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Title:
System and method for diagnosing an emission control arrangement for a combustion engine
Document Type and Number:
WIPO Patent Application WO/2019/059837
Kind Code:
A1
Abstract:
The invention relates to a method for diagnosing an emission control arrangement for a combustion engine (231) in operation, comprising at least a first SCR configuration (260) and a second SCR configuration (270) arranged in a series The method comprises the steps of: -determining (s420) a first degree of NOx content reduction for the first SCR configuration (260); -determining (s425) a second degree of NOx content reduction for the second SCR configuration(270); -determining (s430) a total degree of NOx content reduction for the emission control arrangement on the basis of the thus determined first degree of NOx content reduction and the second degree of NOx content reduction; -comparing (s435) the total degree of NOx content reduction for the emission control arrangement with a predetermined reference degree of NOx content reduction for the emission control arrangement; and -determining (s440) that the emission control arrangement is operating as desired if the total degree of NOx content reduction exceeding the predetermined reference degree of NOx content reduction. The invention relates also to a computer program product comprising program code (P) for a computer (200; 210; 500) for implementing a method according to the invention. The invention relates also to a system for diagnosing an emission control arrangement for a combustion engine in operation, comprising at least a first SCR configuration and a second SCR configuration arranged in a series,and a motor vehicle (100) equipped with the system.

Inventors:
HÄLLEBERG, Roger (Kristinedalsvägen 28, Nacka, 131 46, SE)
LUNDSTRÖM, Mikael (Snickerigatan 10, Hägersten, 126 26, SE)
Application Number:
SE2018/050964
Publication Date:
March 28, 2019
Filing Date:
September 21, 2018
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
SCANIA CV AB (151 87 Södertälje, 151 87, SE)
International Classes:
F01N11/00; F01N3/20
Foreign References:
US20150096287A12015-04-09
US20170051654A12017-02-23
US20150040543A12015-02-12
US20090035194A12009-02-05
DE102017124757A12017-12-28
DE102018110452A12018-07-12
Attorney, Agent or Firm:
GARDEMARK, Niklas (Scania CV AB, Södertälje, 151 87, SE)
Download PDF:
Claims:
Claims

1. A method for diagnosing an emission control arrangement for a combustion engine (231) in operation, the emission control arrangement comprising at least a first SCR configuration (260) and a second SCR configuration (270) arranged in a series, the method comprising the steps of:

- determining (s405) a set of operational parameter values for the emission control arrangement;

- determining and dosing (s410) an amount of reducing agent for the first SCR configuration (260) for obtaining a predetermined NOx content downstream of the first SCR configuration;

- determining and dosing an amount (s415) of reducing agent for the second SCR

configuration (270) for obtaining a predetermined NOx content downstream of the second SCR configuration;

- determining (s420) a first degree of NOx content reduction for the first SCR configuration (260);

- determining (s425) a second degree of NOx content reduction for the second SCR configuration (270);

- determining (s430) a total degree of NOx content reduction for the emission control arrangement on the basis of the thus determined first degree of NOx content reduction and the second degree of NOx content reduction;

- comparing (s435) the total degree of NOx content reduction for the emission control arrangement with a predetermined reference degree of NOx content reduction for the emission control arrangement; and

- determining (s440) that the emission control arrangement is operating as desired if the total degree of NOx content reduction exceeds the predetermined reference degree of NOx content reduction.

2. The method according to claim 1, comprising the steps of:

- comparing (s435) the first degree of NOx content reduction for the first SCR configuration (260) with a predetermined first reference degree of NOx content reduction; and

- determining (s440) that the first SCR configuration (260) is operating as desired if the first degree of NOx content reduction is exceeding the predetermined first reference degree of

NOx content reduction, and if not, generating an error code for the first SCR configuration (260).

3. The method according to claim 1 or 2, comprising the steps of: - comparing (s435) the second degree of NOx content reduction for the second SCR configuration (270) with a predetermined second reference degree of NOx content reduction; and

- determining (s440) that the second SCR configuration (270) is operating as desired if the second degree of NOx content reduction is exceeding the predetermined second reference degree of NOx content reduction, and if not, generating an error code for the second SCR configuration (270).

4. The method according to anyone of claim 1-3, comprising the step of:

- including in the emission control arrangement further SCR configurations in series and applying corresponding degrees of NOx content reduction determinations for the thus extended emission control arrangement, totally and individually.

5. The method according to anyone of claim 1-3, comprising the step of:

- including in the emission control arrangement further SCR configurations in parallel a applying corresponding degrees of NOx content reduction determinations for the thus extended emission control arrangement, totally and individually.

6. A system for diagnosing an emission control arrangement for a combustion engine (231) in operation, the emission control arrangement comprising at least a first SCR configuration (260) and a second SCR configuration (270) arranged in a series, the system comprising: - means (200; 210; 500; 247; 241; 242; 251) arranged for determining a set of operational parameter values for the emission control arrangement;

- means (200; 210; 500; 237a) arranged for determining and dosing an amount of reducing agent for the first SCR configuration (260) for obtaining a predetermined NOx content downstream of the first SCR configuration (260); - means (200; 210; 500; 237b) arranged for determining and dosing an amount of reducing agent for the second SCR configuration (270) for obtaining a predetermined NOx content downstream of the second SCR configuration (270);

- means (200; 210; 500; 251, 252) arranged for determining a first degree of NOx content reduction for the first SCR configuration (260); - means (200; 210; 500; 252, 253) arranged for determining a second degree of NOx content reduction for the second SCR configuration;

- means (200; 210; 500) arranged for determining a total degree of NOx content reduction for the emission control arrangement on the basis of the thus determined first degree of NOx content reduction and the second degree of NOx content reduction; - means (200; 210; 500) arranged for comparing the total degree of NOx content reduction for the emission control arrangement with a predetermined reference degree of NOx content reduction for the emission control arrangement; and

- means (200; 210; 500) arranged for determining that the emission control arrangement is operating as desired if the total degree of NOx content reduction exceeds the predetermined reference degree of NOx content reduction.

7. The system according to claim 6, comprising: - means (200; 210; 500) arranged for comparing the first degree of NOx content reduction for the first SCR configuration (260) with a predetermined first reference degree of NOx content reduction; and

- means (200; 210; 500) arranged for determining that the first SCR configuration (260) is operating as desired if the first degree of NOx content reduction is exceeding the

predetermined first reference degree of NOx content reduction, and if not, generating an error code for the first SCR configuration (260).

8. The system according to claim 6 or 7, comprising: - means (200; 210; 500) arranged for comparing the second degree of NOx content reduction for the second SCR configuration (270) with a predetermined second reference degree of NOx content reduction; and

- means (200; 210; 500) arranged for determining that the second SCR configuration (270) is operating as desired if the second degree of NOx content reduction is exceeding the predetermined second reference degree of NOx content reduction, and if not, generating an error code for the second SCR configuration (270).

9. The system according to anyone of claims 6-8, comprising:

- further SCR configurations in series; and - means (200; 210; 500) for applying corresponding degrees of NOx content reduction determinations for the thus extended emission control arrangement, totally and individually.

10. The system according to anyone of claims 6-8, comprising:

- further SCR configurations in parallel; and - means (200; 210; 500) for applying corresponding degrees of NOx content reduction determinations for the thus extended emission control arrangement, totally and individually.

11. A vehicle (100; 110) comprising a system according to anyone of claims 6-10.

12. The vehicle (100; 110) according to claim 11, which vehicle is any from among a truck, bus or passenger car.

13. A computer program (P) for diagnosing an emission control arrangement for a combustion engine in operation, the emission control arrangement comprising at least a first SCR configuration (260) and a second SCR configuration (270) arranged in a series, wherein the computer program (P) comprises program code for causing an electronic control unit (200; 500) or a computer (210; 500) connected to the electronic control unit (200; 500) to perform the steps according to anyone of the claims 1-5.

14. A computer program product containing a program code stored on a computer-readable medium for performing method steps according to anyone of claims 1-5, when the computer program is run on an electronic control unit (200; 500) or a computer (210; 500) connected to the electronic control unit (200; 500).

15. A method for diagnosing an emission control arrangement for a combustion engine (231) in operation, the emission control arrangement comprising at least a first SCR configuration

(260) and a second SCR configuration (270) arranged in a series, the method comprising the steps of:

- determining (s420) a first degree of NOx content reduction for the first SCR configuration (260); - determining (s425) a second degree of NOx content reduction for the second SCR configuration (270);

- determining (s430) a total degree of NOx content reduction for the emission control arrangement on the basis of the thus determined first degree of NOx content reduction and the second degree of NOx content reduction; - comparing (s435) the total degree of NOx content reduction for the emission control arrangement with a predetermined reference degree of NOx content reduction for the emission control arrangement; and

- determining (s440) that the emission control arrangement is operating as desired if the total degree of NOx content reduction exceeding the predetermined reference degree of

NOx content reduction.

Description:
System and method for diagnosing an emission control arrangement for a combustion engine

TECHN ICAL FI ELD The present invention relates to a method for diagnosing an emission control arrangement for a combustion engine in operation. The invention relates also to a computer program product comprising program code for a computer for implementing a method according to the invention. It relates also to a system for diagnosing an emission control arrangement for a combustion engine in operation and a motor vehicle equipped with the system.

BACKGROUND ART

Vehicle combustion engine emission control systems are today arranged with catalytic configurations e.g. for conversion of NO x gas. The emission control systems may comprise a DOC-unit (Diesel Oxidation Catalyst), DPF-unit (Diesel Particulate Filter), SCR-unit (Selective Catalytic Reduction) and an ammonia slip catalyst. I n such a system a reducing agent is provided for reducing a prevailing NO x -content of an exhaust gas of the engine.

It is required to determine a total degree of NO x content reduction for emission control system comprising SCR-units. I n a case where the emission control system comprises two or more SCR units arranged in series it is common to determine the total degree of NO x content reduction by on the basis of a measured NO x content of an engine exhaust gas downstream the engine and a measured NO x content in a tail pipe downstream the SCR units. This method works satisfactory today, but as national/regional laws, regulations and directives continuously increases the demands for lowering exhaust gas NO x content from e.g. heavy vehicles there is a need for improving existing methods for determining total degree of NO x content reduction for emission control system comprising SCR-units.

US 2014/0106460 Al relates to a method for controlling and/or diagnosing an emission control system of a vehicle having a first SCR region upstream of a second SCR region. US 2017/0051654 Al discloses an apparatus comprising a nitrogen oxide module structured to determine a NOx conversion efficiency fault based on the amount of NOx exiting the engine and the amount of NOx exiting the exhaust aftertreatment system, and a SCR diagnostic module structured to determine which one of a DFP-SCR and a SCR that is responsible for the efficiency fault.

SUMMARY OF THE I NVENTION

An object of the present invention is to propose a novel and advantageous method for diagnosing an emission control arrangement for a combustion engine in operation.

Another object of the invention is to propose a novel and advantageous system and a novel and advantageous computer program for diagnosing an emission control arrangement for a combustion engine in operation. Another object of the present invention is to propose a novel and advantageous method providing a cost effective and reliable diagnosing of an emission control arrangement for a combustion engine in operation.

Another object of the invention is to propose a novel and advantageous system and a novel and advantageous computer program providing a cost effective and reliable diagnosing functionality of an emission control arrangement for a combustion engine in operation.

Yet another object of the invention is to propose a method, a system and a computer program achieving a robust, accurate and automated diagnosing functionality of an emission control arrangement for a combustion engine in operation.

Yet another object of the invention is to propose an alternative method, an alternative system and an alternative computer program for diagnosing an emission control arrangement for a combustion engine in operation. Some of these objects are achieved with a method according to claim 1. Other objects are achieved with a system in accordance with what is depicted herein. Advantageous embodiments are depicted in the dependent claims. Substantially the same advantages of method steps of the innovative method hold true for corresponding means of the innovative system.

According to an aspect of the invention there is provided a method for diagnosing an emission control arrangement for a combustion engine in operation, the emission control arrangement comprising at least a first SCR configuration and a second SCR configuration arranged in a series, the method comprising the steps of:

- determining a set of operational parameter values for the emission control arrangement;

- determining and dosing an amount of reducing agent for the first SCR configuration for obtaining a predetermined NO x content downstream of the first SCR configuration;

- determining and dosing an amount of reducing agent for the second SCR configuration for obtaining a predetermined NO x content downstream of the second SCR configuration;

- determining a first degree of NO x content reduction for the first SCR configuration;

- determining a second degree of NO x content reduction for the second SCR configuration;

- determining a total degree of NO x content reduction for the emission control arrangement on the basis of the thus determined first degree of NO x content reduction and the second degree of NO x content reduction;

- comparing the total degree of NO x content reduction for the emission control arrangement with a predetermined reference degree of NO x content reduction for the emission control arrangement; and

- determining that the emission control arrangement is operating as desired if the total degree of NO x content reduction exceeds the predetermined reference degree of NO x content reduction. In case it is determined that the emission control arrangement is not operating as desired, the method may further comprise generating an error message for the emission control arrangement.

The first SCR configuration is arranged upstream of the second SCR configuration. In the step of determining and dosing an amount of reducing agent for the first SCR configuration for obtaining a predetermined NO x content downstream of the first SCR configuration, the predetermined NO x content downstream of the first SCR configuration may be upstream the second SCR configuration.

Determining an amount of reducing agent for the first SCR configuration for obtaining a predetermined NO x content downstream of the first SCR configuration may be performed on the basis of one or more of the parameter values of the of operational parameter values. Likewise, determining an amount of reducing agent for the second SCR configuration for obtaining a predetermined NO x content downstream of the second SCR configuration may be performed on the basis of one or more of the parameter values of the of operational parameter values.

The set of operational parameter values may comprise a prevailing exhaust gas mass flow from the combustion engine. The set of operational parameter values may comprise a prevailing temperature of the first SCR configuration. The set of operational parameter values may comprise a prevailing temperature of the second SCR configuration. The set of operational parameter values may comprise a prevailing NO x content downstream of the combustion engine and upstream of the first SCR configuration. The set of operational parameter values may comprise the above specified examples of parameters in any combination.

The predetermined NO x content downstream of the first SCR configuration may be selected or determined on the basis of a prevailing NO x content downstream of the combustion engine and upstream of the first SCR configuration.

The predetermined NO x content downstream of the second SCR configuration may be selected or determined on the basis of a prevailing NO x content downstream of the first SCR configuration and upstream of the second SCR configuration. The total degree of NO x content reduction for the emission control arrangement is determined on the basis of the thus determined first degree of NO x content reduction and the second degree of NO x content reduction and not only on the basis of a prevailing NO x content upstream of the first SCR configuration and a prevailing NO x content downstream of the second SCR configuration. This inter alia has the advantage of reducing the risk for errors in the determined total degree of NO x content reduction and therefore increases the accuracy in diagnosis of the emission control arrangement.

The predetermined reference degree of NO x content reduction may be determined according to prevailing national/regional laws/regulations/directives. The predetermined reference degree of NO x content reduction may be e.g. 75%, 80%, 85%, 90%, 95%, 97%, 98% or 99%.

Hereby a reliable and accurate method is achieved according to an embodiment of the invention.

The method may further comprise the steps of: - comparing the first degree of NO x content reduction for the first SCR configuration with a predetermined first reference degree of NO x content reduction; and

- determining that the first SCR configuration is operating as desired if the first degree of NO x content reduction is exceeding the predetermined first reference degree of NO x content reduction, and if not, generating an error code for the first SCR configuration. Hereby it is advantageously achieved an accurate and reliable way of diagnosing the first SCR configuration.

The predetermined first reference degree of NO x content reduction may be e.g. 75%, 80%, 85%, 90%, 95%, 97%, 98% or 99%.

The method may further comprise the steps of:

- comparing the second degree of NO x content reduction for the second SCR configuration with a predetermined second reference degree of NO x content reduction; and - determining that the second SCR configuration is operating as desired if the second degree of NOx content reduction is exceeding the predetermined second reference degree of NO x content reduction, and if not, generating an error code for the second SCR configuration.

Hereby it is advantageously achieved an accurate and reliable way of diagnosing the first SCR configuration.

The predetermined second reference degree of NO x content reduction may be e.g. 75%, 80%, 85%, 90%, 95%, 97%, 98% or 99%.

The method may comprise the step of: - including in the emission control arrangement further SCR configurations in series and applying corresponding degrees of NO x content reduction determinations for the thus extended emission control arrangement, totally and individually.

Hereby a versatile method is achieved. The inventive method is applicable to emission control arrangement having a plurality of SCR configurations. The method may comprise the step of:

- including in the emission control arrangement further SCR configurations in parallel and applying corresponding degrees of NO x content reduction determinations for the thus extended emission control arrangement, totally and individually.

Hereby a versatile method is achieved. The inventive method is applicable to emission control arrangement having a plurality of SCR configurations.

According to an aspect of the invention there is provided a system for diagnosing an emission control arrangement for a combustion engine in operation, the emission control arrangement comprising at least a first SCR configuration and a second SCR configuration arranged in a series, the system comprising: - means arranged for determining a set of operational parameter values for the emission control arrangement;

- means arranged for determining and dosing an amount of reducing agent for the first SCR configuration for obtaining a predetermined NO x content downstream of the first SCR configuration;

- means arranged for determining and dosing an amount of reducing agent for the second SCR configuration for obtaining a predetermined NO x content downstream of the second SCR configuration;

- means arranged for determining a first degree of NO x content reduction for the first SCR configuration;

- means arranged for determining a second degree of NO x content reduction for the second SCR configuration;

- means arranged for determining a total degree of NO x content reduction for the emission control arrangement on the basis of the thus determined first degree of NO x content reduction and the second degree of NO x content reduction;

- means arranged for comparing the total degree of NO x content reduction for the emission control arrangement with a predetermined reference degree of NO x content reduction for the emission control arrangement; and

- means arranged for determining that the emission control arrangement is operating as desired if the total degree of NO x content reduction exceeds the predetermined reference degree of NO x content reduction.

The system may comprise:

- means arranged for comparing the first degree of NO x content reduction for the first SCR configuration with a predetermined first reference degree of NO x content reduction; and - means arranged for determining that the first SCR configuration is operating as desired if the first degree of NO x content reduction is exceeding the predetermined first reference degree of NO x content reduction, and if not, generating an error code for the first SCR configuration.

The system may comprise:

- means arranged for comparing the second degree of NO x content reduction for the second SCR configuration with a predetermined second reference degree of NO x content reduction; and

- means arranged for determining that the second SCR configuration is operating as desired if the second degree of NO x content reduction is exceeding the predetermined second reference degree of NO x content reduction, and if not, generating an error code for the second SCR configuration.

The system may comprise:

- further SCR configurations in series; and

- means for applying corresponding degrees of NO x content reduction determinations for the thus extended emission control arrangement, totally and individually. The system may comprise:

- further SCR configurations in parallel; and

- means for applying corresponding degrees of NO x content reduction determinations for the thus extended emission control arrangement, totally and individually.

According to an aspect of the invention there is provided a vehicle comprising a system according to what is presented herein. The vehicle may be any from among a truck, bus or passenger car. According to an embodiment the system is provided for a marine application or industrial application.

According to an aspect of the invention there is provided a computer program for diagnosing an emission control arrangement for a combustion engine in operation, the emission control arrangement comprising at least a first SCR configuration and a second SCR configuration arranged in a series, wherein the computer program comprises program code for causing an electronic control unit or a computer connected to the electronic control unit to perform anyone of the method steps depicted herein, when run on the electronic control unit or the computer.

According to an aspect of the invention there is provided a computer program for diagnosing an emission control arrangement for a combustion engine in operation, the emission control arrangement comprising at least a first SCR configuration and a second SCR configuration arranged in a series, wherein the computer program comprises program code stored on a computer-readable medium for causing an electronic control unit or a computer connected to the electronic control unit to perform anyone of the method steps depicted herein.

According to an aspect of the invention there is provided a computer program for diagnosing an emission control arrangement for a combustion engine in operation, the emission control arrangement comprising at least a first SCR configuration and a second SCR configuration arranged in a series, wherein the computer program comprises program code stored on a computer-readable medium for causing an electronic control unit or a computer connected to the electronic control unit to perform anyone of the method steps depicted herein, when run on the electronic control unit or the computer.

According to an aspect of the invention there is provided a computer program product containing a program code stored on a computer-readable medium for performing anyone of the method steps depicted herein, when the computer program is run on an electronic control unit or a computer connected to the electronic control unit.

According to an aspect of the invention there is provided a computer program product containing a program code stored non-volatile on a computer-readable medium for performing anyone of the method steps depicted herein, when the computer program is run on an electronic control unit or a computer connected to the electronic control unit. According to an aspect of the invention there is provided a method for diagnosing an emission control arrangement for a combustion engine in operation, the emission control arrangement comprising at least a first SCR configuration and a second SCR configuration arranged in a series, the method comprising the steps of: - determining a first degree of NO x content reduction for the first SCR configuration;

- determining a second degree of NO x content reduction for the second SCR configuration;

- determining a total degree of NO x content reduction for the emission control arrangement on the basis of the thus determined first degree of NO x content reduction and the second degree of NO x content reduction; - comparing the total degree of NO x content reduction for the emission control arrangement with a predetermined reference degree of NO x content reduction for the emission control arrangement; and

- determining that the emission control arrangement is operating as desired if the total degree of NO x content reduction exceeding the predetermined reference degree of NO x content reduction.

According to an aspect of the invention there is provided a system for diagnosing an emission control arrangement for a combustion engine in operation, the emission control arrangement comprising at least a first SCR configuration and a second SCR configuration arranged in a series, the system comprising:

- means arranged for determining a first degree of NO x content reduction for the first SCR configuration;

- means arranged for determining a second degree of NO x content reduction for the second SCR configuration; - means arranged for determining a total degree of NO x content reduction for the emission control arrangement on the basis of the thus determined first degree of NO x content reduction and the second degree of NO x content reduction; - means arranged for comparing the total degree of NO x content reduction for the emission control arrangement with a predetermined reference degree of NO x content reduction for the emission control arrangement; and

- means arranged for determining that the emission control arrangement is operating as desired if the total degree of NO x content reduction exceeding the predetermined reference degree of NO x content reduction.

Further objects, advantages and novel features of the present invention will become apparent to one skilled in the art from the following details, and also by putting the invention into practice. Whereas the invention is described below, it should be noted that it is not confined to the specific details described. One skilled in the art having access to the teachings herein will recognise further applications, modifications and incorporations in other fields, which are within the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For fuller understanding of the present invention and its further objects and advantages, the detailed description set out below should be read in conjunction with the accompanying drawings, in which the same reference notations denote similar items in the various diagrams, and in which:

Figure 1 schematically illustrates a vehicle according to an embodiment of the invention; Figure 2a schematically illustrates a system according to an embodiment of the invention; Figure 2b schematically illustrates a system according to an embodiment of the invention; Figure 2c schematically illustrates a system according to an embodiment of the invention; Figure 2d schematically illustrates a system according to an embodiment of the invention; Figure 2e schematically illustrates a system according to an embodiment of the invention; Figure 2f schematically illustrates a system according to an embodiment of the invention; Figure 3 schematically illustrates a diagram according to an aspect of the invention; Figure 4a is a schematic flowchart of a method according to an embodiment of the invention;

Figure 4b is a schematic function diagram 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

Figure 1 depicts a side view of a vehicle 100. The exemplified vehicle 100 comprises a tractor unit 110 and a trailer 112. The vehicle 100 may be a heavy vehicle, e.g. a truck or a bus. It may alternatively be a car.

The inventive method and system are applicable to various vehicles, such as e.g. a mining machine, tractor, dumper, wheel-loader, platform comprising an industrial robot, forest machine, earth mover, road construction vehicle, road planner, emergency vehicle or a tracked vehicle.

The inventive method and system are applicable to various reducing agent dosing systems comprising at least two SCR units being arranged in series.

The invention is suitable for application in various systems comprising a combustion engine and an associated emission control arrangement comprising a reducing agent dosing system having at least two SCR units arranged in series. The invention is suitable for application in various systems comprising a combustion engine and a catalytic configuration having at least two SCR units being arranged in series. The catalytic configuration may comprise at least one reducing agent dosing unit, each dosing unit being arranged for providing a reducing agent upstream of a corresponding SCR unit. The catalytic configuration may comprise one or more DOC units. The catalytic configuration may comprise one or more DPF units. It should be noted that the invention is applicable to various catalytic configurations and is therefore not confined to catalytic configurations for motor vehicles. The innovative method and the innovative system according to one aspect of the invention are well suited to other platforms which comprise a combustion engine and a catalytic configuration having at least two SCR units arranged in series than motor vehicles, e.g. watercraft. The watercraft may be of any kind, e.g. motorboats, steamers, ferries or ships.

The innovative method and the innovative system according to one aspect of the invention are also well suited to, for example, systems which comprise industrial combustion engines and/or combustion engine-powered industrial robots and an associated emission control arrangement comprising at least two SCR units being arranged in series.

The innovative method and the innovative system according to one aspect of the invention are also well suited to various kinds of power plants, e.g. an electric power plant which comprises a combustion engine-powered generator and an associated emission control arrangement comprising at least two SCR units arranged in series.

The innovative method and the innovative system are also well suited to various combustion engine systems comprising an associated emission control arrangement having at least two SCR units arranged in series.

The innovative method and the innovative arrangement are well suited to any engine system which comprises an engine, e.g. on a locomotive or some other platform, and an associated emission control arrangement having at least two SCR units arranged in series.

The innovative method and the innovative system are well suited to any system which comprises a NO x -generator and an associated emission control arrangement having at least two SCR units arranged in series.

The term "link" refers herein to a communication link which may be a physical connection such as an opto-electronic communication line, or a non-physical connection such as a wireless connection, e.g. a radio link or microwave link. The term "line" refers herein to a passage for holding and conveying a fluid, e.g. a reducing agent in liquid form or fuel. The line may be a pipe of any size and be made of any suitable material, e.g. plastic, rubber or metal. The term "reductant" or "reducing agent" refers herein to an agent used for reacting with certain emissions in an SCR system. These emissions may for example be NO x -gas. The terms "reductant" and "reducing agent" are herein used synonymously. In one version, the reductant is a urea-containing solution, such as so-called AdBlue. Other kinds of reductants may of course be used. AdBlue is herein cited as an example of a reductant, but one skilled in the art will appreciate that the innovative method and the innovative system are feasible with other types of reductants.

The terms "SCR unit" and "SCR configuration" are herein used synonymously. The SCR unit/SCR configuration may also be referred to as "reduction catalyst device". The SCR units of the emission control arrangement may be any suitable SCR units. According to one example the SCR unit may comprise an SCRF unit, comprising a coated filter. The SCR unit may according to other examples provide a combination of SCR functionality and at least one additional functionality (other than NO x conversion), such as SCR functionality and DOC functionality, SCR functionality and ammonia slip catalyst functionality, etc. The SCR unit may comprise ceramic materials used as a carrier, such as titanium oxide, and active catalytic components which usually are oxides of base metals, such as vanadium, molybdenum and tungsten.

Figure 2a schematically illustrates a system 291 according to an example embodiment of the invention. The system 291 is situated in the tractor unit 110 and may be part of an emission control arrangement. The emission control arrangement may alternatively be denoted exhaust gas processing configuration. It comprises in this example a tank 205 arranged to hold a reductant. The tank 205 is adapted to holding a suitable amount of reductant and also to being replenishable as necessary. The tank 205 may be adapted to hold e.g. 75 or 50 litres of reductant. A first line 271 is provided to lead the reductant to a pump 230 from the tank 205. The pump 230 may be any suitable pump. The pump 230 may be arranged to be driven by an electric motor (not depicted). The pump 230 may be adapted to drawing the reductant from the tank 205 via the first line 271 and supplying it via a second line 272 to a first dosing unit 237a and a second dosing unit 237b. A valve unit 221 is arranged downstream the second dosing unit 237b. The reductant is pressurized downstream the pump 230 and upstream the valve unit 221. Thus the reductant is provided under pressure to the first dosing unit 237a and the second dosing unit 237b. The first dosing unit 237a and the second dosing unit 237b may also be referred to as a reducing agent dosing unit. Each of the dosing units 237a and 237b comprises an electrically controlled dosing valve by means of which a flow of reductant added to the exhaust system can be controlled. The pump 230 is adapted to pressurising the reductant in the second line 272. The pressure of the reductant is built up in the system 291 by the valve unit 221. Operation of the valve unit 221 may be controlled by a first control unit 200.

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 send control signals S230 via the link L230. The first control unit 200 is arranged to control operation of the pump 230 so as to for example adjust flows of the reducing agent within the system 299. The first control unit 200 is arranged to control an operation power of the pump 230 e.g. by controlling the electric motor.

The dosing units 237a and 237b are adapted to supplying the reductant to an exhaust system (see Fig. 2b) of the vehicle 100. More specifically, they are adapted to supplying a suitable amount of reductant in a controlled way to an exhaust system of the vehicle 100. In this version, two SCR units (see Fig. 2b and Fig. 2c) are situated downstream of the respective locations in the exhaust system where the supply of reductant takes place.

A third line 273 running between the throttle unit 221 and the tank 205 is adapted to leading back to the tank 205 a certain amount of the reductant fed to the dosing units 237a and 237b. This configuration results in advantageous cooling of the dosing units 237a and 237b. The dosing units 237 and 237b are thus cooled by a flow of the reductant when it is pumped through them from the pump 230 to the container 205.

The first control unit 200 is arranged for communication with the first dosing unit 237a via a link L237a. The first control unit 200 is arranged to send control signals S237a via the link L237a. The first control unit 200 is arranged to control operation of the first dosing unit 237a so as to for example control dosing of the reducing agent to the exhaust gas system of the vehicle 100. The first control unit 200 is arranged for communication with the second dosing unit 237b via a link L237b. The first control unit 200 is arranged to send control signals S237b via the link L237b. The first control unit 200 is arranged to control operation of the first dosing unit 237b so as to for example control dosing of the reducing agent to the exhaust gas system of the vehicle 100.

The first control unit 200 is arranged to control operation of the first dosing unit 237a and second dosing unit 237b independently.

A second control unit 210 is arranged for communication with the first control unit 200 via a link L210. It may be releasably connected to the first control unit 200. It may be a control unit external to the vehicle 100. It may be adapted to one or more steps of the method disclosed herein. It may be used to cross-load software to the first control unit 200, particularly software for applying the innovative method. It may alternatively be arranged for communication with the first control unit 200 via an internal network on board the vehicle 100. It may be adapted to performing functions corresponding to those of the first control unit 200, such as e.g. diagnosing an emission control arrangement for a combustion engine in operation, comprising at least a first SCR configuration and a second SCR configuration arranged in a series.

Figure 2b schematically illustrates a system 292 of the vehicle shown i Figure 1 according to an embodiment of the invention. The system 292 may constitute a part of the inventive system for diagnosing an emission control arrangement for an internal combustion engine 231 in operation, comprising at least a first SCR configuration and a second SCR

configuration arranged in a series.

The internal combustion engine 231 is during operation causing an exhaust gas flow which is lead via a first passage 255 to a first SCR-unit 260. A second passage 255 is arranged to convey the exhaust gas flow from the first SCR-unit 260 to second SCR unit 270. A third passage 275 is arranged to convey the exhaust gas flow from the second SCR unit 270 to an environment of the emission control arrangement. It should be noted that the first SCR-unit 260 and the second SCR unit 270 are arranged in series. The emission control arrangement may further comprise one or more DOC-units (not shown). The emission control

arrangement may further comprise one or more ammonia slip catalysts (not shown). The emission control arrangement may further comprise one or more DOC units (not shown). The first dosing unit 237a is arranged to provide the reductant to the first passage 255 upstream of the first SCR-unit 260 and downstream of the engine 231. The first dosing unit 237a is arranged to provide the reductant for use of the first SCR-unit 260. The first control unit 200 is arranged to control operation of the first dosing unit 237a so as to, where applicable, dose reducing agent into the first passage 255.

The second dosing unit 237b is arranged to provide the reductant to the second passage 265 upstream of the second SCR-unit 270 and downstream of the first SCR unit 260. The second dosing unit 237b is arranged to provide the reductant for use of the second SCR-unit 270.The first control unit 200 is arranged to control operation of the second dosing unit 237b so as to, where applicable, dose reducing agent upstream the second SCR-unit 270.

In a case where more than two SCR-units are arranged in series in the emission control arrangement a respective dosing unit is arranged upstream of each of the additional SCR units. The first control unit 200 is arranged to perform the process steps depicted herein, comprising the process steps which are detailed with reference to Figure 4b.

Figure 2c schematically illustrates a system 293 of the vehicle shown i Figure 1 according to an embodiment of the invention. The system 299 may constitute a part of the inventive system for diagnosing an emission control arrangement for a combustion engine in operation, comprising at least a first SCR configuration and a second SCR configuration arranged in a series.

An exhaust gas mass flow sensor 247 is arranged for determining a prevailing exhaust gas mass flow MF in the first passage 255. The exhaust gas mass flow sensor 247 is arranged for communication with the first control unit 200 via a link L247. The exhaust gas mass flow sensor 247 is arranged to send signals S247 comprising information about the prevailing exhaust gas mass flow MF to the first control unit 200 via the link L247.

According to one embodiment the first control unit 200 is arranged to determine a prevailing exhaust gas mass flow MF by means of a model. Hereby e.g. a prevailing engine and engine load may be used by the model so as to determine a prevailing exhaust gas mass flow MF. The first control unit 200 is according to this embodiment arranged to

calculate/model/estimate/determine a prevailing exhaust gas mass flow MF without information from an exhaust gas mass flow sensor, such as the sensor 247.

A first temperature sensor 241 is arranged for communication with the first control unit 200 via a link L241. The first temperature sensor 241 is arranged to measure a prevailing first temperature Tl of the exhaust gas flowing in the first passage 255, upstream of the first SCR unit 260 and downstream of the engine 231. The first temperature sensor 241 is arranged to continuously or intermittently send signals S241 comprising information about the determined prevailing first temperature Tl to the first control unit 200 via the link L241. The first control unit 200 is according to one embodiment arranged to determine a prevailing temperature of the first SCR unit 260 on the basis of the detected first temperature Tl. The first control unit 200 is according to this embodiment arranged to

calculate/model/estimate/determine a prevailing temperature of the first SCR unit 260.

A second temperature sensor 242 is arranged for communication with the first control unit 200 via a link L242. The first temperature sensor 242 is arranged to measure a prevailing second temperature T2 of the exhaust gas flowing in the second passage 265, upstream of the second SCR unit 270 and downstream of the first SCR unit 260. The second temperature sensor 242 is arranged to continuously or intermittently send signals S242 comprising information about the determined prevailing second temperature T2 to the first control unit 200 via the link L242. The first control unit 200 is according to one embodiment arranged to determine a prevailing temperature of the second SCR unit 270 on the basis of the detected second temperature T2. The first control unit 200 is according to this embodiment arranged to calculate/model/estimate/determine a prevailing temperature of the second SCR unit 270.

A first NOx sensor 251 is arranged for communication with the first control unit 200 via a link L251. The first NO x sensor 251 is arranged to measure a prevailing NO x value NO x I N of the exhaust gas flowing in the first passage 255, upstream of the first SCR unit 260 and downstream of the engine 231. The first NO x sensor 251 is arranged to continuously or intermittently send signals S251 comprising information about the determined prevailing NOx value NO x I N to the first control unit 200 via the link L251.

The first control unit 200 is according to one embodiment arranged to determine the prevailing NO x value NO x I N by means of a model. Hereby e.g. a prevailing engine and engine load may be used by the model so as to determine a prevailing NO x value NO x I N. The first control unit 200 is according to this embodiment arranged to

calculate/model/estimate/determine a prevailing NO x value NO x I N without information from the first NO x sensor 251. The first control unit 200 is according to this embodiment arranged to calculate/model/estimate/determine a prevailing NO x value NO x I N in the first passage 255. A second NO x sensor 252 is arranged for communication with the first control unit 200 via a link L252. The second NO x sensor 252 is arranged to measure a prevailing NO x value NO x l of the exhaust gas flowing in the second passage 265, upstream of the second SCR unit 270 and downstream of first SCR unit 260. The second NO x sensor 252 is arranged to continuously or intermittently send signals S252 comprising information about the determined prevailing NO x value NO x l to the first control unit 200 via the link L252.

A third NO x sensor 253 is arranged for communication with the first control unit 200 via a link L253. The third NO x sensor 253 is arranged to measure a prevailing NO x value NO x 2 of the exhaust gas flowing in the third passage 275 downstream of second SCR unit 270. The third NO x sensor 253 is arranged to continuously or intermittently send signals S253 comprising information about the determined prevailing NO x value NO x 2 to the first control unit 200 via the link L253. It may be noted that NO x sensors previously known in the art, and which may be used in the emission control arrangement as disclosed herein, often have a possible measurement error which is dependent of the value to be measured. Such a possible measurement error may for example be ±10% of the value to be measured.

The first control unit 200 is arranged to determine a set of operational parameter values for the emission control arrangement. The set of operational parameters values are given by the determined exhaust gas mass flow MF, the temperature of the first SCR-unit 260, the temperature of the second SCR unit 270 and the NO x value NO x IN.

The first control unit 200 is arranged to determine an amount of reducing agent for the first SCR unit 260 for obtaining a predetermined NO x content downstream of the first SCR unit 260. The first control unit 200 is arranged to determine an amount of reducing agent for the first SCR unit 260 on the basis of the determined set of operational parameter values The first control unit 200 is arranged for dosing reducing agent by means of the first dosing unit 237a for achieving the predetermined NO x content downstream the first SCR unit 260. The first control unit 200 is arranged to determine an amount of reducing agent for the second SCR unit 270 for obtaining a predetermined NO x content downstream of the second SCR unit 270. The first control unit 200 is arranged to determine an amount of reducing agent for the second SCR unit 270 on the basis of the determined set of operational parameter values The first control unit 200 is arranged for dosing reducing agent by means of the second dosing unit 237b for achieving the predetermined NO x content downstream the second SCR unit 270.

The first control unit 200 is arranged to determine a first degree of NO x content reduction for the first SCR unit 260. The first control unit 200 is arranged to determine the first degree of NOx content reduction for the first SCR unit 260 on the basis of the NO x value NO x IN in the first passage 255 and the NO x value NO x l of the exhaust gas flowing in the second passage 265. Hereby the first degree of NO x content reduction is determined over only the first SCR unit 260.

The first control unit 200 is arranged to determine a second degree of NO x content reduction for the second SCR unit 270. The first control unit 200 is arranged to determine the second degree of NO x content reduction for the second SCR unit 270 on the basis of the NO x value NO x l in the second passage 265 and the NO x value NO x 2 of the exhaust gas flowing in the third passage 275. Hereby the second degree of NO x content reduction is determined over only the second SCR unit 270. The first control unit 200 is arranged to determine a total degree of NO x content reduction for the emission control arrangement on the basis of the thus determined first degree of NO x content reduction and the second degree of NO x content reduction. If for example the first degree of NO x content reduction is 90% and the second degree of NO x content reduction is 90%, the total degree of NO x content reduction for the emission control arrangement is 99%, i.e. 100(l-(l-0.90)(l-0.90))=99%.

The first control unit 200 is arranged to compare the total degree of NO x content reduction for the emission control arrangement with a predetermined reference degree of NO x content reduction for the emission control arrangement. The predetermined reference degree of NO x content reduction may be predetermined observing engine emission regulations or engine emission laws. The predetermined reference degree of NO x content reduction value may be stored in a memory of the first control unit 200.

The first control unit 200 is arranged to determine that the emission control arrangement is operating as desired if the total degree of NO x content reduction is exceeding the

predetermined reference degree of NO x content reduction. If the degree of NO x content reduction is exceeding the predetermined reference degree of NO x content reduction emission control is functioning as desired and in accordance with laws and regulations.

Hereby it is determined that the emission control arrangement is operating as desired even if any of the first SCR unit 260 and the second SCR unit is not operating as desired, given that the total degree of NO x content reduction is exceeding the predetermined reference degree of NO x content reduction.

According to an embodiment the first control unit 200 is arranged to compare the first degree of NO x content reduction for the first SCR unit 260 with a predetermined first reference degree of NO x content reduction. Hereby the first control unit 200 is further arranged to determine that the first SCR unit 260 is operating as desired if the first degree of NO x content reduction is exceeding the predetermined first reference degree of NO x content reduction. The first control unit 200 is arranged to generate an error code for the first SCR unit 260 if the first degree of NO x content reduction is not exceeding the predetermined first reference degree of NO x content reduction. The predetermined first reference degree of NO x content reduction value may be stored in a memory of the first control unit 200.

According to an embodiment the first control unit 200 is arranged to compare the second degree of NO x content reduction for the second SCR configuration with a predetermined second reference degree of NO x content reduction Hereby the first control unit 200 is further arranged to determine that the second SCR unit 270 is operating as desired if the second degree of NO x content reduction is exceeding the predetermined second reference degree of NO x content reduction. The first control unit 200 is arranged to generate an error code for the second SCR unit 270 if the second degree of NO x content reduction is not exceeding the predetermined second reference degree of NO x content reduction. The predetermined second reference degree of NO x content reduction value may be stored in a memory of the first control unit 200.

According to one embodiment more than two SCR configurations (units) are arranged in series (see e.g. Fig. 2d-f) in the emission control arrangement. Hereby the first control unit 200 is arranged to apply corresponding degrees of NO x content reduction determinations for the thus extended emission control arrangement, totally and individually. Hereby the first control unit 200 is arranged to determine degrees of NO x content reduction for each of the SCR units arranged in series in the emission control arrangement. The first control unit 200 is arranged to determine a total degree of NO x content reduction for the emission control arrangement on the basis of the thus determined NO x content reductions corresponding to each of the SCR units.

According to one embodiment more than two SCR configurations (units) are arranged in series (see e.g. Fig. 2e-f) in the emission control arrangement as well as at least one SCR unit in parallel. Hereby the first control unit 200 is arranged to apply corresponding degrees of NO x content reduction determinations for the thus extended emission control arrangement, totally and individually. Hereby the first control unit 200 is arranged to determine degrees of NO x content reduction for each of the SCR units arranged in series and parallel in the emission control arrangement in a suitable way. The first control unit 200 is arranged to determine a total degree of NO x content reduction for the emission control arrangement on the basis of the thus determined NO x content reductions corresponding to each of the SCR units. The inventive method is thus applicable to various emission control arrangements having multiple SCR units. The first control unit 200 is arranged to determine a degree of NO x content reduction for each of the SCR units of the emission control arrangement, determine a total degree of NO x content reduction and to compare the total degree of NO x content reduction with a predetermined reference degree of NO x content reduction and to determine that the emission control arrangement is operating as desired if the total degree of NO x content reduction exceeding the predetermined reference degree of NO x content reduction. Figure 2d schematically illustrates a configuration comprising N SCR units (SCR unit 1- SCR- unit N) being arranged in series downstream a combustion engine (not shown), where N is a positive integer. Figure 2d hereby schematically illustrates that the inventive method is applicable to any emission control arrangement comprising at least two SCR units being arranged in series. Hereby a degree of NOx content reduction is determined for each of the SCR units (SCR unit 1- SCR-unit N). By using NO x sensors being arranged upstream and downstream of each SCR unit (SCR unit 1- SCR-unit N) corresponding degrees of NO x content reduction may be determined. The provided NO x sensors are arranged to detect NOx content (NO x IN, NO x l, NO x 2,..., NO x N) upstream and downstream of each SCR unit (SCR unit 1- SCR-unit N).

A total degree of NO x content reduction is hereby determined on the basis of the individually determined degrees of NO x content reduction, which total degree of NO x content reduction is compared with a predetermined reference degree of NO x content reduction so as to determine if the emission control arrangement is operating as desired or not.

According to one embodiment there are fewer reducing agent dosing units than SCR units of the emission control arrangement. This kind of configuration may be applicable to all different emission control arrangements according to an aspect of the invention. It it thus possible to e.g. provide one dosing unit upstream a first SCR unit being arranged first in an SCR unit sequence downstream of the engine 231 and potentially one or more dosing units upstream other SCR units downstream of the first SCR unit. According to one example embodiment wherein the emission control arrangement comprises four SCR units arranged in series a first dosing unit is arranged upstream of a first SCR unit in the SCR unit sequence and downstream of the engine 231. A second dosing unit is hereby arranged upstream of a third SCR unit in the SCR unit sequence and downstream of a second SCR unit in the SCR unit sequence. Hereby there is no dosing unit provided upstream of the second SCR unit and a fourth SCR unit in the SCR unit sequence.

Figure 2e schematically illustrates a configuration comprising four SCR units (SCR unit la, SCR unit lb, SCR-unit 2a and SCR unit 2b) being arranged parallel and in series downstream a combustion engine (not shown). Figure 2e hereby schematically illustrates that the inventive method is applicable to any emission control arrangement comprising two SCR units being arranged in series and parallel. Hereby a degree of NO x content reduction is determined for each of the SCR units. By using NO x sensors being arranged upstream and downstream of each SCR unit corresponding degrees of NO x content reduction may be determined. The provided NO x sensors are arranged to detect NO x content (NO x INl, NO x la, NO x lb, NO x IN2 NO x 2a, NO x 2b) upstream and downstream of each SCR unit. Hereby NO x INl and NO x IN2 each is about 50% of the initial NO x content NO x IN being provided by the combustion engine.

A total degree of NO x content reduction is hereby determined on the basis of the individually determined degrees of NO x content reduction, which total degree of NO x content reduction is compared with a predetermined reference degree of NO x content reduction so as to determine if the emission control arrangement is operating as desired or not.

Figure 2f schematically illustrates a configuration comprising three SCR units (SCR unit la, SCR-unit lb and SCR unit 2a) whereby the SCR unit la and SCR-unit 2a are being arranged in series downstream a combustion engine (not shown) and the SCR unit lb is arranged in parallel with the SCR unit la and in series with the SCR-unit 2a. Figure 2f hereby

schematically illustrates that the inventive method is applicable to an emission control arrangement comprising more than two SCR units being arranged in series and parallel. Hereby a degree of NO x content reduction is determined for each of the SCR units. By using NO x sensors being arranged upstream and downstream of each SCR unit corresponding degrees of NO x content reduction may be determined. The provided NO x sensors are arranged to detect NO x content (NO x IN, NO x la, NO x lb, NO x IN2 NO x 2a) upstream and downstream of each SCR unit. Hereby the NO x content being provided to each of the SCR unit la and SCR-unit 2a is about 50% of the initial NO x content NO x IN being provided by the combustion engine.

A total degree of NO x content reduction is hereby determined on the basis of the individually determined degrees of NO x content reduction, which total degree of NO x content reduction is compared with a predetermined reference degree of NO x content reduction so as to determine if the emission control arrangement is operating as desired or not. Hereby a NO x content NO x I N/2 and the NO x content NO x la downstream of SCR unit la is used for determining a degree of NO x content reduction for the SCR unit lb. Hereby a NO x content NOJ N/2 and the NO x content NO x lb downstream of SCR unit lb is used for determining a degree of NO x content reduction for the SCR unit lb. Hereby a NO x content (NO x la + NO x lb) upstream of the SCR unit 2a and a NO x content NO x 2a is used for determining a degree of NO x content reduction for the SCR unit 2a.

I n some emission control arrangements parallel SCR units are considered as one unit regarding NO x measurements. I n this case the SCR units SCR unit la and SCR unit lb could be considered as one SCR unit. Hereby only one NO x sensor may be provided for measuring the combined exhaust gas flows downstream of the SCR units SCR unit la and SCR unit lb. In general, parallel SCR units are mainly provided for emission control arrangements due to reasons of space. The inventive method is hereby adapted accordingly when it comes to determining the respective degrees of NO x content reduction for the SCR units of the emission control arrangement.

I n light of the description of the previous paragraph an alternative embodiment of the emission control arrangement depicted with reference to Figure 2e is available. In this embodiment the passages downstream of the SCR unit la and SCR unit lb is arranged so that the respective exhaust gas flows are combined. At this position one single NOx sensor is arranged for measuring the prevailing NO x content. Downstream of this position passages are arranged to divide the exhaust gas flow in substantially equal parts and lead the respective exhaust gas flows to the SCR unit 2a and SCR unit 2b. Hereby the two parallel SCR units SCR unit la and SCR unit lb are considered as one SCR configuration and the two parallel SCR units SCR unit 2a and SCR unit 2b are considered as one SCR configuration. The inventive method is hereby adapted accordingly when it comes to determining the respective degrees of NO x content reduction for the SCR units of the emission control arrangement. Figure 3 schematically illustrates a diagram wherein a N0 X content NO x is presented as a function of position P of the emission control arrangement presented in Figure 2a or Figure 2c.

The NOx content axis is hereby given in Log(10) values. Hereby is provided a first interval P0- PI, which is corresponding to positions within the first passage 255, wherein the position P0 is directly downstream of the engine 231 and the position PI is at an entry of the first SCR unit 260. Hereby is provided a second interval P1-P2, which is corresponding to positions within the second passage 265, wherein the position PI is directly downstream of the first SCR unit 270 and the position P2 is at an entry of the second SCR unit 270. Hereby is provided a third interval P2-P3, which is corresponding to positions within the third passage 275, wherein the position P2 is directly downstream of the second SCR unit 270 and the position P3 is at an end of the third passage 275.

According to this example the NO x content NO x IN corresponding to the first interval P0-P1 is lOOOppm. According to this example the NO x content NO x l corresponding to the second interval P0-P1 is lOOppm. According to this example the NO x content NO x 2 corresponding to the third interval P0-P1 is lOppm. This means that the degree of NO x content reduction for the first SCR unit 260 is 90% and that the degree of NO x content reduction for the second SCR unit 270 also is 90%. The total NO x content reduction of the emission control arrangement is hereby 99%.

In accordance with the invention and based on the emission control arrangement presented with reference to Figure 2a-2c one example is given below.

Example 1

Hereby is assumed that the emission control arrangement is set to achieve at least a total NO x degree reduction of 99%. This is the predetermined reference degree of NO x content reduction. The first SCR unit 260 is controlled so as to achieve a 90% NO x degree reduction and the second SCR unit 260 is controlled so as to achieve a 90% NO x degree reduction.

NO x IN is measured to be lOOOppm. ΝΟχΙ is measured to be lOOppm. ΝΟχ2 is measured to be lOppm.

Thus, the first degree of NO x content reduction for the first SCR unit 260 is determined to be 90% and the second degree of NO x content reduction for the second SCR unit 270 is determined to be 90%.

Hereby the total degree of NO x content reduction for the emission control arrangement is determined to be 99%. This is performed on the basis of the thus determined first degree of NOx content reduction and the second degree of NO x content reduction.

100(l-(l-0.90)(l-0.90))=99% According to this example it is determined that the emission control arrangement is operating as desired since the total degree of NO x content reduction is not below the predetermined reference degree of NO x content reduction.

End of Example 1

Corresponding calculations are performed for various emission control arrangements wherein individually determined degrees of NO x content reduction are combined accordingly to form a total degree of NO x content reduction which in turn is compared to a

predetermined reference degree of NO x content reduction for determining if emission control arrangement is operating as desired or not.

Figure 4a schematically illustrates a flow chart of a method for diagnosing an emission control arrangement for a combustion engine 231 in operation, comprising at least a first SCR configuration and a second SCR configuration arranged in a series.

The method comprises a first method step s401. The method step s401 comprises the steps of: - determining a set of operational parameter values (MF, Tl, T2, NO x IN) for the emission control arrangement;

- determining and dosing an amount of reducing agent for the first SCR configuration for obtaining a predetermined NO x content downstream of the first SCR configuration; - determining and dosing an amount of reducing agent for the second SCR configuration for obtaining a predetermined NO x content downstream of the second SCR configuration;

- determining a first degree of NO x content reduction for the first SCR configuration;

- determining a second degree of NO x content reduction for the second SCR configuration;

- determining a total degree of NO x content reduction for the emission control arrangement on the basis of the thus determined first degree of NOx content reduction and the second degree of NO x content reduction;

- comparing the total degree of NO x content reduction for the emission control arrangement with a predetermined reference degree of NO x content reduction for the emission control arrangement; and - determining that the emission control arrangement is operating as desired if the total degree of NO x content reduction exceeding the predetermined reference degree of NO x content reduction.

After the method step s401 the method ends/is returned.

Figure 4b schematically illustrates a method for diagnosing an emission control arrangement for a combustion engine 231 in operation, comprising a first SCR configuration 260 and a second SCR configuration 270 arranged in a series. This embodiment refers to the emission control arrangement presented with reference to Figures 2a-2c.

The method comprises a first method step s405. The method step s405 comprises the step of determining a set of operational parameter values for the emission control arrangement. Hereby a prevailing exhaust gas mass flow MF is determined by means of the exhaust gas mass flow sensor 247 and/or by the exhaust gas mass flow model. Hereby the temperature of the first SCR-unit 260 is determined by means of the first temperature sensor 241. Hereby the temperature of the second SCR unit 270 is determined by means of the second temperature sensor 242. Hereby the NO x value NO x IN is determined by means of the first ΝΟχ sensor 251 and/or by the NO x content model. After the method step s405 a subsequent method step s410 is performed.

The method step s410 comprises the step of determining and dosing an amount of reducing agent for the first SCR configuration 260 for obtaining a predetermined NO x content downstream of the first SCR configuration 260. The amount of reducing agent for the first SCR configuration 260 is determined on the basis of the set of operational parameter values. The predetermined NO x content is determined on the basis of the NO x content NO x IN.

Alternatively a dosing amount is dosed for obtaining a predetermined degree of NO x content reduction for the first SCR configuration 260. The amount of reducing agent for the first SCR configuration 260 is determined on the basis of the set of operational parameter values. This is performed by means of the first control unit 200. Dosing is performed according to certain routines and on the basis of the determined amount of reducing agent for the first SCR configuration 260. The first control unit 200 is hereby controlling operation of the first dosing unit 237a so as to obtaining the predetermined NO x content downstream of the first SCR configuration 260. After the method step s410 a subsequent method step s415 is performed.

The method step s415 comprises the step of determining and dosing an amount of reducing agent for the second SCR configuration 270 for obtaining a predetermined NO x content downstream of the second SCR configuration 270. The amount of reducing agent for the second SCR configuration 270 is determined on the basis of the set of operational parameter values. The predetermined NO x content is determined on the basis of the NO x content NO x l. Alternatively a dosing amount is dosed for obtaining a predetermined degree of NO x content reduction for the second SCR configuration 270. This is performed by means of the first control unit 200. Dosing is performed according to certain routines and on the basis of the determined amount of reducing agent for the second SCR configuration 270. The first control unit 200 is hereby controlling operation of the second dosing unit 237b so as to obtaining the predetermined NO x content downstream of the second SCR configuration 270.

After the method step s415 a subsequent method step s420 is performed.

The method step s420 comprises the step of determining a first degree of NO x content reduction for the first SCR configuration 260. This is performed by the first control unit 200. The first degree of NO x content reduction for the first SCR configuration 260 is calculated on the basis of the NO x content value NO x IN (detected upstream of the SCR configuration 260) and the NO x content value NO x l (detected downstream of the SCR configuration 260).

After the method step s420 a subsequent method step s425 is performed.

The method step s425 comprises the step of determining a second degree of NO x content reduction for the second SCR configuration 270. This is performed by the first control unit 200. The second degree of NO x content reduction for the second SCR configuration 270 is calculated on the basis of the NO x content value NO x l (detected upstream of the SCR configuration 270) and the NO x content value NO x 2 (detected downstream of the SCR configuration 270).

After the method step s425 a subsequent method step s430 is performed.

The method step s430 comprises the step of determining a total degree of NO x content reduction for the emission control arrangement on the basis of the thus determined first degree of NO x content reduction and the second degree of NO x content reduction. This is performed by means of the first control unit 200. Hereby a total degree of NO x content reduction for the emission control arrangement is determined on the basis of the

determined degrees of NO x content reduction of all the SCR configurations of the emission control arrangement and thus not only on the basis of the NO x content values NO x IN and ΝΟχ2, i.e. ΝΟχ content values upstream and downstream of all SCR configurations of the emission control arrangement.

After the method step s430 a subsequent method step s435 is performed.

The method step s435 comprises the step of comparing the total degree of NO x content reduction for the emission control arrangement with a predetermined reference degree of NOx content reduction for the emission control arrangement. This is performed by means of the first control unit 200. The predetermined reference degree of NO x content reduction for the emission control arrangement may be determined on basis of e.g. national/regional laws and regulations. The predetermined reference degree of NO x content reduction may be e.g. 75%, 80%, 85%, 90%, 95%, 97%, 98% or 99%.

The method step s435 may comprise the step of comparing the first degree of NO x content reduction for the first SCR configuration 260 with a predetermined first reference degree of NOx content reduction. This is performed by means of the first control unit 200. The first predetermined reference degree of NO x content reduction for the first SCR configuration 260 may be determined on basis of e.g. national/regional laws and regulations or by a manufacturer of the vehicle 100. The predetermined first reference degree of NO x content reduction may be e.g. 75%, 80%, 85%, 90%, 95%, 97%, 98% or 99%. The method step s435 may comprise the step of comparing s435 the second degree of NO x content reduction for the second SCR configuration 270 with a predetermined second reference degree of NO x content reduction. This is performed by means of the first control unit 200. The second predetermined reference degree of NO x content reduction for the second SCR configuration 270 may be determined on basis of e.g. national/regional laws and regulations or by a manufacturer of the vehicle 100. The predetermined second reference degree of NO x content reduction may be e.g. 75%, 80%, 85%, 90%, 95%, 97%, 98% or 99%.

After the method step s435 a subsequent method step s440 is performed. The method step s440 comprises the step of determining that the emission control arrangement is operating as desired if the total degree of NO x content reduction exceeding the predetermined reference degree of NO x content reduction. If the total degree of NO x content reduction is equal to or exceeding the predetermined reference degree of NO x content reduction it is determined that the emission control arrangement is operating as desired. If the total degree of NO x content reduction is below the predetermined reference degree of NO x content reduction it is determined that the emission control arrangement is not operating as desired.

The method step s440 may comprise the step of determining that the first SCR configuration 260 is operating as desired if the first degree of NO x content reduction is exceeding the predetermined first reference degree of NO x content reduction, and if not, generating an error code for the first SCR configuration 260.

The method step s440 may comprise the step of determining that the second SCR

configuration 270 is operating as desired if the second degree of NO x content reduction is exceeding the predetermined second reference degree of NO x content reduction, and if not, generating an error code for the second SCR configuration 270.

After the method step s440 the method is ended/returned.

The inventive method is applicable to emission control arrangements including further SCR configurations in series and applying corresponding degrees of NO x content reduction determinations for the thus extended emission control arrangement, totally and individually.

The inventive method is applicable to emission control arrangements including further SCR configurations in parallel and applying corresponding degrees of NO x content reduction determinations for the thus extended emission control arrangement, totally and individually.

Figure 5 is a diagram of one version of a device 500. The control units 200 and 210 described with reference to Figure 2 may in one version comprise the device 500. The device 500 comprises 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 element 530 in which a computer program, e.g. an operating system, is stored for controlling the function of the device 500. The device 500 further comprises 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 interruption controller (not depicted). The non-volatile memory 520 has also a second memory element 540.

The computer program P comprises routines for diagnosing an emission control

arrangement for a combustion engine in operation, comprising at least a first SCR configuration and a second SCR configuration arranged in a series.

The computer program P may comprise routines for determining a set of operational parameter values for the emission control arrangement.

The computer program P may comprise routines for determining and dosing an amount of reducing agent for the first SCR configuration for obtaining a predetermined NO x content ΝΟχΙ downstream of the first SCR configuration.

The computer program P may comprise routines for determining and dosing an amount of reducing agent for the second SCR configuration for obtaining a predetermined NO x content ΝΟχ2 downstream of the second SCR configuration. The computer program P may comprise routines for determining a first degree of NO x content reduction for the first SCR configuration.

The computer program P may comprise routines for determining a second degree of NO x content reduction for the second SCR configuration.

The computer program P may comprise routines for determining a total degree of NO x content reduction for the emission control arrangement on the basis of the thus determined first degree of NO x content reduction and the second degree of NO x content reduction.

The computer program P may comprise routines for comparing the total degree of NO x content reduction for the emission control arrangement with a predetermined reference degree of NO x content reduction for the emission control arrangement. The computer program P may comprise routines for determining that the emission control arrangement is operating as desired if the total degree of NO x content reduction exceeding the predetermined reference degree of NO x content reduction.

The computer program P may comprise routines for comparing the first degree of NO x content reduction for the first SCR configuration with a predetermined first reference degree of NOx content reduction.

The computer program P may comprise routines for determining that the first SCR configuration is operating as desired if the first degree of NO x content reduction is exceeding the predetermined first reference degree of NO x content reduction, and if not, generating and error code for the first SCR configuration.

The computer program P may comprise routines for comparing the second degree of NO x content reduction for the second SCR configuration with a predetermined second reference degree of NO x content reduction.

The computer program P may comprise routines for determining that the second SCR configuration is operating as desired if the second degree of NO x content reduction is exceeding the predetermined second reference degree of NO x content reduction, and if not, generating and error code for the second SCR configuration.

The computer program P may comprise routines for applying corresponding degrees of NO x content reduction determinations for an extended emission control arrangement, totally and individually, wherein further SCR configurations has been included in the emission control arrangement in series.

The computer program P may comprise routines for applying corresponding degrees of NO x content reduction determinations for an extended emission control arrangement, totally and individually, wherein further SCR configurations has been included in the emission control arrangement in parallel. The computer program P may comprise routines for performing any of the process steps detailed with reference to Figure 4b.

The program P may be stored in an executable form or in compressed form in a memory 560 and/or in a read/write memory 550.

Where it is stated that the data processing unit 510 performs a certain function, it means that it conducts 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 via a data bus 511. The read/write memory 550 is arranged to communicate with the data processing unit 510 via a data bus 514. The links L210, L230, L231, L237a, L237b, L241, L242, L247, L251, L252 and L253, for example, may be connected to the data port 599 (see Fig. 2a, 2b, 2c).

When data are received on the data port 599, they are stored temporarily in the second memory element 540. When input data received have been temporarily stored, the data processing unit 510 will be prepared to conduct code execution as described above.

Parts of the methods herein described may be conducted by the device 500 by means of the data processing unit 510 which runs the program stored in the memory 560 or the read/write memory 550. When the device 500 runs the program, method steps and process steps herein described are executed.

The foregoing description of the preferred embodiments of the present invention is provided for illustrative and descriptive purposes. It is not intended to be exhaustive, nor to limit the invention to the variants described. Many modifications and variations will obviously suggest themselves to one skilled in the art. The embodiments have been chosen and described in order to best explain the principles of the invention and their practical applications and thereby make it possible for one skilled in the art to understand the invention for different embodiments and with the various modifications appropriate to the intended use.

The components and features specified above may within the framework of the invention be combined between different embodiments specified.