SE1350273A1 - Apparatus and method for selecting the maximum reducing agent dosage in an SCR system for exhaust gas purification - Google Patents

Abstract

The invention relates to a method for selecting maximum reducing agent dosage in an SCR system for exhaust gas purification, where evaporation of a metered amount of reducing agent is sought. The method comprises the step of: - selecting (s440) said maximum reducing agent dosage on the basis of an exhaust gas mass flow (MF), an effective evaporation temperature (Tv; T1; T2) and a reducing agent temperature (Tu). The invention also relates to a computer program product comprising program code (P) a computer (200; 210) for implementing a method according to the invention. The invention also relates to a device for selecting the maximum reducing agent dosage in an SCR system and a motor vehicle equipped with the device. Figure 2 for publication

Description

There is a constant need to reduce the amount of emissions from engines of motor vehicles. This applies not least to heavy motor vehicles such as e.g. trucks and buses as legal requirements for ever smaller emissions are continuously tightened.

The ability to extend reducing agents including urea can constitute a strictly large NOX gas an exhaust gas aftertreatment system based on SCR can reduce. It is important to limit the amount of being able to set limits on the amount of reductant that can be extended under certain given operating conditions. There are currently known problems associated with reducing agent dosing, which relate to the formation of reducing agent crystals in exhaust systems.

In order to avoid the formation of reducing agent crystals, according to the prior art, a folder-based model for reducing agent dosing is stored in a control unit of the vehicle, which model depends on the parameters exhaust mass flow and exhaust temperature. However, even when this model is used to determine a limit for the maximum dosage of reductant under certain operating conditions, said problems with the formation of reducing agent crystals can arise.

In cases where said folder-based model for reducing agent dosing is set too conservatively, this will result in an undesirably high fuel consumption of said engine.

US 6119448 describes a method for dosing urea.

US 20090199540 describes a method for controlling a dosing valve for dosing urea.

SUMMARY OF THE INVENTION There is a need to improve control and selection of maximum reducing agent dosage in an SCR system where both a reduced risk of reduction of reducing agent crystals and the possibility of not causing unnecessarily high fuel consumption in the vehicle are achieved.

An object of the present invention is to provide a new and advantageous method for selecting the maximum reducing agent dosage in an SCR system for exhaust gas purification.

Another object of the invention is to provide a new and advantageous device and a new and advantageous computer program for selecting the maximum reducing agent dosage in an SCR system for exhaust gas purification.

A further object of the invention is to provide a method, an apparatus and a computer program for achieving a reliable and user-friendly choice of maximum reducing agent dosage in an SCR system for exhaust gas purification.

A further object of the invention is to provide an alternative method, an alternative device and an alternative computer program for selecting maximum reducing agent dosage in an SCR system for exhaust gas purification process for selecting reducing agent dosage in an SCR system for exhaust gas purification according to claim 1.

These objects are achieved with one of maximum According to one aspect of the invention, a method for selecting maximum reducing agent dosage is provided in an SCR system for exhaust gas purification, where evaporation of a metered amount of reducing agent is sought. The method may comprise the step of: - selecting said maximum reducing agent dosage on the basis of an effective reducing agent temperature. By also taking into account external conditions in the environment of said SCR system and thereby implementing the inventive method for selecting maximum reducing agent dosage by introducing reducing agent temperature, the above-mentioned disadvantages of, for example, crystal formation of metered reducing agent can be avoided. A temperature of ambient air affects a temperature of said reducing agent.

According to one aspect of the invention, there is provided a method of selecting a maximum reducing agent dosage in an SCR system for exhaust gas purification, in which narrowing of a metered amount of reducing agent is sought. The method may comprise the step of: - selecting said maximum reducing agent dosage on the basis of an exhaust gas mass flow, a temperature of exhaust gases from an engine and a reducing agent temperature.

In this case, an existing model for selecting the maximum reducing agent dosage can be advantageously extended and include reducing agent temperature. Hereby an improved procedure is achieved the parameter for selection of reducing agent dosage.

According to one embodiment, an existing map model based on the parameters of exhaust gas flow and an effective evaporation temperature can advantageously provide both an effective evaporation temperature and the temperature of said reducing agent. extended and thereby include Actual dosage of reducing agent may be lower than said maximum reducing agent dosage.

According to one embodiment, an existing map model based on the parameters exhaust mass flow and an exhaust gas temperature can be advantageously extended and hereby include both exhaust gas temperature and temperature of said reducing agent.

In this case, an automated selection of the maximum reducing agent dosage can be achieved. Temperature sensors for measuring a temperature of said reducing agent are relatively inexpensive and reliable, which advantageously means that the inventive method is cost-effective.

In this case, a relatively low fuel consumption of an engine of the vehicle over time can be furthermore. The formation of solid reducing agent crystals in an exhaust system can be avoided to a greater degree than according to the prior art. achieved.

Said maximum reducing agent dosage can be selected on the basis of an established matrix exhibiting for evaporation maximum reducing agent dosage depending on exhaust gas mass flow and a reference parameter depending on both effective evaporating temperature and reducing agent temperature.

Said maximum reducing agent dosage can be selected on the basis of an empirically determined reducing agent dosage in matrix showing for evaporation maximum dependence on exhaust gas mass flow and a reference parameter depending on both effective evaporating temperature and reducing agent temperature.

Said maximum reducing agent dosage can be selected on the basis of a predetermined matrix in the determined reducing agent dosage showing for evaporation maximum dependence on exhaust gas mass flow and a reference parameter depending on both effective evaporating temperature and reducing agent temperature.

Information on the maximum reducing agent dosage for evaporation depending on the exhaust gas mass flow and a reference parameter depending on both the effective evaporation temperature and the reducing agent temperature can be stored in a memory of a control unit in a suitable manner.

Said reference parameter can be defined as a suitable function which depends on both effective evaporation temperature and reducing agent temperature.

Said reference parameters can alternatively be defined as a suitable function which depends on both exhaust gas temperature and reducing agent temperature.

Said reference parameter can be determined according to a relationship defined by: Tref = Tv-K1 * Tu + K2 where: Tv is effective evaporation temperature; Tu is reducing agent temperature; and Kf and K2 are predetermined constants.

Kf and K2 can be empirically determined. Kf and K2 can be determined in an appropriate way. Kf and K2 can be predetermined constants.

The effective evaporation temperature can be set to the exhaust gas temperature or a temperature of a component in a configuration of an exhaust duct and an SCR catalyst of said SCR system.

The inventive process can be carried out during operation when the vehicle is stationary, for example when an engine of the vehicle is idling.

The inventive method can be performed during operation, for example when the vehicle is propelled on a suitable road section. The process according to the invention can be carried out when the vehicle is propelled in circumstances when favorable operating conditions can be achieved, which operating conditions can include that a minimum temperature of the vehicle's SCR catalyst is reached and that an exhaust gas flow favorable for the process is achieved.

The inventive extension of an existing model can increase the accuracy of the model and thus enables quality problems caused by crystal formation of dosed reducing agent to be avoided without having to provide an excessive safety margin in many driving cases.

The procedure is easy to implement in existing motor vehicles. Software for SCR systems for exhaust gas purification, according to the invention can be installed in a control unit of the vehicle selection of maximum reducing agent dosage at a in the manufacture of the same. A buyer of the vehicle can thus be given the opportunity to choose the function of the procedure as an option. Alternatively, software including program code for performing the innovative procedure for selecting maximum reducing agent dosage in an SCR exhaust purification system may be installed in a control unit of the vehicle when upgrading at a service station. In this case, the software can be loaded into a memory in the control unit.

Program code that includes program code for selecting reducing agent dosing in an SCR system for exhaust gas purification, where evaporation of a metered amount of reducing agent is sought, can be easily updated or replaced. Furthermore, different parts of the program code for selecting the maximum reducing agent dosage in an SCR system for exhaust gas purification can be replaced independently of each other. This modular configuration is advantageous from a maintenance perspective.

According to one aspect of the invention, an apparatus for selecting the maximum reducing agent dosage is provided in an SCR system for exhaust gas purification, where evaporation of a metered amount of reducing agent is sought. The device may comprise means adapted to select said maximum reducing agent dosage on the basis of an exhaust gas mass flow, an effective evaporating temperature as well as a reducing agent temperature.

In the device, said maximum reducing agent dosage can be selected on the basis of an empirically determined matrix showing for evaporation maximum reducing agent dosage depending on exhaust gas mass flow and a reference parameter depending on both effective evaporating temperature and reducing agent temperature.

In the device, said reference parameter can be determined according to a relationship defined by: Tref = TV-K1 * Tu + K2 where: Tv is the effective evaporation temperature; Tu is reducing agent temperature; and Kf and K2 are predetermined constants.

Kf and K2 can be empirically determined. Kf and K2 can be determined appropriately. Kf and K2 can be predetermined constants.

In the device, said maximum reducing agent dosage can be selected on the basis of an empirically determined matrix showing for evaporation maximum reducing agent dosage depending on exhaust gas flow and a reference parameter depending on both exhaust temperature and reducing agent temperature.

In the device, the effective evaporation temperature can be set to the exhaust gas temperature or a temperature of a component in a configuration of an exhaust duct and an SCR catalyst of said SCR system.

According to one aspect of the present invention, there is provided a motor vehicle comprising a device according to any one of claims 5-8.

According to one aspect of the present invention, there is provided a motor vehicle comprising a device for selecting the maximum reducing agent dosage in an SCR system for exhaust gas purification.

The motor vehicle can be anything from a truck, bus or car.

According to one aspect of the invention, there is provided a computer program for selecting maximum reducing agent dosage in an SCR system for exhaust gas purification, said computer program comprising program code stored on a computer readable medium to cause an electronic control unit or another computer connected to the electronic the control unit to perform the steps according to any one of claims 1-4.

According to one aspect of the invention, there is provided a computer program of selecting a maximum reducing agent dosage in an SCR system for exhaust gas purification, said computer program comprising program code for causing an electronic control unit or another computer connected to the electronic control unit to perform the steps of any of claims 1-4. .

According to one aspect of the invention, there is provided a computer program product comprising a program code stored on a computer readable medium for performing the method steps of any of claims 1-4, when said computer program is run on an electronic control unit or another computer connected to the electronic control unit. .

Additional objects, advantages and novel features of the present invention will become apparent to those skilled in the art from the following details, as well as through the practice of the invention. While the invention is described below, it should be understood that the invention is not limited to the specific details described. Those skilled in the art having access to the teachings herein will recognize additional applications, modifications, and incorporations within other fields which are within the scope of the invention. OVERVIEW DESCRIPTION OF THE DRAWINGS For a more complete understanding of the present invention and further objects and advantages thereof, reference is now made to the following detailed description which is to be read in conjunction with the accompanying drawings in which like reference numerals refer to like parts in the various figures, and in which: 1 schematically illustrates a vehicle, according to an embodiment of the invention; 2 schematically illustrates reducing agent dosing in an SCR system for exhaust gas purification, according to a Figure a device for selecting the maximum embodiment of the invention; Figure 3a schematically illustrates a diagram according to an aspect of the invention; Figure 3b schematically illustrates a diagram according to an aspect of the invention; Figure 4a schematically illustrates a flow chart of a method, according to an embodiment of the invention; Figure 4b schematically illustrates in further detail a flow chart of a method, according to an embodiment of the invention; and Figure 5 schematically illustrates a computer, according to an embodiment of the invention.

DETAILED DESCRIPTION OF FIGUREFINE Referring to Figure 1, a side view of a vehicle 100 is shown. The exemplary vehicle 100 consists of a tractor 110 and a trailer 112.

The vehicle can be a heavy vehicle, such as a truck or a bus. The vehicle can alternatively be a car. It should be noted that the invention is suitable for application to a suitable SCR system and is not limited to motor vehicle SCR systems.

The innovative method and the innovative device of an SCR system, according to an aspect of the invention, are well suited for platforms involving an SCR system other than motor vehicles, such as e.g. watercraft.

The watercraft can be of any suitable type, such as e.g. motorboats, ships, ferries or ships.

The innovative method and the innovative device of an SCR system according to an aspect of the invention are also well suited for e.g. systems including, for example, a stone crusher or the like.

The innovative method and the innovative device of an SCR system according to an aspect of the invention are also well suited for e.g. systems including industrial engines and / or motorized industrial robots.

The innovative method and the innovative device of an SCR system according to an aspect of the invention are also well suited for different types of power plants, such as e.g. an electric power plant comprising a diesel generator.

The innovative method and the innovative device of an SCR system are well suited for any suitable engine system which includes an engine and an SCR system, such as e.g. at a locomotive or other platform.

The innovative procedure and innovative device of an SCR system are well suited for an arbitrary system that includes a NOX generator and an SCR system.

Here, the term "link" refers to a communication link which may be a physical line, such as an optoelectronic communication line, or a non-physical line, such as a wireless connection, for example a radio or microwave link.

Here, the term "conduit" refers to a passage for holding and transporting a fluid, such as e.g. a reductant in liquid form. The pipe can be a pipe of any dimension. The conduit may consist of any suitable material, such as e.g. plastic, rubber or metal.

Here, the terms "reductant" or "reducing agent" refer to an agent used to react with certain emissions in an SCR system. These "reductants" and "reducing agents" are used synonymously herein. Said reductant is according to an emissions can e.g. be NOX gas. The terms execution so-called AdBIue. Of course, other types of reductants can be used.

Here, AdBlue is mentioned as an example of a reductant, but a person skilled in the art realizes that the innovative method and the innovative device can be realized for other types of reductants. According to an exemplary embodiment, said reducing agent comprises a urea solution. Said urea solution involves a suitable urea concentration. Referring to Figure 2, there is shown a device 299 of the vehicle 100.

The device 299 may be arranged in the tractor 110. The device 299 may form part of an SCR system or include an SCR system.

The device 299 according to this example comprises a container 205 which is arranged to pour a reductant. The container 205 is arranged to contain a suitable amount of reductant and is further arranged to be able to be refilled if necessary.

A first conduit 271 is provided to direct the reductant to a pump 230 from the container 205. The pump 230 may be any suitable pump. The pump 230 may be a diaphragm pump comprising at least one filter. The pump 230 may be arranged to be operated by means of an electric motor (not shown). The pump 230 may be arranged to pump up the reductant from the container 205 via the first line 271 and via a second line 272 supply said reductant to a dosing unit 250. The dosing unit 250 may comprise an electrically controlled dosing device, by means of which a flow of reductant added to the exhaust system can be controlled. The pump 230 is arranged to pressurize the reductant in the second line 272. The dosing unit 250 is arranged with a throttling unit, which can also be called throttling valve, against which said pressure of the reductant can be built up in the device 299.

The dosing unit 250 is arranged to supply said reductant to an exhaust duct 290 of the vehicle 100. More specifically, the dosing unit 250 is arranged to supply in a controlled manner a suitable amount of reductant to a 290 of the vehicle 100, according to an aspect of the inventive method. According to this embodiment, an SCR catalyst 270 is arranged downstream of a position of the exhaust system where the exhaust duct reductant is supplied. The amount of reductant added to the exhaust system is intended to be used in the SCF1 catalyst to reduce the amount of unwanted emissions.

The dosing unit 250 may be arranged at said exhaust duct 290 which is arranged to direct exhaust gases from an internal combustion engine (not shown) of the vehicle 100 to the SCR catalyst and further to an environment of the vehicle.

A third conduit 273 is presently disposed between the metering unit 250 and the container 205. The third conduit 273 is arranged to return a certain amount of the reductant fed to the metering valve 250 to the container 205.

The first control unit 200 is arranged for communication with the pump 230 via a link L230. The first control unit 200 is arranged to control operation of the pump 230. According to one example, the first control unit 200 is arranged to control the pump 230 by means of an electric motor (not shown). The first control unit 200 is arranged to influence a working pressure in the second line 272. This can be done in various suitable ways. According to one example, the first control unit 200 is arranged to change a prevailing speed RPM of the pump 230. In this case, the pressure can be changed in a desired manner. By increasing the speed FlP1V1 of the pump 230, the working pressure can be increased. By lowering the speed FlP1V1 of the pump 230, the working pressure can be reduced.

The first control unit 200 is arranged for communication with a first temperature sensor 240 via a link L240. The temperature sensor 240 is arranged to detect a prevailing temperature T1 of an exhaust stream from the vehicle's engine. According to an example, the first temperature sensor 240 is arranged at said exhaust duct 290 directly downstream of the vehicle engine and upstream of a dosing unit 250. The temperature sensor 240 may be provided at location 290. The first temperature sensor 240 is arranged to continuously detect a rescue suitable at said exhaust gas channel. of the exhaust stream and send signals including information about said rescue temperature T1 via the link L240 to the first control unit 200.

The first control unit 200 is arranged for communication with a second temperature sensor 260 via a link L260. The second temperature sensor 260 may be arranged to detect a saving temperature T2 of a surface in the exhaust system where the reducing agent is evaporated. The second temperature sensor 260 may be arranged to detect a saving temperature T2 of the exhaust duct 290 at a suitable location. The second temperature sensor 260 may be arranged to detect a prevailing temperature T2 of a suitable surface or component of the exhaust duct 290.

According to one example, the second temperature sensor 260 is arranged at the exhaust duct 290 upstream of the dosing unit 250. According to another example, 260 is arranged in an evaporator unit (not shown) or in the SCR catalyst 270 downstream of the second temperature sensor dosing unit 250. The second temperature sensor 260 is arranged to continuously detecting a saving temperature T2 of a surface or component of the exhaust duct 290 and sending signals including information about said prevailing temperature T2 via the link L260 to the first control unit 200.

According to one embodiment, the first control unit 200 and / or the second control unit 210 are arranged to calculate said first temperature T1. This can be done by means of a stored calculation model. The first control unit 200 and / or the second control unit 210 may be arranged to calculate said first temperature T1 on the basis of, for example, a prevailing exhaust gas mass flow MF, prevailing speed F1PM of the engine and prevailing load of the engine.

According to one embodiment, the first control unit 200 and / or the second control unit 210 are arranged to calculate said second temperature T2. This can be done by means of a stored calculation model. The first control unit 200 and / or the second control unit 210 may be arranged to calculate said second temperature T2 on the basis of, for example, a prevailing exhaust gas mass flow MF, prevailing speed RPM of the engine and prevailing load of the engine.

Here, said first temperature T1 and said second temperature T2 are referred to as effective evaporation temperature. Thus, the effective evaporation temperature Tv can be set to the exhaust gas temperature T1 or a temperature T2 of a component in a configuration of the exhaust duct 290 and an SCR catalyst 270 of said SCR system.

An exhaust mass flow sensor 255 is arranged for communication with the first control unit 200 via a link L255. Exhaust gas flow sensor 255 is arranged to continuously determine a prevailing exhaust gas mass MF of the exhaust gas stream upstream of the SCR catalyst 270. According to an example, exhaust gas flow sensor 255 is arranged at the exhaust duct 290 upstream of said metering gas flow. MF upstream of the SCR catalyst 270 to the first control unit 200.

According to one embodiment, the first control unit 200 and / or the second control unit 210 are arranged to determine said exhaust gas mass flow MF. This can be done by means of a stored calculation model. The first control unit 200 and / or the second control unit 210 may be arranged to calculate said exhaust gas mass flow MF on the basis of, for example, a saving, saving speed RPM of the engine and a boost pressure or cylinder pressure of the engine. calculate an exhaust mass flow MF of the exhaust gases from the vehicle's engine. The first control unit 200 is arranged to continuously determine an exhaust mass flow MF of the exhaust gases from the engine of the vehicle. This can be done in any suitable way.

The first control unit 200 may be arranged that a NOX sensor 265 is arranged for communication with the first control unit 200 via a link L265. The NOX sensor 265 is arranged to continuously determine a saving NOX content of the exhaust gas stream downstream of the SCR catalyst 270. The NOX sensor 265 is arranged to continuously send signals including information of a saving NOX content downstream of the first SCR catalyst 270 to the SCR catalyst 270. the control unit 200.

According to one embodiment, the first control unit 200 and / or the second control unit 210 are arranged to calculate a NOX content upstream of the SCR catalyst 270. This can be done by means of a stored calculation model. The first control unit 200 and / or the second control unit 210 may be arranged to calculate said NOX content upstream of said SCR catalyst 270 on the basis of, for example, a rescuing exhaust gas mass flow MF, rescuing speed RPM of the engine and rescuing load of the engine. The first control unit 200 may be arranged to control operation of the engine of the vehicle 100 on the basis of said determined NOX content upstream of said SCR catalyst 270 and / or said determined NOX content downstream of said SCR catalyst 270.

The first control unit 200 is arranged for communication with a third temperature sensor 275 via a link L275. The temperature sensor 275 is arranged to detect a prevailing temperature Tu of said reducing agent. According to one example, the third temperature sensor 275 is provided with the 272 250.

The temperature sensor 275 may be provided at a suitable location in the second line upstream of said dosing unit the device 299. According to one embodiment, said third temperature sensor is the container 205. According to one embodiment, the temperature sensor 275 is arranged at the pump 230. According to one embodiment, the third is the third temperature sensor 275 arranged at a third line 273. The second temperature sensor 275 is arranged to continuously detect a prevailing temperature Tu of the reducing agent and send signals including information about said prevailing temperature Tu via the link L240 to the first control unit 200.

According to one embodiment, the first control unit 200 and / or the second control unit 210 are arranged to calculate said temperature Tu of the reducing agent. This can be done by means of a stored calculation model. The first control unit 200 and / or the second control unit 210 may be arranged to continuously calculate temperature Tu of the reducing agent on the basis of, for example, a temperature measure of the reducing agent in the container at start-up of the device 299 and an amount of energy supplied to said reducing agent by heating. Said heating can, for example, take place by means of suitable means. Said means may comprise a number of electric heating elements, which are placed in suitable places, such as for instance in the container 205 or at one of the first line 271, the second line 272 and the third line 273. Said first control unit 200 may be arranged to continuously select a suitable reducing agent dosage of the dosing unit 250 on the basis of a fixed exhaust mass flow MF, a fixed effective evaporating temperature T1 or T2 and a reducing agent temperature Tu.

Said first control unit 200 may be arranged to continuously select a suitable reducing agent dosage of the dosing unit 250 on the basis of a fixed exhaust mass flow IV1F, a fixed temperature T1 of the exhaust gases together with a reducing agent temperature Tu.

Said first control unit 200 may be arranged to continuously select a suitable reducing agent dosage of the dosing unit 250 on the basis of a fixed exhaust mass flow IV1F, a fixed temperature T2 nos a portion of the exhaust duct 290 together with a reducing agent temperature Tu.

Said first control unit 200 may be arranged to continuously select a suitable reducing agent dosage of the dosing unit 250 on the basis of a fixed exhaust mass flow MF, a fixed temperature T2 of the SCR catalyst 270 and a reducing agent temperature Tu. Said suitable reducing agent dosage may be maximally lower than said reducing agent dosage.

Said first control unit 200 may be arranged to continuously select a suitable maximum reducing agent dosage of the dosing unit 250 on the basis of a fixed exhaust mass flow MF, a fixed temperature T2 nos a portion of the exhaust duct 290 together with a reducing agent temperature Tu. Said suitable reducing agent dosage may be lower than said maximum reducing agent dosage.

Said first control unit 200 may be arranged to continuously select a suitable maximum reducing agent dosage of the dosing unit 250 on the basis of a fixed exhaust mass flow l1 / IF, a fixed temperature T2 of the SCF1 catalyst 270 together with a reducing agent temperature Tu. In the first control unit 200 there is an empirically determined matrix stored indicating for evaporation maximum reducing agent dosage depending on exhaust gas mass flow and a reference parameter depending on both effective evaporating temperature T1 or T2 and reducing agent temperature Tu arranged for display means 280 via a link L280. Said display means 280 may be presently arranged in a driver's cab of the vehicle 100. The said comprise a so-called display means 280 may be fixedly mounted in the vehicle 100. The first control unit 200 is communication with display means capable of touch screen. Said display means 280 may be a mobile electronic device. Said display means 280 may include, for example, a display screen. The first control unit 200 is arranged to present an error code or other relevant information regarding the innovative method. The first control unit 200 may be arranged to, by means of said presentation means 280, continuously, intermittently or, if necessary, present information on said stored matrix. An operator can, by means of said display means, change stored data as desired.

The first control unit 200 is arranged for communication with the dosing unit 250 via a link L250. The first control unit 200 is arranged to control the operation of the dosing unit 250 in order to e.g. regulate the supply of the reductant to the exhaust system of the vehicle 100.

A second control unit 210 is arranged for communication with the first control unit 200 via a link L210. The second control unit 210 may be releasably connected to the first control unit 200. The second control unit 210 may be a control unit external to the vehicle 100. The second control unit 210 may be arranged to perform the innovative method steps according to the invention. The second control unit 210 can be used to upload software to the first control unit 200, in particular software for performing the innovative method. The second control unit 210 may alternatively be arranged for communication with the first control unit 200 via an internal network in the vehicle. The second control unit 210 may be arranged to perform substantially the same functions as the first control unit 200, such as e.g. selecting the maximum reducing agent dosage in an SCR exhaust gas purification system, according to one aspect of the present invention.

Figure 3a schematically illustrates an empirically determined matrix exhibiting for evaporation maximum reducing agent dosage depending on exhaust gas flow MF and a reference parameter Tref depending on both effective evaporation temperature Tv and reducing agent temperature Tu.

Said exhaust mass flow MF is stated in kg / minute. Said reference parameter Tref is given in degrees Kelvin. The latrine comprises a number of values Mu11-Mu44 which values for exhaust gas mass flow MF and a given reference temperature Tref. indicates maximum reducing agent dosage for a given Said values Mu11-Mu44 are predetermined and stored in a memory of said first control unit 200. Said values Mu11-Mu44 are empirically determined and stored in a memory of said first control unit 200. Said Mu11-Mu44 can be used according to one aspect of the reducing agent dosing procedure. The first control unit is arranged to control the values of inventive maximum reducing agent dosage on the basis of information from said matrix and prevailing operating conditions, including said exhaust gas mass flow l \ / IF and reference temperature Tref.

According to an embodiment of the present invention, a model-based function is provided for determining for reducing agent dosage depending on exhaust mass flow l1 / IF and an evaporation maximum 21 reference parameters Tref depending on both effective evaporation temperature Tv and reducing agent temperature Tu. Said function can be any suitable function. Said function can be any suitable function.

According to one aspect, a model-based function is provided for determining in real time the maximum reducing agent dosage for evaporation depending on the exhaust gas flow NIF and a reference parameter Tref depending on both the effective evaporation temperature Tv and the reducing agent temperature Tu.

According to an exemplary embodiment, the effective evaporation temperature Tv can be set to the exhaust gas temperature T1 or a temperature T2 of a component in a configuration of an exhaust duct or an SCR catalyst of said SCR system. Figure 3b illustrates reference temperature reference Tu for said reducing agent is shown. schematically a diagram where a graph of a A temperature Tu regarding a temperature of said reducing agent is given in degrees Kelvin. A reference temperature Tref is given in degrees Kelvin, which reference temperature depends on the temperatures T1 and T2. Said reference temperature reference Tu is given in degrees Kelvin. The matrix comprises a lVlu11-lVlu44 reducing agent dosage for a given exhaust gas mass flow MF and a given number of values which indicate values for maximum reference temperature Tref.

In this case, a reference temperature reference Tu can be used, for example 330 Kelvin. operating temperature of said reducing agent and is a desired suitable SCR system reducing agent temperature. In this case, the said constants Kf and K2. Said reference temperature reference Tu can also be called working temperature in said respect can be chosen so that the condition Tv = Tu is fulfilled at the set reference temperature.

In this case, an advantageous connection is achieved Tref = Tv-K1 * Tu + K2. 22 In the event that the reference temperature reference Tu reduces the risk of crystal formation of the reducing agent temperature Tu below the metered reducing agent, but a fuel consumption of the vehicle's engine is increased. In the event that the reducing agent temperature Tu exceeds the reference temperature reference Tu, a fuel consumption of the vehicle's engine is reduced, but the risk of crystal formation of dosed reducing agent is increased.

Figure 4a schematically illustrates a flow chart of a method for selecting maximum reducing agent dosage in an SCR system for exhaust gas purification, where evaporation of a metered amount of reducing agent is sought, according to an embodiment of the invention. The method comprises a first method step s401. Step s401 includes the step of: - selecting the maximum reducing agent dosage on the basis of an exhaust gas mass flow, an effective evaporation temperature as well as a reducing agent temperature.

After step s401, the process is terminated.

Figure 4b schematically illustrates a flow chart of a method for selecting maximum reducing agent dosage in an SCR system for exhaust gas purification, where evaporation of a metered amount of reducing agent is sought, according to an embodiment of the invention.

The method includes a first method step s410. Process step s410 may include the step of continuously determining a rescuing exhaust gas mass flow MF. This can be done by means of the exhaust mass flow sensor 255. Alternatively, a saving exhaust mass flow MF can be calculated in a suitable manner by means of said first control unit 200 or After the process step s410, a subsequent process step s420 is performed. said second control unit 210.

Method step s420 includes the step of continuously determining a salvage This can be done by means of the first temperature sensor 240, which is arranged to determine an exhaust temperature effective evaporation temperature. 23 upstream of the SCF1 catalyst 270. This can alternatively be done by means of the second temperature sensor 260, which is arranged to determine an exhaust gas temperature upstream of the SCF1 catalyst 270. Alternatively, a prevailing effective evaporation temperature can be suitably calculated by means of said first control unit 200 or said second control unit 210. After the process step s420, a subsequent process step s430 is performed.

Process step s430 includes the step of continuously determining a prevailing temperature Tu of said reducing agent. This can be done by means of the third temperature sensor 275. Alternatively, a prevailing temperature Tu of said reducing agent can be calculated in a suitable manner by means of said first control unit 200 or said second control unit 210. After the process step s430, a subsequent process step s440 is performed. maximum The process step s440 the step of reducing agent dosage on the basis of said exhaust gas mass flow l \ / IF, effectively includes selecting the evaporator temperature in addition to a reducing agent temperature Tu. Step s440 may include the step of continuously, intermittently and / or, where appropriate, selecting a maximum reducing agent dosage based on an effective reducing agent temperature. Step s440 may include the step of exhaust gas flow, an evaporation temperature plus a continuous, intermittent and / or where applicable selecting maximum reducing agent dosage based on an exhaust mass flow, an exhaust temperature Tf plus a reducing agent temperature Tu.

Said selection of maximum reducing agent dosage can be made in a suitable manner on the basis of at least said reducing agent temperature Tu.

Said maximum reducing agent dosage can be selected on the basis of an empirically determined reducing agent dosage depending on the exhaust gas mass flow MF and a matrix showing for evaporation a maximum of 24 reference parameters Tref depending on both effective evaporating temperature Tv and reducing agent temperature Tu.

After the process step s440, a subsequent process step s450 is performed.

The process step s45O the step of reducing agent dosing on the basis of said choices. This can be done by said first control unit 200 by means of the process step s45O the process is terminated. includes controlling said dosing unit 250.

Referring to Figure 5, there is shown a diagram of an embodiment of a device 500. The controllers 200 and 210 described with reference to Figure 2 may in one embodiment include the device 500. The device 500 includes a non-volatile memory 520, a data processing unit 510, and a read / write memory 550. The non-volatile memory 520 has a first memory portion 530 in which a computer program, such as an operating system, is stored to control the operation of the device 500. Further, the device 500 includes a bus controller, a serial communication port , I / O means, an A / D converter, a time and date input and transfer unit, an event counter and an interrupt controller (not shown). The non-volatile memory 520 also has a second memory portion 540.

A computer program P is provided which may include routines for selecting a maximum reducing agent dosage in an SCR system for exhaust gas purification, where evaporation of a computer program P may include routines for continuously determining a prevailing exhaust mass flow MF. The computer program P may include routines for continuously determining a prevailing effective evaporation temperature. According to a dosed amount of reducing agent is sought. In that case, said effective evaporation temperature can be set to the prevailing temperature T1 of the exhaust gases from said engine. According to one embodiment, said effective evaporation temperature can be set to the prevailing temperature T2 of a component in a configuration of said exhaust duct 290 and said SCR catalyst 270 of said SCR system. The computer program P may comprise routines for continuously determining a prevailing temperature Tu of said reducing agent. The computer program P may comprise routines for selecting the maximum reducing agent dosage on the basis of said prevailing exhaust gas mass flow MF, said effective evaporating temperature T1 or T2 and said reducing agent temperature Tu. The computer program P may comprise routines for controlling reducing agent dosing by means of said 250 on reducing agent dosing. dosage unit basis of said choice of maximum The program P can be stored in an executable manner or in a compressed manner in a memory 560 and / or in a read / write memory 550.

When it is described that the data processing unit 510 performs a certain function, it should be understood that the data processing unit 510 performs a certain part of the program which is stored in the memory 560, or a certain part of the program which is stored in the read / write memory 550.

The data processing device 510 can communicate with a data port 599 via a data bus 515. The non-volatile memory 520 is intended for communication with the data processing unit 510 via a data bus 512. The separate memory 560 is intended to communicate with the data processing unit 510 via a data bus 511. the data processing unit 510 via a data bus 514. To the data port 599, e.g. the links L210, L230, L240, L250, L255, L260, L265, L275 and L280 and are connected (see Figure 2).

The read / write memory 550 is arranged to communicate with When data is received on the data port 599, it is temporarily stored in the second memory part 540. When the data processing unit 510 is arranged to perform code execution in a manner described above. received input data has been temporarily stored, is 26 According to one embodiment, signals received at the data port 599 include information about the prevailing temperature T1 of the exhaust gases. According to one embodiment, signals received at the data port 599 comprise information about the temperature T2 of a component in a configuration of an exhaust duct and an SCR catalyst of said SCR system. According to one embodiment, signals received at the data port 599 include information about a prevailing exhaust mass flow MF. According to one embodiment, signals received at the data port 599 include information about a prevailing temperature Tu of said reducing agent. The received signals on the data port 599 can be used by the device 500 for exhaust gas mass flow IVF, an effective evaporation temperature Tv and a selecting said reducing agent dosage on the basis of a reducing agent temperature Tu. The received signals on the data port 599 500 for reducing agent dosing on the basis of an exhaust gas mass flow MF, an effective can be used by the device to control said evaporating temperature Tv in addition to a reducing agent temperature Tu. The received signals on the data port 599 may be used by the device 500 to control said reducing agent dosage based on said selected reducing agent dosage. Parts of the methods described herein may be performed by the device 500 by means of the data processing unit 510 running the program stored in the memory 560 or the read / write memory 550. When the device 500 runs the program, the methods described herein are executed.

The foregoing description of the preferred embodiments of the present invention has been provided for the purpose of illustrating and describing the invention. It is not intended to be exhaustive or to limit the invention to the variations described. Obviously, many modifications and variations will occur to those skilled in the art. The embodiments were selected and described to best explain the principles of the invention and its practical applications, thereby enabling those skilled in the art to understand the invention for various embodiments and with the various modifications appropriate to the intended use.

Claims (12)

10 15 20 25 30 27 PATENT REQUIREMENTS Method for selecting maximum reducing agent dosage in an SCR system for exhaust gas purification, where evaporation of a metered amount of reducing agent is sought, characterized by the step of: - selecting (s440) said maximum reducing agent dosage on the basis of an exhaust gas mass flow (MF), an effective evaporation temperature (Tv; T1; T2) together with a reducing agent temperature (Tu). Method according to claim 1, reducing agent dosage is selected on the basis of an established matrix exhibiting according to which said maximum evaporation maximum reducing agent dosage depends on exhaust gas mass flow (MF) and a reference parameter (Tref) depending on both effective evaporating temperature (Tv; T1; reducing agent T2); (Tu). A method according to 2, wherein said reference parameter (Tref) is determined according to a relationship defined by: Tref = TV-K1 * Tu + K2 where: Tv is effective evaporation temperature; Tu is reducing agent temperature; and K1 and K2 are predetermined constants. A process according to any one of the preceding claims, wherein the effective evaporation temperature (T1; T2) is set to the exhaust gas temperature (T1) or a temperature (T2) of a component in a configuration of an exhaust duct (290) and an SCR catalyst (270) in said SCR system. 10 15 20 25 30 28 Device for selecting maximum reducing agent dosing in an SCR system for exhaust gas purification, where narrowing of a dosed amount of reducing agent is sought, characterized by: (200; 210; 500) reducing agent dosing on the basis of an exhaust mass flow (MF), an efficient - means adapted selecting said maximum evaporation temperature (t1; T2) plus a reducing agent temperature (Tu). Device according to claim 5, wherein said maximum reducing agent dosage is selected on the basis of an established matrix exhibiting for evaporation maximum reducing agent dosage depending on exhaust gas mass flow (MF) and a reference parameter (Tref) depending on both effective evaporating temperature (T1; T2) and reducing agent temperature. Tu). Device according to claim 6, wherein said reference parameter is determined according to a relationship defined by: Tref = TV-K1 * Tu + K2 where: Tv is the effective evaporation temperature; Tu is reducing agent temperature; and K1 and K2 are predetermined constants. Device according to claims 5-7, the effective evaporation temperature (T1; T2) is set to the exhaust gas temperature (T1) or any one of which the temperature (T2) of a component in a configuration of an exhaust duct (290 and an SCR catalyst (270) ) in said SCR system. Motor vehicle (100: 110) comprising a device according to any one of claims 5-8. 10 15 29 A motor vehicle (100; 110) according to claim 9, wherein the motor vehicle is something of a truck, bus or passenger car. Computer program (P) selecting the maximum reducing agent dosage in an SCR system for exhaust gas purification, wherein said computer program (P) comprises program code for causing an electronic control unit (200; 500) or another computer (210; 500) connected to the electronic the control unit (200; 500) to perform the steps according to any one of claims 1-4. A computer program product comprising a program code stored on a computer readable medium for performing the method steps according to any one of claims 1-4, when said program code is executed on an electronic control unit (200; 500) or another computer (210; 500) connected to the electronic control unit (200; 500).