt. Doch die Annahme ist aufgrund der vergleichsweise sehr kurzen Verdampfungsdauern (kleine Mengen, hohe Kompressionstemperaturen) ebenfalls akzeptierbar.
• Annahme 3: Schlagartige Durchmischung - auf Basis von schlagartiger Einspritzung und schlagartiger Verdampfung ist eine instantane Durchmischung die logische Konsequenz aufgrund guter Diffussionseigenschaften der gasförmigen Bestandteile. Sie erleichtert die Bilanzierung von Gesamtmassen im Brennraum.

First of all, some assumptions are made for the calculation of the cooling:

• Assumption 1: Sluggish injection - the SOI and the EOI are assumed to be instantaneous for the sake of simplicity. This premise is realistic due to the classic quantity distribution (large injection in the suction cycle, small injection near the ignition). It can be assumed for a modeled instantaneous injection timing E2 that it is halfway between SOI and EOI.
• Assumption 2: Sudden vaporization - it is assumed that the vaporization process for the entire mass is instantaneous but does not take place in time. The determined temperature deltas tend to be slightly overestimated. But the assumption is also acceptable due to the comparatively very short evaporation times (small quantities, high compression temperatures).
• Assumption 3: Sudden mixing - based on sudden injection and sudden evaporation, instantaneous mixing is the logical consequence due to the good diffusion properties of the gaseous components. It simplifies the balancing of total masses in the combustion chamber.

The energy balance of the ignition spray can be derived from the three assumptions: (A): d _Qw ~0 (wall heat); (B): pdV=0 (work term); (C): dH _leak = 0 (leaks)

With the assumptions, the following balancing of the energies of the mixture in the combustion chamber results: $$\begin{array}{l}{u}_{mixt}=\overline{u}+\mathrm{i.e}{u}_{vap}\\ m_{tOt}\cdot c_v\left(T_{afte\mathrm{right}}\right)\cdot T_{afte\mathrm{right}}=m_{tOt}\cdot c_v\left(T\right)+m_{K\mathrm{right}aftstOff}\cdot \left(H_{vap}-H_{evap}-H_{Heat\mathrm{and}p}\right)\end{array}$$

Since cooling has little effect on the isochoric heat capacity c _v , agreement can be assumed for c _v in all terms and equation (12) simplifies to: $$\Delta T=\overline{T}=T_{afte\mathrm{right}}=\frac{m_{K\mathrm{right}aftstOff}}{m_{tOt}}\cdot \frac{H_{Heat\mathrm{and}p}+H_{evap}-H_{vap}}{c_v\left(T\right)}$$

Equation (10) provides the mean cylinder temperature before injection for Equation (13). Equation (13) can thus calculate the cooling of the cylinder charge.

The required enthalpies can be assumed as follows:

The heating enthalpy h _heatup = c _p,KST liquid · (T _evap - T _KST ) is used to heat the fuel from its initial temperature to the evaporation temperature. For the evaluation, c _p and T _evap are read from a table for the respective fuel and stored in the control unit. The temperature T _KST at which the fuel (KST) is injected in liquid form is usually also measured by the engine control unit for the pilot control of the injection and can be made available.

The evaporation enthalpy h _evap is taken from a table as a fuel constant.

The heat of the vapor from the fuel is quantified as h _vap = u _vap ( T̅ ) + R · T̅̅ , where the internal vapor energy u _vap and the gas constant R can also be found in a table for the respective fuel.

In a very rough but sufficient approximation, it can be assumed for liquid injected fuel that the difference between the calorific value and the lower calorific value (both available from tables for common fuels) correlate with the fuel heating and evaporation: $$\left(H_O-H_{\mathrm{and}}\right)\sim \left(H_{Heat\mathrm{and}p}+H_{evap}\right)$$

Equation (13) for the control device application can thus be reduced significantly, while accepting acceptable losses in accuracy, in particular if K ₃ (T)=(H ₀ −H _u ) is determined in the range around T _KST . $$\Delta T\sim \frac{m_{K\mathrm{right}aftstOff}}{m_{tOt}}\cdot \frac{K_3\left(T_{KST}\right)-{\mathrm{and}}_{vap}\left(T\right)-R\cdot T}{c_v\left(T\right)}$$

1. (i) Gleichung (10) durch Gleichung (13) mit größerer Genauigkeit, und/oder
2. (ii) Gleichung (11) durch Gleichung (15) mit kleinerer, aber ausreichender Genauigkeit, die auf jeden Fall mit einer Rechenleistung zu bewerkstelligen ist, die für eine Echtzeit-Steuergeräteberechnung ausreicht.

The temperature reduction .DELTA.T by the second, near-ignition injection E2 can therefore be determined with the help of

1. (i) Equation (10) by Equation (13) with greater accuracy, and/or
2. (ii) Equation (11) by Equation (15) with smaller, but sufficient accuracy, which can be accomplished in any case with a computing power that is sufficient for a real-time control device calculation.

Both Equation (10) and Equation (11) require a parameter p for the pressure in the diagnosed cylinder Z as a variable input variable.

How a diagnostic cylinder pressure p̅ _zyl,diag can be determined for this parameter p can be seen from the following description of equations (16) - (31), where φ ₁ is the crank angle of P1 (e.g. KW=655°) and φ ₂ corresponds to the crank angle of P2 (for example KW=673°), and p _{- cyl,diag} = p _{- cyl,diag,655-673} applies.

The determination is based on a pressure balance of the diagnosed cylinder based on the measured speed curve: $$\frac{\mathrm{i.e}}{\mathrm{i.e}t}\left(\frac{1}{2}\cdot {\mathrm{<figure-callout\; id="0"\; label="J"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">J</figure-callout>}}_0\cdot {\omega }^2\right)=\left(M_{tan}-M_R-M_L\right)\cdot \omega$$

J0, J

Allg. / anteiliges Massenträgheitsmoment

φ

Winkelstellung der Kurbelwelle

ω

Winkelgeschwindigkeit

Mtan

Moment durch Gaskraft im Zylinder und oszillierender Massenkraft

MR

Moment durch Reibungsverluste

ML

Moment durch Lastabnahme

MM

Anteiliges Moment durch rotatorische Massenträgheit

nmot

Aktuell anliegende Motordrehzahl

symbol meaning

J0, J

General / proportional mass moment of inertia

φ

Angular position of the crankshaft

ω

angular velocity

Mtan

Moment due to gas force in the cylinder and oscillating mass force

MR

moment due to friction losses

ML

moment due to load reduction

mm

Partial moment due to rotational mass inertia

nmot

Current engine speed

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

If the equation is meaningfully divided into a "direct component" and an "alternating component", the following sub-equations are obtained: $$\overline{M_{tan}}=\overline{M_R}-\overline{M_L}$$

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”: $$J\cdot \dot{\omega }=\widetilde{M_{tan}}-\widetilde{M_R}-\widetilde{M_M}$$

A conversion from time-based derivation to crank angle-based difference formation takes place with the help of the relationship $$\begin{array}{l}\omega =\frac{\mathrm{i.e}\phi }{\mathrm{i.e}t}=\pi \cdot \frac{n_{m\mathrm{<figure-callout\; id="30"\; label="O\; t"\; filenames="DE102021130562A1\_0046.png"\; state="\{\{state\}\}">O</figure-callout>}t}}{30}\text{by}\\ \dot{\omega }\approx {\left(\frac{\pi }{30}\right)}^2\cdot nmOt\cdot \frac{\Delta nmOt}{\Delta \phi }\end{array}$$

The decisive quantities from equation (16) are further detailed for the evaluation. The relationship for the resulting moment from the inner-cylindrical gas force and results in: $$\widetilde{M_{tan}}=\left[A_K\cdot \left[p_{\mathrm{e.g}yt}\left(\phi \right)-p_0\right]-m_{Os\mathrm{e.g}}\cdot \ddot{s}\left(\phi \right)\right]\cdot {\mathrm{right}}_k\frac{\text{sin}\left(\phi +\beta \right)}{\text{cos}\beta }$$

AK

Kolbendeckfläche = const.

rK

Wirkradius der Kurbelwelle entspricht halben Hub = const.

1P1

Pleuellänge = const.

mosz

Oszillatorische Massenteil entspricht Kolbenbaugruppe und anteiliger Pleuelmasse = const.

pzyl

Im Zylinder vorherrschender Druck

p0

Referenzdruck, Kurbelgehäusedruck

β(φ)

Pleuelschwenkwinkel in Abhängigkeit der Kurbelwinkelstellung

s̈(φ)

Kolbenbeschleunigung in Abhängigkeit von der Kolbenstellung

symbol meaning

AK

Piston top area = const.

rK

Effective radius of the crankshaft corresponds to half the stroke = const.

1P1

connecting rod length = const.

mosz

Oscillating mass part corresponds to piston assembly and proportionate connecting rod mass = const.

pcyl

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 (18) yields: $$\ddot{s}\left(\phi ,\dot{\phi },\ddot{\phi }\right)={\mathrm{right}}_k\cdot \ddot{\phi }\cdot \text{sin}\phi +{\mathrm{right}}_k\cdot {\dot{\phi }}^2\cdot \text{cos}\phi +\raisebox{1ex}{${\mathrm{<figure-callout\; id="2"\; label="right\; k"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">right</figure-callout>}}_k$}\!\left/ \!\raisebox{-1ex}{$2$}\right.\cdot \ddot{\phi }\cdot {\lambda }_{pt}\cdot \text{sin}\left(2\cdot \phi \right)+{\mathrm{right}}_k\cdot {\dot{\phi }}^2\cdot {\lambda }_{pt}\cdot \text{cos}\left(2\cdot \phi \right)$$

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

(19.5)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. $$\beta \left(\phi \right)=\text{arcsin}\left({\lambda }_{pt}\cdot \text{sin}\phi \right)$$

(19.5)

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

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

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

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

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

or as also used in the following the reference to the crankcase pressure $$p_{}$$$${}_0=p_{K\mathrm{and}\mathrm{right}bGeH}=p_{\mathrm{and}mG}-DPS$$

where DPS stands for the vacuum (pressure difference) in the intake manifold.

The friction torque from Equation (13) 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. $$\overline{M_R}=cOnst.$$

$$J=const.$$

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

After inserting the relationships from equations (24) to (26), one can conclude the following simplification with the application constant K_RM: $$\overline{M_{tan}}=J\cdot \dot{\omega }+K_{RM}$$

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 measuring points P1 and P2 in the compression of cylinder Z1. For the cylinder pressure p _P1 in the cylinder Z1 applies at the measuring point P1 p ₁ (t ₁ , n ₁ ), for the cylinder pressure p _P2 at the measuring point P2 p ₂ (t ₂ , n ₂ ). It can be seen that the measured rotational speed n falls during the diagnosis time window 112, so that n ₁ >n ₂ applies.

The angular velocity gradient from equation (27) 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_{m\mathrm{<figure-callout\; id="2"\; label="O\; t"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">O</figure-callout>}{t}_{}{}_2}+n_{m\mathrm{<figure-callout\; id="1"\; label="O\; t"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">O</figure-callout>}{t}_{}{}_1}}{2}\cdot \frac{n_{m\mathrm{<figure-callout\; id="2"\; label="O\; t"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">O</figure-callout>}{t}_{}{}_2}-n_{m\mathrm{<figure-callout\; id="1"\; label="O\; t"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">O</figure-callout>}{t}_{}{}_1}}{{\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_2-{\mathrm{<figure-callout\; id="1"\; label="\phi "\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_1}\\ \dot{\omega }\approx \frac{1}{2}\cdot {\left(\frac{\pi }{30}\right)}^2\cdot \frac{n_{m\mathrm{<figure-callout\; id="2"\; label="O\; t"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">O</figure-callout>}{t}_{}{}_2}{}^2-n_{m\mathrm{<figure-callout\; id="1"\; label="O\; t"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">O</figure-callout>}{t}_{}{}_1}{}^2}{{\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_2-{\mathrm{<figure-callout\; id="1"\; label="\phi "\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_1}\\ \dot{\omega }\approx K_{\omega }\cdot \frac{n_{m\mathrm{<figure-callout\; id="2"\; label="O\; t"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">O</figure-callout>}{t}_{}{}_2}{}^2-n_{m\mathrm{<figure-callout\; id="1"\; label="O\; t"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">O</figure-callout>}{t}_{}{}_1}{}^2}{{\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_2-{\mathrm{<figure-callout\; id="1"\; label="\phi "\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_1}\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 (18) is subsequently expanded to include the relationships from equations (19) to (23) and constants are identified. $$\begin{array}{l}\widetilde{M_{tan}}=\left[\frac{\left({\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">p</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">p</figure-callout>}}_2-2\cdot p_{\mathrm{and}mG}+2\cdot DPS\right)}{2}\cdot A_K-m_{Os\mathrm{e.g}}\cdot \ddot{s}\left(\phi \right)\right]\cdot {\mathrm{right}}_k\cdot \frac{\text{sin}\left(\phi +\beta \right)}{\text{cos}\beta }\\ \widetilde{M_{tan}}=\left[\frac{\left({\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">p</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">p</figure-callout>}}_2-2\cdot p_{\mathrm{and}mG}+2\cdot DPS\right)}{2}\cdot A_K-m_{Os\mathrm{e.g}}\cdot \ddot{s}\left(\phi \right)\right]\cdot K_K\end{array}$$

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 (26) and (25) into equation (24), solving for the cylinder pressures and combining all constants, the result is: $$\begin{array}{l}\left[\frac{\left({\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">p</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.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_{m\mathrm{<figure-callout\; id="2"\; label="O\; t"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">O</figure-callout>}{t}_{}{}_2}{}^2-n_{m\mathrm{<figure-callout\; id="1"\; label="O\; t"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">O</figure-callout>}t1}{}^2}{{\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_2-{\mathrm{<figure-callout\; id="1"\; label="\phi "\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_1}+K_{\mathrm{<figure-callout\; id="1"\; label="R\; M\; p"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">R</figure-callout>}M}& \\ \frac{p_{}}{}\frac{{}_1+{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">p</figure-callout>}}_2}{2}=\frac{J\cdot K_{\omega }}{K_K\cdot A_K}\cdot \frac{n_{m\mathrm{<figure-callout\; id="2"\; label="O\; t"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">O</figure-callout>}{t}_{}{}_2}{}^2-n_{m\mathrm{<figure-callout\; id="1"\; label="O\; t"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">O</figure-callout>}t1}{}^2}{{\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_2-{\mathrm{<figure-callout\; id="1"\; label="\phi "\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_1}+\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}-D\mathrm{<figure-callout\; id="1"\; label="P\; S\; p"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">P</figure-callout>}S& \\ \frac{p_{}}{}\frac{{}_1+{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">p</figure-callout>}}_2}{2}={\mathrm{<figure-callout\; id="1"\; label="K"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">K</figure-callout>}}_1\cdot \frac{n_{m\mathrm{<figure-callout\; id="2"\; label="O\; t"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">O</figure-callout>}{t}_{}{}_2}{}^2-n_{m\mathrm{<figure-callout\; id="1"\; label="O\; t"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">O</figure-callout>}t1}{}^2}{{\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_2-{\mathrm{<figure-callout\; id="1"\; label="\phi "\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_1}+{\mathrm{<figure-callout\; id="2"\; label="K"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">K</figure-callout>}}_2+\frac{m_{Os\mathrm{e.g}}\cdot \ddot{s}\left(\phi \right)}{A_K}+p_{\mathrm{and}mG}-DPS\end{array}$$

All pressure variables and speeds in equation (30) 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 (19) can be formulated for the two discrete points: $${\ddot{s}}_{\mathrm{right}e\mathrm{i.e}}\left(\phi ,\dot{\phi }\right)={\mathrm{right}}_k\cdot {\left[\frac{\frac{\pi }{30}\left(n_{m\mathrm{<figure-callout\; id="1"\; label="O\; t"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">O</figure-callout>}{t}_{}{}_1}+n_{mO{t}_2}\right)}{2}\right]}^2\cdot \left[\text{cos}\left(\frac{{\mathrm{<figure-callout\; id="1"\; label="\phi "\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_2}{2}\right)+\text{cos}\left({\mathrm{<figure-callout\; id="1"\; label="\phi "\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_1+{\phi }_2\right)\right]$$

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 (30) can be used to determine the diagnostic cylinder pressure from the speed change in compression: $${\overline{p}}_{\mathrm{e.g}yi,\mathrm{i.e}iaG}={\mathrm{<figure-callout\; id="1"\; label="K"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">K</figure-callout>}}_1\cdot \frac{n_{m\mathrm{<figure-callout\; id="2"\; label="O\; t"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">O</figure-callout>}{t}_{}{}_2}{}^2-n_{m\mathrm{<figure-callout\; id="1"\; label="O\; t"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">O</figure-callout>}t1}{}^2}{{\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_2-{\mathrm{<figure-callout\; id="1"\; label="\phi "\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_1}+{\mathrm{<figure-callout\; id="2"\; label="K"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">K</figure-callout>}}_2+\frac{m_{Os\mathrm{e.g}}\cdot {\ddot{s}}_{\mathrm{right}e\mathrm{i.e}}\left(\phi n_{mOt}\right)}{A_K}+p_{\mathrm{and}mG}-DPS$$

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

In this way, the diagnostic cylinder pressure p̅ _zyl,diag = p̅ _{zyl,diag,655-675} can be determined during driving for the diagnostic time window 112 of the diagnosed cylinder Z at the time interval t12 = t[P1;P2] and used to determine the lowering of the Temperature levels ΔT are used.

In the exemplary embodiment, the vehicle is being driven while the method is being carried out, in particular the internal combustion engine 1 is in steady-state operation. During driving operation, a live engine control function continuously reads speed values n for the crankshaft KT and uses them to determine a speed development—cf. 1-3 .

• S10: Auswahl eines zu diagnostizierenden Zylinders Z1.
• S20: Bestimmen eines Diagnose-Zeitfensters 112, das das zweite Einspritzen E2 von Kraftstoff in den ausgewählten Zylinder Z1 berücksichtigt.
• S30: Ermitteln einer Drehzahlentwicklung 101 des Verbrennungsmotors 1 während des Diagnose-Zeitfensters 112 mit einer echtzeitfähigen Samplingqualität.
• S40: in Abhängigkeit von der ermittelten Drehzahlentwicklung 101 im Diagnose-Zeitfenster 112 wird eine Druckkennzahl p_diag für den Druck im Brennraum des Zylinders im Diagnosezeitfenster 112 ermittelt.
• S50: in Abhängigkeit von der ermittelten Druckkennzahl p_diag wird eine Referenztemperatur T̅̅ (für den Zustand vor der zweiten Einspritzung E2) im identifizierten Zylinder Z1 ermittelt.
• S60: in Abhängigkeit von der ermittelten Referenztemperatur T̅̅ wird eine isochore Wärmekapazität c_v ermittelt.
• S70: Aufstellen einer Energiebilanz ${\displaystyle \sum {}_1^{\mathrm{<figure-callout\; id="1"\; label="n\; U\; Z"\; filenames="DE102021130562A1\_0042.png,DE102021130562A1\_0043.png"\; state="\{\{state\}\}">n</figure-callout>}}{U}_Z{1}_{}}$
  
  im Zylinder Z1 für die zweite Einspritzung E2, wobei für die Energiebilanz ein Energiegehalt eines ungezündeten Zündgemischs U_mixt nach der zweiten Einspritzung gegenübergestellt wird einer Summe eines Energiegehalts U̅ vor der zweiten Einspritzung E2 und einer Verdampfungswärme dU_vap des bei der zweiten Einspritzung E2 eingespritzten Kraftstoffs.
• S71: Auflösen der Energiebilanz nach der Temperaturänderung (sprich Temperaturabsenkung) ΔT. Einsetzen des ermittelten Werts für die eine isochore Wärmekapazität c_v bei der ermittelten Referenztemperatur T̅.
• S71: Durch Auflösen der Ermitteln der Absenkung ΔT des Temperaturniveaus in Abhängigkeit von der ermittelten Referenztemperatur und der ermittelten Nacheinspritztemperatur, insbesondere als Temperaturdifferenz der ermittelten Referenztemperatur und der ermittelten Nacheinspritztemperatur.
• S80: Ermitteln einer Nacheinspritztemperatur T_after aus den ermittelten Werten für die Referenztemperatur T̅̅ und die Temperaturabsenkung ΔT.

As in 6 shown, the method carried out in the exemplary embodiment is initially described in summary below:

• S10: Selection of a cylinder Z1 to be diagnosed.
• S20: Determination of a diagnosis time window 112, which takes into account the second injection E2 of fuel into the selected cylinder Z1.
• S30: determining a speed development 101 of the internal combustion engine 1 during the diagnosis time window 112 with a real-time capable sampling quality.
• S40: a pressure index p _diag for the pressure in the combustion chamber of the cylinder in the diagnosis time window 112 is determined as a function of the speed development 101 determined in the diagnosis time window 112 .
• S50: a reference temperature is determined as a function of the determined pressure index p _diag T̅̅ (for the state before the second injection E2) determined in the identified cylinder Z1.
• S60: depending on the determined reference temperature T̅̅ an isochoric heat capacity c _v is determined.
• S70: Draw up an energy balance ${\displaystyle \sum {}_1^n{u}_{Z1}}$
  
  in cylinder Z1 for the second injection E2, whereby for the energy balance an energy content of an unignited ignition mixture U _mixt after the second injection is compared with a sum of an energy content U̅ before the second injection E2 and a heat of vaporization dU _vap of the fuel injected during the second injection E2.
• S71: Resolving the energy balance after the temperature change (i.e. temperature reduction) ΔT. Insertion of the determined value for the one isochoric heat capacity c _v at the determined reference temperature T̅.
• S71: By resolving the determination of the reduction ΔT in the temperature level as a function of the determined reference temperature and the determined post-injection temperature, in particular as a temperature difference between the determined reference temperature and the determined post-injection temperature.
• S80: Determination of a post-injection temperature T _after from the determined values for the reference temperature T - and the temperature reduction ΔT.

In the exemplary embodiment, various options are provided for using the specific values of the temperature drop ΔT and/or the temperature T _after after the second injection E2 for onboard diagnosis 204 and/or offboard diagnosis 208 and/or control tasks 206 using engine control 2 (cf. 6 ).

For this purpose, the determined values are continuously stored in a non-volatile memory 202 of the engine control unit 2 or stored for further use while the motor vehicle or stationary engine is being driven. If, for example, the associated value for the temperature drop ΔT and/or the temperature T _after is evaluated for each cylinder Z for each ignition, a new value ΔT and/or T _after is stored in memory 202 for each ignition—in particular with a time stamp and/or or output values for determining and/or specifying the diagnosed cylinder, for example Z1.

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

Reference List

1

combustion engine

2

furnishings

4

unit of account

6

Crankshaft speed acquisition unit

7

Cylinder pressure determination unit

10

Torque curve of the combustion engine over one engine cycle

16

Cylinder temperature determination unit

18

lambda probe

150

Speed development diagram

101

speed curve

112

diagnostic time window

200

engine control unit

202

Storage

204

Diagnostic component of an engine control

206

Control component of an engine control

208

Offboard diagnostic calculator

Sxx

process steps

E2

second, near-ignition injection

KT

crank drive

week

crank angle

Lst

stoichiometric fuel-air ratio, fuel specific

m

gas mass in the cylinder

M

Torque of a cylinder in 1

n

rotational speed

p

cylinder pressure

pcyl, diag

Pressure index, here diagnostic cylinder pressure

P

Measurement times at the beginning and end of the diagnosis time window

p0

Atmospheric pressure under standard conditions (1013hPa)

R

ideal gas constant

rf

Relative cylinder air charge (% of charge at standard conditions)

t12

Time interval of the diagnosis time window

T̅̅

Reference temperature of the gas mixture before the second injection

T0

Ambient temperature under standard conditions (293K)

tafter

lowered temperature value

Tz

Temperature level in the cylinder without a second injection

TE2

Temperature level in the cylinder with the second injection

ΔT

lowering of the temperature level

V

cylinder volume

V max

maximum cylinder volume at bottom dead center of the crankshaft

xrg

residual gas content

Z

cylinder

ZZP

ignition timing of a cylinder

λ

combustion air ratio

QUOTES INCLUDED IN DESCRIPTION

This list of 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

• DE 102018209252 A1 [0071]

Claims (10)

Method for determining a reduction (ΔT) in a temperature level (Tz) in a cylinder (Z1, Z2, Z3, Z4) of an internal combustion engine (1), the reduction being achieved by means of a second injection close to ignition or a first or single injection of fuel , having the steps: - selection of a cylinder (Z1) to be diagnosed, - determination of a diagnostic time window (112), which lies in particular before the second injection of fuel into the selected cylinder, - determination of a speed development (101) of the internal combustion engine (1 ) during the diagnosis time window, in particular with a real-time sampling quality, characterized by the step: - determining the reduction (ΔT) and/or a reduced absolute value (T _after ) of the temperature level (Tz) in the selected cylinder as a function of the determined speed development. procedure according to claim 1 , characterized by the steps: - determining a reference temperature (T̅) in the identified cylinder at the time or immediately before, in particular the second, injection, and - determining the reduction (ΔT) of the temperature level as a function of the determined reference temperature. procedure according to claim 2 , characterized in that the reference temperature (T̅) in the identified cylinder is determined as a function of a pressure index (p _diag ) for the cylinder in the diagnosis time window, which depends on the speed development in the diagnosis time window. procedure according to claim 2 or 3 , characterized in that the reference temperature is determined as a function of a cylinder volume (V) and/or a residual gas content (xrg) and/or a combustion air ratio (λ). Method according to one of claims 2 until 4 , characterized in that the residual gas content (xrg) and/or the combustion air ratio (λ) - is predetermined as a constant for one, several or all operating cases of the internal combustion engine, and/or - is read out from a pre-filled characteristic diagram as a function of an engine load and the engine speed is, and/or - is calculated from other engine and/or operating and/or environmental variables, and/or - is measured by means of a suitable sensor. Method according to one of the preceding claims, characterized by the steps: - establishing an energy balance in the cylinder for the, in particular second, injection, in particular immediately after the, in particular second, injection, and/or - determining a post-injection temperature (T _after ) from the established energy balance, and / or - determining the reduction (ΔT) of the temperature level as a function of the determined reference temperature and the determined post-injection temperature. Control means (2) for determining a reduction in a temperature level in a cylinder (Z1, Z2, Z3, Z4) of an internal combustion engine (1), in particular embodied in an engine control unit for an internal combustion engine of a passenger car, set up for this purpose, in particular by means of a method according to one of the preceding ones Claims to hand over values of the lowering (ΔT) of a temperature level (T) determined and/or stored in a memory - to a control component (206) of the control means for real-time regulation of functions of the internal combustion engine as a function of the transmitted values, and/or - To a diagnostic component (204) of the control means for further onboard diagnostic functions. tax funds according to claim 7 , having a non-volatile memory (202), characterized in that the control means is set up to store one or more characteristics of the lowering of the temperature level determined at one or different diagnosis times, in particular, in the memory. tax funds according to claim 8 , set up to transfer values of the lowering of the temperature level stored in the memory to an offboard computer (208) for offline diagnostic functions. Internal combustion engine (1) with several cylinders (Z), characterized by a control means (2) according to one of Claims 7 until 9 .

Images