DE102017216787A1 - Method for controlling a temperature of an SCR catalyst - Google Patents

Abstract

The invention relates to a method for controlling a temperature (T) of an SCR catalytic converter for an internal combustion engine by means of route information retrieved from a computer network.

Description

The present invention relates to a method for controlling a temperature of an SCR catalyst by means of route information retrieved from a computer network (also known as "cloud"). Furthermore, the invention relates to a computer program that performs each step of the method when it runs on a computing device, and a machine-readable storage medium that stores the computer program. Finally, the invention relates to an electronic control unit which is set up to retrieve the route information from the computer network and to control the temperature of the SCR catalytic converter.

State of the art

Today, in the after-treatment of exhaust gases of an internal combustion engine, the SCR (Selective Catalytic Reduction) method is used to reduce nitrogen oxides (NOx) in the exhaust gas. The DE 103 46 220 A1 describes the basic principle. Here, a 32.5% urea-water solution (HWL), commercially known as AdBlue ^® metered into the exhaust gas. Typically, for this purpose, a metering system is provided with a metering module to meter the HWL upstream of an SCR catalyst in the exhaust stream. From the HWL splits off ammonia, which is then bound to the reactive surface of the SCR catalyst. There, the ammonia combines with the nitrogen oxides, resulting in water and nitrogen. The HWL is conveyed by means of a conveyor module with a feed pump from a reducing agent tank through a pressure line to the dosing.

A conversion rate of the SCR catalyst greatly depends on a temperature of the SCR catalyst. At least within the temperature window typically used in operation, for example 200 ° C to 500 ° C, the rate of conversion increases with increasing temperature.

In addition, the HWL freezes at low temperatures. For example, the freezing point of the often used AdBlue ^® solution is around -11 ° C. In order to use the HWL must be thawed in this case before. Various methods and devices are known for thawing the HWL or preventing the HWL from freezing.

Disclosure of the invention

The method relates to an SCR catalytic converter of an SCR system for an internal combustion engine, in particular in a motor vehicle. The SCR catalyst is arranged in an exhaust line of the internal combustion engine and acts on the exhaust gas. The SCR system includes the SCR catalyst and a delivery and metering system associated with the SCR catalyst. In this delivery and metering system, a reducing agent solution is conveyed through a delivery module from a reducing agent tank and fed through a metering module to the SCR catalyst. The method is used to control a temperature of the SCR catalyst, by means of which the conversion rate for nitrogen oxides can be changed. The control is based on route information from which, for example, a length of the route, a travel time, a route profile, an engine operating area, a traffic volume on the route, and the like can be predicted. The route information is retrieved from a computer network, also known by the term "cloud". By means of this route information, it is possible, for example for an electronic control unit, to determine operating conditions for the internal combustion engine, the SCR catalytic converter and the delivery and metering system. Such operating conditions may include, for example, the ride length and ride duration, a predicted load and speed of the engine, a speed of the vehicle, and thus a predicted exhaust mass flow. Based on this, the control of the temperature of the SCR catalyst is enabled to react early to the conditions of the route.

As a result, the temperature of the SCR catalyst can be controlled so as to ensure optimum reduction of nitrogen oxides. Moreover, the temperature of the SCR catalyst after heating can be maintained. On the other hand, under certain operating conditions, energy / fuel consumption can be reduced. For example, one of these specific operating conditions is the case that a route is too short to heat the SCR catalyst in time. In addition, more track conditions may cause the heating of the SCR catalyst is unfavorable. Under these operating conditions can be dispensed with the heating of the SCR catalyst. The reduction of the nitrogen oxide emission in this case, for example, then only via an optionally existing nitrogen oxide storage catalyst (NSC - Nitrogen oxide Storage Catalyst) take place. In addition, if the heating can not be accelerated due to the route conditions, additional measures can be dispensed with.

In order to keep the nitrogen oxide emission low, often rapid changes in the temperature of the SCR catalyst are required. The change in temperature can preferably be achieved in two ways, which can also complement each other: First, one in the Internal combustion engine injected fuel mass can be varied. If the injected fuel mass increases, this leads to an increased temperature of the exhaust gas flowing out of the internal combustion engine. The heat of the exhaust gas then heats the SCR catalyst. In this case, a suitable mass and / or a suitable mass flow of the fuel are determined on the basis of the route information. With this measure, the fuel consumption can be reduced. On the other hand, an electrical heating element can be provided, by means of which the temperature of the SCR catalyst can be changed. For example, the electric heating element can be arranged in the reducing agent tank and there heat the reducing agent solution. Finally, the SCR catalyst can be heated via the metered heated reducing agent solution. The control of the electric heating element is performed based on the route information. With this measure, the electrical energy for operating the electric heating element can be reduced, so that a battery discharges more slowly to supply the electric heating element.

In one aspect, a heating time of the SCR catalyst may be controlled by means of the route information. The heating-up time is the time that elapses during the heating of the SCR catalytic converter from a low temperature, in particular from a temperature at the start of the internal combustion engine, to a desired higher operating temperature at which the SCR preferably takes place. If there are not enough sections on a planned route in which the SCR catalytic converter reaches its operating temperature as a result of the engine load, additional fuel can be injected in order to reduce the heating time. Accordingly, the reduction of nitrogen oxides takes place earlier, so that the nitrogen oxide emission is reduced. In addition, as already mentioned, an electric heating element can be connected in order to further reduce the heating time. Especially with short trips, therefore with a short distance and / or short travel time, it is thus possible for the SCR catalyst to quickly reach the desired operating temperature. If by means of the route information the opposite case is recognized that the heating time can not (significantly) be shortened significantly, an unnecessary heating in the form of additional injected fuel and / or the heating element can be dispensed with. As a result, fuel and / or electrical energy can be saved for operating the heating element.

In another aspect, the temperature of the SCR catalyst may be maintained at low engine load. Due to the low engine load, the temperature of the exhaust gas can drop and thus also decrease the temperature of the SCR catalyst, with the result that the conversion rate also decreases. The low engine load occurs, for example, in a "stop and go" operation, in city traffic or at low vehicle speed. From the route information, such driving conditions can be anticipated. The controller can react early so that the temperature of the SCR catalyst can be maintained. For this purpose, the SCR catalyst additionally heat is supplied, for example, as already described by the additionally injected fuel and / or by means of the electric heating element. As a result, the operating temperature can be maintained for a long time even at a low engine load. In addition, the SCR catalyst is available even at low engine load and a lower efficiency of SCR at low engine load is counteracted. Thus, the nitrogen oxide emission is reduced.

At low temperatures, the reducing agent solution can freeze. The frozen reductant solution can not be dosed into the SCR catalyst and is therefore thawed. A thawing time refers to the time in which the reducing agent solution is frozen from the frozen state, i. from the solid phase, into the liquid phase passes. According to one aspect, it may be provided to control the thawing time of the reducing agent solution by means of the route information. If the reducing agent solution does not (completely) douse during a planned route, additional heat can be supplied to the conveying and metering system in a manner known per se. Preferably, the additional heat is supplied to the reducing agent tank and the reducing agent solution stored therein via the electrical heating element arranged in the reducing agent tank. As a result, the thawing time of the reducing agent solution is shortened and it can be metered into the SCR catalytic converter earlier, which reduces the nitrogen oxide emission. If it becomes clear from the route information that the reducing agent solution does not thaw on the planned route, the supply of heat can be dispensed with, thereby saving energy.

Preferably, the heating time of the SCR catalyst and the thawing time of the reducing agent solution can be synchronized. Based on the route information, heat is supplied to the SCR catalyst and the delivery and metering system in the manner already described, so that the heat-up time of the SCR catalyst and the defrost time of the reductant solution are the same, and the reductant solution thaws substantially exactly when the SCR catalyst is defrosted. Catalyst has reached its desired operating temperature. This synchronization allows the SCR system to be operational at the same time and reduce nitric oxide emissions. In the synchronization, the longer time is preferred to the shorter time adjusted to make the SCR system operational as soon as possible.

From the route information, the case can be recognized that on the planned route either the SCR catalyst can not be heated to operating temperature or the reducing agent solution can not be thawed, therefore the SCR system is not ready in time. In this case, the heat input to both components of the SCR system, i. the SCR catalyst and the delivery and metering system can be dispensed with, which can save fuel / energy that would otherwise have been wasted because the SCR system is not operational. For example, can be dispensed with the thawing of the reducing agent solution when the heating time of the SCR catalyst z. B. is not achieved due to a too short planned route. On the other hand, can be dispensed with the heating of the SCR catalyst, if the thawing time of the reducing agent solution is not reached.

Furthermore, the temperature of the SCR catalytic converter can be controlled by means of the route information as a function of operating parameters of at least one further catalytic converter, which is optionally arranged in the exhaust gas line and acts on the exhaust gas. Such a catalyst may be, for example, a nitrogen oxide storage catalyst (NSC), a lean NOx trap (LNT) and / or an oxidation catalyst. While the conversion rate of the SCR catalyst is greatest at a high temperature of the SCR catalyst, the nitrogen oxide storage catalyst and the lean NOx trap achieve best results in a low temperature range. By means of the route information, an optimal combination of the various catalysts can be found, in which the reduction of the nitrogen oxide emission over a wide temperature range and, accordingly, over a wide load range is achieved.

As already mentioned, the route information can be called up from the computer network. Preferably, the route information can be retrieved via a wireless radio link from the computer network. The wireless radio connection is particularly preferably a wireless Internet connection which can access the computer network by means of so-called "cloud computing". As a result, the route information can be stored outside of the electronic control unit, which is particularly advantageous for mobile use in the motor vehicle.

For example, to obtain the route information for the presumed route, a navigation signal may be used. In addition, already driven routes can be included.

The computer program is set up to perform each step of the method, in particular when it is performed on a computing device or controller. It allows the implementation of the method in a conventional electronic control unit without having to make any structural changes. For this purpose it is stored on the machine-readable storage medium.

The electronic control unit is set up to retrieve the route information, in particular by means of a wireless radio connection, preferably a wireless Internet connection, from the computer network. By applying the computer program to such an electronic control unit, the electronic control unit is obtained, which is set up to control the temperature of the SCR catalytic converter by means of the route information.

list of figures

• 1 zeigt einen schematischen Aufbau eines SCR-Systems mit einem SCR-Katalysator und einem Förder- und Dosiersystem, bei dem ein Ausführungsbeispiel des erfindungsgemäßen Verfahrens durchgeführt werden kann.
• 2a bis 2c zeigen jeweils in einem Diagramm über die Zeit die Ausgangstemperatur eines Verbrennungsmotors (a), die Temperatur eines Oxidationskatalysators (b) und die Temperatur des SCR-Katalysators (c) aus 1 gemäß einem Ausführungsbeispiel des erfindungsgemäßen Verfahrens und gemäß dem Stand der Technik.
• 3 zeigt in einem Diagramm die Kombination von Ausschnitten III der Diagramme aus den 2a bis 2c für das Ausführungsbeispiel der Erfindung.

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

• 1 shows a schematic structure of an SCR system with an SCR catalyst and a delivery and metering system, in which an embodiment of the method according to the invention can be performed.
• 2a to 2c each show in a graph over time the output temperature of an internal combustion engine (a), the temperature of an oxidation catalyst (b) and the temperature of the SCR catalyst (c) 1 according to an embodiment of the method according to the invention and according to the prior art.
• 3 shows in a diagram the combination of excerpts III of the diagrams from the 2a to 2c for the embodiment of the invention.

Embodiments of the invention

1 shows a schematic structure of an SCR system with a delivery and metering system 1 for an SCR catalyst 2 and an oxidation catalyst 3 for exhaust aftertreatment of an internal combustion engine, not shown, in a motor vehicle. The oxidation catalyst 3 and the SCR catalyst 2 are consecutively in an exhaust system 4 arranged the internal combustion engine and act on the expelled from the engine exhaust gas. In other Embodiments are additional or alternative to the oxidation catalyst 3 more catalysts, such as. As a nitrogen oxide storage catalyst (NSC) and / or a lean NOx trap (LNT), provided together with the SCR catalyst 2 act on the exhaust gas. About the exhaust system 4 and the exhaust therein is heat from the engine via the oxidation catalyst 3 to the SCR catalyst 2 transported. The conveying and dosing system 1 has a feed pump 11 containing a reducing agent solution from a reducing agent tank 12 via a pressure line 13 to a metering valve 14 promotes. In the pressure line 13 is a filter 15 arranged, which filters the reducing agent solution. About the metering valve 14 the reductant solution then enters the exhaust line 4 upstream of the SCR catalyst 2 metered. Non-metered reducing agent solution flows over one with the pressure line 13 connected return 16 into the reducing agent tank 12 back. In the return 16 is a control valve 17 arranged, which by the return 16 flowing reducing agent solution based on the temperature of the reducing agent solution controls.

Furthermore, a reducing agent temperature sensor 18 provided that the temperature of the reducing agent solution within the reducing agent tank 12 measures. In addition, in the reducing agent tank 12 a level gauge 19 arranged, the level of the reducing agent solution in the reducing agent tank 12 measures. Moreover, in this embodiment, an electric heating element 8th in the reducing agent tank 12 arranged, which is arranged, the reducing agent solution in the reducing agent tank 12 to warm up.

In the exhaust system 4 is a first temperature sensor 51 upstream of the oxidation catalyst 3 arranged, there is a starting temperature T _M of the exhaust gas flowing from the internal combustion engine. A second temperature sensor 52 is downstream of the oxidation catalyst 3 arranged and measures there a temperature _OK of the oxidation catalyst 3 , A third temperature sensor 53 is again downstream of the SCR catalyst 2 arranged and measures the temperature there T _SCR of the SCR catalyst 2 , Finally, downstream of the SCR catalyst 2 a lambda probe 41 in the exhaust system 4 arranged there determines a combustion air ratio (lambda value). Furthermore, there is an electronic control unit 6 provided, which at least with the feed pump 11 and the metering valve 14 is connected and can control these. In addition, the temperature sensors 51 . 52 . 53 and the lambda probe 41 in the exhaust system 4 and the reducing agent temperature sensor 18 and the level gauge 19 of the reducing agent tank 12 with the electronic control unit 6 connected and send this their measured values.

The electronic control unit 6 is set up route information from a computer network 7 retrieve. Such a computer network 7 is also known as "cloud". This is the electronic control unit 6 with a receiver 61 connected to the the route information via a wireless radio link from the computer network 7 can receive and to the electronic control unit 6 forwards. In a preferred embodiment, the wireless radio connection is a wireless internet connection in which the electronic control unit 6 through "cloud computing" to the "cloud" (computer network 7 ) can access. The receiver 61 may in a further embodiment in the electronic control unit 6 integrated or be a part of this. In addition, the receiver 61 Also be designed as a transceiver, ie as a combination of receiver and transmitter, so that additional data to the computer network 7 can be sent. In still other embodiments, an additional transmitter is for communication with the computer network 7 intended.

To obtain the route information for the presumably selected route, for example, a navigation signal of a satellite navigation system such. As GPS, are used. In addition, already driven routes can be included.

• - eine Länge einer zu fahrenden Strecke;
• - eine Fahrtzeit;
• - ein Streckenprofil
• - Motorbetriebsbedingungen; und
• - das Verkehrsaufkommen auf der Strecke.

The route information provides information about z. B .:

• a length of a route to be traveled;
• - a travel time;
• - a route profile
• - engine operating conditions; and
• - the traffic on the route.

• - die Fahrtlänge und Fahrtdauer;
• - eine prädizierte Last und Drehzahl des Verbrennungsmotors;
• - eine Geschwindigkeit des Fahrzeugs; und
• - einen prädizierten Abgasmassestrom.

The electronic control unit calculates from this route information among others:

• - the length of the journey and the duration of the journey;
• a predicted load and speed of the internal combustion engine;
• a speed of the vehicle; and
• - a predicted exhaust mass flow.

In embodiments of the invention, which are explained in detail below, the fuel mass injected into the internal combustion engine is controlled by means of the electronic control unit 6 varies based on the route information. The electronic control unit 6 is with the internal combustion engine and its injection device and the electric heating element 8th Connects and controls the temperature based on the route information T _SCR of the SCR catalyst 2 , The heated reductant solution is then, as already described, the SCR catalyst 2 fed. As a result, the temperature T _SCR of the SCR catalyst 2 increase.

A regulation of the temperature of the reducing agent solution is carried out by the electric heating element 8th , the control valve 17 and the reducing agent temperature sensor 18 by means of the electronic control unit 6 also based on the route information. If the reducing agent solution is frozen, which occurs in a commonly used urea-water solution (AdBlue) from about -11 ° C, the thawing time of the reducing agent solution can be changed.

The 2a to 2c each show a diagram of the temperature sensors 51 . 52 . 53 in the exhaust system 4 measured temperatures over time. In each of the diagrams are a course according to the prior art - hereinafter referred to as basic history - and a course according to an embodiment of the method - hereinafter called RWU history (Rapid Warm Up) -, in which compared to the prior Technology an additional fuel mass is injected based on the route information shown. The control of the temperature T _SCR of the SCR catalyst 2 occurs as a function of operating parameters of the oxidation catalyst 3 , In other embodiments, the control of the temperature takes place T _SCR of the SCR catalyst 2 depending on operating parameters of other catalysts, such. As the nitrogen oxide storage catalyst (NSC) and / or the lean NOx trap. The latter are the best at reducing nitrogen oxide emissions in a low temperature range, making them an optimal combination with the SCR catalyst 2 in which the reduction of nitrogen oxide emission over a wide temperature range is achieved.

2a shows a base history 510 the starting temperature T _M of the internal combustion engine and an RWU course 515 the starting temperature T _M of the internal combustion engine. The RWU course 515 lies above the base curve over the entire considered period t 510 , As a result, on the one hand t higher temperatures are reached over the entire time period and, on the other hand, desired temperature values are reached earlier.

2 B shows a base history 520 the temperature _OK of the oxidation catalyst 3 and an RWU history 525 the temperature _OK of the oxidation catalyst 3 , The RWU course 525 is also above the base curve over the entire considered period t 520 , Likewise, on the one hand, higher temperatures are reached over the entire time period t and, on the other hand, desired temperature values are reached earlier.

2c shows a base history 530 the temperature T _SCR of the SCR catalyst 2 and an RWU history 535 the temperature T _SCR of the SCR catalyst 2 , The RWU course 535 is also above the base curve over the entire considered period t 530 , As a result, higher temperatures are reached over the entire period t. In addition, the heating time t _h for the SCR catalyst 2 reduced. In this embodiment, a desired operating temperature T _{B_SCR} of the SCR catalyst 2 be at 200 ° C. The base history 530 the temperature T _SCR of the SCR catalyst 2 according to the prior art reaches the desired operating temperature T _{B_SCR} after 97 seconds, marked by the dot 531 , The RWU course 535 the temperature T _SCR of the SCR catalyst 2 according to the embodiment of the invention reaches the desired operating temperature T _{B_SCR} at the point 536 after just 57 seconds. That is the heating time t _h is 57 seconds, which is 40 seconds shorter than the base curve 530 , As a result, due to shortened heating time t _h Nitrogen oxides are already reduced 40 seconds earlier.

The in the 2a to 2c marked sections III of the diagrams are in 3 shown in combination. In the diagram of 3 are the RWU history 515 the starting temperature T _M of the internal combustion engine, the RWU course 525 the temperature _OK of the oxidation catalyst 3 and the RWU history 535 the temperature T _SCR of the SCR catalyst 2 according to the in the 2a to 2c shown embodiment of the invention shown. As already explained, an additional fuel mass was injected based on the route information in the internal combustion engine, whereby the change in temperature T _SCR of the SCR catalyst 2 is increased and consequently its heating time t _h is shortened. The diagram in 3 is in three windows F1 . F2 . F3 divided, in which the electronic control unit 6 performs different control methods. In the first window F1 An adaptation of the internal combustion engine to minimize a hydrocarbon emission. For this there is a lambda control, which is the signal of the lambda probe 41 used, idle. An injector such as a high-pressure fuel storage (common rail) for injecting fuel is operated at an elevated pressure. It is set a reduced thrust on the engine. In addition, a reduced exhaust gas recirculation is performed.

In the second window F2 the oxidation catalyst jumps 3 at. The internal combustion engine is controlled so that its outlet temperature T _M elevated. In RWU history 515 the starting temperature T _M can be seen a corresponding increase from 140 ° C at 20 seconds to 275 ° C at 30 seconds. Furthermore, the injector is operated at elevated pressure and set a reduced thrust on the engine. In addition, a mass correction of the fuel is performed. In this second time window F2 an optimized exhaust gas recirculation is carried out, by which the starting temperature T _M of the internal combustion engine increases. Furthermore, there is a delayed injection of fuel into the internal combustion engine. The resulting incomplete combustion leads to a higher starting temperature due to the hot unburned fuel T _M of the internal combustion engine. As a result of the increased starting temperature T _M of the internal combustion engine, the temperature also rises _Okay of the oxidation catalyst 3 and finally the temperature T _SCR of the SCR catalyst 2 ,

In the third time window F3 is the throughout the oxidation catalyst 3 Existing heat used to make up the SCR catalyst 2 heat. Im through the second temperature sensor 52 measured course 525 the temperature _OK of the oxidation catalyst 3 is therefore a strong increase. A corresponding increase is accordingly in the course 535 the temperature T _SCR of the SCR catalyst 2 determine to which the heat from the oxidation catalyst 3 is transmitted. In this third time window F3 the pressure in the injector is reduced and increases the thrust on the engine. In addition, the exhaust gas recirculation is further increased The fuel is still injected delayed. In addition, secondary injections, in which additional fuel is injected, prevented. In this third time window reaches the outlet temperature T _M of the internal combustion engine reaches its maximum value of approx. 330 ° C and does not increase any further.

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 10346220 A1 [0002]

Claims (11)

Method for controlling a temperature (T _SCR ) of an SCR catalytic converter (2) for an internal combustion engine by means of route information retrieved from a computer network (7). Method according to Claim 1 characterized in that for varying the temperature (T _SCR ) of the SCR catalyst (2) an injected fuel mass is varied based on the route information. Method according to Claim 1 or 2 characterized in that for changing the temperature (T _SCR ) of the SCR catalyst (2), an electric heating element (8) is controlled based on the route information. Method according to one of the preceding claims, characterized in that a heating time (t _h ) of the SCR catalyst (2) is controlled by means of the route information. Method according to one of the preceding claims, characterized in that the temperature (T _SCR ) of the SCR catalyst (2) is maintained at low engine load. Method according to one of the preceding claims, characterized in that a thawing time of a reducing agent solution for the SCR catalyst is controlled by means of the route information. Method according to one of the preceding claims, characterized in that the temperature (T _SCR ) of the SCR catalytic converter (2) is controlled as a function of operating parameters of at least one further catalytic converter by means of the route information. Method according to one of the preceding claims, characterized in that the stretch information is retrieved via a wireless radio link from the computer network (7). Computer program, which is set up, each step of the procedure according to one of Claims 1 to 8th perform. Machine-readable storage medium on which a computer program is based Claim 9 is stored. Electronic control unit (6), which is adapted to operate by means of a method according to one of Claims 1 to 8th To retrieve route information from a computer network (7) and to control by means of this a temperature (T _SCR ) of an SCR catalyst (2).

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