DE102021006009A1 - Method for adapting an injector of a burner for heating an exhaust aftertreatment device in an exhaust system - Google Patents

Abstract

The invention relates to a method for adapting an injector (20) of a burner (18) for heating an exhaust gas aftertreatment device (14) in an exhaust gas system (10) through which exhaust gas from an internal combustion engine (12) can flow, wherein the injector (20) is designed to to inject fuel into a combustion chamber of the burner (18). A characteristic curve (26) defined by a linear equation is used, which assigns associated mass values to different activation durations of the injector (20), which characterize the respective masses of fuel that can be injected into the combustion chamber by means of the injector (20) during the respective activation durations. An injection is carried out in which one of the mass values and the control duration assigned to one mass value by the characteristic curve (26) are selected. During injection, the injector (20) is activated with the selected activation duration and thereby injects the fuel into the combustion chamber during the selected activation duration.

Description

The invention relates to a method for adapting an injector of a burner for heating an exhaust gas aftertreatment device in an exhaust system of an internal combustion engine.

The DE 10 2009 058 131 A1 discloses a device with at least one internal combustion engine, with an exhaust system and with a burner for introducing heat into the exhaust system. A conveyor for supplying air to the burner is also provided. The device also includes a hydraulic motor for driving the conveying device and a hydraulic pump for driving the hydraulic motor.

The object of the present invention is to create a method by means of which an injector of a burner, which is provided for heating an exhaust gas aftertreatment device in an exhaust gas system of the internal combustion engine through which exhaust gas from an internal combustion engine can flow, can be particularly advantageously adapted and thus operated particularly precisely.

This object is achieved by a method having the features of patent claim 1. Advantageous configurations with expedient developments of the invention are specified in the remaining claims.

The invention relates to a method for adapting an injector, also referred to as a fuel injector, of a burner for heating an exhaust gas aftertreatment device in an exhaust system of the internal combustion engine through which exhaust gas of an internal combustion engine, in particular a motor vehicle, can flow. In particular, the exhaust gas can be heated by means of the burner and the exhaust gas aftertreatment device can be heated via the exhaust gas. The injector is designed to inject a fuel, in particular a liquid fuel, into a combustion chamber of the burner. The fuel injected into the combustion chamber is mixed, in particular with air, in the combustion chamber, as a result of which a mixture is formed. The mixture is burned, which heats up the exhaust gas aftertreatment. In particular, an exhaust gas of the burner, also referred to as burner exhaust gas, is produced by burning the mixture, with the burner providing its burner exhaust gas. The burner exhaust gas can flow through the exhaust system and in particular mix with the exhaust gas from the internal combustion engine, as a result of which the exhaust gas from the internal combustion engine and thus the exhaust gas aftertreatment device can be heated.

In the method, a linear and thus straight line characteristic is used, which is defined by a straight line equation. For example, the characteristic curve is stored in a memory device of an electronic computing device, by means of which the method is carried out. The characteristic assigns associated mass values to different activation durations of the injector. The mass values characterize the respective masses or quantities of the fuel, with the masses or quantities of the fuel being able to be injected into the combustion chamber by means of the injector during the respective activation period. In other words, the characteristic curve assigns exactly one of the mass values to one of the respective activation durations, so that the characteristic curve says, so to speak, which mass or quantity of fuel, and therefore which fuel mass or quantity, can be injected into the combustion chamber by means of which activation duration. In this context, it is particularly conceivable that the mass values belonging to the activation durations are setpoint values which, for example, relate to a setpoint state of the injector. In particular due to manufacturing or manufacturing-related tolerances, however, it can happen that when the injector is activated with one of the activation durations, it is not the mass or quantity associated with this activation duration that is injected into the combustion chamber, but actually a different mass or quantity of fuel. This can be due, for example, to the fact that an actual geometry of at least one or more through-flow openings of the injector through which the fuel can flow actually deviate from a desired target size or target geometry. The method now makes it possible to compensate for such deviations.

For this purpose, at least one injection is carried out in the method and thus in particular by means of the electronic computing device, in which one of the mass values and the activation duration assigned to one mass value by the characteristic curve are selected. During injection, the injector is activated with the selected activation period, as a result of which the injector injects the fuel into the combustion chamber during the selected activation period. Furthermore, at least one actual heating value is determined in the method, which characterizes an actual heating in the exhaust system resulting from the injection. For example, the actual heating is a heating of the exhaust gas aftertreatment device and in particular the actual heating can be a heating of the exhaust gas.

In the method, the actual heating value is compared with a target heating value. The setpoint heating value characterizes, for example, a setpoint heating, i.e. a heating which was to be expected in particular due to the selected control duration. For example, if the injector is not worn or slightly worn and the actual geometry does not deviate or differs slightly from the target geometry, the actual heating value corresponds to the target heating value or the actual heating value differs only slightly from the target heating value. In other words, the actual heating corresponds to the expected heating or the actual heating deviates only slightly from the expected heating, so that a desired heating corresponding to the respective control duration can be brought about by controlling the injector with the respective control duration. In particular, due to wear and / or excessive, especially production-related tolerances, it can now happen that the selected control duration has not led to the expected heating, or that the actual heating was greater than the expected heating, so that the expected or desired warming, a different, in particular longer or shorter control duration would have had to be selected. In order to compensate for such deviations, the method provides that a factor of the straight-line equation that characterizes a slope of the characteristic curve changes depending on the comparison of the actual heating value with the target heating value, i.e. is adjusted, in particular in such a way that from a respective activation of the injector with the respective activation duration results in a respective expected heating. As a result, when the injector is activated with the respective activation duration, this activation also leads to the desired heating corresponding to the activation, so that the injector can also be operated precisely over a long running time or service life.

The invention is based in particular on the following findings and considerations: The fuel mass that is metered into the burner or into the combustion chamber via the fuel injector can vary due to manufacturing tolerances and/or due to changes over the running time or service life. This scattering of the introduced fuel mass can be reduced by the adaptation. For this purpose, the characteristic curve is used, which is a straight line because the characteristic curve has a linear characteristic curve and is defined by the straight-line equation. Manufacturing tolerances and changes over the running time only change the gradient of the characteristic curve. The fuel mass can be adjusted via a signal in the exhaust system, also referred to as the exhaust system, in particular at or at an operating point. It can be seen that in the method the slope of the characteristic curve is adjusted, ie changed, as a result of which the adaptation takes place. The invention enables a reduction in the scatter of the metered fuel mass, in particular when the injector is new and over its running time or service life. Stable operation of the burner can thus be guaranteed over a long service life. Emission limits are better adhered to. In particular, the adaptation of the injector is to be understood as an adaptation of the mass of fuel that can be injected into the combustion chamber by means of the injector during the respective activation period, also referred to as the injection quantity.

The injection of the fuel into the combustion chamber of the burner, which is designed as a swirl chamber, for example, is also referred to as metering or fuel metering. The fuel is, for example, a diesel fuel, in particular when the internal combustion engine is designed as a diesel engine. A desired metering quantity of the fuel is defined via the characteristic curve, which is designed as a straight line, and thus via the linear equation, in such a way that the respective associated mass values are assigned to the control durations through the characteristic curve. Thus, in each case exactly one of the activation durations is assigned to exactly one of the mass values. In particular, it is conceivable that the respective mass value characterizes a respective mass or quantity that is injected or can be injected into the combustion chamber by means of the injector during the respective activation period. It is also conceivable that the respective mass value characterizes a respective mass flow resulting in particular from the control duration, the mass flow also being referred to as the fuel mass flow.

It is usually not possible to correct scattering of the metered quantity, in particular when the injector is new or over a period of time, but this is now possible with the invention. In particular, the invention enables the mass or quantity of the fuel, in particular the fuel mass flow, to be adapted, in particular by comparison with a signal which is available in the exhaust system. This signal characterizes the actual heating, for example, or the actual heating is determined on the basis of the signal.

In an advantageous embodiment of the invention, it is provided that the actual heating value is determined as a function of a residual oxygen content in the exhaust gas flowing through the exhaust system, with the residual oxygen content being measured using a lambda probe.

In an advantageous embodiment of the invention, it is provided that the actual heating value in is determined as a function of an amount of unburned hydrocarbons contained in the exhaust gas flowing through the exhaust system, the amount of unburned hydrocarbons being measured by a sensor.

In an advantageous embodiment of the invention, it is provided that the actual heating value is determined as a function of at least one temperature of the exhaust gas flowing through the exhaust system, with the temperature being measured using a temperature sensor.

Further advantages, features and details of the invention result from the following description of preferred exemplary embodiments and from the drawing. The features and combinations of features mentioned above in the description and the features and combinations of features mentioned below in the description of the figures and/or shown alone in the figures can be used not only in the combination specified in each case, but also in other combinations or on their own, without going beyond the scope of the leave invention.

• 1 eine schematische Darstellung einer Abgasanlage einer Verbrennungskraftmaschine, mit einem Brenner, welcher einen Injektor aufweist;
• 2 ein Diagramm zum Veranschaulichen eines Verfahrens zur Adaption des Injektors; und
• 3 ein weiteres Diagramm zur weiteren Veranschaulichung des Verfahrens.

The drawing shows in:

• 1 a schematic representation of an exhaust system of an internal combustion engine, with a burner which has an injector;
• 2 a diagram to illustrate a method for adapting the injector; and
• 3 another diagram to further illustrate the procedure.

Elements that are the same or have the same function are provided with the same reference symbols in the figures.

1 shows a schematic representation of an exhaust system 10 of an internal combustion engine 12 of a motor vehicle, in particular a motor vehicle. For example, the internal combustion engine 12, also referred to as an internal combustion engine, is designed as a diesel engine. In a fired operation of the internal combustion engine 12, combustion processes take place in the internal combustion engine 12, from which exhaust gas of the internal combustion engine 12 results. The internal combustion engine 12 is assigned the exhaust system 10 through which the exhaust gas from the internal combustion engine 12 can flow. The exhaust system 10 has at least one exhaust gas aftertreatment device 14, by means of which the exhaust gas can be aftertreated. For example, exhaust gas aftertreatment device 14 has at least one or more catalytic converters and/or at least one or more filters. The filter can in particular be a diesel particle filter (DPF). Furthermore, the exhaust system 10 can have at least one or more sensors. In 1 Arrows 16 illustrate the exhaust gas flowing through the exhaust system 10 . In other words, the arrows 16 illustrate a flow of the exhaust gas through the exhaust system 10. In the exhaust system 10, a burner 18 is also arranged, which has an in 1 injector 20 shown particularly schematically and also referred to as a fuel injector. The burner 18 has a combustion chamber designed, for example, as a swirl chamber, with the injector 20 being able to inject a particularly liquid fuel, which is, for example, diesel fuel, into the combustion chamber. The fuel can be burned in the combustion chamber, in particular with air, as a result of which the exhaust system 10 can be heated. In particular, the exhaust gas flowing through the exhaust system 10 can be heated by the combustion of the fuel in the combustion chamber. Since the heated exhaust gas, in particular after it has been heated by the burner 18, flows through the exhaust gas after-treatment device 14, the burner 18 can be used to heat the exhaust gas, that is, by heating the exhaust gas

Exhaust aftertreatment device 14 are heated. In particular, the characteristic curve 26 assigns the mass values, in particular mass flows, to the control durations at a fuel pressure of 3.5 bar, in particular at a relative fuel pressure of 3.5 bar of the fuel.

A method for adapting the injector 20 is described below. 2 shows a diagram on whose abscissa 22 control durations of the injector 20 are plotted, the control durations being based on the image plane of FIG 2 increase to the right. On the ordinate 24 of the in 2 Mass values, in particular mass flows, are plotted in the diagram shown, which are related to the image plane of 2 get bigger towards the top. into the into 2 In the diagram shown, a characteristic curve 26 designed as a straight line and therefore linear is entered, which is used to operate the injector 20 . This means that the fuel is injected into the combustion chamber by means of the injector 20 as a function of the characteristic curve 26 . The mass values are, for example, quantities or masses of fuel that can be injected into the combustion chamber when injector 20 is activated with the respective activation durations. In particular, it is conceivable that the mass values are mass flows or the mass values characterize mass flows which, when injector 20 is controlled with the respective control durations, are provided by the injector 20 or injected into the combustion chamber. It can be seen that the characteristic curve 26 assigns the associated mass values, in particular mass flows, plotted on the ordinate 24 to the different activation durations plotted on the abscissa 22 .

The characteristic curve 26, which is stored, for example, in a memory device of an electronic computing device and is configured as a straight line, is defined by an equation for a straight line, which is stored, for example, in the memory device.

In the method, at least one injection is carried out, for example, in which one of the mass flows and the activation duration assigned to one mass flow by characteristic curve 26 are selected. During the injection, the injector 20 is activated with the selected activation period, as a result of which the injector 20 injects the fuel into the combustion chamber during the selected activation period. In the method, at least one actual heating value is determined, for example, which characterizes actual heating in exhaust system 10 resulting from the injection. The actual heating value is compared to a target heating value. In particular, when the actual heating value deviates from the target heating value or when a deviation of the actual heating value from the target heating value exceeds a specifiable or predetermined limit, a factor of the linear equation that characterizes a slope of characteristic curve 26 becomes dependent on the comparison of the actual heating value is changed with the target heating value, i.e. adjusted.

The method thus makes it possible to adapt the mass or quantity, ie the respective mass flow, also referred to as fuel mass flow, of injector 20 by comparison with a signal available in exhaust gas system 10 . The progression of the characteristic curve 26 of the mass flow plotted over the activation duration is linear in the injector 20 used, in particular for an operating range of the burner 18, and is stored in the electronic computing device designed, for example, as a control device or also referred to as a control device. This means that the characteristic curve 26 follows the linear equation, also referred to as a function, which reads, for example: y(x)=mx+b, in particular at a constant fuel pressure, which is 3.5 bar, for example, in particular relatively. This linearity also remains when the nozzle hole diameters are different in a new state due to production controls or change over time (enlargement of the nozzle holes, for example coking). Each nozzle hole is a respective through-flow opening of the injector 20, through which through-flow opening the fuel flows when the injector 20 injects the fuel into the combustion chamber. The mass flow is also denoted by m., for example, and results, for example, in: $$\dot{m}=\rho \ast C\ast A$$

It is therefore sufficient if the adjustment is made at a point in the range of the maximum burner heating output. Based on the signal in the exhaust system 10, the actual mass flow can be determined and a new gradient m can be defined. In other words, in the above-mentioned function, m denotes the factor mentioned and thus the gradient of the characteristic curve 26 . The course of the characteristic curve is adapted by the adapted slope m and the metering of the fuel mass flow is thus adapted. The quantity quality can thus be improved in the new condition and over the term. The stability of the combustor 18 is improved and emission limits can be met. Furthermore, a spread of an OBSFC (onboard fuel consumption) can be reduced.

3 shows a diagram which basically corresponds to that in 2 corresponds to the diagram shown. A necessary fuel mass flow for the maximum burner output is denoted by 28 . The mass flow is then injected by means of a reference injector or by means of the injector 20 when the injector 20 is designed as a reference injector and is controlled with a corresponding control duration. In the case of a so-called minimal injector, ie when the injector 20 is designed as a minimal injector, less fuel mass is supplied for the same control duration, that is to say it is injected into the combustion chamber. In 3 30 denotes the fuel mass flow, and it also occurs with the same control duration if the injector 20 is worn compared to its new condition, for example, or has excessive production-related tolerances and is therefore not designed as the reference injector but as the minimal injector. While the same control duration leads to fuel mass flow 28 in the case of an injector that is not worn or in the case of an injector which has no or only small tolerances due to production and is therefore the reference injector, in the case of the minimal injector the same control duration leads to fuel mass flow 30, which is lower than fuel mass flow 28 .

• - bei stehender Verbrennungskraftmaschine, beispielsweise wenn das Kraftfahrzeug an einer Ampel steht oder segelt
• - im Schubbetrieb
• - im Zugbetrieb

The method now allows a correction of the fuel mass flow by adjusting the Straight line equation, especially in the following operating ranges of the burner 18:

• - When the internal combustion engine is stationary, for example when the motor vehicle is at a traffic light or is sailing
• - in overrun mode
• - in train operation

In order to carry out the adaptation, it is possible to activate the burner 18 in a defined manner during overrun or at the beginning of a stop phase, even if the burner 18 does not necessarily have to be activated for emission reasons.

The adjustment can take place by using a temperature signal in the exhaust system 10, also referred to as the exhaust system. A temperature sensor, for example, which can be arranged downstream of the burner 18 in particular, is used to adjust the actual mass flow.

For example, a reference variable, also referred to simply as a reference, is determined using a new average or reference injector. The burner 18 is activated and operated in the range of its maximum heat output, for example with λ (lambda)=1.04. After a defined period of time, the temperature delta (T_End - T_Beginn) of the sensor in the exhaust system, and therefore the heating resulting from the injection, is determined. The thermal energy supplied can be determined using the product mB x Hu. The product cp x (m+mB) x (T_End - T_Beginn) results in the thermodynamically calculable combustion temperature. The reference is determined under real conditions, taking into account the wall heat losses, and stored in the control unit. $$\text{mB}\times \text{whoa}=\text{cp}\times \left(\text{mL}+\text{mB}\right)\times \left(\text{T}\_\text{End}-\text{T}\_\text{beginning}\right)$$

Here, mB denotes the mass of the fuel, also referred to as fuel, mL denotes the mass of air, Hu denotes the lower calorific value and cp denotes the specific heat capacity.

If a minimum injector is in use, then the temperature (T_End) at the end of the burner 18 is at a lower level after a defined time. The minimal injector has a flatter characteristic curve, which is the difference 3 is recognizable, i.e. with the same control duration, the metered fuel mass is lower compared to the average injector (reference injector). The fuel mass or fuel quantity introduced over a defined period of time can be determined because all the remaining variables in the above equation are known. The actual fuel mass flow is thus known. The gradient of the characteristic curve can be adjusted so that the desired mass flow can be metered in the adapted state. The procedure is identical if the characteristic curve 26 of the injector 20 changes over the running time due to a reduction in the hole diameter or if a maximum injector is in use.

Alternatively or additionally, the adjustment can be made by using a λ signal in the exhaust system. As an alternative or in addition, the fuel mass flow can thus be adjusted by means of a λ sensor, also referred to as a lambda probe. The gradient m of the characteristic curve 26 can be adjusted so that the desired mass flow can be metered in the adapted state.

Alternatively or additionally, the adjustment can be made using an HC sensor in the exhaust system. HC denotes unburned hydrocarbons that can be contained in the exhaust gas. The slope of the characteristic curve 26 can be adjusted so that the desired mass flow can be metered in the adapted state.

The injector 20 is, for example, what is known as a port fuel injector. This is normally closed. A spring presses a needle into its seat. If a coil is energized, the needle rises from its seat and after a short time (approx. one millisecond, time for needle flight phase approx. 0.3 milliseconds) it reaches a needle stroke stop. At this point in time, the mass flow at constant injection pressure and constant density is only dependent on the cross-section of the nozzle holes. The cross-section of the nozzle holes is selected in such a way that the needle is in the stop when it is actuated, even for the smallest fuel mass flow. The needle is in the non-ballistic area.

If, for example, there is a minimum injector or a maximum injector or a coked injector in the system, then the A value, for example, is greater or less than a target value. The air mass flow for the burner 18 can be made available via a separate air pump and can be monitored or recorded via a sensor such as a hot film air mass meter (HFM). Since the air mass of the air that is burned in the combustion chamber with the injected fuel is known, since it is measured by means of the sensor, for example, the actual fuel mass that was injected into the combustion chamber by means of the injector 20 can be concluded and compared with a target value the. The gradient m of the characteristic curve 26 can be adjusted so that the desired mass flow can be metered in the adapted state.

Reference List

10

exhaust system

12

internal combustion engine

14

exhaust aftertreatment device

16

Arrow

18

burner

20

injector

22

abscissa

24

ordinate

26

curve

28

mass flow

30

mass flow

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 102009058131 A1 [0002]

Claims (4)

Method for adapting an injector (20) of a burner (18) for heating an exhaust gas aftertreatment device (14) in an exhaust system (10) through which exhaust gas from an internal combustion engine (12) can flow, the injector (20) being designed to inject a fuel into a combustion chamber of the burner (18), with the steps: - Use of a linear characteristic curve (26) defined by a straight-line equation, which assigns associated mass values to different activation durations of the injector (20), which characterize the respective masses of fuel that can be injected into the combustion chamber by means of the injector (20) during the respective activation durations, - carrying out at least one injection in which: ◯ one of the mass values and the control duration assigned to one mass value by the characteristic curve (26) are selected, and ◯ the injector (20) is activated with the selected activation duration and thereby injects the fuel into the combustion chamber during the selected activation duration, - Determining at least one actual heating value, which characterizes an actual heating in the exhaust system resulting from the injection, - comparing the actual heating value with a desired heating value, and - Changing a factor of the linear equation that characterizes a slope of the characteristic curve (26) as a function of the comparison of the actual heating value with the target heating value. procedure after claim 1 , characterized in that the actual heating value is determined as a function of a residual oxygen content in the exhaust gas flowing through the exhaust system (10), the residual oxygen content being measured by means of a lambda probe. procedure after claim 1 or 2 , characterized in that the actual heating value is determined as a function of an amount of unburned hydrocarbons contained in the exhaust gas system (10) flowing through the exhaust gas, the amount of unburned hydrocarbons being measured by a sensor. Method according to one of the preceding claims, characterized in that the actual heating value is determined as a function of at least one temperature of the exhaust gas flowing through the exhaust system (10), the temperature being measured by means of a temperature sensor.

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