DE102016215858A1 - Method and device for controlling an internal combustion engine - Google Patents

Abstract

Disclosed is a method and a device for controlling an internal combustion engine, wherein the air mass flow of the internal combustion engine is determined, wherein the air mass flow is corrected by means of detected values in an exhaust system and the internal combustion engine is controlled in dependence of the corrected air mass flow.

Description

The invention relates to a method and a device for controlling an internal combustion engine.

State of the art

From the DE 10 2011 101 537 A1 is a method for recirculating exhaust gas of an internal combustion engine of a vehicle, in which exhaust gas is returned via a low-pressure line in an intake manifold of the internal combustion engine known. In this case, a pressure difference is determined in the region of the low-pressure line and the pressure difference used to monitor the low-pressure exhaust gas recirculation. If a malfunction of the low-pressure exhaust gas recirculation occurs, a data value indicating the malfunction is stored in a memory.

Disclosure of the invention

In internal combustion engines, systems with more precise air mass sensors are increasingly gaining ground due to stricter legislation. Hot-air air-mass sensors (HFM) are used primarily in the passenger car sector, and so-called Pressure Based Air Flow Meters (PFM) in the truck and commercial vehicle sector. The advantages of the more accurate air mass sensors, such as of the PFM sensor is that optimum combustion can be made in terms of power and emissions. In order to control the combustion as optimally as possible with respect to generated emissions, exhaust aftertreatment systems such as internal exhaust gas recirculation and special catalysts, such as. Selective SCR catalysts used. Below the fresh air mass flow is simplified in the following of an air mass flow, as well as under the fresh air mass also spoken by an air mass.

In the field of commercial vehicles, the engines produced are used in many different vehicles. Therefore, there are many different configurations or applications for the same engine here. Normally, the area of the engine includes the engine itself, the exhaust gas recirculation, the turbocharger and the exhaust aftertreatment system.

The area of air intake, i. the upstream part of the compressor of the exhaust gas turbocharger, the intercooler between the turbocharger and the throttle or the intake manifold are not counted to the engine area.

For air mass sensors, which are arranged upstream of the compressor of the turbocharger, such. Heißfilmluftmassensensoren, have different variants of air filters and its contamination with z. As dust, water or ice a big effect on the air mass sensor signal. In the case of air mass sensors arranged downstream of the turbocharger, such as e.g. PFM air mass sensors, the variants of the intercoolers, the variants of the connecting pieces of the tubes have an influence on the air mass signal.

For both sensor types there are systematic deviations in the sensor signal for the different components or air intake tract geometries.

Lower quality of the measured air mass sensor signal may result in higher fuel consumption, inferior exhaust levels, and increased consumption of urea (Adblue) in selectively catalytic reduction exhaust aftertreatment systems.

Today commercial vehicles with more than 59 kW of power usually already have a urea injection system to reduce nitrogen oxide emissions. Typically, for the analysis of the exhaust gas to two nitrogen oxide sensors (NOx sensors) are installed in the exhaust system, with the help of the implementation of the selective catalytic reduction of the SCR system adjusts. These sensors can measure the nitrogen oxide concentration in the exhaust gas and also the air-fuel mixture or air-fuel ratio λ.

The invention relates to a method and a device for controlling an internal combustion engine and a computer program on a storage medium for carrying out the method.

In a first aspect, a control of an internal combustion engine is proposed, in which an air mass flow of the internal combustion engine is determined, wherein the air mass flow is corrected by means of detected values in an exhaust system and the internal combustion engine is controlled in dependence of the corrected air mass flow.

This has the advantage that with the aid of the values determined in the exhaust gas line, the air mass flow can be corrected in such a way that systematic errors, which are caused by, for example, B. caused by different geometries of the intake tract of the internal combustion engine or component tolerances can be corrected. This makes it possible to comply with mandatory emissions legislation and to detect and avoid inadmissible emissions of exhaust gases. This also has a positive effect on fuel consumption, since the engine is operated optimized for emissions. In the event that the internal combustion engine with an SCR system If necessary, unnecessary SCR system urea consumption can be prevented because optimized combustion produces less nitrogen oxides and thus less urea is needed to convert nitrogen oxides into clean exhaust products.

The measures listed in the dependent claims advantageous refinements and improvements of the main claim entered method are possible.

It is particularly advantageous if, depending on the corrected air mass flow, e.g. an exhaust gas recirculation valve is controlled to adjust the recirculated exhaust gas. Thus, emissions of the internal combustion engine, such as e.g. Nitrogen oxides and soot formation can be optimized, so that it can lead to lower fuel consumption or lower consumption of urea.

A further advantage results if the corrected air mass flow are formed as a function of a nitrogen oxide sensor value and a nitrogen oxide model value. Since the amount of air supplied has a great influence on the combustion and thus on the emissions generated, it is advantageous to have systematic errors, e.g. be generated by component tolerances of hot air mass flow sensors or PFM sensors to correct. As a result, harmful emissions of the internal combustion engine can be reduced.

It is furthermore advantageous if the corrected air mass flow is determined as a function of an air / fuel sensor value and an air / fuel model. This has the particular advantage that the corrected mass air flow can be easily determined by comparing the air fuel sensor value of the NOx sensor positioned upstream with the air fuel model value calculated in the control unit. Thereby, e.g. Component tolerances of the sensors used to detect the air mass flow, e.g. Hot film air mass sensors or PFM sensors, to be corrected. As a result, harmful emissions of the internal combustion engine can be reduced.

Another advantage arises when the corrected air mass flow is determined as a function of a selective catalytic correction function.

It is particularly advantageous if the selective catalytic correction function is formed as a function of an injection quantity of the urea of the selective catalytic system. The selective catalytic correction function corrects the amount of urea to be injected. By correcting the air mass flow as a function of the selective catalytic correction function, less nitrogen oxides are produced during the combustion of the internal combustion engine and thus less urea is required for the selective catalytic system. As a result, harmful emissions of the internal combustion engine can be reduced and further fuel can be saved, since the internal combustion engine can be operated optimally.

In other aspects, the invention relates to a device, in particular a control device and a computer program, which are set up for executing one of the methods, in particular programmed. In yet another aspect, the invention relates to a machine-readable storage medium on which the computer program is stored.

drawing

The invention is described in more detail below with reference to the accompanying drawings and to exemplary embodiments. Show

1 shows a schematic representation of an internal combustion engine with exhaust gas recirculation,

2 a functional diagram for explaining the method in which the corrected air mass flow is formed as a function of a nitrogen oxide model value and a nitrogen oxide sensor value,

3 4 is a functional diagram for explaining the method in which the corrected air mass flow is formed as a function of an air-fuel model value and an air-fuel sensor value,

4 a functional diagram for explaining the method in which the corrected air mass flow is formed in response to a selective catalytic correction function.

Description of the embodiments

1 shows a schematic representation of an internal combustion engine 10 with an air system 4 , about the internal combustion engine 10 air 50 is supplied, and an exhaust system 11 , via the exhaust gases in the flow direction 51 from the internal combustion engine 10 be dissipated. The representation is limited to relevant parts for the following presentation.

In the air conditioning 4 is in the flow direction of the air 50 Seen arranged: An air filter 1 , a hot film air mass sensor (HFM) 2 , a compressor 5 an exhaust gas turbocharger 6 , a charge air cooler 7 , a PFM sensor 8th and a throttle 9 , In a preferred embodiment, either a hot film air mass sensor is provided 2 (HFM) or a PFM sensor 8th (PFM) installed in the system for determining the air mass flow.

In the exhaust system 11 is starting from the internal combustion engine 10 in the flow direction of the exhaust gas 51 arranged: an exhaust gas turbine 12 , an oxidation catalyst (DOC) 13 , a diesel particulate filter 15 (DPF), a first nitric oxide sensor 16 , a selective catalytic system 17 with an SCR catalyst and a second nitrogen oxide sensor 18 , The nitrogen oxide sensors are in an alternative embodiment, also able to determine an air-fuel mixture λ. The described values can, for. B. as sensor values or as model values and are eg a control unit 100 provided as sensor data.

Upstream of the exhaust gas turbine 12 the exhaust gas turbocharger 6 , ie on a high pressure side of the exhaust system, branches off the exhaust system 11 an exhaust gas recirculation line 24 off, the upstream of the engine 10 and the downstream of the throttle 9 in the air conditioning 4 empties. Downstream of the internal combustion engine 10 are located along the exhaust gas recirculation line 24 an HD EGR valve 22 and HD EGR cooler 23 and. The recirculation of exhaust gas serves to reduce the emission of the internal combustion engine 10 ,

2 shows a functional diagram for explaining the method in which the corrected air mass flow in dependence of a nitrogen oxide model value and a nitrogen oxide sensor value is formed. In one step 500 the nitrogen oxide sensor value is offset with a model nitrogen oxide value. Here is the nitrogen oxide sensor 16 upstream of the selective catalytic system 17 be used, which detects the raw emissions of the exhaust gas. The nitrogen oxide model value is based on a raw emission nitrogen oxide model on the control unit 100 calculated. Alternatively or additionally, an exponent NOx model can also be used for the model. The offsetting between the nitrogen oxide sensor value and the nitrogen oxide model value can take place, for example, in the form of a division or subtraction.

In one step 510 Subsequently, depending on the result of the calculation between the nitrogen oxide sensor value and the nitrogen oxide model value, a correction factor is selected, for example, from a table stored in the control unit. The correction factor of the table may also be replaced by a complex function such as a model-based nitrogen oxide offset calculation in proportion to the air mass deviation based on an inverse raw emission nitrogen oxide model.

In one step 520 Then, the correction factor determined from the table or the model with the air mass flow sensor value of the HFM or PFM sensor ( 2 ; 8th ) to a corrected mass air flow value. The calculation can be done eg by means of a multiplication or addition.

In one step 530 Then, the desired air mass flow value is offset by means of the corrected air mass flow value to a control deviation. This can be done for example in the form of a subtraction.

In one step 540 Subsequently, the control deviation is supplied to the exhaust gas recirculation controller, which then controls the exhaust gas recirculation valve 22 performs. Subsequently, the process again at step 500 to be continued.

3 shows a functional diagram for explaining the method in which the corrected air mass flow is formed in dependence on an air-fuel model value and an air-fuel sensor value. In a second embodiment, the air mass flow is corrected by means of an air-fuel sensor value and an air-fuel model value. This is the nitric oxide sensor 16 used, which can also determine an air-fuel ratio in this embodiment. Alternatively or additionally, a lambda sensor can also be used, which downstream of the internal combustion engine 10 and upstream of the exhaust gas turbine 12 is arranged. The air-fuel model is determined by means of the signal of the air mass flow sensor and the fuel injection quantity and by the control unit 100 calculated.

In one step 600 is the air-fuel model value of injection quantity and desire mass sensor ( 2 ; 8th ) with the air-fuel sensor value from the NOx or lambda sensor. This allocation can be done for example by a division. Depending on this result, a correction factor is then determined from a table stored in the control unit. Alternatively, the correction factor can also be calculated, for example, by the already known Fuel Mass Observer model. The fuel mass observer model can detect and correct drifting of the fuel signal by means of the lambda sensor. In German, the Fuel Mass Observer is also z. B. known as fuel mass observers. The actual correction can be done via the adjustment of the desired air mass flow and / or via the adjustment of the desired fuel injection quantity. A Fuel Mass Observer is for example in the patent DE 10 2004 044 463 A1 disclosed.

In one step 620 is then the correction factor determined from the table with the air mass sensor value of the HFM or PFM sensor ( 2 ; 8th ) to a corrected mass air flow value. This can be done, for example, by multiplying the sensor value by the correction factor.

In one step 630 Then, the desired air mass flow value is offset by means of the corrected air mass flow value to a control deviation. This can be done for example in the form of a subtraction.

Subsequently, in one step 640 the control deviation fed to the exhaust gas recirculation controller, which then controls the exhaust gas recirculation valve 22 performs. Subsequently, the process again at step 600 to be continued.

4 shows a functional diagram for explaining a method in which the corrected air mass flow is formed in response to a selective catalytic correction function. In a third embodiment, based on a selective catalytic correction function which corrects the metered amount of urea, a corrected air mass flow value is calculated. For this purpose, a selective catalytic correction function or the selective catalytic NH3 level observer can be used. An NH3 level observer is eg the DE 20 1210 221 574 refer to. These functions can be used, for example, to detect the quality of the AdBlue, ie to correct the ratio of water to urea in the tank of the vehicle and, above that, to correct the required dosing quantity.

In one step 700 a splitting factor is determined. The splitting factor can be determined by a complex function such as a model-based back calculation of the nitrogen oxide deviation in relation to the weighted air mass / injection deviation based on an inverse raw emission nitrogen oxide model.

Subsequently, in one step 710 the splitting factor is offset with the corrected selective catalytic correction factor, eg by means of a division. Subsequently, a correction factor is determined by means of this result from a table stored in the control unit. Alternatively, a more complex function for determining the correction factor can again be used here.

In one step 720 is then the correction factor determined from the table with the air mass sensor value of the HFM or PFM sensor ( 2 ; 8th ) to a corrected mass air flow value.

Subsequently, in one step 730 the desired air mass flow value is offset with the corrected air mass flow value to a control deviation. This can be done for example by a subtraction.

Subsequently, in one step 740 the control deviation fed to the exhaust gas recirculation controller, which then a corrected control of the exhaust gas recirculation valve 22 performs. Subsequently, the process again at step 700 to be continued.

In a further embodiment, the correction mechanisms described above are combined. Thus, the corrected air mass flow is formed as a function of the nitrogen oxide sensor value and the nitrogen oxide model value and / or in dependence on the air-fuel sensor value and the air-fuel model value and / or in dependence on the selective catalytic correction function. This has the particular advantage that it can be found out by the combination of the above-mentioned mechanisms which of the components used is subject to a tolerance deviation. It is particularly useful to correct that component which has a major influence on the tolerance deviation. This leads to optimized operation of the internal combustion engine, so that emissions such as e.g. Nitrogen emissions can be reduced.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• DE 102011101537 A1 [0002]
• DE 102004044463 A1 [0035]
• DE 201210221574 [0039]

Claims (10)

Method for controlling an internal combustion engine ( 10 ), characterized in that an air mass flow of the internal combustion engine ( 10 ), wherein the air mass flow by means of in an exhaust system ( 11 ) of detected values is corrected and the internal combustion engine ( 10 ) is controlled in dependence of the corrected air mass flow. A method according to claim 1, characterized in that an exhaust gas recirculation valve ( 22 ) is controlled in dependence of the corrected air mass flow. Method according to one of the preceding claims, characterized in that the corrected air mass flow is determined as a function of a nitrogen oxide sensor value and a nitrogen oxide model value. Method according to one of the preceding claims, characterized in that the corrected air mass flow in dependence of an air-fuel sensor value and an air-fuel model value is determined. Method according to one of the preceding claims, characterized in that the corrected air mass flow is determined as a function of a selective catalytic correction function. A method according to claim 5, characterized in that the selective catalytic correction function in dependence of an injection quantity of a urea of a selective catalytic system ( 17 ) is formed. A method according to claim 1, characterized in that the air mass flow by means of a hot film air mass sensor ( 2 ) and / or a pressure-based air flow meter ( 8th ) is determined. Computer program which is set up to carry out a method according to one of Claims 1 to 7. Electronic storage medium with a computer program according to claim 8. Device, in particular control device, which is adapted to carry out a method according to claim 1 to 7.

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