CN112443378A

CN112443378A - Method for regenerating an exhaust gas particulate filter

Info

Publication number: CN112443378A
Application number: CN202010871094.5A
Authority: CN
Inventors: A·弗里茨克; 金忱
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2019-08-27
Filing date: 2020-08-26
Publication date: 2021-03-05
Also published as: DE102019212815A1

Abstract

The invention relates to a method for regenerating an exhaust gas particulate filter of a motor vehicle, wherein the course of the regeneration is simulated at different starting points in time on a predicted driving route of the motor vehicle. In order to perform the regeneration, a starting point is selected, in which case the predeterminable optimization criterion of the regeneration is probably best met.

Description

Method for regenerating an exhaust gas particulate filter

Technical Field

The invention relates to a method for regenerating an exhaust gas particulate filter of a motor vehicle. The invention furthermore relates to a computer program implementing each step of the method and to a machine-readable storage medium storing the computer program. Finally, the invention relates to an electronic control device designed to implement the method.

Background

In order to comply with emission regulations, diesel particulate filters (diesel filters) are required in the exhaust line of motor vehicles having diesel engines. The particulate filter must be cleaned of soot deposits at certain intervals so that its flow resistance does not reduce the engine power. For this purpose, the soot layer is burnt off, with carbon dioxide and water vapor being formed from the soot. Exhaust gas temperatures of typically more than 550 ℃ are required for burning soot. These temperatures are reached unreliably in vehicle use, so that additional measures are taken for regeneration. For this purpose, energy is additionally introduced into the particle filter, for example by heating the particle filter by means of an electric heating disk, using a fuel burner or by reinjecting fuel into the combustion chamber of the engine. The selection of the point in time at which the regeneration of the particulate filter is introduced is for example directed toward the section of the motor vehicle which is being driven and the pressure difference which is caused via the particulate filter. In addition, specific boundary conditions, such as a sufficient engine temperature or exhaust gas temperature, must be ensured. It must also be ensured that appropriate conditions prevail during the entire regeneration. Regeneration is generally terminated when the soot accumulation of the particulate filter falls to a predefined threshold value. This is called complete regeneration.

It is energetically disadvantageous that regeneration is initiated which cannot be completed by the end of the vehicle travel. It should furthermore be noted that the regeneration of the particulate filter is an exothermic process. Therefore, when the motor vehicle transitions to idle, there is a risk of: in the case of highly loaded particle filters, the exhaust gas mass flow is reduced, and a temperature increase in the particle filter occurs with a simultaneous increase in the oxygen partial pressure, which can lead to damage to the particle filter. Therefore, JP 2003314250 a proposes estimating from the data of the motor vehicle navigation system how much time is still available until the end of the run. And furthermore estimates from earlier regenerated data how long the regeneration will likely last. The start of regeneration is suppressed if a comparison of these data (Abgleich) should conclude that the regeneration of the particulate filter may no longer be able to be terminated before the end of the travel is reached.

Disclosure of Invention

The method for regenerating an exhaust gas particulate filter of a motor vehicle provides for predicting a driving route of the motor vehicle. This may be done, for example, based on user input into the vehicle navigation system. However, it is also possible to apply a method for predicting a travel route that is independent of user input. The regeneration process is simulated at different starting points in time on the predicted driving route. For the actual start of the regeneration, the starting points are then selected at those starting points in which the predeterminable optimization criterion of the regeneration is probably best fulfilled.

For this reason, a simulation of the regeneration changing process has been performed while traveling on the travel route in the past. At each of the starting points in time, a simulation of the regeneration is then carried out, wherein the simulation can be supplied with the parameters from the current operating data of the motor vehicle. If a later prediction of the driving route of the motor vehicle results: the motor vehicle is to be moved back on the driving route for which the regeneration profile has been simulated, so that, in the case of a desired regeneration of the exhaust gas particulate filter, an optimum regeneration starting point in time can be selected from the already existing simulation data.

The at least one soot accumulation of the exhaust gas particle filter, the speed of the motor vehicle and the exhaust gas temperature of the motor vehicle are preferably taken into account as parameters when simulating the course of the regeneration at different starting points in time. For this reason, soot accumulation may be expressed as a soot mass. In the first step of the simulation, the soot mass is set to a value at which regeneration is normally initiated. As exhaust gas temperature, preferably the exhaust gas temperature upstream of the exhaust gas particulate filter and particularly preferably also upstream of the turbine of the exhaust gas turbocharger of the motor vehicle is used. This value can be measured, in particular, by means of a temperature sensor located shortly downstream of the internal combustion engine.

In particular, at each simulation, a waiting time related to the exhaust mass flow and the exhaust temperature may be waited before starting the simulation. The following facts are hereby taken into account: after the start of the actual regeneration, this continues for a certain time until the exhaust system is warmed up to such an extent that the soot actually burns off.

The different start times are preferably selected such that each start time has a predeterminable minimum distance from the preceding start time and furthermore lies at a time at which there is no inhibition of the start of regeneration. Ideally, all simulated regenerations start in this way with a respective spacing from one another, which corresponds to a predeterminable minimum spacing. A uniform simulation sequence is thereby achieved, in which, on the one hand, the minimum interval should be selected so short that a large selection of starting points of time is available, one of which can be used for actually starting the regeneration, and, on the other hand, not so many simulations are carried out, so that in this case an unacceptably high computational effort would result. On the other hand, however, a simulation of a regeneration which cannot actually be carried out is also avoided, since the starting point in time of the regeneration is, for example, when the motor vehicle is in a standstill, which is the criterion for the start of the regeneration on account of the low exhaust gas mass flow at idle.

In a preferred embodiment of the method, the optimization criterion is the period of time required to reduce the soot accumulation of the exhaust gas particulate filter to a predeterminable value. The predeterminable value is in particular a value of soot accumulation, which is stored as a threshold value in the control unit of the motor vehicle, in which case the actually executed regeneration is also suspended.

Alternatively to a pure optimization based on the duration, in a further exemplary embodiment of the method, it is preferred that the optimization criterion is a value F, which is calculated at least from the time period required for reducing the soot accumulation of the exhaust gas particulate filter to a predeterminable value and from the energy quantity required for the regeneration. This calculation can be made according to equation 1:

(formula 1)

Where Δ t represents the time period, and E represents the energy amount. f. of₁Is a cost factor of the regeneration duration that is applicable, and f₂Is an applicable cost factor for the amount of energy used (energy). It is particularly preferred to enter other addends into the value F according to equation 1 in order to obtain a more precise (noch differential zierters) optimization criterion. In particular, the formation of nitrogen oxides and oil dilution during regeneration can also be taken into account here.Each of these values is assigned its own cost factor.

From the simulation of the regeneration profile, it can also be recognized from which point in time the regeneration may no longer be able to be carried out completely on the predicted route. "fully executing" is understood here to mean that the soot accumulation can be reduced to a value set for suspending regeneration. It is preferable not to select a starting point at which regeneration may not be carried out completely, in order to thus avoid a strong heating of the exhaust gas particulate filter, which on the one hand is then no longer available for regeneration in the stationary state of the motor vehicle due to a lack of exhaust gas mass flow, and on the other hand carries the risk of damaging the exhaust gas particulate filter.

In principle, different starting points in time on the predicted driving route can be determined, for example, by means of a segment index or on the basis of the route section of the motor vehicle. However, it is preferred that different starting points in time are selected with the same linear spacing from each other. In order to simplify the calculations required for this purpose, it is furthermore preferred that the prediction of the driving route is carried out such that successive points are provided on the driving route at the same linear distance from one another. The driving route can thus be defined by several points in connection with the further prediction and in this way be stored with a small data volume.

The computer program is set up to carry out each step of the method, in particular when the computer program is run on a computing device or an electronic control device. It is made possible to implement different embodiments of the method on an electronic control device without having to make structural changes thereto.

By installing (Aufspielen) a computer program into a conventional electronic control unit, an electronic control unit is obtained which is set up for carrying out the regeneration of an exhaust gas particle filter of a motor vehicle by means of the method.

Drawings

Embodiments of the invention are illustrated in the drawings and are set forth in more detail in the description that follows.

Fig. 1 shows a schematic representation of selected elements of a motor vehicle whose exhaust gas particulate filter can be regenerated by means of a method according to an exemplary embodiment of the present invention.

Fig. 2 schematically shows an implementation of selected calculation steps in a method according to an embodiment of the invention.

Fig. 3 shows the time course of the vehicle speed and the soot accumulation of the exhaust gas particulate filter in an embodiment of the method according to the invention in two graphs.

Fig. 4 shows a flow chart of an embodiment of a method according to the invention.

Detailed Description

Fig. 1 shows an internal combustion engine 10, which is currently embodied as a diesel engine. The internal combustion engine has an exhaust gas turbocharger 20. A compressor 21 of the exhaust gas turbocharger 20 is arranged in the air supply device 11 of the internal combustion engine 10. The intake pipe 12 of the internal combustion engine 10 is located between the compressor 21 and the internal combustion engine 10. The exhaust gases of the combustion engine 10 are discharged into an exhaust line 13. The turbine 22 of the exhaust-gas turbocharger 20 is arranged in the exhaust line. A temperature sensor 14 for measuring the exhaust gas temperature in the exhaust line 13 is located between the turbine 22 and the internal combustion engine 10. An exhaust gas particulate filter 15 is arranged in the exhaust line 13 downstream of the turbine 22. The internal combustion engine 10 is controlled by an electronic control device 16.

In one embodiment of the method according to the invention, each time the motor vehicle passes through a driving route, a large regeneration of the exhaust gas particle filter 15 is simulated on the driving route. For this purpose, the driving route is divided into sequences having the same linear spacing from one another. The beginning and end of each sequence are stored as data points using their GPS data. Each simulation is performed in multiple iterations. As shown in fig. 2, in each traversal (Durchlauf), the soot accumulation (Ru β beladung) mtot of the exhaust gas particulate filter 15 is used as input variable. Then, for each other traversal, the output arguments of the previous traversal are used as input arguments. The soot accumulation mSot is fed to the first characteristic curve 31. Furthermore, the temperature T3 currently measured by means of the temperature sensor 14 in the exhaust line 13 upstream of the turbine 22 is used as a further calculated input variable and supplied to the second characteristic curve 32. The speed Vehv of the motor vehicle is used as a third input variable and supplied to the third characteristic curve 33. The values obtained from the three

characteristic curves

31, 32, 33 are multiplied by one another in order to determine the soot mass dmSotBurn of combustion. This soot mass is subtracted from the current soot accumulation mSot in order to obtain a new value of soot accumulation mSot.

Fig. 3 shows the course of the vehicle speed Vehv over time t for a driving route that has elapsed within a time period of 1900 seconds. Each simulation of regeneration was started at 25 g of fictitious soot accumulation mNott. Currently, this is the accumulation of soot, in which case in conventional operation of the motor vehicle regeneration of the exhaust gas particulate filter would be initiated without using the method according to the invention. The simulation traversal according to fig. 2 is then repeated so many times until the soot accumulation mSot has been reduced to 10 g. This is a value where exhaust particulate filter regeneration is discontinued during operation of the vehicle, as attempts to burn off other soot will no longer be energy efficient. Thus regeneration that reduces the soot accumulation mSot to 10g is understood to be complete regeneration.

For performing the simulation, the minimum interval for the currently predetermined simulation starting point is 50 seconds. The simulation is started at this minimum interval as long as there is no condition for which the start of regeneration of the exhaust particulate filter 15 is prohibited. However, the time interval between the start of each simulation may also increase due to the existence of the inhibit condition. The first simulation therefore does not already start at the start of the motor vehicle, but only after a time t of 125 seconds, since a sufficient minimum speed Vehv of the motor vehicle has not been reached until then for the regeneration to start. In practice, some other points in time are not used which would be suitable for the start mode because of the minimum interval, since the vehicle speed Vehv is too low at the respective point in time.

As can be seen in fig. 3, the last time (letztmals) when regeneration is started after 775 seconds, full regeneration can be achieved. The simulation of all the later-started regenerations ends in the case of soot accumulations mSot of more than 10g, since the vehicle is stopped after 1800 seconds of travel. The simulation result is stored together with the travel route. For this purpose, for each stored travel route, the following information is available, on the one hand, from which starting point in time of the regeneration the complete regeneration can no longer be considered until the end of the travel (last mile home), and on the other hand, can be estimated for each starting point in time of the regeneration: how long will be until the soot accumulation mSot drops to a value of 10g and regeneration has thus been completely terminated. If the regeneration duration is used as an optimization criterion, the optimum regeneration start time point can be selected in this way with the possible regenerations.

In a further embodiment of the method, the optimum starting point in time is not selected solely on the basis of the smallest possible regeneration duration. Instead, a value F is calculated for each simulated regeneration according to equation 1, which value depends on the one hand on the regeneration duration

And on the other hand on the energy E used for regeneration. The starting point in time is then considered to be optimal according to the regeneration for which the value F becomes minimal.

In one embodiment of the method according to the invention, a prediction 40 of the driving route of the motor vehicle is attempted after the start of the motor vehicle. If the driver does not enter his driving destination into the navigation system of the motor vehicle, the starting position of the motor vehicle is compared with the starting position of the previous driving route of the motor vehicle. If consistency is found here, it is estimated based on the time and the working day at which the stored travel route was started in the past and the current working day and the current time: the driver will most likely traverse which of these travel routes and use that travel route as the predicted travel route. If the predicted driving route is not realized in this way, the method according to the invention is ended 51 and the motor vehicle returns to its conventional regeneration strategy of the exhaust gas particle filter 15, which is stored in the electronic control unit 16. If the prediction of the travel route is successful, a check 41 is made: whether the soot accumulation mSot is already so large that there is a regeneration requirement for the current driving of the motor vehicle. If this is not the case, the method is likewise ended 51 by a return to the conventional regeneration strategy. And if there is a regeneration request, further checking 42: whether the soot accumulation mSot has reached a threshold for overloading the exhaust particulate filter 15 with soot. If this should be the case, regeneration needs to be introduced immediately and the regeneration is started 52. If the soot accumulation mtot is high enough that the exhaust gas particulate filter 15 should be regenerated during a preceding trip, although it is not so high that immediate regeneration would need to be started, a further test 43 is carried out: whether it would be possible to terminate regeneration completely on the predicted travel route. If this is not possible, the regeneration is actively suppressed 53 and is postponed in this way. Returning to step 40, it is checked whether the vehicle is therefore located on the predicted route or whether the vehicle deviates from the predicted route, as it was previously given a prediction of the route. If regeneration is not inhibited, then a test 44: whether the optimal regeneration initiation point determined based on the simulation of the possible regeneration initiation points has been reached. If this is not the case, the start of regeneration is also temporarily suppressed 53. Otherwise, regeneration is initiated 52.

Conventional regeneration strategies that can be stored in the control device 16 already contain, in addition to the soot accumulation mtot, a so-called measure for the regeneration benefit as a parameter for starting regeneration, the value of which can be used for starting regeneration more frequently at a beneficial point than at a disadvantageous point. Here, the benefit is determined, for example, on the basis of the type of road stored in the navigation system, wherein driving on expressways is considered to be beneficial for regeneration, while driving on urban roads is considered to be disadvantageous for regeneration. In the presently described embodiment of the method according to the invention, regeneration is initiated 52 by intervening in a conventional regeneration strategy. For this purpose, the measure of the benefit is set to its maximum value by the procedure of the method according to the invention when the test 44 has concluded that the optimum starting position for regeneration has been reached, and regeneration is triggered in this way. Whereas for the suppression 53 the metric is set to "very unfavorable". If the soot mass should rise to a very high value, the electronic control device 16 will start an "emergency regeneration" even in "very unfavorable" situations, which contributes to the robustness of the solution. In particular, error handling in the solution according to the invention is also saved in this way, since in case of doubt the conventional logic circuit simply takes over. This enables the present embodiment of the method according to the invention to be implemented in the electronic control device 16 with the regenerated software already present, without having to completely replace the regenerated software by new software.

Claims

1. A method for regenerating (52) an exhaust gas particulate filter (15) of a motor vehicle, wherein a regeneration profile is simulated at different starting points in time on a predicted driving route of the motor vehicle, and for carrying out the regeneration (52), a starting point is selected at which a predeterminable optimization criterion for the regeneration is likely to be best met.

2. Method according to claim 1, characterized in that the time courses of the soot accumulation (mSot) of the exhaust gas particulate filter (15), the speed (Vehv) of the motor vehicle and the exhaust gas temperature (T3) of the motor vehicle have been determined separately for the predicted driving route when driving earlier on the driving route, and these parameters (mSot, Vehv, T3) are used when simulating the course of the regeneration at different starting points in time.

3. Method according to claim 1 or 2, characterized in that different starting time points are selected such that each starting time point has a predeterminable minimum interval from a preceding starting time point and is located at a time point at which there is no inhibition of the start of the regeneration (52).

4. The method according to any one of claims 1 to 3, characterized in that the optimization criterion is a period of time required for reducing the soot accumulation (mNot) of the exhaust gas particulate filter (15) to a predeterminable value.

5. The method according to any one of claims 1 to 3, characterized in that the optimization criterion is a value calculated at least from the time period required for reducing the soot accumulation (mNot) of the exhaust gas particulate filter (15) to a predeterminable value and from the amount of energy required for the regeneration.

6. The method according to any one of claims 1 to 5, characterized in that no starting point is selected at which the regeneration (52) may not be performed completely on the predicted driving route.

7. The method according to any one of claims 1 to 6, characterized in that different starting time points are selected at the same straight line interval on the predicted driving route.

8. Method according to claim 7, characterized in that the prediction of the driving route is made such that successive points are provided on the driving route with the same straight-line spacing from each other.

9. A computer program set up for carrying out each step of the method according to any one of claims 1 to 8.

10. A machine readable storage medium having stored thereon a computer program according to claim 9.

11. An electronic control device (16) which is set up for carrying out a regeneration (52) of an exhaust gas particulate filter (15) of a motor vehicle by means of a method according to one of claims 1 to 8.