SE537270C2 - Device and method for detecting defective NOx sensors - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for detecting defective NOx sensors.

The invention also relates to a computer program product comprising program code for a computer for implementing a method according to the invention. The invention also relates to a device for detecting defective NOx sensors and a motor vehicle equipped with the device. 10 BACKGROUND Today, there are strict regulations in many areas regarding emissions of unwanted gases and particles from vehicles. Vehicle manufacturers are constantly working to improve the after-treatment system to make it possible to further reduce the amount of unwanted emissions in exhaust gases. Unwanted gases formed in vehicle engines, for which there are restrictions, are, for example, nitrogen oxides (NOx, 5k / en denoted NOR).

One way to reduce the amount of NOx in exhaust gases is to use a so-called after-treatment system, for example an SCR system (Selective Catalytic Reduction). Said after-treatment system can also be called exhaust treatment system.

This system comprises an SCR catalyst and a reductant, e.g. urea. In the SCR catalyst, said reductant and NOx gas can react and be converted to nitrogen gas and water.

The amount of NOx in exhaust gases is measured with at least one NOx sensor that is placed in the exhaust system, for example downstream of the SCR catalyst. The sensor is used to detect the amount of NOx in exhaust gases emitted from the vehicle. The signal from the NOx sensor can be used to control, for example, the amount of reductant used in the SCR system or to generate error codes where the amount of NOx is higher than a certain predetermined value. 1 537 270 An error code generated when the amount of NOx in the exhaust gases is higher than a certain predetermined value is registered in a control system of the vehicle. In some cases, such an error code may mean that a warning light starts flashing in the vehicle and the Good is recommended to drive to a service station within a certain predetermined time. In some cases, an error code generated on the basis of a NOx sensor signal means that the vehicle's maximum speed is limited until the cause of the error code has been identified. In some cases, an error code may be generated on the basis of an incorrect NOx sensor signal, which error code may indicate that urea of a quality that does not meet certain predetermined requirements has anyants.

A defective NOx sensor detects an incorrect amount of NOx in exhaust gases. A defective NOx sensor can cause incorrect error codes associated with an increased amount of NOx to be generated. In the event of a service of the vehicle 6 an error code associated with an increased NOx content has been generated, a first service measure may be to replace the NOx sensor. The NOx sensor is a relatively simple component to replace and service personnel may want to make sure that the NOx sensor does not cause an incorrectly detected amount of NOx in the exhaust gases before they start a more complicated troubleshooting of the vehicle. In cases where the NOx sensor is not defective, the NOx sensor is replaced immediately. SUMMARY OF THE INVENTION An object of the present invention is to provide a new and advantageous method for detecting at least one defective NOx sensor.

Another object of the invention is to provide a new and advantageous device and a new and advantageous computer program for detecting at least one defective NOx sensor.

A further object of the invention is to provide a method, apparatus and computer program for effecting a reliable and unusual detection of at least one defective NOx sensor. These objects are achieved by a method for detecting at least one defective NOx sensor according to claim 1 and a device according to claim 9.

Advantageous embodiments are set out in the independent claims.

According to one aspect of the present invention there is provided a method of detecting at least one defective NOx sensor arranged in an exhaust duct from an engine, comprising the steps of: - continuously determining an NOx content of exhaust gases from said engine in said exhaust duct by said NOx sensor ; determining a rate of change of said continuously determined NOx content; comparing a magnitude of said rate of change with a predetermined value; and - in the event that said magnitude of said rate of change exceeds said predetermined value, take this as an indication p5 that said NOx sensor is defective.

The inventors have realized that NOx sensors may have built-in defects. Said built-in defects of said NOx sensor may cause said NOx sensor to display incorrect food values for a limited period of time. After this time period, the NOx sensor 5terg5 to display the correct value.

The inventors have realized that an indication of said defect in said NOx sensor can be determined by, with the aid of the continuously determined NOx content of exhaust gases Iran an engine, determining a rate of change of said continuously determined NOx content. The magnitude of said rate of change is compared with a predetermined value, and dA said magnitude of said rate of change exceeds said predetermined value, this is taken as an indication p5 that said 3 537 270 NOx sensor is defective. The name predetermined value is an appropriate value which in fOrvag can be determined with the help of empirical data.

Said rate of change can be determined by calculating a time derivative of a curve determined on the basis of the continuously determined NOx levels of said exhaust gases.

The size has the said rate of change can be an absolute value of said size. Said rate of change can be indicated by a positive or negative sign. The method may comprise the step of: - comparing said rate of change has said continuously fixed NOx content with a predetermined rate of change has said NOx content, wherein said expected rate of change has said NOx content determined by means of a corresponding NOx sensor or arranged in a calculation model.

The inventors have realized that an indicator of an erroneous first NOx sensor is a detected rate of change, the said continuously determined NOx content in exhaust gases from the engine exceeding a predetermined value. In some cases, however, a rate of change may have the NOx content, where said rate of change exceeds a predetermined value be expected, for example due to different operating conditions of the engine. In these cases, the determined rate of change does not show the NOx content, where the said rate of change exceeds a predetermined value, a defective first NOx sensor. In cases where the said fixed rate of change exceeds a predetermined value and where the said rate of change is not related, the said rate of change of the said fixed NOx content indicates an incorrect first NOx sensor. 4 537 270 DS a rate of change of the NOx content has been determined, where the said rate of change exceeds a predetermined value, a comparison is made of the determined rate of change of the NOx content with a related rate of change of the NOx content. Said expected rate of change of the NOx content can be determined by means of a corresponding second NOx sensor arranged in an exhaust duct from an engine. Said corresponding second NOx sensor may, according to one embodiment, be arranged on the same flow side of the SCR catalyst in said exhaust duct as said first NOx sensor, for example an upstream side or a downstream side. According to an alternative, said corresponding second NOx sensor is arranged on the second flow side of the SCR catalyst in said exhaust duct. In the case where the corresponding second NOx sensor is arranged on the second flow side of the SCR catalyst in said exhaust duct, consideration must be given to the movement of the exhaust gas in said exhaust duct. In cases where said corresponding second NOx sensor is located upstream of said SCR catalyst and cI5 said first NOx sensor to be detected defective is located downstream of said SCR catalyst, the exhaust gases will first be n5 named corresponding second NOx sensor, and thereafter, after a period of time determined by how fast the exhaust gases are transported in the exhaust duct, the said exhaust gas comes p5 which a feed is carried out n5 the first NOx sensor. In order to be able to compare the respective rate of change of the NOx content, appropriate time synchronization is advantageously used.

The method may comprise the step of: comparing the rate of change of said continuously determined NOx content with a predetermined rate of change of said NOx content, wherein said expected rate of change of said NOx content is determined by a calculation model, wherein said motor operation includes. 537 270 A related rate of change of said NOx content determined by means of a first NOx sensor can according to an exemplary embodiment be determined by means of a corresponding second NOx sensor and / or a calculation model.

Said corresponding second NOx sensor may be provided upstream of said first NOx sensor of said exhaust duct, for example upstream of an SCR catalyst of the exhaust duct. The corresponding second NOx sensor may be presently located downstream of said first NOx sensor of said exhaust duct, for example downstream of an SCR catalyst of the exhaust duct.

In cases where the second NOx sensor is arranged upstream or downstream of the first NOx sensor, the said comparison can be adapted to parameters which affect the respective measured NOx content. Said parameters may refer to where said NOx sensor Jr is located in relation to the SCR catalyst, or any time delay to ensure that the respective NOx sensor determines NOx content of substantially the same volume of exhaust gases.

According to an exemplary embodiment, a expected rate of change of the NOx content of said exhaust gases can be generated by means of a calculation model. Said calculation model can be based on various operating parameters such as the amount of fuel injected into the engine, operating condition of the engine, the amount of reducing agent accumulated in the exhaust duct, etc., as well as external parameters such as the slope of the ground, rising air resistance of the vehicle etc.

The method may comprise the step of: - determining, on the basis of said comparison of said rate of change of said continuously determined NOx content with said expected rate of change of said NOx content, whether said rate of change is related. 6 537 270 Said comparison of said rate of change of said continuous fixed NOx content with a predetermined rate of change of said NOx content is performed to determine whether the fixed rate of change of NOx content is predetermined.

According to one example, a rate of change of the NOx content, where said rate of change exceeds a predetermined value, may occur when a accelerator pedal of the vehicle is rapidly released completely. According to another example, a rate of change of the NOx content, where said rate of change exceeds a predetermined value, may occur when the accelerator pedal is rapidly pressed to the bottom. There are also other examples of operating cases where the rate of change of the NOx content where said rate of change exceeds a predetermined water can occur, as in a start-up process of a NOx sensor.

For the above-mentioned cases, the said rate of change of the NOx content, where the said rate of change exceeds a predetermined value, is related.

The method may further comprise the step that if said rate of change of said continuously determined NOx content deviates from said expected rate of change of said NOx content, taking this as an established defect of said NOx sensor.

If a detected rate of change of said continuous fixed NOx content in exhaust gases from an engine exceeds a predetermined value and when said continuous continuous determined NOx content deviates from said expected change rate of said NOx content, this is taken as a found permanent defect in said NOx. .

The procedure may comprise the step of: 7 537 270 - in the case where a defect has been found with said NOx sensor and when a time period in which said size has said fixed rate of change exceeds said predetermined value is followed by a time period with increased fixed NOx content in comparison with a fixed NOx content during a time period before said time period when said magnitude of said fixed rate of change exceeds said predetermined value, generating an error code associated with defective NOx sensor.

The inventors have realized that when a defect is found in said first NOx sensor, and when a time period in which said magnitude of said fixed rate of change exceeds said predetermined value is added by a time period of increased fixed NOx content compared to a fixed NOx content during a time period before said time period when said magnitude has said fixed rate of change exceeds said predetermined value, this is usually associated with intermittent malfunction of said first NOx sensor. For these cases, an error code is generated associated with a defective first NOx sensor.

The inventors have realized that when a defect is found in said first NOx sensor, and when a time period in which said magnitude of said fixed rate of change exceeds said predetermined value is followed by a time period with a lower fixed NOx content compared to a fixed NOx content below a time period before said time period when said magnitude of said fixed rate of change exceeds said predetermined value, this is generally associated with intermittent malfunction of said first NOx sensor. For these cases, an error code associated with a defective first NOx sensor is generated.

Since the NOx content varies with time depending on a number of factors, such as the radiating operating state of the engine, an average of the NOx content during a time period may occur and an average of the NOx content over a period of time after said time period when said size has been determined. rate of change exceeds said predetermined value used. In the event of an observed increase of 8,537,270 or a decrease after the time period when the magnitude of said determined rate of change exceeds said predetermined value, an error code associated with a defective NOx sensor is generated.

According to one example, said increase in the NOx content is found only when the difference between the mean value of the NOx content during a time period before and a time period after said time period d5 said magnitude of said fixed rate of change exceeds said predetermined value exceeds a predetermined value.

According to one example, said lowering of the NOx content is found only when the difference between the mean value of the NOx content during a time period before and a time period after said time period d5 said magnitude of said fixed rate of change exceeds a fixed value.

According to an embodiment, the said error code associated with the said NOx sensor is generated only when the increase is not related. This can be checked by comparing the NOx content determined with a first NOx sensor with a NOx content determined by a corresponding second NOx sensor or alternatively by comparing with a NOx content determined with a calculation model.

According to an exemplary embodiment, said error code associated with said NOx sensor is generated only when the collection is not related. This can be checked by comparing the NOx content determined with a first NOx sensor with a NOx content determined by a corresponding second NOx sensor or alternatively by comparing with a NOx content determined with a calculation model.

According to an exemplary embodiment, said increase in the NOx content is found rada when the increase is expected, but when said increase exceeds said expected increase by a certain predetermined value. 9 537 270 According to an exemplary embodiment, said lowering of the NOx content is found r5da d5 the lowering is expected but d5 said lowering is below said expected lowering by a certain predetermined value.

The procedure may comprise the step of: in case a defect is found has said NOx sensor and d'a a period of time where said magnitude has said fixed rate of change exceeds said predetermined value is followed by a time period of elevated fixed NOx content compared to a fixed NOx content during a time period before said time period d5 said magnitude of said fixed rate of change exceeds said predetermined value, replacing a generated error code associated with elevated NOx content with said generated error code associated with defective NOx sensor.

In cases where the said first NOx sensor, which has been found to be defective, the incorrect food value has been determined, the said NOx content, the choice increased as sanctified and the said established food value returned to the expected food value of the said NOx content, an operator, e.g. at a service station, state that the incorrectly detected food values are probably due to the fact that said first NOx sensor only temporarily detected incorrect NOx levels. The procedure may include the step of: -the; - comparing the number of occurrences, where the magnitude of said rate of change exceeds said predetermined value, with a predetermined number; and in the event that said number of occurrences exceeds said predetermined number, take this as a matter indication p5 that said NOx sensor is defective. 537 270 The inventors have realized that a first NOx sensor which during a certain period of time has detected a number of occurrences where the magnitude of said rate of change exceeds said predetermined value and where said number of occurrences exceeds a predetermined number, indicates with a probability that said first NOx sensor is defective.

Said time period may be a certain predetermined time period, for example with a duration between 5 minutes and 5 hours of operating time. Said time period may be an appropriate period of time, for example 20 or 100 operating hours of the vehicle.

The inventive process can be carried out during operation, for example the vehicle is propelled on a suitable wagon section.

The inventive procedure can be carried out during operation when the vehicle is stationary, for example in a workshop or service facility.

The procedure can be implemented in existing motor vehicles. Program code is capable of detecting at least one defective NOx sensor arranged in an exhaust duct from an engine according to the invention can be installed in a control unit of the vehicle during manufacture thereof. A buyer of the vehicle can thus get. possibility to select the function of the procedure as an option. Alternatively, program code for performing the innovative method of detecting at least one defective NOx sensor arranged in an exhaust duct from an engine may be installed in a control unit of the vehicle when upgrading at a service station. In this case, the program code can be loaded into a memory in the control unit.

Program code for troubleshooting when detecting at least one defective NOx sensor arranged in an exhaust duct from an engine can be updated or replaced. Furthermore, different parts of the program code for detecting and handling at least one defective NOx sensor arranged in an exhaust duct from an engine can be replaced independently of one another. This modular configuration is advantageous from an underpass perspective.

According to one aspect of the present invention, there is provided an apparatus for detecting at least one defective NOx sensor arranged in an exhaust duct of an engine, comprising: means adapted to continuously determine an NOx content of exhaust gases from said engine in said exhaust duct, means adapted to determine a rate of change of said continuously determined NOx content; means adapted to compare a magnitude of said rate of change with a predetermined N./51*de; and means adapted that, in the event that the valley size of said rate of change exceeds said predetermined value, take this as an indication that said NOx sensor is defective.

According to one aspect of the invention, there is provided an apparatus for detecting at least one defective NOx sensor arranged in an exhaust duct from an engine, comprising: means adapted to compare said rate of change of said continuously determined NOx content with a predetermined rate of change of said NOx. slippery.

The device may comprise: - means adapted to determine, on the basis of naninda comparison of said rate of change of said continuously determined NOx content with said expected rate of change of said NOx content, whether said rate of change is expected.

The device may comprise: 12 537 270 means adapted that, when said rate of change of said continuously determined NOx content deviates from said expected rate of change of said NOx content, take this as an established defect in said NOx sensor.

According to one aspect, the step of taking this includes an established defect in said NOx sensor comprising the step of determining that said NOx sensor is defective.

The device may further comprise: means adapted that, in the event that a defect is found in said NOx sensor 10 and d5 a period of time where said magnitude of said fixed rate of change exceeds naninda predetermined values followed by a time period of increased fixed NOx content compared to a fixed NOx content during a time period before said time period d5 said magnitude of said fixed change rate exceeds said predetermined value, generating an error code associated with defective NOx sensor.

The device may further comprise: means adapted that, in the event that a defect is found in said NOx sensor and d5 a time period in which said magnitude of said fixed rate of change exceeds said predetermined value, it is joined by a time period of elevated NOx content compared to a fixed NOx content during a time period before said time period d5 said magnitude of said fixed rate of change exceeds said predetermined value, replacing a generated error code associated with elevated NOx content with said generated error code associated with defective NOx sensor.

The device may comprise: - means adapted to, during a certain predetermined period of time, register the number of cases in which the magnitude of said rate of change exceeds said predetermined value; 13 537 270 - means adapted to compare the number of cases, where the magnitude of said rate of change exceeds said predetermined value, by a predetermined number; and - means adapted that, in the event that said number of occurrences exceeds said predetermined number, take this as a matter indication p5 that said NOx sensor is defective.

According to one aspect of the present invention, there is provided a motor vehicle comprising the device for detecting at least one defective NOx sensor arranged in an exhaust duct from an engine. The motor vehicle can be a truck, bus or car.

According to one aspect of the invention, there is provided a computer program for detecting at least one defective NOx sensor arranged in an exhaust duct from an engine, said computer program comprising program code for causing an electronic control unit or another computer connected to the electronic control unit to perform the steps of any of claims 1-8.

According to one aspect of the invention, there is provided a computer program for detecting and managing at least one defective NOx sensor arranged in an exhaust duct from an engine, said computer program comprising program code stored on a computer readable medium for causing an electronic control unit or a another computer connected to the electronic control unit to perform the steps according to any one of claims 1-8.

According to one aspect of the invention, there is provided a computer program product comprising a program code stored on a computer readable medium performing the method steps according to any one of claims 1-8, when said program code is crossed by an electronic control unit or another computer connected to the computer. electronic control unit. Additional objects, advantages and novel features of the present invention will become apparent to those skilled in the art from the following details, as well as through the practice of the invention. While the invention is described below, it was apparent that the invention is not limited to the specific details described. Those skilled in the art having access to flavor aromas will again appreciate further applications, modifications and incorporations within other fields which are within the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the present invention and further objects and parts thereof, reference is now made to the following detailed description which is to be read in conjunction with the accompanying drawings in which like reference numerals refer to like parts throughout the figures. which: Figure 1 schematically illustrates a vehicle, according to an embodiment of the invention; Figure 2 schematically illustrates a device for detecting at least one defective NOx sensor arranged in an exhaust duct from an engine, according to an embodiment of the invention; Figure 3a schematically illustrates a diagram, according to an aspect of the invention; Figure 3b schematically illustrates a diagram, according to an aspect of the invention; Figure 3c schematically illustrates a diagram, according to an aspect of the invention; Figure 3d schematically illustrates a diagram, according to an aspect of the invention; Figure 3e schematically illustrates a diagram, according to an aspect of the invention; Figure 3f schematically illustrates a diagram, according to an aspect of the invention; Figure 3g schematically illustrates a diagram, according to an aspect of the invention; Figure 4a schematically illustrates a flow chart of a method, according to an embodiment of the invention; Figure 4b schematically illustrates in further detail a flow chart of a method, according to an aspect of the invention; and 537 270 Figure 5 schematically illustrates a computer, according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE 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 may 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 combustion engine and is thus not limited to an engine of a motor vehicle. The inventive method and the inventive device according to an aspect of the invention are suitable for other platforms which include an engine or motor vehicle, such as e.g. watercraft. The watercraft can be of any suitable type, such as e.g. engine parts, ships, lighthouses or ships.

The inventive method and the inventive device according to an aspect of the invention are also suitable for e.g. systems including, for example, a stone crusher or the like.

The inventive method and the inventive device according to an aspect of the invention are also suitable for e.g. systems including industrial engines and / or motorized industrial robots.

The inventive method and the inventive device according to an aspect of the invention also illuminate choices for different types of power plants, such as e.g. an electric power plant comprising a diesel-powered electricity generator. The inventive method and the inventive device are suitable for any suitable engine system which includes an engine, such as e.g. at a locomotive or other platform.

The innovative procedure and the innovative device are suitable for an arbitrary system that includes a NOx generator.

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

If the term "line" to a passage is used to hold and transport a fluid, such as e.g. a reductant in liquid form. The pipe can be a rudder of any dimension. The cable can consist of an arbitrary, suitable material, such as e.g. plastic, rubber or metal !.

Hari refers to the terms "reductant" or "reducing agent" as 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. Said reductant is according to an embodiment so-called AdBlue. Of course, other types of reductants can be used. In this, AdBlue is mentioned as an example of a reductant, but a person skilled in the art realizes that the innovative procedure and the innovative device can be realized for other types of reductants.

Referring to Figure 2, a device 299 of the vehicle 100 is shown. The device 299 may be located in the tractor 110. The device 299 may form part of or include a device for detecting at least one defective NOx sensor. 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 filled if necessary. According to this example, the device comprises an internal combustion engine 206 and an exhaust duct 290.

A first line 271 is arranged to direct the reductant to a pump 230 from the container 205. The pump 230 may be arranged to pump up the reductant from the container 205 via the first line 271 and via a second line 272 supply said reductant to a dosing unit 250. The dosing unit 250 may include an electrically controlled dosing device, by means of which a flow of reductant added to the exhaust duct 290 can be controlled.

The dosing unit 250 Jr arranged to supply said reductant to said exhaust duct 290 of the vehicle 100. According to this embodiment Jr an SCR catalyst 270 arranged downstream of a layer of the exhaust system clar supply of the reductant takes place. The amount of reductant supplied to the exhaust system Jr is intended to be used in the SCR catalyst 270 to reduce the amount of unwanted emissions.

A diesel oxidation catalyst 259 Jr presently arranged in the exhaust duct 290 downstream of said engine 206. Said diesel oxidation catalyst 259 Jr presently arranged in the exhaust duct 290 upstream of narrinda SCR catalyst 270.

The said diesel oxidation catalyst 259 may be referred to as a DOC unit.

A third conduit 273 is provided 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 bealer 205.

The first control unit 200 is arranged for communication with the pump 230 via a long L230. The first control unit 200 is arranged to control operation of the pump 230. 18 537 270 A first NOx sensor 255 Jr arranged at the exhaust duct 290. The first NOx sensor 255 Jr arranged for communication with the first control unit 200 via a long L255. The first NOx sensor 255 is arranged to continuously determine a convincing NOx content of the exhaust stream in the exhaust duct 290 upstream of said 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 sensor 255 is arranged to continuously send signals including information about a moving NOx content upstream of the SCR catalyst 270 to the first control unit 200. According to one embodiment, by means of the first control unit 200, a change rate H 'of said, is determined by named first NOx sensor 255, continuously fixed NOx content. The control unit 200 is arranged to compare a magnitude of said rate of change H 'with a predetermined value H'max and in case the magnitude of said rate of change H' exceeds said predetermined value H 'max, take this as an indication that the first NOx sensor 255 Jr defective.

According to an exemplary embodiment, the first NOx sensor 255 is arranged to continuously determine a moving NOx content of the exhaust stream in the exhaust duct 290 downstream of said SCR catalyst 270.

A second NOx sensor 265 is provided at the exhaust duct 290. The second NOx sensor 265 is arranged for communication with the first control unit 200 via a long L265. The second NOx sensor 265 is arranged to continuously determine a radiating NOx content of the exhaust stream in the exhaust duct 290 downstream of said 5CR catalyst 270. The second NOx sensor 265 is arranged to continuously send signals including information of a corresponding NOR content downstream of said 5CR catalyst 270. SCR catalyst 270 to the first control unit 200. According to one embodiment, with the aid of the first control unit 200, a rate of change H 'of said, by means of said second NOx sensor 265, continuously determined NOx content is determined. The control unit 200 is arranged to compare a magnitude of said change rate H 'with a predetermined value H'max and in case said magnitude has said change rate H' exceeds said predetermined value H'max, take this as an indication that said second NOx sensor 265 is defective.

According to an exemplary embodiment, the second NOx sensor 265 is arranged to continuously determine a moving NOx content of the exhaust stream in the exhaust duct 290 upstream of said SCR catalyst 270.

According to an exemplary embodiment, the first control unit 200 is arranged to determine a predetermined rate of change H'exp of said NOx content by means of a continuously fixed NOx content where said continuously determined NOx content is determined by means of said first or other NOx sensors 255, 265. According to an exemplary embodiment, a predetermined rate of change H'exp of said NOx content is determined by means of a continuously determined NOx content where said continuously determined NOx content is determined by means of a third NOx sensor (not shown) arranged in said exhaust duct 290. in one embodiment, at least a third NOx sensor (not shown) may be provided for communication with the first control unit 200 via a dedicated link. Said third NOx sensor may be arranged to continuously determine a moving NOx content having the exhaust stream upstream or downstream of said SCR catalyst 270. Said third NOx sensor is arranged to continuously send signals including information about said radiating NOx content to the first control unit. 200.

The first controller 200 is arranged to compare said determined expected rate of change H'exp with said determined rate of change H 'to determine whether said first or second NOx transducers 255, 265 are defective.

The first control unit 200 is arranged to compare said rate of change H 'of said continuously determined NOx content, where said rate of change 537 270 H' is determined by means of the feed value from said first NOx sensor 255, with a related change rate H ' NOx content, where said expected rate of change H'exp of said NOx content is determined by said corresponding second NOx sensor 265 or said corresponding third NOx sensor. According to one embodiment, the first control unit 200 is arranged to compare said rate of change H 'of said continuously determined NOx content, where said rate of change H' is determined by means of the feed value from said first NOx sensor 255, with a predetermined rate of change in said NOx content where said expected rate of change H'exp is determined using the food value from said second NOx sensor 265 or third NOx sensor.

The first control unit 200 is arranged to compare said rate of change H 'with said continuously determined NOx content, where said rate of change is determined by means of the food value from said second NOx sensor 265 with a related rate of change H'exp at narrinda NOx. wherein said expected rate of change H'exp of said NOx content is determined by said corresponding first NOx sensor 255 or said corresponding third NOx sensor. According to one embodiment, the first control unit 200 is arranged to compare said rate of change H 'of said continuously determined NOx content, where said rate of change H' Jr is determined by means of the food value from said second NOx sensor 265 at a related rate of change H ' NOx content where said expected rate of change H'exp is determined by the food value from said first NOx sensor 255 or said third NOx sensor.

According to an exemplary embodiment, the first control unit 200 is arranged to calculate said expected change rate H'exp of said NOx content upstream of said SCR catalyst 270. This can be done by means of a calculation model which is stored in a memory in the first control unit 200. The first control unit 200 may be arranged to bet-Una said expected rate of change H'exp of said NOx content upstream of said SCR catalyst 270 on the basis of 21 537 270 operating conditions of said engine such as, amount of injected fuel in the engine, rotating engine speed, power output and erasing load on the engine etc.

According to one embodiment, the first control unit 200 is arranged to control said expected change rate H'exp of said NOx content downstream of said SCR catalyst 270. This can be done by means of a calculation model. The first control unit 200 may be arranged to calculate said expected rate of change H'exp of said NOx content downstream of said SCR catalyst 270 on the basis of operating conditions of said engine such as, amount of injected fuel, variable engine speed, power output and radiating load of the engine etc.

The first control unit 200 is arranged to detect at least one defective NOx sensor 255, 265 arranged in an exhaust duct 290 from an engine 206. The first control unit 200 is arranged to: continuously determine an NOx content of exhaust gases from said engine 206 in said exhaust duct 290. named NOx sensors 255, 265; determining a rate of change H 'of said continuously determined NOx content; comparing a magnitude of said rate of change H 'with a predetermined water H' max; and if the case where said magnitude of said rate of change H 'exceeds said danger-determined value H'max, take this as an indication p5 that said NOx sensor 255, 265 Sr is defective.

The first control unit 200 may be arranged to compare said rate of change H 'of said continuous fixed NOx content with a related rate of change H'exp of said NOx content, where said expected rate of change H' exp of said NOx content is determined by means of a corresponding NOx. sensor 255; 265 arranged in said exhaust duct 290 and / or a calculation model. The first control unit 200 may be arranged to determine said expected rate of change H'exp by means of a calculation model, said calculation model comprising operating conditions of said motor.

The first control unit 200 is arranged to determine, on the basis of said comparison of said rate of change H 'of said continuously determined NOx content with said expected rate of change H'exp of said NOx content, whether said rate of change H' Jr is related.

The first control unit is arranged to, when the narrative rate of change H 'of said continuously determined NOx content deviates from said expected rate of change H'exp of said NOx content, take this as an established defect in said NOx sensor 255; 265.

The first control unit is arranged to - in case cla a defect is found in the said NOx sensor 255; 265 and when a time period where said magnitude of said fixed rate of change H 'exceeds said predetermined value H'max is followed by a time period of increased fixed NOx content in comparison with a fixed NOx content during a time period before said time period d5 said magnitude of said fixed rate of change H 'exceeds said predetermined value H'max, generating an error code associated with defective NOx sensor 255, 265.

The first control unit 200 is arranged that, in the event of a defect being found in said NOx sensor 255, 265 and a period of time where said magnitude of said fixed rate of change H 'exceeds said predetermined value H'max is followed by a time period of increased fixed NOx content in comparison with a fixed NOx content during a time period before said time period when said size of said fixed rate of change H 'exceeds said predetermined value 23 537 270 H', replacing a generated error code associated with increased NOx content with said generated error code associated defective NOx sensor 255, 265.

The first control unit 200 Jr arranged to - during a certain predetermined period of time, register a number of occurring cases X where the magnitude of said change rate H 'exceeds said predetermined value H' max; compare the number of cases X, where the magnitude of said rate of change H 'exceeds said predetermined value H'max, with a predetermined number Xmax; and in the event that said number of occurring cases X exceeds said predetermined number Xmax, take this as a matter indication p5 that said NOx sensor 255, 265 is defective. Xmax can be an appropriate number, for example 1, 3, 5 or 10. Xmax can be an appropriate number exceeding 10.

The first control unit 200 is arranged for communication with presentation means 280 via a long L280. Said display means 280 may be provided in a driver's 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 and / or other relevant information regarding the innovative method of detecting at least one defective NOx sensor arranged in an exhaust duct 290 from an engine 206. The first control unit 200 may be arranged to by means of said presentation means 280 present a result on whether the said NOx sensor 255, 265 is defective or not. 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 NOx sensors 255, 265 perform a satisfactory function. The first control unit 200 is arranged for communication with a communication unit 285 via a line L285. Said communication unit 285 may be present in, 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 include, for example, a display screen. The first control unit 200 is arranged to automatically or upon request present an error code and / or other relevant information regarding the innovative method for detecting at least one defective NOx sensor 255, 265 arranged in an exhaust duct 290 from an engine 206. The first control unit 200 may be arranged to, by means of said communication terminal 285, present a result as to whether the first 255 and / or other 265 NOx sensors are defective or not.

A second control unit 210 is arranged for communication with the first control unit 200 via a long L210. The second control unit 210 may be releasably connected to the first control unit 200. The second control unit 210 may be a control unit external to the vehicle 100. The second control unit 210 may be arranged to perform the inventive method steps according to the invention. The second control unit 210 can be used to load software to the first control unit 200, in particular software for carrying out the inventive 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. to detect Stnninstone a defective NOx sensor 255, 265 arranged in an exhaust duct 290 from an engine 206.

The second control unit 210 may be arranged to: 537 270 - continuously determine a NOx content of exhaust gases from said engine 206 in said exhaust duct 290 by means of said NOx sensors 255, 265; determining a rate of change H 'of said continuously determined NOx content; comparing a magnitude of said rate of change H 'with a predetermined value H'max; and in the event that said magnitude of said rate of change H 'exceeds said predetermined value H'max, take this as an indication p5 that said NOx sensor 255, 265 is defective.

Referring to Figure 3a, a diagram is shown in which NOx content in exhaust gases from an engine 206 is given as a function of time T. NOx content is given in terms of ppm (parts per million). Time T is given in terms of seconds (s).

According to one aspect of the invention, the NOx content of exhaust gases Iran is determined by an engine 206 of an exhaust duct 290 by means of at least one NOx sensor 255, 265 continuously. Figure 3a shows a curve 1 generated by the continuous food value detected by said NOx sensor 255, 265 where said NOx sensor 255, 265 determines the NOx content in an exhaust duct 290 which directs exhaust gases from an engine 206. A control unit 200, 210 determines a rate of change H 'of said continuously determined NOx content. A magnitude of said rate of change H 'is compared with a predetermined value H'max and in the event that said magnitude of said rate of change H' exceeds said predetermined value H 'max, this is taken as an indication p5 that said NOx sensor 255, 265 is defective. .

In Figure 3a, a magnitude of said change rate H 'where said magnitude exceeds said predetermined value H'max has been detected at time T2.

Said rate of change H 'can be determined by deriving said curve 1 with respect to time. The magnitude of said rate of change can alternatively be obtained by analyzing a fixed size of a food value of the NOx content of said exhaust gas at a number of times. Since the NOx content differs more than a predetermined value between two subsequent times, for example the time T1 and the time T2 in Figure 3a, it can be determined that the magnitude of said change rate H 'exceeds said predetermined value H'max and armed indicates said change rate H' at time T2 that the said NOx sensor 255, 265 is defective.

According to one aspect of the present invention, determining whether said NOx sensor 255, 265 Jr may be defective includes the step of considering whether said NOx content in connection with said rate of change H 'exceeds said predetermined \ Mr-de H'max exceeds a predetermined threshold value Tv1. If said NOx content exceeds said predetermined threshold value Tv1 in connection with said change rate H 'exceeding said predetermined value H'max, it can be determined with high probability that said NOx sensor 255, 265 Jr is defective. The said predetermined threshold value Tv1 is a suitable water.

According to one aspect of the present invention, determining whether said NOx sensor 255, 265 is defective p5 correspondingly comprises the step of considering whether said NOx content, in connection with said rate of change H 'exceeding said predetermined value H'max, is less than one predetermined threshold value Tv2. If said NOx content falls below said predetermined threshold value Tv2 in connection with said rate of change exceeding said predetermined value H'max, it can be established with good probability that said NOx sensor 255, 265 is defective. The aforementioned predetermined threshold value Tv2 is an appropriate value.

The said threshold values Tv1 and 1v2 are illustrated 5k / en in the diagrams described with reference to Figures 3b-3f. 27 537 270 The magnitude of said rate of change H 'is an absolute amount of said rate of change H'. The said rate of change H 'can thus also be negative, as shown in Figure 3a after the time T2.

Since it is determined that the said magnitude of said fixed rate of change H 'exceeds a certain predetermined value, H'max compares said fixed rate of change H' in Figure 3a with a related rate of change H'exp. Said expected rate of change H'exp is determined from a related NOx content where said expected NOx content is obtained from a calculation model where the engine operating mode can be used as parameters in said model, or alternatively from a NOx content which is continuously determined by a corresponding NOx sensor. 265 arranged at said exhaust duct 290. The expected NOx content is represented by curve 2 in figure 3a. In Figure 3a it can be stated that at time T2 the determined rate of change network exceeds predetermined value H'max. At time T2 or alternatively at time corresponding to time T2 of Curve 2, which represents said expected NOx content, it can be read that the expected rate of change H'exp does not correspond to said fixed rate of change H '. Thus, it can be stated that the said NOx sensor 255, 265 in Figure 3a is defective.

Figure 3a shows that a time period where said magnitude of said fixed rate of change H 'exceeds said predetermined value H'max is followed by a time period T3-T4 with increased fixed NOx content H2 in comparison with a fixed NOx content H1 for a time period TO -T1 danger said period of time when said magnitude of said fixed rate of change H 'exceeds said predetermined value H'max. Said fixed NOx content varies from time to time so that an average value of said NOx content can be used to perform said comparison of NOx content before and after said time period where said magnitude of said fixed change rate H 'exceeds said predetermined value H'exp. In 28 537 270 the following description resides. H1 and H2 are interpreted as the mean value of the NOx content over a period of time.

DS named NOx sensor 255, 265 is found to be defective generated, at the elevated value H2 after a time period d5 said fixed rate of change H 'exceeds said predetermined value H'exp, an error code associated with increased NOx content H2. According to one embodiment, said error code associated with defective NOx sensor 255, 265 may replace an error code associated with elevated NOx content H2. The said error code associated with a defective NOx sensor is generated when the aforementioned NOx content H2 is not Sr expected. In Figure 3a it can be deduced from curve 2 representing the expected NOx content that said increase H2 is not Sr related because the expected NOx content does not show any increase in the NOx content after said time period dS said magnitude of said fixed rate of change H 'exceeds named predetermined varde H'exp. According to one embodiment, said error code associated with defective NOx sensor can be generated d5 said increase of NOx content H2 after time Ti Jr related, but dS said increase of NOx content after time Ti differs more than a predetermined value from said expected increased NOx -slippery.

Said NOx sensors 255, 265 may be located ph any arbitrary stable position of the exhaust duct 290, for example upstream or downstream of the SCR catalyst 270.

Referring to Figure 3b, a diagram is shown where NOx content in exhaust gases from an engine 206 is given as a function of time T. NOx content is given in terms of ppm. Time T is given in terms of seconds (s).

Figure 3b shows that the obtained NOx content Sven can show a negative minimum value. 29 537 270 Referring to Figure 3c, a diagram is shown where NOx content is given as a function of time T. NOx content is given in terms of ppm. Time T is given in terms of seconds (s).

The magnitude of said rate of change H 'is an absolute amount of said rate of change. Said rate of change can thus also be negative, which is the case at the time Ti in Figure 3c.

Figure 3c shows that a time period in which the fixed magnitude of said fixed rate of change H 'exceeds said predetermined value H'max is followed by a time period T2-T3 with a lower fixed NOx content H2 in comparison with a fixed NOx content H1 for a period of time. TO-T1 for said time period d5 nJmnda magnitude of said fixed change rate H 'exceeds said predetermined value H'max. When said NOx sensor 255, 265 is found to be defective as said determined rate of change H 'exceeds said predetermined value H' at time Ti and cla said rate of change does not correspond to a related rate of change H'exp of said NOx content, generated, at the law value H2, error code associated with a lower NOx content H2. According to one embodiment, said error code associated with defective NOx sensor 255, 265 may replace a generated error code associated with a lower NOx content H2. Said error code is generated cla said lower NOx content H2 not Jr fOrvantat. In Figure 3c it can be deduced from curve 2 which represents the expected NOx content that said decrease H2 is not Jr related because the expected NOx content does not indicate any decrease in the NOx content. According to one embodiment, said error code associated with defective NOx sensor 255, 265 may be generated when said increase in NOx content H2 after time Ti Jr is related, but d5 said decrease in NOx content after time Ti differs more than a predetermined value from said expected elevated NOx content.

With reference to Figure 3d, the NOx content is given as a function of time T. The NOx content is given in terms of ppm. Time T is given in terms of seconds (s). 537 270 Figure 3d shows an example where a time period where said magnitude of said fixed rate of change H 'exceeds said predetermined value H'max is followed by a time period T2-T3 with fixed NOx content H2 which coincides with a fixed NOx content H1 below a time period TO-T1 before said time period when said magnitude of said fixed rate of change H 'exceeds said predetermined value H'max. Thus, no error code associated with a defective NOx sensor is generated according to the embodiment illustrated in Figure 3d.

Referring to Figure 3e, a diagram is shown where the NOx content is given as a function of the time T. The NOx content is given in terms of ppm. Time T is given in terms of seconds (s).

The detected NOx content is continuously determined by means of a NOx sensor 255, 265 arranged in an exhaust duct 290 which directs exhaust gases from an engine 206 is represented by curve 1 in figure 3d. Curve 2 represents a reference curve, either continuously determined with a corresponding NOx sensor 255, 265 arranged in the exhaust duct 290 or calculated with the aid of a calculation model. It appears that at time Ti a magnitude of said rate of change H 'is detected where said magnitude exceeds said predetermined value H'max. After a comparison with a predetermined rate of change H'exp, it can be stated that said NOx sensor is defective as a magnitude of said rate of change H ', where said magnitude exceeds said predetermined value H'max at time Ti, does not correspond to an expected rate of change H 'exp.

Referring to Figure 3f, a diagram is shown where the NOx content is given as a function of the time T. The NOx content is given in terms of ppm. Time T is given in terms of seconds (s).

The detected NOx content is continuously determined by means of a NOx sensor 255, 265 arranged in an exhaust duct 290 which directs exhaust gases from an engine 206 is represented by curve 1 in Figure 3f. Curve 2 represents a reference curve, either continuously determined with a corresponding NOx sensor 255, 265 arranged in the exhaust duct 290 31 537 270 or calculated with the aid of a calculation model. It appears that at the time TO a magnitude of said change rate H 'is detected where said magnitude exceeds said predetermined value H'max. After a comparison with a predetermined rate of change H'exp, it can be stated that the said determined rate of change H 'at time TO is predetermined. Furthermore, at times T1, T2, T3 and T4 it can be stated that said NOx sensor is defective d5 a magnitude of said rate of change H 'where said magnitude exceeds said predetermined value H'max at time T1, 12, T3 and 14 does not correspond of a expected rate of change H'exp. According to this exemplary embodiment, a record is made of the number of occurrences X where the magnitude of said rate of change exceeds said predetermined water H'exp and where said occurrence cases are not expected. In cases where the said number of cases X exceeds a predetermined number of Xmax during a predetermined time period, this is taken as a matter-of-fact indication that the said NOx sensor 255, 265 is defective. Said time period can according to an embodiment be between 5 seconds and 60 minutes. Said time period can according to an embodiment be between 1 and 24 hours. Said predetermined number of Xmax may be between 1 and 20, or alternatively between 1 and 100 or alternatively between 1 and 1000.

Referring to Figure 3g, a diagram is shown in which the rate of change of NOx content is given as a function of time T. The rate of change of said NOx content is given in terms of ppm / second. Time T is given in terms of seconds (s). Figure 3g shows the said fixed rate of change H ', the said expected rate of change H'exp and the said predetermined value H'max.

In Figure 3g it can be read that at the time TO the said determined rate of change H 'exceeds the said predetermined value H'max. This indicates that a NOx sensor that measured the NOx levels from which the said rate of change was calculated is defective. At time TO, it is also shown that the expected rate of change H'exp exceeds said predetermined value H'max. Thus, a defective NOx sensor cannot be detected at time TO.

At time Ti, said fixed rate of change H 'exceeds the predetermined value H'max. This indicates that a NOx sensor that measured the NOx levels from which the said rate of change H 'was calculated is defective. Since said rate of change H 'at time Ti is not related, which can be read out by comparing H' with said expected rate of change H'exp, at time Ti it can be stated that a NOx sensor which measured the NOx levels from which said rate of change H ' calculated is defective.

Figure 4a schematically illustrates a flow chart of a method for detecting and managing at least one defective NOx sensor 255, 265 arranged in an exhaust duct 290 from an engine 206. The method includes a method step s401.

The process step s401 includes the steps of: - continuously determining a NOx content of exhaust gases in said engine 206 in said exhaust duct 290 by means of said NOx sensors 255, 265; - determine a rate of change H 'has the said continuously determined NOx content; - comparing a magnitude has the said rate of change H 'with a predetermined value H'max; and - in the event that said size has said change rate H 'exceeds said predetermined value H'max, take this as an indication that said NOx sensor 255; 265 is defective.

After step s401, the procedure is terminated.

Figure 4b schematically illustrates a flow chart of a part of a method for detecting at least one defective NOx sensor 255, 265 arranged in an exhaust duct 290 from an engine 206 according to an aspect of the present invention. The process comprises a first process step s410. The method step s410 may include the step of activating the inventive method. Said activation can be performed by an operator having the vehicle 100. Said activating can be performed by workshop personnel or service personnel having a workshop or service facility. Said activation can take place by means of said presentation means 280 and / or said communication unit 285. Said activation can take place automatically when said motor 206 is started.

The process step s410 comprises the step of continuously determining a NOx content of exhaust gases in an exhaust duct 290. The process step s410 comprises the step of determining a rate of change H 'of said continuously determined NOx content.

After the procedure step s410, a subsequent procedure step s420 is performed.

The method step s420 includes the step of comparing the magnitude of said change rate H 'with a predetermined value H'max. The said comparison can be performed continuously. The process step s420 includes the step of obtaining in the event that said magnitude of said rate of change H 'exceeds said predetermined value H'max, take this as an indication p5 that said NOx sensor 255; 265 is defective.

After the procedure step s420, a subsequent procedure step s430 is performed.

The process step s430 includes the step of comparing said rate of change H 'of said continuously determined NOx content determined by at least one of the first NOx sensor 255 and the second NOx sensor 265 with a related rate of change H'exp of said NOx. Said expected rate of change H'exp of said NOx content is determined by means of a corresponding NOx sensor arranged in said exhaust duct 290 and / or a calculation model. 34 537 270 According to one example, said rate of change H 'of said continuously determined NOx content determined by the first NOx sensor 255 may be compared with an expected rate of change H'exp of said NOx content determined by the second NOx sensor 265, or vice versa.

After the step step s430, a subsequent step step s440 is performed.

Procedure step s440 includes the step that in the event that a magnitude of said fixed change rate H 'exceeds a predetermined value H'max and d5 said change rate H' deviates from said expected change rate H'exp of said NOx content, take this as an established defect named NOx sensor 255; 265.

After step s440, one subsequent step s450 is performed.

The process step s450 includes the step that in the event d5 a defect is found in said NOx sensor 255; 265 and d5 a time period where said magnitude of said fixed rate of change H 'exceeds said predetermined value H'max is followed by a time period of increased fixed NOx content in comparison with a fixed NOx content during a time period of said magnitude of said fixed rate of change. 'Exceeds said predetermined value H', generate an error code associated with defective NOx sensor 255, 265.

Said NOx content usually varies over time, in which case, for example, an average value of said NOx content H1, H2 during a time period before and after a time period, respectively, the said magnitude of said fixed rate of change H 'exceeds said predetermined value H'max can be used for namnda jamfOrelse.

If an elevated NOx content H2 after a time period where said magnitude of said fixed rate of change H 'exceeds said predetermined value H'max compared to a NOx content H1 before said time period is determined, a 537,270 subsequent procedure step s460 is performed. In cases where an elevated NOx content is not found, a subsequent procedure step s470 is performed.

The process step s460 includes the step of: in case d5 a defect is found in said NOx sensors 255, 265 and dA a time period where said magnitude of said fixed change rate H 'exceeds said predetermined value H'max is followed by a time period with increased NOx content H2 in comparison with a fixed NOx content H1 for a period of time danger said size of said fixed change rate H 'exceeds said predetermined value H', generating an error code associated with defective NOx sensor 255, 265. The procedure step s460 may further comprise step replace a generated error code associated with increased NOx content with said generated error code associated with defective NOx sensor 255, 265.

After the procedure step s460, a subsequent procedure step s470 is performed.

Process step s470 involves an end or continuation of the inventive process. A continuation of the inventive process meant that the process was started again according to process step s410.

Referring to Figure 5, there is shown a diagram of an embodiment of a device 500. The controllers 200 and 210 described with reference to Figure 2 may in one embodiment include the device 500. The device 500 includes a non-volatile memory 520, a data processing unit 510, and a read / write memory 550. The non-volatile memory 520 has a first memory portion 530 used in a computer program, such as an operating system, stored to control the operation of the device 500. Further, the device 500 includes a bus controller, a serial communication port, I / O means, an AID converter, a time and date input and transfer unit, a trade calculator and an interrupt controller (not shown). The non-volatile memory 520 also has a second memory portion 540. 36 537 270 A computer program P is provided which may include routines for detecting and at least one defective NOx sensor 255, 265 arranged in an exhaust duct 290 from an engine 290 including the steps of : - continuously determining an NOx content of exhaust gases from said engine 206 in said exhaust duct 290 by means of said NOx sensor 255; 265; determining a rate of change H 'of said continuously determined NOx content; comparing a magnitude of said rate of change H 'with a predetermined value H'max; and - in the event that said magnitude of said rate of change H 'exceeds said predetermined value H'max, take this as an indication p5 that said NOx sensor 255, 265 Jr is defective.

The computer program P may comprise routines for comparing said rate of change H 'of said continuously determined NOx content with a predetermined rate of change H'exp of said NOx content, wherein said expected rate of change H'exp of said NOx content is determined by means of a corresponding NOx sensors 255, 265 arranged in said exhaust duct 290 and / or a calculation model.

The computer program P may comprise routines for comparing said rate of change H 'of said continuously determined NOx content with a predetermined rate of change H'exp of said NOx content, wherein said expected rate of change H'exp of said NOx content is determined by means of a calculation. calculation model includes operating conditions of said engine.

The computer program P may comprise routines for - determining, p5 on the basis of said comparison of said rate of change H 'of said continuously determined NOx content with said expected rate of change H'exp of said NOx content, whether said rate of change H' Jr related.

The computer program P may include routines so that when said change rate H 'has said continuously determined NOx content deviates from said expected change rate H'exp has said NOx content, take this as an established defect in said NOx sensor 255, 265.

The computer program P may include routines so that - in the event that a defect is found, the said NOx sensor 255, 265 and d5 have a time period in which the said size has the said fixed rate of change exceeds the said predetermined value H'max is followed by a time period of increased fixed NOx content in comparison with a fixed NOx content during a time period before said time period d5 said size has said fixed change rate H 'exceeds said predetermined value H', generating an error code associated with defective NOx sensor 255, 265.

The computer program P may comprise routines for - in the event that a defect is found, the said NOx sensor 255, 265 and d5 have a time period in which the said size has the said fixed change rate H 'exceeds the said predetermined value H'max is followed by a time period with increased fixed NOx content in comparison with a fixed NOx content during a time period before said time period when said size has said fixed rate of change H 'exceeds said predetermined value H', replace a generated error code associated with increased NOx content with said generated error code associated with defective error code NOx sensors 255, 265.

The computer program P may comprise routines for 38 537 270 - during a certain predetermined time period, registering the number of occurrences X where the size of said change rate H 'exceeds said predetermined value H' max; - compare the number of occurrences X, where the magnitude of said rate of change H 'exceeds said predetermined value H'max, by a predetermined number Xmax; and - in the event that said number of occurring cases X exceeds said predetermined number of Xmax, take this as a matter indication p5 that said NOx sensor 255, 265 is defective.

The program P can be stored p5 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. Read / write memory 550 Jr arranged to communicate with the data processing unit 510 via a data bus 514. To the data port 599, e.g. the lanes L210, L230, L240, L250, L255, L260, L265, L280 and L285 are connected (see Figure 2).

Night data is received at 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 execution of code p5 in a manner described above. According to one embodiment, signals received p5 the data port 599 include information about the NOx content upstream of the SCR catalyst 270. According to one embodiment, signals received at the p5 data port 599 include information about the NOx content downstream of the SCR catalyst 270.

The received signals p5 the data port 599 may be used by the device 500 to detect and manage at least one defective NOx sensor arranged in an exhaust duct 290 from an engine 206.

Parts of the methods described herein may be performed by the device 500 by means of the data processing unit 510 which the Icor program stored in the memory 560 or the lasiskry memory 550. When the device 500 Icor program, the methods described 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 in order 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 which may be appropriate to the intended use.

Claims (19)

A method for detecting at least one defective NOx sensor (255; 265) arranged in an exhaust duct (290) from an engine (206), comprising the step of: - continuously determining an NOx content of exhaust gases from said engine. (206) in said exhaust duct (290) by means of said NOx sensor (255; 265), characterized by the steps of: 1. determining a rate of change (H ') of said continuous determined NOx content; - comparing a magnitude of said rate of change (H ') with a predetermined value (FI'max); and 2. in the event that said magnitude of said rate of change (H ') exceeds said predetermined value (H'max), take this as an indication that said NOx sensor (255; 265) is defective. A method according to claim 1, comprising the step of: - comparing said rate of change (H ') of said continuously determined NOx content with a predetermined rate of change (H'exp) of said NOx content, wherein said expected rate of change (H'exp) of said NOx content is determined by means of a corresponding NOx sensor (255; 265) arranged in said exhaust duct (290) and / or a calculation model. The method of claim 2, wherein said calculation model comprises operating conditions of said motor (206). A method according to claim 2 or 3, comprising the step of: 1. determining, on the basis of said comparison of said rate of change (H ') of said continuously determined NOx content with said expected rate of change (H' exp) of said NOx content , whether the said rate of change (H ') is related. 41 537 270 A method according to any one of claims 2-4, wherein, d5 said rate of change (H ') of said continuously determined NOx content deviates from said expected rate of change (H'exp) of said NOx content, taking this as an established defect in named NOx sensor (255; 265). A method according to claim 5, comprising the step of: - in case d a defect is found in said NOx sensor (255; 265) and dA a time period where said magnitude of said fixed rate of change (H ') exceeds said predetermined value (H 'max) is followed by a time period with an elevated fixed NOx content in comparison with a fixed NOx content during a time period before said time period d5 said magnitude of said fixed rate of change (H') exceeds said predetermined value (H '), generating an error code associated with defective NOx sensor (255; 265). A method according to claim 6, comprising the step of: - in the case where a defect is found in said NOx sensor (255; 265) and when a time period in which said magnitude of said fixed rate of change (H ') exceeds said predetermined value (H 'max) is followed by a time period of elevated fixed NOx content in comparison with a fixed NOx content during a time period before said time period d5 said magnitude of said fixed rate of change (H') exceeds said predetermined value (H'max), replacing a generated error code associated with elevated NOx content with said generated error code associated with defective NOx sensor (255; 265). A method according to any one of claims 1-7, comprising the steps of: 42 537 270 1. during a certain predetermined time period, registering the number of occurrences (X) where the magnitude of said rate of change (H ') exceeds said predetermined value (H'max) ; 2. compare the number of occurrences (X), where the magnitude of said rate of change (H ') exceeds said predetermined value (H'max), by a predetermined number (Xmax); and 3. in the event that said number of occurrences (X) exceeds said predetermined number (Xmax), take this as a matter indication p5 that said NOx sensor (255; 265) is defective. A device for detecting at least one defective NOx sensor (255; 265) arranged in an exhaust duct (290) from an engine (206), comprising: 1. means (255; 265) adapted to continuously determine a NOx content of exhaust gases from said engine (206) in said exhaust duct (290), characterized by: 2. means (200; 210; 500) adapted to determine a rate of change (H ') of said continuously determined NOx content; Means (200; 210; 500) adapted to compare a magnitude of said rate of change (H ') with a predetermined value (H'max); and - means (200; 210; 500) adapted that, in the event that said magnitude of said rate of change (H ') exceeds said predetermined value (H'max), take this as an indication p5 that said NOx sensor (255; 265 ) is defective. The apparatus of claim 9, comprising: 1. means (200; 210; 500) adapted to compare said rate of change (H ') of said continuously determined NOx content with a predetermined rate of change (H'exp) of said NOx content. Device according to claim 10, comprising: 43 537 270 1. means (200; 210; 500) adapted to determine, on the basis of said comparison of said rate of change (H '), said continuously determined NOx content with said expected rate of change ( H'exp) has said NOx content, whether said rate of change (H ') is related. An apparatus according to claim 10 or 11, comprising: 1. means (200; 210; 500) adapted that, in said rate of change (H ') of said continuously determined NOx content deviates from said expected rate of change (H'exp) has said NOx content, take this as an established defect in the said NOx sensor (255; 265). A device according to claim 12, comprising: 1. means (200; 210; 500) adapted that, in the event that a defect is found in said NOx sensor (255; 265) and in a period of time where said size has said fixed rate of change (H ') exceeds said predetermined value (H'max) followed by a time period with increased fixed NOx content in comparison with a fixed NOx content during a time period before said time period in said size has said fixed change rate (H') exceeds said predetermined value (H '), generate an error code associated with defective NOx sensor (255; 265). Device according to claim 13, comprising: - means (200; 210; 500) adapted that, in the event that a defect is found to have said NOx sensor (255; 265) and in a period of time where said magnitude of said determined rate of change ( H ') exceeds said predetermined value (H'max) followed by a time period with increased fixed NOx content compared to a fixed NOx content during a time period before said time period in said size has said fixed rate of change (H') exceeds said predetermined varde (H '), 44 537 270 replaced a generated error code associated with increased NOx content with said generated error code associated with defective NOx sensor (255; 265). Device according to any one of claims 9-14, comprising: - means (200; 210; 500) adapted to, during a certain predetermined period of time, register the number of cases (X) in which the magnitude of said rate of change (H ') exceeds said predetermined value (H'max); Means (200; 210; 500) adapted to compare the number of occurrences (X), where the magnitude of said rate of change (H ') exceeds said predetermined value (H'max), by a predetermined number (Xmax); and 2. bodies (200; 210; 500) adapted that, in the event that the number of cases occurring (X) exceeds said predetermined number (Xmax), take this as a matter indication p5 that said NOx sensor (255; 265) is defective. Motor vehicle (100; 110) comprising a device according to any one of claims 9-15. A motor vehicle (100; 110) according to claim 16, wherein the motor vehicle is any of a truck, bus or passenger car. A computer program (P) for detecting at least one defective NOx sensor (255; 265) arranged in an exhaust duct (290) from an engine (206), said computer program (P) comprising program code for causing an electronic control unit (200). 500) or another computer (210; 500) connected to the electronic control unit (200; 500) for performing the steps according to any one of claims 1-8. A computer program product comprising a program code stored on a computer readable medium for performing the method steps of any of claims 1-8, 537 270 when said program code is crossed on an electronic control unit (200; 500) or another computer (210; 500) connected to the electronic control unit (200; 500). 46 537 270 1/7 L28 299 270 25290 271 i- 100 1