CN110529223B

CN110529223B - Method for reducing ammonia emissions in the exhaust gas of an internal combustion engine

Info

Publication number: CN110529223B
Application number: CN201910434145.5A
Authority: CN
Inventors: A.施瓦茨
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2018-05-24
Filing date: 2019-05-23
Publication date: 2023-04-18
Anticipated expiration: 2039-05-23
Also published as: DE102018208129A1; CN110529223A; KR20190134488A

Abstract

The invention relates to a method for reducing ammonia emissions in the exhaust gas of an internal combustion engine of a vehicle, wherein the internal combustion engine has an exhaust gas line, wherein a reducing agent separated from ammonia or containing ammonia can be metered into the exhaust gas flow in the exhaust gas line in order to reduce nitrogen oxides, comprising the following steps: a route section which is located ahead of the vehicle and which the vehicle is estimated to be travelling is known and on the basis of this the amount of reducing agent required in the route section is estimated.

Description

Method for reducing ammonia emissions in the exhaust gas of an internal combustion engine

Technical Field

The invention relates to a method for reducing ammonia emissions in the exhaust gas of an internal combustion engine of a vehicle, wherein the internal combustion engine has an exhaust gas line, wherein an ammonia-separating or ammonia-containing reducing agent can be metered into the exhaust gas stream in the exhaust gas line in order to reduce nitrogen oxides. The invention also relates to a related controller and a related motor vehicle.

Background

In order to reduce nitrogen oxides (NOx) in internal combustion engines, such as in diesel engines, so-called Selective Catalytic Reduction (SCR) technology is used in vehicles, such as cars and trucks. Here, an aqueous urea solution (HWL, trade name AdBlue) having, for example, a urea content of 32.5 vol% is metered into the exhaust gas stream. The urea is then converted to ammonia (NH) due to the heat of the exhaust gases ₃ ). The ammonia is absorbed by the SCR catalyst and bound to the surface. The ammonia thus provided acts as a reductant to reduce undesirable nitrogen oxides (NOx, e.g., NO and NO) present in the exhaust gas ₂ ) Conversion to nitrogen (N) ₂ ) And water (H) ₂ O). Therefore, HWL is an example of a reducing agent that separates out ammonia. In order to achieve the best possible NOx conversion, the HWL dosing is adjusted such that a constantly high ammonia filling level is present in the SCR catalyst as far as possible, so that the ammonia storage performance of the SCR catalyst is utilized to the maximum. Here, the ammonia fill level refers to the amount of ammonia bound on the catalyst surface. Due to the high ammonia fill level, sufficient ammonia for NOx conversion can be provided even at a briefly reduced exhaust gas temperature, for example in low load operation or at another motor start. Therefore, in operating states in which high ammonia storage is possible, more HWL is dosed than is necessary for NOx conversion in order to replenish the SCR catalyst with ammonia.

However, the storage capacity of the SCR catalyst decreases significantly after a certain limit temperature has been reached. If it reachesReaching or exceeding the limit temperature, the SCR catalyst releases ammonia relatively abruptly. Exceeding the limit temperature may occur, for example, during uphill driving, during braking or during acceleration. In order to prevent ammonia emissions (so-called ammonia slip) from occurring, a catalytic material is applied downstream of the SCR catalyst in the flow direction, which catalytic material oxidizes the ammonia that escapes with residual oxygen in the exhaust gas (so-called clean-up catalysis, CUC). However, in this case, in particular at high exhaust gas temperatures, the oxidation of ammonia can lead to secondary emissions, such as laughing gas (N) ₂ O). This is judged to be severe because of its potentially harmful effect (carbon dioxide equivalent). Furthermore, even after performing CUC, undesirable residual ammonia emissions may result.

Disclosure of Invention

The basic problem of the invention is solved by a method according to the invention for reducing ammonia emissions in the exhaust gases of a vehicle internal combustion engine. Advantageous embodiments are given in the preferred exemplary embodiments. Furthermore, features which are essential for the invention can be found in the following description and the drawings, wherein the features can be essential for the invention not only individually but also in different combinations without repeated detailed specification.

Thus, it can be provided that a route section which is located ahead of the vehicle and which the vehicle is estimated to be travelling is known. Based on which the amount of reducing agent needed in the route section is estimated. If the vehicle then does travel in this predicted route section, the quantity of reducing agent predicted predictively in step b can be dosed into the exhaust-gas flow, in particular precisely, in this route section.

The present invention therefore has the particular advantage over conventional dosing strategies known in the prior art that no attempt is made to fill the SCR catalyst with a maximum ammonia fill level. Instead, it is first predetermined which route section ahead of the vehicle is estimated to be traveled. The amount of reductant required is then predicted for that route segment. For example, if the route section is predicted to consume little or no fuel, no attempt is made to compensate for the ammonia filling level in the SCR catalyst that has fallen in the preceding route section with high ammonia consumption to the maximum extent by means of additional dosing. Instead, only as much reductant as actually needed for NOx conversion according to the prediction is replenished.

In summary, it is possible according to the invention to reduce undesirable ammonia emissions of a vehicle due to an undesirable ammonia release. In particular, residual ammonia emissions may be reduced after the exhaust stream passes through the CUC. In addition, other undesirable secondary emissions, such as laughing gas, can be reduced. Furthermore, the consumption of the reducing agent as a whole can be reduced.

In one embodiment, at least one additional piece of information is determined in step a about the route section which is estimated to be traveled, in particular the vehicle speed which is expected in this route section and/or an electronic horizon (elektronische horizon), which may in particular contain the expected road gradient. In particular, the expected gradient value in the route section estimated to be traveled may contribute to a reliable prediction. The electronic horizon (EH, also referred to as virtual horizon) may comprise, in particular, information about the road gradient and/or the curve curvature of the route section which the vehicle estimates to be traveled. While the electronic level map may also include legal speed limits and/or additional attributes such as intersections, traffic signal facilities, number of lanes and/or tunnels, etc. For example, the electronic Horizon may be provided by a so-called Horizon Provider (HP), which may be a component of a navigation system of a vehicle, for example. In order to more accurately determine the expected vehicle speed and/or the electronic level map, for example, a Car2x method, particularly a Car2Car method, may be used for the learned information. The route that is likely to be traveled can be known, in particular, based on the route selection made by the vehicle driver from the input made for the destination guidance of the navigation system.

In a further embodiment, in order to estimate the expected reducing agent demand, in step b at least one expected motor parameter for the route section is initially determined. Based on this, the expected ammonia demand in that route section can be known. The motor parameters can be configured, for example, as motor power, motor raw emissions, exhaust gas temperature or exhaust gas mass flow. In particular, a vehicle drive train model and/or a motor model (motormodel) can know the expected motor power, the motor raw emissions, the exhaust gas temperature and the exhaust gas mass flow for the route section estimated to be traveled. Based on this, the exhaust gas aftertreatment model may provide information about the expected ammonia demand in this route section (and/or also about the ammonia fill level in the SCR catalyst and/or its maximum storage capacity).

In a particularly advantageous manner, the expected ammonia slip in this route section is known in step b for prediction. In this case, it should be noted that the ammonia storage performance of the SCR catalyst is regularly dependent on the exhaust gas temperature. In this case, the ammonia storage capacity of the SCR catalyst can be reduced from a maximum value as the temperature increases, so that excess ammonia which can no longer be stored is released. Starting from a certain limit temperature, ammonia release may occur suddenly. The release of ammonia is referred to as ammonia slip. Here, however, ammonia slip may also include a loss of ammonia, which, although converted in CUC, is lost for the SCR reaction. Thus, the ammonia slip model may preferably provide information about the expected ammonia slip in the route segment estimated to be traveled. In particular, it is possible to determine whether a coasting phase (Schubphase) of the vehicle, a braking phase of the vehicle or a (full) load phase of the vehicle is expected in this route section. The load prediction of the internal combustion engine as a whole can be performed. In particular during a fully loaded uphill drive or a downhill drive with braking operation, the exhaust gas temperature may exceed a limit value, which may lead to ammonia slip suddenly. The truck therefore has a relatively powerful motor brake, whereby the exhaust gas temperature is at the ignition operating level of the internal combustion engine even during braking operation.

It is conceivable to decide in a further step c whether the amount of reducing agent required, which is known predictably, is also actually dosed. In particular, a prediction quality of the possibly required amount of ammonia in the route section estimated to be traveled can be predicted in step c. Thus, for example in rush hour traffic with many vehicles, which may lead to relatively dynamic traffic conditions, the pre-calculation is difficult and the prediction quality may be low due to high traffic dynamics. It may then be decided, based on this evaluation, whether a predictively known amount of reducing agent is also actually added to the exhaust flow when the vehicle is actually travelling in the predicted route section. It is therefore particularly conceivable that, in the case of low prediction quality, a conventional dosing strategy is to be carried out in which the detected reduced ammonia fill level of the SCR catalyst is compensated for by the supplementary dosing of the reducing agent in order to ensure that sufficient ammonia is available for reducing the nitrogen oxides, even if the demand for reducing agent is increased as a result and/or undesirable ammonia emissions occur as a result of ammonia slip.

It is also conceivable that, even if it has been decided that the predictively known amount of reducing agent is injected in the predicted route section, the decision is made again in real time also when actually traveling in that route section: whether the amount is actually injected. It is particularly conceivable that errors occur in hardware and/or software, so that it may be expedient to use conventional dosing strategies to ensure adequate reduction of nitrogen oxides. In particular, it is also conceivable that situations without GPS connection occur, for example in tunnels or due to terrain or buildings, so that conventional dosing strategies are of interest here.

It is also conceivable that the route section to be traveled is estimated to be the Most Probable Path (MPP). If the driver of the vehicle has set destination guidance based on the navigation system, a route to be estimated to be traveled in the future is known based on this. Conversely, without destination guidance, the Most Probable Path (MPP) can be predicted. For example, the MPP may be known from a base road grade or from an evaluation of a route that the vehicle has traveled. It is also conceivable to know, in addition to the MPP, other conceivable possible drivable route sections and possible alternative routes and to estimate the quantity of reducing agent required for these alternatives on the basis thereof. The MPP may be known, for example, by a vehicle navigation system, a vehicle assistance system, and/or a vehicle controller.

In addition, it can be provided that in step b, the expected temperature in the exhaust pipe is additionally known with a predictive measure and compared with a setpoint temperature value, and an action is preferably triggered on the basis thereof. Thus, the prediction may also be extended to thermal management. Thus, for example, when a longer low-load phase of the internal combustion engine is detected, the exhaust gas temperature can be increased. Internal combustion engines can be used for this purpose. Although this may increase fuel consumption, the exhaust gas temperature may be increased in an advantageous manner to achieve the reduction of nitrogen oxides. This is because below the limit temperature exhaust gas aftertreatment by the SCR method is not possible or can only be carried out inefficiently. The limit temperature may be, for example, 200 °. The low load phase may occur, for example, during traffic congestion or during driving in city centers. The action may also be to slightly inhibit a motor cooling device (e.g., a fan, coolant pump, or thermostat) to keep the exhaust temperature high enough.

The basic problem of the invention is also solved by a controller which is designed and set up to carry out the method according to the invention. Such a controller may therefore comprise, in particular, a software program, wherein the software program is designed and set up to carry out the method according to the invention. The controller may be, for example, a dosing controller for dosing the reducing agent into the exhaust pipe. On the other hand, it may also be a superordinate motor controller of the vehicle.

Finally, the object underlying the invention is also achieved by a vehicle comprising an internal combustion engine having an exhaust line, wherein an ammonia-separating or ammonia-containing reducing agent for reducing nitrogen oxides can be dosed into the exhaust gas flow in the exhaust line, and a control device according to the invention. The vehicle may be, for example, a car, or in particular a truck, more particularly a long-haul truck. In this case, the vehicle can comprise a navigation system and/or a driver assistance system for predicting the route section estimated to be traveled, in order to predict the route section itself, and in particular also relevant information, such as an expected vehicle speed and/or an electronic horizon.

In this case, it is conceivable for the vehicle to comprise a low-pressure exhaust-gas recirculation device, wherein the reducing agent can be dosed by the dosing device in the flow direction of the exhaust-gas flow before the exhaust gas is removed for the low-pressure exhaust-gas recirculation device. In this case, the exhaust gas removal for the low-pressure exhaust gas recirculation device can be in particular between the SCR catalytic converter and the CUC. By means of the vehicle according to the invention, the ammonia content in the low-pressure exhaust-gas recirculation system can be reduced in any case, so that in particular there is the possibility of manufacturing the components of the low-pressure exhaust-gas recirculation system and also, for example, also other components of the internal combustion engine from less expensive materials, since corrosion damage can certainly be expected with less probability due to the reduced ammonia load over the entire service life.

Drawings

Further features, application possibilities and advantages of the invention will be given from the following description of embodiments of the invention with reference to the accompanying drawing description. In the drawings:

FIG. 1 shows a schematic cross-sectional view through an exhaust pipe having a HWL dosing device and an SCR catalyst;

FIG. 2 shows a schematic illustration of an internal combustion engine configured as a diesel motor, having a high-pressure exhaust gas recirculation device and a low-pressure exhaust gas recirculation device;

FIG. 3 shows a diagrammatic representation of a section of an exhaust-gas aftertreatment device of the internal combustion engine according to FIG. 2;

FIG. 4 shows a method flow of a method according to the invention according to an embodiment;

FIG. 5 shows a possible graphical representation of ammonia storage performance of the SCR catalyst with respect to exhaust gas temperature;

fig. 6 shows a schematic representation of the predictive parameters obtained by means of the method according to fig. 4.

Detailed Description

Functionally equivalent elements and regions have the same reference numerals in the following figures and a detailed explanation is not repeated.

Fig. 1 shows an exhaust gas line 10 of an internal combustion engine designed as a diesel motor. An exhaust gas flow (indicated by arrow 12) is conveyed in the exhaust pipe 10. The internal combustion engine is an internal combustion engine of a vehicle. In fig. 3, a vehicle 14 configured as an over-the-road truck is shown by way of example, which may have internal combustionA machine duct 10. For cleaning the exhaust gas in the exhaust line 10, a dosing device 16 and an SCR catalyst 18 downstream of the dosing device are arranged on the exhaust line 10. The SCR catalytic converter 18 is configured overall as a honeycomb and has a catalytically active material on its surface. An aqueous urea solution (HWL, trade name AdBlue) having, for example, a urea content of 32.5 vol% can be dosed from the tank 20 into the exhaust pipe 10 by means of the dosing device 16. HWL is a reductant 22 that is stripped of ammonia. The dosing device 16 injects the HWL 22 into the exhaust gas flow in the form of fine droplets, wherein an even distribution of the droplets in the exhaust pipe is sought. The HWL 22 thus introduced into the exhaust gas then undergoes pyrolysis and hydrolysis to convert the urea to ammonia. The ammonia thus provided acts as undesirable nitrogen oxides (NOx, e.g., NO and NO) present in the exhaust gas ₂ ) The actual reducing agent of (a). Where ammonia is bound on its surface by SCR catalyst 18. The nitrogen oxides can then be converted into Nitrogen (NO) with the aid of ammonia ₂ ) And water (H) ₂ O). Downstream of the SCR catalyst 18 there is also a NOx sensor 24 for measuring the nitrogen oxide content after passing through the SCR catalyst 18. In particular, CUC (Clean Up Catalyst), not shown, may also be provided downstream of the SCR Catalyst 18. For controlling the dosing device 16, a controller 26 is present. It may be a dosing controller for the dosing device 16. In particular, however, it is also conceivable for the controller 26 to be a controller of a superordinate motor control device of the vehicle 14.

Fig. 2 and 3 schematically show another possible embodiment for exhaust gas cleaning of the exhaust gas of an internal combustion engine. Fig. 2 schematically shows an internal combustion engine 11 in its entirety, which is designed as a diesel motor, having a motor 13, a compressor 15 and a turbine 17. The internal combustion engine 11 may in turn be mounted in a vehicle 14, for example. The internal combustion engine comprises here a high-pressure exhaust gas recirculation device 19 and a low-pressure exhaust gas recirculation device 21, as well as an exhaust gas aftertreatment device 23. Here, the compressor 15 and the turbine 17 form a turbocharger. In a known manner, combustion air 25 is delivered to the motor 13 and exhaust air 27 is delivered out of the motor 13.

Fig. 3 shows a section of an exhaust gas aftertreatment device 23, which comprises the exhaust gas pipe 10. In this embodiment, the SCR catalyst is integrated in a Diesel Particulate Filter (DPF) 28. Such an arrangement is also known as SCRF. Here, the proportioning device 16 is arranged upstream of the SCRF 28. Downstream of SCRF28, a second SCR Catalyst 30 is arranged, which has an integrated CUC (Clean Up Catalyst) 33. A take-off line 32 for the low-pressure exhaust gas recirculation device 21 is arranged between the SCRF28 and the second SCR catalyst 30. Various sensors, such as Lambda/NOx sensor 31 and NOx sensor 34, and temperature sensor 36, are arranged in or on the exhaust pipe 10. There is also a controller 26 for controlling the dosing device 16. In this case, the control device can also or alternatively be a dosing control device for the dosing device 16. In particular, however, it is also conceivable for the controller 26 to be a controller of a superordinate motor control of the vehicle 14.

The controller 26 according to the embodiment of fig. 1 and the controllers according to the embodiments of fig. 2 and 3 are designed and set up to carry out the method described below with reference to fig. 4 to 6.

First, position data of the vehicle 14 can be detected in a first method step 40 (see fig. 6). Furthermore, the traffic data (TMC or Car2X data, in particular Car2Car data) of the vehicle 14 may be received, in particular wirelessly (denoted by reference numeral 42 in fig. 6). Further, map data may be provided.

Further, the driving destination may be learned in step 42. This can be, in particular, a destination specification in the navigation system of the vehicle 14. Furthermore, information about the vehicle speed desired by the driver can be detected in step 42, for example, wherein this information can be provided by a driving assistance system of the vehicle 14, for example.

Based on the information from

steps

40 and 42, in a subsequent step 44, a prediction may be provided regarding a route segment 45 (see fig. 6) that is located ahead of the vehicle 14 and is estimated to be traveled. The route section 45 may have a length X of between five and ten kilometers, for example. The route section 45 can be known, for example, based on route guidance of the navigation system to the driving destination entered by the driver. If, on the other hand, no destination guidance is specified in the navigation system, in step 44 the Most Probable route (Most Probable Path) may alternatively be known, for example with reference to the base road class and/or with reference to statistical data about the traveled route. It is also conceivable to determine various alternative route sections that are likely to be traveled in this step as a supplement or alternative to the MPP. In this case, further method steps described below may be used to perform all alternative predicted route guidance.

In step 44, further information about the route section 45 estimated to be traveled, in particular the expected road gradient, may also be provided. In particular, the information may be a so-called electronic horizon (also called virtual horizon). The electronic horizon is understood in particular to be the road gradient and the road curvature, but also legal speed limits and additional attributes, such as intersections, traffic signal systems, number of lanes and tunnels. The electronic horizon may be provided by a so-called "horizon provider", which may in particular be a component of the navigation system of the vehicle 14.

Finally, the expected speed in the predicted route section 45 may be known in step 44. For this purpose, data of an electronic level map can be used, but of course traffic data (TMC or Car2X data, in particular Car2Car data) can also be used.

Steps 40 through 44 may be performed by a navigation system of the vehicle 14. On the other hand, it is also conceivable that the navigation system only supplies information about the destination guidance of the navigation system of the vehicle 14 or position data (GPS) and further map data to the controller 26, and that the controller 26 in step 44 knows a prediction about the route section 45 estimated to be traveled and a prediction about the speed that can occur in this route section 45.

In step 46, the information obtained in step 44, in particular the predicted route section 45, the electronic level map and the expected speed in this route section 45, is evaluated by means of a vehicle drive train model and a motor model. From this, the desired motor parameters for this route section 45, for example the motor power, the motor raw emissions (NOx), the exhaust gas temperature and/or the mass flow, can be determined. As is shown highly schematically in fig. 6, the route section 45 in this case comprises seven segments 47, 49, 51, 53, 55, 57 and 59. In these route sections 47 to 59, motor loads of not the same high can be expected, which is schematically shown in the upper region 61 of the illustration of fig. 6. Thus, partial loading is expected in sections 47, 51, and 59. In the section 49, a full load can be expected during uphill travel. In the section 55, a motor braking operation during downhill driving is to be expected. In sections 53 and 57, an unfired coasting operation is expected.

The expected exhaust gas temperature profile in the predicted route section 45 determined in step 46 is shown in fig. 6 in region 67. It can be seen here that the exhaust gas temperature rises sharply during uphill driving in route section 49 and reaches a maximum value 69 there. It can also be seen that in the braking operation in the route section 55, the exhaust gas temperature also rises sharply, and at the end of this route section 55 the temperature difference 71 compared with the maximum 69 is only slight.

Based on the expected motor power in route section 45, the expected ammonia demand is learned in step 48 by the exhaust aftertreatment model. It can also be taken into account in the model how much ammonia is stored in the SCR catalyst 18 at the actual point in time (this can be seen in particular from the relationship between the storage capacity of the SCR catalyst 18 and the exhaust gas temperature in the exhaust pipe 10, as is shown in fig. 5 by way of example and schematically).

It should be noted, however, that the ammonia storage capacity of SCR catalyst 18 varies with temperature, as can be seen in FIG. 5. As can be seen from the curve 63, there is a maximum value 65 with a maximum storage capacity. From the limit temperature T _G Initially, the storage capacity drops almost abruptly. In view of this, in method step 50, it is known from the estimated expected route section 45 and the information relating thereto (e.g. gradient profile, road curvature, traffic information, car2X information) whether a coasting phase, a braking phase or a loaded or fully loaded phase of the vehicle 14 is expected (see area 61 of fig. 6). Based on these findings, information is then provided in step 52 with respect to the expected ammonia slip in the individual sections 47 to 59 in the route section 45 by means of an ammonia slip model.In the present case, ammonia slip may include both residual ammonia released after passing through the CUC, and ammonia losses that are lost to the SCR reaction despite being converted in the CUC.

The ammonia slip known in step 52 is shown in fig. 6 in region 69. It can be seen here that at the end of the uphill drive (route section 49) or of the braking drive in the motor braking mode (route section 55), ammonia slip occurs at the transition to the route section 51 or 57 (so-called transient motor mode), in which ammonia is released from the SCR catalytic converter. This is because, as can be seen in fig. 5, in this case too the exhaust gas temperature and thus the SCR catalyst 18 exceed the limit temperature T _G . Here, the release of ammonia takes place relatively abruptly, as can also be seen in fig. 5.

In the next step, it is decided in step 54 whether the data learned by steps 44 to 52 are used to learn the required amount of HWL 32. In particular, the quality of the prediction information obtained in steps 44 to 52 is evaluated. Thus, for example, it is conceivable that the information is of low quality, since the vehicle 14 is in the peak traffic hours of the vehicle, from which relatively dynamic traffic conditions can be derived, whose pre-calculation is difficult, in particular it is difficult to predict how the surroundings of the vehicle 14 (in particular the traffic density) will develop in the future.

Collectively, steps 44 through 54 are configured as predictive method steps that precalculate the likely future state of the vehicle 14, as indicated by arrow 64. Rather, the method steps 56 to 62 described in detail below are performed in real time, as indicated by arrow 66.

If this time-wise precalculation, i.e. the prediction made using method steps 44 to 52, is used, then in a next step 56, the HWL dosing required at a determined waypoint is calculated on the basis of the information obtained from steps 44 to 52, which HWL dosing is precisely dosed when the vehicle 14 actually reaches the predicted waypoint of the route section 45.

It may then be checked again in step 58 whether a conventional dosing strategy is still to be employed, represented by step 60. This may be particularly the case if errors are diagnosed in the hardware and/or the controller. The conventional dosing strategy according to step 60 is represented by the injection quantity curve in the area 71 of fig. 6, i.e. by the diagram 73. In this case, when the ammonia filling level in the SCR catalyst 18 drops due to a high ammonia reaction with the exhaust gas flow and/or due to an increased exhaust gas temperature, the dosing HWL is supplemented in order to maintain the filling level in the SCR catalyst 18 as high as possible during vehicle operation.

If the estimated dosing strategy is used, in method step 62, the hardware, i.e., in particular the dosing device 16, is controlled by the controller 26 to inject the injection amount of the HWL calculated in step 56 when the vehicle actually reaches the pre-calculated point of the route section 45 in real time. The HWL injection quantity curve obtained in fig. 4 is represented by a diagram 75 in the region 71 in fig. 6.

As can be seen from the diagram 75, in particular during uphill driving in the route section 49, significantly less HWL is added to the exhaust pipe 10 than in a conventional dosing strategy (diagram with reference numeral 73), since downhill driving with motor braking operation is expected in the predicted route section 55.

While method steps 44 to 54 are used here to calculate (predict) in a temporal manner the expected HWL requirement for the predicted route section 45 in advance, steps 56 to 62 are used in particular to inject the HWL quantity predicted by the prediction process at the route point, based on knowledge of the prediction according to steps 44 to 54, and when the vehicle 14 also actually reaches the predicted route point.

In summary, the residual ammonia emissions after the CUC (see reference numeral 33 in fig. 3) can be reduced by the method according to the invention, contributing to an improvement in the so-called secondary emissions (ammonia or laughing gas). This also advantageously reduces the overall HWL consumption. Finally, in the case of the low-pressure exhaust gas recirculation apparatus (see reference numeral 21 in fig. 2), the ammonia load of the low-pressure exhaust gas recirculation apparatus 21 and the ammonia load of the other portions of the internal combustion engine 11 (see fig. 2) can be reduced during the service life. Thereby, the risk of corrosion damage caused by ammonia load may be reduced, in particular may be manufactured from relatively cheap materials.

Claims

1. Method for reducing ammonia emissions in the exhaust gas of an internal combustion engine (11) of a vehicle (14), wherein the internal combustion engine (11) has an exhaust gas line (10), wherein a reducing agent (22) separated from ammonia or containing ammonia can be metered into the exhaust gas flow (12) in the exhaust gas line (10) in order to reduce nitrogen oxides, comprising the following steps:

a. -learning a route section (45) which is located in front of the vehicle (14) and which the vehicle is likely to be travelling;

b. estimating an amount of reductant (22) required in the route section based thereon; and is provided with

c. Determining whether to use a predictively known amount of the desired reductant (22) is specified by: the prediction quality of the possible required ammonia amount in the estimated route section to be traveled can be predicted, and in the case of low prediction quality, a conventional dosing strategy is carried out, and even if it has already been decided to inject the predictively known required amount of reducing agent (22) in the predicted route section, the decision is made again in real time also actually traveling in that route section: whether to actually inject a predictively known amount of reductant (22) required.

2. Method according to claim 1, characterized in that at least one additional information about the route section (45) is known in step a, which at least one additional information comprises the expected vehicle speed in the route section (45) and/or an electronic horizon which may comprise the expected road gradient.

3. Method according to claim 1 or 2, characterized in that for the purpose of prediction, in step b at least one expected motor parameter for the route section (45) is first known, and on the basis thereof the expected ammonia demand in the route section (45) is known.

4. Method according to claim 3, characterized in that for the purpose of prediction, the expected ammonia slip in the route section (45) is known in step b.

5. Method according to claim 1 or 2, characterized in that the route section (45) likely to be travelled is the Most Probable Path (MPP).

6. Method according to claim 1 or 2, characterized in that in step b additionally an expected temperature in the exhaust pipe (10) is predictively known and compared with a nominal temperature value and an action is triggered on the basis thereof.

7. A controller (26) constructed and arranged to perform the method according to any one of the preceding claims.

8. Vehicle (14) comprising an internal combustion engine (11) with an exhaust line (10) and a control unit (26) according to claim 7, wherein a reducing agent (22) separated from ammonia or containing ammonia can be dosed into the exhaust gas flow (12) in the exhaust line (10) for reducing nitrogen oxides.

9. Vehicle (14) according to claim 8, having a low-pressure exhaust-gas recirculation device (21), wherein the reducing agent (22) can be dosed by a dosing device (16) in the flow direction of the exhaust-gas flow (12) before exhaust gas removal for the low-pressure exhaust-gas recirculation device (21).