SE536950C2 - Device and method for troubleshooting an SCR system - Google Patents

Abstract

The invention relates to a method of troubleshooting an SCR system comprising a dosing unit (250) for dosing reducing agent into a single engine exhaust duct (290) upstream of an SCR catalyst (270) for reducing NOX content in an exhaust gas flow from said engine, comprising the step of: - determining (s310) NOX content in the exhaust gas flow downstream of said SCR catalyst (270). The process comprises the steps of: - under predetermined operating conditions of said SCR catalyst (270) successively changing (s320) the dosage of said reducing agent; determining (s330) whether the SCR catalyst (270) is capable of reducing said NOX content in (270) to a predetermined extent during said successively changing dosage; the exhaust gas flow downstream of said SCR catalyst and - based on the result of said determination, determine (s340) whether said SCCR catalyst (270) is defective or not from a NOX content reduction point of view. The invention also relates to a computer program product comprising program code (P) for a computer (200; 210) for implementing a method according to the invention. The invention also relates to a device for troubleshooting a SCR system and a motor vehicle equipped with the device. Figure 2 for publication

Description

20 25 30 536 950 In the event of certain faults or operating deviations in SCR systems in vehicles, an error code is generated today. error code may, however, be too service personnel may have great difficulty in identifying a source of error at SCR- This nonspecific, why the system. In some cases where error code regarding said SCR system is generated, it may be another system that does not work as intended, which in turn can adversely affect the SCR system, whereby error code is generated incorrectly for the SCR system.

Although it may be difficult to identify exactly which component of the SCR system is faulty, it is desirable to be able to exclude at least one or some of the components included in an SCR system. This is particularly relevant for the SCR catalyst, for example, as it is expensive and time consuming to disassemble this component from the vehicle for, for example, ocular inspection or other troubleshooting methods.

US 2011296905, DE102010028846 and US201032605 describe different methods of troubleshooting an SCR system.

SUMMARY OF THE INVENTION An object of the present invention is to provide a new and advantageous method for troubleshooting an SCR system.

Another object of the invention is to provide a new and advantageous device and a new and advantageous computer program for troubleshooting an SCR system.

A further object of the invention is to provide a method, an apparatus and a computer program for achieving a reliable and user-friendly troubleshooting of an SCR system. These objects are achieved by a troubleshooting method in an SCR system according to claim 1.

According to one aspect of the invention, there is provided a method of troubleshooting an SCR system comprising a metering unit for metering reducing agent into an engine exhaust duct upstream of an SCR catalyst for reducing NOX content in an exhaust stream from said engine. The process comprises the steps of: - determining NOX content in the exhaust gas stream downstream of said SCR catalyst; - under predetermined operating conditions of said SCR catalyst, successively change the dosage of said reducing agent; determining whether the SCR catalyst is capable of reducing said NOX content in the exhaust gas stream downstream of said SCR catalyst to a predetermined extent during said successively changing dosage; and - based on the result of said determination, determining whether or not said SCR catalyst is defective from a NOX content reduction point of view.

The process may comprise the step of: - providing said predetermined operating conditions in the form of a predetermined minimum temperature level of said SCR catalyst and a predetermined process may be exhaust gas mass flow. comprising the step of providing said predetermined operating conditions in the form of a predetermined minimum temperature level of said SCR catalyst and a substantially constant and / or predetermined exhaust gas mass flow. The method may comprise the step of providing said predetermined operating conditions in the form of a predetermined minimum temperature level of an exhaust duct from an engine and a substantially constant and / or predetermined exhaust mass flow.

The method may comprise the step of providing said predetermined operating conditions in the form of a predetermined minimum temperature level of exhaust gases in an exhaust duct which is arranged to direct said exhaust gases from an engine to and / or predetermined exhaust gas mass flow. Said predetermined minimum temperature level may be an environment and a substantially constant 536 950 300 Celsius. Said predetermined temperature level may be, for example, 350 degrees, for example degrees Celsius. Said predetermined minimum temperature level may be in a range of, for example, 300-400 degrees Celsius.

The inventive method can be implemented as a workshop test. The inventive process can be carried out during operation when the vehicle is stationary, for example in a workshop or service facility.

The inventive method can be performed during operation, for example when the vehicle is propelled on a suitable road section. The inventive process can be carried out when the vehicle is propelled under circumstances where 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.

According to one aspect of the invention, the inventive process can be performed by means of data detected by a NOX sensor downstream of said SCR catalyst, the other required data being able to be modeled or calculated in a suitable manner. In this case, a cost-effective implementation of the inventive method is achieved.

The method may comprise the step of: - achieving said predetermined operating conditions by controlling the operation of said engine. Said predetermined operating conditions may refer to a certain speed of said engine. Said predetermined operating conditions may refer to a predetermined load of said engine. Said predetermined operating conditions may relate to a certain fuel dosage of said engine. In this case, said predetermined operating conditions can be achieved in an automatic and controlled manner, which advantageously entails that a desired operating condition of the vehicle is achieved. Said operating conditions may include a condition in which an exhaust gas flow from an engine of the vehicle is substantially constant.

The step of successively changing said dosage may involve continuously increasing or decreasing the dosage. In this case, an accurate troubleshooting procedure can be provided.

The step of successively changing said dosage may involve gradually increasing or decreasing the dosage. In this case, a relatively fast troubleshooting procedure in an SCR system can be advantageously achieved.

The process may comprise the step of: - waiting for a state of continuity of the reduction of NOX content downstream of said SCR catalyst. In this case, more accurate measurements of NOX content downstream of said SCR catalyst can be achieved, which can advantageously mean that a high probability correct determination of whether said SCR catalyst is defective or not can be determined from a NOX content reduction point of view. advantageous measurement by means of a NOX sensor downstream of the SCR. When changing the dosage of reducing agent, a certain time for said NOX donor may be required for stabilization.

The step of determining whether said SCR catalyst is capable of reducing said NOX content of the exhaust gas stream downstream of said SCR catalyst may to a predetermined extent include the step of: - determining absolute values of said NOX content of the exhaust gas stream downstream of said SCR catalyst, and / or determining: - determining absolute values regarding said NOX content in the exhaust gas flow upstream of said SCR catalyst; determining absolute values regarding said NOX content in the exhaust gas flow downstream of said SCR catalyst; and determining a degree of NOX conversion of the SCR catalyst, based on said NOX content of the exhaust gas stream upstream of said SCR catalyst and said NOX content of the exhaust gas stream downstream of said SCR catalyst.

In this case, two different ways of determining the performance of said SCR catalyst are advantageously provided. In this case, a versatile method for partial detection is provided via an SCR system, where both only said NOX content and said NOX exhaust gas flow downstream of said SCR catalyst conversion rate of the SCR catalyst can be used.

The process may comprise the step of: - representing said SCR catalyst reduction of NOX content downstream of said SCR catalyst during said successively changing dosage as absolute values of said NOX content downstream of said SCR catalyst as a function of reducing agent dosage or NOX conversion rate as a function of reducing agent dosage. In this case, according to one embodiment, a relatively inexpensive implementation of the method according to the invention is achieved when an extremely limited number of sensors (a NOX sensor downstream of the SCR catalyst) is required. In this case, according to one embodiment, a well-defined basis is provided for calculations according to the method of the invention, since a degree of NOX conversion well reflects a prevailing performance of the SCF1 catalyst.

Said NOX content downstream of said SCR catalyst as a function of reducing agent dosing may include a minimum. In this case, a method with one can be provided. relatively limited required computing capacity Said NOX conversion rate as a function of reducing agent dosing may include a maximum. In this case, a method with a relatively limited required computing capacity can be provided. The process may comprise the step of: - presenting said results of said determination regarding reduction of said NOX content in the exhaust gas flow downstream of said SCR catalyst (270) to a predetermined extent in the form of an error code. Said error code can be presented to an operator of the vehicle by suitable means. According to one embodiment, said error code can be stored in a memory of a control unit of the vehicle, which error code can at a later stage be presented to service personnel of, for example, a workshop by means of suitable means. According to one embodiment, said error code can be automatically sent via a suitable network to a so-called fleet management system or a farm owner.

The process may comprise the step of: - performing a check of the operation of the SCR system in addition to said SCR catalyst. In this case, the elimination of sources of error in the SCR system or the vehicle can be effected in an efficient manner, which can advantageously lead to a reliable method for troubleshooting a SCR system. For example, any leakage of exhaust gases or reducing agents can be detected.

In this case, a check of the function of various relevant sensors in the vehicle can be performed. Said sensors can be, for example, NOX sensors, exhaust mass flow sensors or temperature sensors. This can advantageously result in a reliable troubleshooting procedure in an SCR system.

The procedure is easy to implement in existing motor vehicles. A troubleshooting tool in an SCR system according to the invention can be installed in a control unit of the vehicle in the manufacture thereof. 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 troubleshooting procedure of an SCR 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. 10 15 20 25 30 536 950 Software that includes program code for troubleshooting an SCR system can be easily updated or replaced. Furthermore, different parts of the software that include program code for debugging an SCR system can be replaced independently.

This modular configuration is advantageous from a maintenance perspective.

According to one aspect of the invention, there is provided a troubleshooting device in an SCR system comprising a metering unit for metering reducing agent into an engine exhaust duct upstream of an SCR catalyst for reducing NOX content in an exhaust stream from said engine. The device comprises: - means adapted to determine NOX content in the exhaust gas flow downstream of said SCR catalyst; means adapted to, under predetermined operating conditions of said SCR catalyst, reducing agents; successively changing the dosage of said means adapted to determine whether the SCR catalyst is capable of reducing said NOX content in the exhaust gas flow downstream of said SCR catalyst to a predetermined extent during said successively changing dosage; and means adapted, based on the result of said determination, to determine defect from a NOX whether or not said SCR catalyst is a content reduction point.

The device may comprise: means adapted to provide said predetermined operating conditions in the form of a predetermined minimum temperature level of said SCR catalyst and a predetermined exhaust gas mass flow. Said exhaust mass flow can be a substantially constant exhaust mass flow. Said exhaust mass flow may be an exhaust mass flow defined by a value which is within a predetermined range. Said exhaust mass flow can be a well-defined exhaust mass flow. 10 15 20 25 30 536 950 Said exhaust mass flow may be of a magnitude defined by a predetermined value.

The device may comprise: - means adapted to achieve said predetermined operating conditions by controlling the operation of said motor.

The device may comprise: - means adapted to change said dosage by continuously increasing or decreasing the dosage.

The device may comprise: - means adapted to successively change said dosage by gradually increasing or decreasing the dosage.

The device may comprise: - means adapted to wait for a state of continuity of the reduction of NOX content downstream of said SCR catalyst.

In the device, said means adapted to determine whether said SCR catalyst is capable of reducing said NOX content in the exhaust gas flow downstream of said SCR catalyst to a predetermined extent comprise: - means adapted to determine absolute values regarding said NOX content in the exhaust gas flow downstream of said SCR catalyst. ; and / or: - means adapted to determine absolute values regarding said NOX content in the exhaust gas flow upstream of said SCR catalyst; means adapted to determine absolute values regarding said NOX content in the exhaust gas flow downstream of said SCR catalyst; and - means adapted to determine a NOX conversion rate of the SCR catalyst, based on said NOX content in the exhaust gas flow upstream of said SCR catalyst and said NOX content in the exhaust flow downstream of said SCR catalyst.

The device may comprise: - means adapted to represent said SCR catalyst reduction of NOX content downstream of said SCR catalyst during said successive altered dosage as absolute values of said NOX content downstream of said SCR catalyst as a function of reduction medium dosing or NOX conversion rate. of reducing agent dosage.

In the device, said NOX content downstream of said SCR catalyst as a function of reducing medium dosing may include a minimum.

In the device, said NOX conversion rate as a function of reduction medium dosing may include a maximum.

The device may comprise: means adapted to present said result of said determination regarding reduction of said NOX content in the exhaust flow downstream of said SCR catalyst (270) to a predetermined extent in the form of an error code.

The device may comprise: - means adapted to perform a check of the function of the SCR system in addition to said SCR catalyst.

The above objects are also achieved with a motor vehicle which includes the troubleshooting device of an SCR system. The lotor vehicle can be a truck, bus or car.

According to one aspect of the invention, there is provided a computer program for SCR systems, wherein program code for causing an electronic controller or another computer troubleshooting in said computer program comprises 106 connected to the electronic controller to perform the steps of any of claims 1-12.

According to one aspect of the invention, there is provided a computer program for SCR systems, wherein program code stored on a computer readable medium for causing a troubleshooting of said computer program comprises an electronic control unit or another computer connected to the electronic control unit to perform the steps of any of claims 1-12.

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 1-12, when said program code 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 practice of the invention. Since 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 and incorporate within other further applications, modifications areas, which are within the scope of the invention. SUMMARY 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 where 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; Figure 2 schematically illustrates a troubleshooting device in an SCR system, according to an embodiment of the invention; Figure 3a schematically illustrates a flow chart of a method, according to an embodiment of the invention; Figure 3b schematically illustrates in further detail a flow chart of a method, according to an embodiment of the invention; Figure 4a schematically illustrates a diagram according to an aspect of the invention; Figure 4b schematically illustrates a diagram according to an aspect of the invention; and illustrating a computer, Figure 5 schematically according to an embodiment of the invention.

DETAILED DESCRIPTION OF FIGURES 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 any suitable SCR system and is not limited to SCR systems of motor vehicles. The innovative method and the innovative SCR system according to an aspect of the invention are well suited for platforms which include 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 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. 12 10 15 20 25 30 536 950 The innovative method and the innovative SCR system according to an aspect of the invention are also well suited for e.g. systems including industrial engines and / or powered industrial robots.

The innovative method and the innovative 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 procedure and the innovative 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 the innovative 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, such as a radio or microwave link.

Here, the term "line" 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 emissions can e.g. be NOX gas. The terms "reductant" and "reducing agent" are used synonymously herein. Said reductant is according to an embodiment so-called AdBlue. 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. Referring to Figure 2, there is shown a device 299 of the vehicle 100.

The device 299 may be arranged in the drawbar 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 hold 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 inflate 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 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 100, according to the method of the invention. According to this embodiment, an SCR catalyst exhaust duct is the vehicle according to an aspect of the 270 arranged downstream of a position of the exhaust system where supply of the reductant takes place. The amount of reductant supplied to the exhaust system is intended to be used in the SCR 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 the operation of the pump 230. According to an 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 of the pump 230, the working pressure can be increased. By lowering the speed 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 gas stream from the vehicle engine. According to one 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 located at 290. The temperature sensor 240 is arranged to continuously detect a prevailing at said suitable exhaust duct. of the exhaust stream and send signals comprising 536,950 information about said current 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 an ambient 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 an ambient temperature T2 of the exhaust duct 290 at a suitable location. The second temperature sensor 260 may be arranged to detect an ambient 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 an example, the second temperature sensor 260 is arranged in the exhaust duct 290 upstream 250. According to a temperature sensor 260 arranged in an evaporator unit (not shown) or the SCR catalyst 270 dosing unit other example is the second downstream dosing unit 250. The second temperature sensor 260 is arranged to continuously detect an ambient temperature T2 of a surface or a component of the exhaust duct 290 and send signals including information about said ambient 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, prevailing speed 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 16 10 15 20 25 30 536 950 and / or the second control unit 210 may be arranged to calculate said second temperature T2 on the basis of, for example, a radiating exhaust mass flow, radiating speed of the engine and saving load of the engine.

A first NOX sensor 255 is arranged for communication with the first control unit 200 via a link L255. The first NOX sensor 255 is arranged to continuously determine a prevailing NOX content of the exhaust gas stream upstream of the SCR catalyst 270. According to an example, the first NOX sensor 255 is arranged at the exhaust duct 290 upstream of said dosing unit 250. The first NOX sensor 255 is arranged to continuously send signals including information about a prevailing NOX content upstream of the SCR catalyst 270 to the first control unit 200.

A second NOX sensor 265 is provided for communication with the first control unit 200 via a link L265. The second NOX sensor 265 is arranged to continuously determine a current NOX content of the exhaust stream downstream of said SCR catalyst 270. The second NOX sensor 265 is arranged to continuously send signals including information of a current NOX content downstream of said 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 calculate said first NOX content upstream of said 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 first NOX content on the basis of, for example, a prevailing exhaust gas mass flow, prevailing speed of the engine and prevailing load of the engine.

The first control unit 200 is arranged to determine a prevailing degree of NOX conversion on the basis of said calculated or measured NOX content upstream of said SCR catalyst and said measured NOX content downstream of said SCR catalyst 270. 17 10 15 20 25 30 536 950 the first control unit 200 is arranged to determine the NOX content of the exhaust gas flow downstream of the SCR catalyst 270. The first control unit 200 is arranged to determine the NOX content of the exhaust gas flow upstream of the SCR catalyst 270. The first control unit 200 is arranged to provide suitable for the purpose operating conditions of said SCR catalyst. The first control unit 200 is arranged to successively change the dosage of said reducing agent under predetermined operating conditions of said SCR catalyst 270. The first control unit 200 is arranged to determine whether the SCR catalyst 270 is capable of reducing said NOX content in the exhaust gas flow downstream of said SCR catalyst to a predetermined extent during said successively changing dosage. The first control unit 200 is arranged to, based on the result of said determination, determine whether or not said SCR catalyst is defective from a NOX content reduction point of view.

The first control unit 200 is arranged for communication with presentation means 280 via a link L280. Said display means 280 may be presently arranged in a cab of the vehicle 100. Said display means 280 may be fixedly mounted in the vehicle 100. Said display means 280 may be a mobile electronic unit. 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 procedure for troubleshooting an SCR system. The first control unit 200 may be arranged to present by means of said presentation means 280 a result as to whether or not said SCR catalyst 270 is defective from a NOX content reduction point of view.

The first control unit 200 is arranged for communication with a communication unit 285 via a link L285. Said communication unit 285 may be present at, for example, a service station, workshop, haulier or a so-called fleet management system. Said communication unit 285 may be provided in a driver's cab of the vehicle 100. Said communication unit 285 may be fixedly mounted in the vehicle 100. Said communication unit 285 may be a mobile electronic unit. Said communication unit 285 may comprise, for example, a display screen. The first control unit 200 is arranged to automatically or upon request present an error code or other relevant information regarding the innovative procedure for troubleshooting an SCR system. The first control unit 200 may be arranged to present by means of said communication terminal 285 a result as to whether or not said SCR catalyst 270 is defective from a NOX content reduction point of view.

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.

The first control unit 200 is arranged to calculate an exhaust mass flow I / IF of the exhaust gases from the engine of the vehicle. The first control unit 200 is arranged to continuously determine an exhaust gas mass flow I / IF of the exhaust gases from the vehicle's engine. This can be done in any suitable way.

According to one embodiment, the subsystem comprises a mass flow sensor (not shown) which is arranged to continuously measure a prevailing exhaust mass flow from the engine of the vehicle 100 in the exhaust duct 290 upstream of said SCR catalyst 270. Said mass flow sensor is continuously transmitted to the first control unit via a dedicated link.

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 19 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 similar functions as the first control unit 200, such as e.g. successively changing the dosage of said reducing agent under predetermined operating conditions of SCR catalyst 270; determining whether the SCR catalyst 270 prefers to reduce a NOX content in the exhaust gas stream downstream of the SCR catalyst 270 to a predetermined extent during said successively changing dosage; and - based on the result of said determination, determining whether or not said SCR catalyst 270 is defective from a NOX content reduction point of view.

Figure 3a schematically illustrates a flow chart of a troubleshooting method in an SCR system comprising a dosing unit for dosing reducing agent into an engine exhaust duct upstream of an SCR catalyst for reducing NOX content in an exhaust flow from said engine, according to an embodiment of the invention. The method comprises a first method step s301. Step s301 includes the steps of: - determining NOX content in the exhaust gas stream downstream of said SCR catalyst; - under predetermined operating conditions of said SCR catalyst, successively change the dosage of said reducing agent; determining whether the SCR catalyst prefers to reduce said NOX content in the exhaust gas stream downstream of said SCR catalyst to a predetermined extent during said successively changing dosage; and - based on the result of said determination, determining whether or not said SCR catalyst is defective from a NOX content reduction point of view. After step s301, the process is terminated. Figure 3b schematically illustrates a flow chart of a troubleshooting method in an SCR system comprising a metering unit 250 for metering a reducing agent into an engine exhaust duct 290 upstream of an SCR catalyst 270 for reducing NOX content. in an exhaust gas flow from said engine, according to an embodiment of the invention.

The method includes a first method step s310. Method step s310 may include the step of activating the inventive method.

Said activation can be performed by an operator of the vehicle 100. Said activation can be performed by workshop personnel or service personnel of a workshop or service facility respectively. Said activation can take place by means of said presentation means 280 and / or said communication unit 285.

Method step s310 may include the step of providing an operating condition suitable for the method of the invention. Process step s310 may include the step of achieving predetermined operating conditions in the form of a predetermined minimum temperature level of said SCR catalyst 270 and a predetermined exhaust mass flow. Said exhaust mass flow can be determined by means of dedicated means, for example a mass flow sensor or suitable calculation means, such as e.g. the first control unit 200.

The process step s310 may include the step of achieving predetermined operating conditions in the form of a predetermined minimum temperature level with respect to said first temperature T1 and / or said second temperature T2.

The method step s310 may include the step of achieving said predetermined operating conditions by controlling the operation of said engine.

Process step s310 includes the step of determining NOX content in the exhaust gas stream downstream of said SCR catalyst. This can be done by measuring by means of the NOX sensor 265.

After the process step s310, a subsequent process step s320 is performed. The process step s320 comprises the step of successively changing the dosage of said reducing agent under predetermined operating conditions of said SCR catalyst. Step s320 may involve successively changing said dosage by continuously increasing or continuously decreasing the dosage. Step s320 may involve successively changing said dosage by incrementally increasing or incrementally decreasing the dosage.

In this case, the first control unit 200 and / or the second control unit 210 can continuously or intermittently determine the performance of the SCFs catalyst 270 by determining a NOX content downstream of said SCR catalyst and / or a NOX conversion rate of the SCR catalyst 270.

It should be noted that NOX levels downstream of the SCR catalyst and / or a NOx conversion rate of the SCR catalyst 270 can be determined for both successively increasing dosing of reducing agents and successively decreasing dosing of reducing agents. According to one embodiment, the dosage can be continuously controlled against both determination of said NOx content downstream of said SCR catalyst increased dosage and against reduced dosage during and / or a NOX conversion rate of the SCR catalyst 270.

According to one embodiment, the dosage can be continuously controlled towards increased dosage from a relatively low dosage while determining said NOx content downstream of said SCR catalyst and / or a NOX conversion rate of the SCR catalyst 270.

According to one embodiment, the dosage can be continuously controlled towards reduced dosage from a relatively high dosage while determining said NOX content downstream of said SCR catalyst and / or a NOX conversion rate of the SCR catalyst 270. 22 10 15 20 25 30 536 950 In this case, the dosage can first be continuously controlled towards reduced dosage from a relatively high dosage, and then continuously directed towards increased dosage from a relatively low dosage, while determining said NOX content SCR catalyst NOX conversion rate of the SCR catalyst 270. downstream of said and According to one embodiment, the dosage can first be continuously controlled towards increased dosage from a relatively low dosage, and then continuously controlled towards decreased dosage from a relatively high dosage, while determining said NOX content downstream of said SCR catalyst and / or a NOX. conversion rate of the SCR catalyst 270.

According to an example, said dosage may sweep towards increased dosage and towards decreased dosage within a suitable dosage range. In this case, a partial range of reducing agents can advantageously be considered. Said sub-intervals may advantageously be a suitably more interesting one with respect to dosing sub-intervals which involve a maximum degree of NOX conversion of the SCR catalyst 270.

After the process step s320, a subsequent process step s330 is performed.

Process step s33O includes the step of determining whether the SCR catalyst is capable of reducing said NOX content in the exhaust gas stream downstream of said SCR catalyst to a predetermined extent during said successively changing dosage. s33O can determine at which reducing agent dosage maximum performance of the SCR catalyst 270 The step includes the step of being presented under given operating conditions. According to one embodiment, a maximum NOX conversion rate is determined, which reflects a maximum performance of the SCR catalyst 270 under given operating conditions. According to one embodiment, a minimum NOX content is determined downstream of the SCR catalyst, which reflects a maximum performance of the SCR catalyst 270 under given operating conditions.

After the process step s330, a subsequent process step s340 is performed.

Process step s340 includes the step of determining, based on the result of said determination, whether or not said SCR catalyst is defective from a NOX content reduction point of view.

This can be done by comparing said determined maximum NOX conversion rate with a predetermined value TH1. If said determined maximum NOX conversion rate exceeds said value TH1, the SCR catalyst 270 is not considered defective. If said determined maximum NOX conversion rate is less than said value TH1, the SCR catalyst 270 is considered defective.

This can alternatively or additionally be performed by comparing said determined minimum NOX content with a predetermined value TH2. If said determined minimum NOX content falls below said value TH2, the SCR catalyst 270 is not considered defective. If said determined minimum NOX content exceeds said value TH2, the SCR catalyst 270 is considered defective.

Method step s340 may include the step of presenting said result of said determination in the form of an error code. Method step s340 may include presenting said results to an operator of the vehicle 100 by, for example, said presentation means 280. Method step s340 may include presenting said results to service personnel of a workshop communication unit 280. or service facility by means of, for example, said. 24 10 15 20 25 30 536 950 Referring to Figure 4a, a diagram is shown in which the NOX conversion degree Fi of the SCFi catalyst 270 is stated as a function of the amount of reducing agent dosed by means of the dosing unit 250. . Said dosed amount of reducing agent may be a reducing agent determined. NOX conversion rate Fi is given in terms of percent [° />]. Appropriately metered dose average dose Dosage of reducing agent D is given in terms of [g / minute].

NOX conversion rate Fi can be determined according to equation 1 below: (1) NOX conversion rate = 1- (NOX content downstream / NOX content upstream) It appears that the SCFi catalyst 270 has a maximum conversion rate Fi1 at a dosage D1. The value Fi1 thus indicates a maximum value for the NOX conversion rate of said curve Fi (D).

According to one aspect of the invention, it can be determined that the SCFi catalyst 270 is not defective from a NOX content reduction point of view if said value Fi1 exceeds a predetermined threshold value TH1. Said predetermined threshold value TH1 may be a suitable value. Said predetermined threshold value TH1 may be, for example, 90%, 95% or 98%. Said predetermined value TH1 may be in a range 95-99 ° />.

According to one aspect of the invention, it can be determined that the SCFi catalyst 270 is defective from a NOX content reduction point of view if said value Fil is below said predetermined threshold value TH1.

It should be noted that dosing of said reducing agent takes place during According to an example, said curve is generated only when a temperature T2 of predetermined operating conditions of said SCFi catalyst. The catalyst 270 exceeds a predetermined temperature Tth and when a relatively high and / or stationary exhaust gas mass flow prevails. According to an example, said curve is generated only when a temperature T1 of the exhaust gases exceeds a predetermined temperature Tth and when a relatively high and / or stationary exhaust gas mass flow prevails. Said operating conditions can be achieved by controlling the engine of the vehicle by means of said first control unit 200 and / or said second control unit 210. C denotes the SCR catalyst 270 is denoted as a function of in terms of ppm (parts per million). Dosage of reducing agent D is given in terms of [g / minute].

It will be seen that the SCR catalyst 270 produces a minimum NOX content C2 downstream of the SCR catalyst 270 at a dosage D2. The value C2 thus indicates a minimum value for NOx content downstream of the SCR catalyst of a function C (D).

According to one aspect of the invention, it can be determined that the SCR catalyst 270 is not defective from a NOX content reduction point of view if said value C2 is below a predetermined threshold value TH2. Said predetermined threshold value TH2 may be a suitable value. Said predetermined threshold value TH2 may be, for example, 40, 50 or 60 ppm. Said predetermined value TH2 may be in a range of 70-100 ppm.

According to one aspect of the invention, it can be determined that the SCR catalyst 270 is defective from a NOX content reduction point of view if said value C2 exceeds said predetermined threshold value TH2.

It should be noted that dosing of said reducing agent takes place under predetermined operating conditions of said SCR catalyst 270. According to an example, said curve C (D) is generated only when a temperature T2 of catalyst 270 exceeds a predetermined temperature Tth and when a relatively high and / or stationary exhaust mass flow prevails. According to an example, said curve C (D) is generated only when a temperature T1 of the exhaust gases exceeds a predetermined temperature Tth and when a relatively high and / or stationary exhaust gas mass flow prevails. Said operating conditions can be achieved by controlling the engine of the vehicle by means of said first control unit 200 and / or said second control unit 210. Referring to Figure 5, a diagram of an embodiment of a device 500 is shown. The control units 200 and 210 described with reference to Figure 2 may in one embodiment 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 part 530 in which a computer program, such as an operating system, is stored to control the operation of the device 500. Furthermore, the device 500 comprises a bus controller, a serial communication port, I / O means, an A / D converter, a time and date input and transmission unit, a 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 troubleshooting routines in an SCR system comprising a dosing unit for dosing reducing agent into an engine exhaust duct upstream of an SCR catalyst for reducing NOX content in an exhaust flow from said engine.

The computer program P may comprise routines for determining NOX content in the exhaust gas flow downstream of said SCR catalyst. The computer program P may comprise routines for reducing agents under predetermined operating conditions of said SCR catalyst. The computer program P may comprise routines for determining successively changing the dosage of said SCR catalyst preferably reducing said NOX content in the exhaust gas stream downstream of said SCR catalyst to a predetermined extent during said successively changing dosage. The computer program P may include routines for, based on the result of said determination, determining whether the NOX content reduction point of view is defective. The computer program P may comprise routines for whether or not said SCR catalyst is from achieving said predetermined operating conditions in the form of a predetermined minimum temperature level of said SCR catalyst and a predetermined exhaust gas mass flow. The computer program P may comprise routines for achieving said predetermined operating conditions by controlling the operation of said motor. The computer program P may comprise routines for waiting for a state of continuity of the reduction of NOX content downstream of said SCR catalyst.

The computer program P may comprise routines for: - determining absolute values regarding said NOX content in the exhaust gas flow downstream of said SCR catalyst, and / or routines for: - determining absolute values regarding said NOX content in the exhaust gas flow upstream of said SCR catalyst; determining absolute values regarding said NOX content in the exhaust gas flow downstream of said SCR catalyst; and - determining a degree of NOX conversion of the SCR catalyst, on the basis of said NOX content in the exhaust gas flow upstream of said SCR catalyst and said NOX content in the exhaust gas flow downstream of said SCR catalyst.

The computer program P may comprise routines for representing said SCR catalyst reduction of NOX content downstream of said SCR catalyst during said successively changing dosage as absolute values of said NOX content downstream of said SCR catalyst as a function of reducing agent dosage or NOX conversion rate as a function of reducing agent dosage. The computer program P may include routines for identifying a minimum of a function for said NOX content downstream of said SCR catalyst P may include routines for identifying a maximum of a function for the SCR catalyst as a function of reducing agent dosage. The computer program NOX conversion rate at as a function of reducing agent dosing.

The computer program P may comprise routines for presenting said results of said determination in the form of an error code. The computer program P may comprise routines for performing a check of the function of the SCR system in addition to said SCR catalyst.

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, L280 and L285 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 received input data has been temporarily stored, the data processing unit 510 is prepared to perform code execution on a as described above.

According to one embodiment, signals received at the data port 599 include information on NOX content upstream of the SCR catalyst 270. According to one embodiment, signals received at the data port 599 include information about NOX content downstream of the SCR catalyst 270. According to one embodiment, signals received at the data port 599 include information about a saving temperature of the exhaust gases upstream of the SCR catalyst 270. According to one embodiment, signals received at the data port 599 include information about a boiling temperature of a suitable surface of or component i of the exhaust duct 290, for example a temperature of the SCR catalyst 270.

The received signals at data gate 599 may be used by device 500 to determine whether or not said SCR catalyst is defective from a NOX content reduction point of view.

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. 30

Claims (26)

10 15 20 25 30 536 950 PATENT REQUIREMENTS A method of troubleshooting an SCR system comprising a metering unit (250) for metering a reducing agent into an engine exhaust duct (290) upstream of an SCR catalyst (270) for reducing NO content in an exhaust gas stream from said engine, comprising the step of: - determining (s310) NOX content in the exhaust gas flow downstream of said SCR catalyst (270), characterized by the steps of: - under predetermined operating conditions of said SCR catalyst (270) successively changing (s320) the dosage of said reducing agent; determining (s330) whether the SCR catalyst (270) is capable of reducing said NOX content in (270) to a predetermined extent during said successively changing dosage; the exhaust gas flow downstream of said SCR catalyst and - based on the result of said determination, determine (s340) whether said SCR catalyst (270) is defective or not from a NOX content reduction point of view. A process according to claim 1, comprising the step of: - providing said predetermined operating conditions in the form of a predetermined minimum temperature level of said SCR catalyst (270) and a predetermined exhaust gas mass flow. A method according to claim 1 or 2, comprising the step of: - achieving said predetermined operating conditions by controlling the operation of said engine. A method according to any one of the preceding claims, wherein the step of successively changing said dosage comprises continuously increasing or continuously decreasing the dosage. 31 10 15 20 25 30 536 950 A method according to any one of claims 1-3, wherein the step of successively changing said dosage comprises incrementally increasing or incrementally decreasing the dosage. A process according to any one of claims 4 or 5, comprising the step of: - waiting for a state of continuity of the reduction of NOx content downstream of said SCR catalyst (270). A process according to any one of the preceding claims, wherein the step of determining whether said SCR catalyst (270) is capable of reducing said NOX content in the exhaust gas stream downstream of said SCR catalyst (270) to a predetermined extent comprises the step of: - determining absolute values of said SCR catalyst (270). NOX content in the exhaust gas stream downstream of said SCR catalyst (270), and / or the steps of: - determining absolute values regarding said NOx content in the exhaust gas stream upstream of said SCR catalyst (270); determining absolute values regarding said NOX content in the exhaust gas flow downstream of said SCR catalyst (270); and determining a NOX conversion rate of the SCR catalyst (270), based on said NOx content of the exhaust gas stream upstream of said SCR catalyst (270) and said NOx content of the exhaust gas stream downstream of said SCR catalyst (270). A process according to any one of the preceding claims, comprising the step of: - representing said SCR catalyst reduction of NOx content downstream of said SCR catalyst (270) during said successively changing dosage as absolute values of said NOX content downstream of said SCR catalyst ( 270) as a function of reducing agent dosage or NO, conversion rate as a function of reducing agent dosage. 32 10 15 20 25 30 536 950 The method of claim 8, wherein said NOX content downstream of said SCR catalyst (270) as a function of reducing agent dosing includes a minimum. The method of claim 8, wherein said NOX conversion rate as a function of reducing agent dosage includes a maximum. A method according to any one of the preceding claims, comprising the step of: - presenting said results of said determination regarding reduction of said NOX content in the exhaust gas flow downstream of said SCR catalyst (270) to a predetermined extent in the form of an error code. A troubleshooting device in an SCR system comprising a metering unit (250) for metering a reducing agent into an engine exhaust duct (290) upstream of an SCR catalyst (270) for reducing NOX content in an exhaust stream from said engine, comprising : - means (265) adapted to determine NOX content in the exhaust gas flow downstream of said SCR catalyst (270), characterized by: - means (200; 210; 500) adapted to, under predetermined operating conditions of said SCR catalyst (270), successively changing the dosage of said reducing agent; means (200; 210; 500) adapted to determine whether the SCR catalyst is capable of reducing said NOX content in the exhaust gas flow downstream of said SCR catalyst (270) to a predetermined extent during said successively changing dosage; and means (200; 210; 500) adapted to determine, based on the result of said determination, whether or not said SCR catalyst (270) is defective from a NOx content reduction point of view. The apparatus of claim 12, comprising: means (200; 210; 500) adapted to provide said predetermined operating conditions in the form of a predetermined minimum temperature level of said SCR catalyst (270) and a predetermined exhaust mass flow. Device according to claim 12 or 13, comprising: - means (200; 210; 500) adapted to provide said predetermined operating conditions by controlling the operation of said engine. Device according to any one of claims 12-14, comprising: - means (200; 210; 500) adapted to change said dosage by continuously increasing or continuously decreasing the dosage. Device according to any one of claims 12-15, comprising: - means (200; 210; 500) adapted to successively change said dosage by gradually increasing or gradually decreasing the dosage. Device according to claim 15 or 16, comprising: - means (200; 210; 500) adapted to wait for a state of continuity of the reduction of NOX content downstream of said SCR catalyst (270). The apparatus of any of claims 12-17, wherein means (200; 210; 500) adapted to determine whether said SCR catalyst (270) is capable of reducing said NOX content in the exhaust gas stream downstream of said SCR catalyst (270) in a predetermined manner extending comprises: - means (200; 210; 500) adapted to determine absolute values regarding said NOX content in the exhaust gas flow downstream of said SCR catalyst (270); and / or: means (200; 210; 500) adapted to determine absolute values of said NOX content in the exhaust gas flow upstream of said SCR catalyst (270); means (200; 210; 500) adapted to determine absolute values of said NOX content in the exhaust gas flow downstream of said SCR catalyst (270); and 536 950 means (200; 210; 500) adapted to determine a NOX conversion rate of the SCR catalyst (270), based on said NOx content in the exhaust gas stream upstream of said SCR catalyst (270). and said NOX content in the exhaust gas stream downstream of said SCR catalyst (270). An apparatus according to any one of claims 12 to 18, comprising: - means (200; 210; 500) adapted to represent said NOx content reduction of said SCR catalyst downstream of said SCR catalyst (270) during said successive altered dosage as absolute values of said NOX content downstream of said SCR catalyst (270) as a function of reducing agent dosage or NOx conversion rate as a function of reducing agent dosage. The apparatus of claim 19, wherein said NOx content downstream of said SCR catalyst as a function of reducing agent dosing includes a minimum. The device of claim 19, wherein said NOX conversion rate as a function of reducing agent dosage includes a maximum. An apparatus according to any one of claims 12-21, comprising: - means (200; 210; 500, 280; 285) adapted to present said result of said determination regarding reduction of said NOX content in the exhaust gas flow downstream of said SCR catalyst (270 ) to a predetermined extent in the form of an error code. Motor vehicle (100; 110) comprising a device according to any one of claims 12-22. A motor vehicle (100; 110) according to claim 23, wherein the motor vehicle is something of a truck, bus or passenger car. 35 10 536 950 A computer program (P) for troubleshooting an SCR system, said computer program (P) comprising program code for causing an electronic controller (200; 500) or another computer (210; 500) connected to the electronic controller (200; Performing the steps according to any one of claims 1-1 1 _ 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 1-11, 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). 36