SE530674C2 - Method and apparatus for monitoring the function of an exhaust after-treatment system - Google Patents

Description

530,674 which represents the temperature of exhaust gases flowing out of the SCR catalyst and this temperature value is compared with a temperature value measured in the exhaust line downstream of the SCR catalyst. Based on the correspondence between these temperature values, such as, for example, the difference between them, it is determined whether or not the SCR catalyst and its injector function satisfactorily and as expected. Similar methods are also previously known from DE 4122 787 A1, US 5,860 277 A and EP 0 756 071 A2. A problem associated with this type of monitoring method that relies on a calculation model is that the calculation model under normal conditions can give fairly accurate calculation values but in certain operating conditions can give calculation values that deviate significantly from the corresponding fair values. . Thus, erroneous error indications can be generated based on test samples recorded under the latter operating conditions.

The function of an SCR catalyst can also be monitored by means of a NOx sensor which is arranged to measure the NOX content in the exhaust gases downstream of the catalyst. This NOx sensor can be supplemented by another NOx sensor which is arranged to measure the NOx content in the exhaust gases upstream of the catalyst in order to provide a comparative value. However, a NOX sensor is an expensive component and an alternative to cope without a NOx sensor upstream of the catalyst is to use a calculation model for calculating the amount of NO produced by the vehicle engine.

Furthermore, another calculation model can be used to calculate the expected conversion of NOX in the catalyst to obtain calculated values of the NOX content in the exhaust gases downstream of the catalyst. These calculated values can then be compared with the measured values from the NOX sensor downstream of the catalyst to detect any disturbances in the catalyst and the associated equipment. The use of calculation models for calculating the magnitude of the NOx content in the exhaust gases can, however, give calculation values that deviate significantly from the corresponding actual values, which in turn can result in the generation of incorrect error indications.

Due to increasingly strict regulations regarding the above-mentioned type of vehicle-borne monitoring, there is a great need for a reliable procedure and a reliable device for monitoring the function of an exhaust after-treatment system.

DESCRIPTION OF THE INVENTION A first object of the present invention is to provide a new and reliable way of monitoring an exhaust aftertreatment system of a motor vehicle.

This object is achieved by means of a method having the features defined in claim 1 and a device having the features defined in claim 10.

According to the invention, the function of the exhaust after-treatment system is monitored based on measured values from a sensor regarding the size of a parameter related to exhaust gases flowing out of an exhaust after-treatment device, for example in the form of a catalyst or filter included in the exhaust after-treatment system. In this case: - a first curve is determined based on measured values from the sensor regarding the size of the parameter during a certain time period, which here is called evaluation period, this first curve representing the measured size of the parameter as a function of time during the evaluation period; a second curve is determined based on values of the size of the parameter during the evaluation period calculated by means of a calculation model, this second curve representing the calculated size of the parameter as a function of time during the evaluation period; - the second curve is compared with the first curve to determine whether the curve shape of the second curve is similar to the curve shape of the first curve or not; and 530 574 - information is generated regarding the function of the exhaust after-treatment system based on measured values from the sensor and corresponding calculation values from the calculation model regarding the size of the parameter during the evaluation period only if it is determined by said comparison that the curve shape of the second curve is similar to the first curve. .

In this specification and the appended claims, the expression "the curve shape of the second curve is similar to the curve shape of the first curve" means that the curves change in approximately the same way, at approximately the same time, in the same direction and to approximately the same extent, i.e. that the changes of the second curve essentially follow the changes of the first curve. Accordingly, if the curve shape of the second curve is equal to the curve shape of the first curve, the second curve rises when the first curve rises and falls when the first curve falls, and with approximately the same absolute value. However, the fact that the curve shape of the second curve is similar to the curve shape of the first curve does not mean that the curves must overlap or coincide. Instead, there can be an approximately constant shift in absolute value between the curves, even if the curve shape of the second curve is similar to the curve shape of the first curve.

The fact that the curve shape of the second curve is similar to the curve shape of the first curve during the evaluation period indicates that the calculation model and the sensor reflect the variations of the parameter in a similar way during the evaluation period, which in this context is considered an indication that the calculation model reproduces the behavior of the parameter in a substantially correct manner during the evaluation period. Measured values from the sensor and corresponding calculation values from the calculation model are thus only taken into account in the generation of information regarding the function of the exhaust after-treatment system in cases where it is considered that the calculation model reflects the variations of the parameter in a substantially correct way during the evaluation period. the measured values and calculation values are rejected in all other cases. In this way, many of the incorrect calculation values from the calculation model can be filtered out, which reduces the risk of incorrect error indications regarding the exhaust after-treatment system.

According to an embodiment of the invention, information regarding the function of the exhaust aftertreatment system is generated based on measured values from the sensor and corresponding calculation values from the calculation model regarding the size of the parameter during the evaluation period only provided that the vehicle's engine is run under steady state operating conditions. A calculation model usually reflects the effects of an exhaust aftertreatment system on a specific parameter with better accuracy under stationary operating conditions compared to transient operating conditions. By rejecting calculation values associated with transient operating conditions of the vehicle engine, it will thus be possible to avoid many of the most incorrect calculation values from the calculation model, which helps to reduce the risk of incorrect error indications regarding the exhaust after-treatment system. In this description and the following claims, the term “stationary operating conditions” refers to a situation where the vehicle's engine runs stationary with a stable engine load and stable speed.

Appropriate criteria for stable engine load and stable speed can be easily determined by a person skilled in the art from case to case depending on the vehicle type and engine type in question.

According to another embodiment of the invention, the second curve is compared with the first curve by means of a curve comparison model or curve recognition model which is designed to compare the slope and / or absolute value of the second curve at certain times during the evaluation period with the slope and / or absolute value of the the first curve at corresponding times to thereby determine whether the curve shape of the second curve is similar to the curve shape of the first curve or not. It has been established 530 674 that this type of model can be advantageous for use in this context.

According to another embodiment of the invention, measured values from the sensor and corresponding calculation values are evaluated from the calculation model regarding the size of the parameter during the evaluation period to form a correspondence value representing the correspondence between said measured values and calculation values during the evaluation period. the function of the exhaust after-treatment system is generated based on this correspondence value. The correspondence value is suitably formed so that it represents the correspondence between the average value of said measured values from the sensor and the average value of said calculation values from the calculation model during the evaluation period or during a part thereof. By using such averages, a further filtering of the calculation values from the calculation model is achieved while avoiding that a few abnormal test samples will have a too significant impact on the generated information. The generated information is thus based on several test samples registered during the evaluation period and a few abnormal test samples among several normal test samples registered during this time period will not in themselves cause an error indication regarding the exhaust after-treatment system.

According to another embodiment of the invention, information regarding the operation of the exhaust after-treatment system is generated by comparing said correspondence value with a look-up value, which has been stored linked to an engine operating point corresponding to the engine operating point prevailing during the evaluation period and which has been generated based on one or several correspondence values previously determined for this engine operating point with the same engine in the same way as the existing correspondence value and with the same sensor and calculation model. As a result, the monitoring of the exhaust after-treatment system will be insensitive to minor and substantially constant offset errors in the sensor and the calculation model caused by individual differences between electronics, catalysts, engines and other installations in different vehicles. An error indication is suitably generated if the difference or ratio between the new correspondence value and the previously stored reference value exceeds a limit value, thereby indicating a malfunction of the exhaust after-treatment system. By basing the monitoring on correspondence values and reference values generated in the above-mentioned manner, it becomes possible to determine said limit value with a relatively low safety margin with regard to the avoidance of incorrect error indications, which in turn means that it becomes possible to detect relatively small faults in the exhaust after-treatment system.

In this description and the following claims, the term “engine operating point” refers to a “point” with a certain combination of engine load and engine speed. Each engine operating point is associated with an engine load of a specific size and an engine speed of a specific size.

A second object of the present invention is to provide a new and reliable way of generating lookup values for use in monitoring the operation of an exhaust aftertreatment system of a motor vehicle provided with a sensor for measuring the size of a parameter related to exhaust gases flowing out. from an exhaust after-treatment device, for example in the form of a catalyst or a filter, which is included in the exhaust after-treatment system.

This object is achieved by means of a method having the features defined in claim 15 and a device having the features defined in claim 23.

In this case, the following steps are performed in a situation where it is determined that the vehicle's engine is running under stationary operating conditions at a certain engine operating point: - a first curve is determined based on measurements from the sensor regarding the size of the parameter over a certain period of time, 530 674 here is called evaluation period, this first curve representing the measured size of the parameter as a function of time during the evaluation period, - a second curve is determined based on values of the size of the parameter during the evaluation period calculated using a calculation model, this second curve representing the calculated magnitude of the parameter as a function of time during the evaluation period, and - the second curve is compared with the first curve to determine whether the curve shape of the second curve is equal to the curve shape of the first curve or not; and - if it is determined by said comparison that the curve shape of the second curve is similar to the curve shape of the first curve, a look-up value for the motor operating point in question is generated based on measured values from the sensor and corresponding calculation values from the calculation model regarding the size of the parameter during the evaluation period.

Such reference values are intended to be generated when the engine and exhaust after-treatment system are considered to be faultless, for example when the vehicle is new or relatively new, and they shall be used as comparative values to be compared with corresponding values determined later in vehicle life to detect abnormalities of a malfunction of the exhaust after-treatment system.

The fact that the curve shape of the second curve is similar to the curve shape of the first curve during the evaluation period indicates that the calculation model and the sensor reflect the variations of the parameter in a similar way during the evaluation period, which in this context is considered an indication that the calculation model at the parameter in a substantially correct manner during the evaluation period. Measured values from the sensor and corresponding calculation values from the calculation model are thus only taken into account in the generation of a look-up value in cases where it is considered that the calculation model reproduces the variations of the parameter in a substantially correct manner during the evaluation period, while measured values and calculation values are rejected. in all other cases. In this way, many of the incorrect calculation values from the calculation model can be filtered out, which reduces the risk of generating incorrect look-up values.

According to an embodiment of the invention, measured values from the sensor and corresponding calculation values from the calculation model are evaluated regarding the size of the parameter during the evaluation period to form a correspondence value representing the correspondence between said measured values and corresponding calculation values during the evaluation period. then based on this correspondence value. Each reference value thus reflects a previously determined correspondence between measured values and corresponding calculation values determined for a certain engine operating point.

An initial lookup value generated for a particular engine operating point based on one or more initial correspondence values is updated according to another embodiment of the invention based on one or more subsequent correspondence values determined for the engine operating point in question. In this way, the reference values can be adjusted to compensate for the drift of the sensor over time.

According to another embodiment of the invention, each such subsequent correspondence value is caused to influence the magnitude of the look-up value to an extent which is caused to decrease as the accumulated operating time of the vehicle engine increases. Correspondence values established during the initial operation of the vehicle, when it is most likely that the exhaust after-treatment system is faultless, are thus given a higher weight than correspondence values established at a later stage during the operational life of the vehicle.

According to another embodiment of the invention, the respective correspondence value is formed so as to represent the correspondence 530 B74 between the average value of said measured value from the sensor and the average value of said calculation values from the calculation model during the evaluation period or during a part thereof. By using such averages, a further filtering of the calculation values from the calculation model is achieved while avoiding that a few abnormal test samples will have too significant an impact on the generated look-up value.

Further advantageous features of the methods and devices according to the invention are stated in the dependent claims and the following description.

The invention also relates to a computer program having the features defined in claim 14 and claim 24, respectively, a computer program product having the features defined in claim 25 and an electronic control unit having the features defined in claim 26.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in more detail below by means of exemplary embodiments with reference to the accompanying drawings, in which: Fig. 1 is a schematic sketch of an internal combustion engine with an associated exhaust after-treatment system, illustrating an embodiment of a device according to the present invention. Fig. 2 is a schematic schematic diagram of an electronic control unit for implementing a method according to the invention, Fig. 3 is a flow chart illustrating a method according to the invention, and Fig. 4 is a flow chart illustrating another method according to the invention. the invention.

EMBODIMENTS OF THE INVENTION A process and apparatus according to the invention will hereinafter be described as implemented / implemented for monitoring the operation of an exhaust after-treatment system comprising a catalyst. However, the invention is in no way limited to these applications, but the invention can be used for monitoring an exhaust aftertreatment system having any type of exhaust aftertreatment device which has an effect on the size of an exhaust parameter which can be measured by a sensor and at the same time calculated on a calculation model. The invention can be used, for example, for monitoring the operation of an exhaust after-treatment system which comprises an exhaust after-treatment device in the form of a filter, such as a particle filter or an open-structure filter.

An internal combustion engine 1 with an associated exhaust after-treatment system 2 is shown schematically in Fig. 1. The exhaust gases leaving the internal combustion engine 1 are passed through an exhaust line 3 and discharged to the environment via an exhaust outlet 4. A catalyst 5 is arranged in the exhaust line 3. The exhaust gases from the internal combustion engine 1 pass through the catalyst 5 before being released to the environment via the exhaust outlet 4. In the example illustrated in Fig. 1, the catalyst 5 is an SCR catalyst. In this case, reducing agent is injected by means of an injection device 6 into the exhaust gases in the exhaust line 3 upstream of the catalyst 5. The injection device 6 comprises one or more injection means 7 arranged in the exhaust line 3 in the form of injection nozzles or the like, and a storage container 8 connected thereto. reducing agents. The injection device 6 also comprises a control means 9, for example in the form of a control valve, which is arranged to regulate the supply of reducing agent to said 1 or more injection means 7, 530 674 12 and a control means 10 connected to the control means 9. The control means 9 is controlled by said control means 10, which determines the amount of reducing agent to be injected into the exhaust gases based on the prevailing operating conditions of the internal combustion engine 1 and the catalyst 5. The injection device 6 may also comprise further components, such as a dosing device, etc. The reducing agent may be urea (CO (NH2) 2), ammonia (NH3) or hydrocarbon (fuel) or any other suitable reducing agent.

A sensor 11 is arranged in the exhaust line 3 downstream of the catalyst 5 to generate measured values regarding the size of a parameter related to exhaust gases flowing out of the catalyst 5. In this example, the sensor 11 is a NOx sensor which is arranged to generate measured values representing the NOx content of the exhaust gases flowing out of the catalyst 5, that is, the NOx content of the exhaust gases at the outlet of the catalyst. The measured values are registered so that they form a series of successive and discrete measured values regarding the size of the parameter.

The device 20 according to the invention comprises calculating means 21 which are arranged to calculate values representing the magnitude of the parameter in question. The calculation values thus constitute theoretically determined values of the size of the parameter at the outlet of the catalyst 5. In the example described here, the calculation values represent the NOx content in the exhaust gases flowing out of the catalyst 5. The calculating means 21 is arranged to calculate the size of the parameter using a suitable calculation model. The calculation model can be designed in any desired manner and use any desired parameters as long as it provides values of the expected size of the parameter at the outlet of the catalyst 5 with a desired accuracy. The device 20 further comprises processing means 22 which is arranged to receive information from the sensor 11 regarding the measured size of the parameter and information from the calculating means 21 regarding the calculated size of the parameter. The processing means 22 is arranged: a) to determine a first curve C1 based on the information from the sensor regarding the measured size of the parameter during a certain time period Tev, which is here referred to as evaluation period, this first curve C1 representing the measured size of the parameter as a function of time during the evaluation period Tev, b) determining a second curve C2 based on the information from the calculating means 21 regarding the calculated size of the parameter during the evaluation period Tev, this second curve C2 representing the calculated size of the parameter as a function of time during the evaluation period Tev, c) comparing the second curve C2 with the first curve C1 to determine whether the curve shape of the second curve C2 is similar to the curve shape of the first curve C1 or not, and d) if it is determined by said comparison that the curve shape of the the second curve C2 is similar to the curve shape of the first curve C1, to generate information regarding e the function of the exhaust aftertreatment system 2 based on the information from the sensor 11 and the corresponding information from the calculating means 21 regarding the size of the parameter during the evaluation period TW.

The evaluation period TSV in the given example can, for example, be in the order of 10-30 seconds. During this time period, measured values and calculation values are repeatedly determined with respect to the size of the parameter, for example with an interval in the order of 10-100 ms. The length of the Tev evaluation period and the interval between each measured value and the calculated value can of course vary widely from case to case, depending on the nature of the exhaust after-treatment system to be monitored.

The processing means 22 is arranged to compare the second curve C2 with the first curve C1 by means of a suitable curve comparison model or curve recognition model. The model can be designed in any suitable way and can be based, for example, on statistical methods that take into account covariance, etc., or on mathematical methods that include the comparison of derivatives and / or absolute values. The model is advantageously designed to compare the slope of the second curve C2 at certain times during the evaluation period Tev with the slope of the first curve C1 at the corresponding times to thereby determine whether the curve shape of the second curve C2 is equal to the curve shape. of the first curve C1 or not. In the latter case, it may also be advantageous to take into account the absolute values of the curves by comparing the absolute value of the second curve C2 at certain times during the evaluation period Tev with the absolute value of the first curve C1 at the corresponding times.

It should be obvious to a person skilled in the art that said comparison can be performed in real time by a comparison analysis which is performed repetitively for each new pair of sample values consisting of a measured value and a corresponding calculation value.

The indication in this description and the subsequent claims that the second curve C2 is compared with the first curve C1 thus does not necessarily mean that the respective curve C1, C2 is completely determined before the comparison is carried out. This comparison can instead advantageously be performed in real time during the determination of the curves C1, C2.

The processing means 22 is suitably arranged to evaluate measured values from the sensor 11 and corresponding calculation values from the calculation model 21 with respect to the size of the parameter during the evaluation period Tev to form a correspondence value VC representing the correspondence, such as the difference, ratio or correlation. measured values and calculation values during the evaluation period. Information regarding the function of the exhaust after-treatment system 2 is then generated based on this correspondence value VC. 530 B74 According to an alternative, the correspondence value VC is compared directly with a given limit value to determine whether the exhaust after-treatment system 2 can be considered to function properly or not. According to another alternative, the processing means 22 is arranged to generate information regarding the function of the exhaust aftertreatment system 2 by comparing the correspondence value VC with a look-up value Vw, which has been stored tied to an engine operating point corresponding to the engine operating point prevailing during the evaluation period TCV. has generated based on one or more correspondence values previously determined for this motor operating point with the same motor in the same way as the existing correspondence value VC and with the same sensor 11 and calculation model. The processing means 22 is suitably arranged to generate an error indication if the difference or ratio between the correspondence value VC and the look-up value Vw exceeds a given limit value in order thereby to indicate a malfunction of the exhaust after-treatment system. An appropriate limit value can be determined empirically through practical tests and / or theoretically based on appropriate calculations.

The processing means 22 is advantageously arranged to form the correspondence value VC in such a way that it represents the correspondence between the average value of said measured values from the sensor 11 and the average value of said calculation values from the calculation means 21 during the evaluation period TCV or during a part thereof. . The correspondence value VC is suitably formed so that it represents the difference between the average value of said measured values and the average value of said calculation values.

A maximum permissible upper limit for the correspondence value VC can be set. In this case, an error indication is suitably generated if a correspondence value VC exceeding this upper limit value is formed.

The processing means 22 is arranged to receive information regarding the operating conditions of the engine 1, such as, for example, information regarding the load and the speed of the engine. The processing means 22 is advantageously arranged to generate information regarding the function of the exhaust after-treatment system 2 based on measured values from the sensor 11 and corresponding calculation values from the calculating means 21 regarding the size of the parameter during the evaluation period Te, only provided that it is determined that the vehicle's engine 1 runs under stationary operating conditions during the evaluation period Tev. The information regarding the operating conditions of the engine 1 is also used to determine the engine operating point that prevails during the evaluation period Tev.

The processing means 22 may be arranged to determine look-up values V1, of the above-mentioned type, i.e. look-up values to be compared with later correspondence values Vc in order to generate information regarding the function of the exhaust after-treatment system 2. In this case, the processing means the means 22 arranged to perform the above-mentioned steps a) -c) in a situation when it is determined that the engine 1 of the vehicle runs under stationary operating conditions at a certain engine operating point. If it is determined by the comparison in step c) that the curve shape of the second curve C2 is similar to the curve shape of the first curve C1, then the processing means 22 is arranged to generate a look-up value V1, for the motor operating point in question based on the information from the 11 and the corresponding information from the calculation means 21 regarding the size of the parameter during the evaluation period Tev.

The processing means 22 may be arranged to generate an initial look-up value V ,,, for a certain motor operating point based on an initial correspondence value V, of the above-mentioned type determined for the motor operating point in question or based on the average value of several successive correspondence values determined at different times for the engine operating point in question. Such reference values V. ,, are determined for several different engine operating points when the vehicle is relatively new and its exhaust after-treatment system 2 can be considered to function correctly. The processing means 22 is advantageously arranged to update the respective reference value 530 674 17 V. "with time based on one or more subsequent correspondence values V0 determined for the respective motor operating point. The processing means 22 is suitably arranged to apply some kind of weighting to such subsequent correspondence values. VC so that each such subsequent correspondence value is caused to affect the magnitude of the corresponding lookup value Vu, to an extent which is caused to decrease as the accumulated operating time of the vehicle engine increases.Each such subsequent correspondence value V is of course also compared with the corresponding to the look-up value VH, which has already been stored to generate information regarding the function of the exhaust after-treatment system 2. A maximum permissible upper limit for each look-up value Vt. can be determined. upper limit genes eras. The device 20 suitably comprises some type of indicating device for displaying an error message and / or emitting an acoustic or luminous warning signal when an error of the monitored system has been detected. An abnormal correspondence value Vc indicates that the catalyst 5 and / or any other component of the exhaust after-treatment system, such as, for example, the injection device 6 or the sensor 11, is not functioning satisfactorily and may, for example, have one or more of the following causes: 5 or a part thereof has been removed, - the catalyst 5 is degenerate or damaged, - the sensor 11 is degenerate or damaged, - the injector 6 does not inject the expected amount of the expected reducing agent, - an error in a used calculation model, - one or more input signals to a used calculation model is incorrect. The possible causes of errors should thus be checked when an error indication has been generated to find and correct the error in question 530 B74 18 The calculation medium 21 and the processing means 22 are advantageously included in one and the same computer unit, for example in the form of an electronic control unit. in a motor vehicle, but can also be arranged in separate and mutually communicating computer units.

It will be apparent to one skilled in the art that the embodiments described above in connection with the monitoring of an exhaust after-treatment system provided with an exhaust after-treatment device in the form of an SCR catalyst could be easily modified to monitor the operation of an exhaust after-treatment system. provided with any other type of exhaust aftertreatment device that has an effect on the size of an exhaust parameter that can be measured by a sensor and at the same time calculated based on a calculation model, such as another type of catalyst or a filter. The parameter could, for example, be the temperature of the exhaust gases flowing out of a catalyst or a filter, in which case the above-mentioned sensor is a temperature sensor which is arranged downstream of the catalyst / filter.

A flow chart illustrating an embodiment of an inventive method for monitoring the operation of an exhaust aftertreatment system of a motor vehicle is shown in Fig. 3. In a first step S1, based on measured values from a sensor, a first curve C1 representing the measured the size of a parameter as a function of time during an evaluation period TW. In a second step S2, based on values of the size of the parameter calculated by means of a calculation model, a second curve C2 is represented which represents the calculated size of the parameter as a function of time during the evaluation period Tev. In a third step S3, the second curve C2 is compared with the first curve C1 to determine whether the curve shape of the second curve C2 is similar to the curve shape of the first curve C1 or not. If the comparison in step S3 shows that the curve shape of the second curve C2 is similar to the curve shape of the first curve C1, information regarding the function of the exhaust aftertreatment system is generated in a fourth step S4 based on measured values from the sensor and corresponding calculation values from the calculation model. the parameter during the TSV evaluation period. The monitoring cycle ends in step S5.

The above-mentioned steps S1-S3 can of course be performed simultaneously in real time. A flow chart illustrating an embodiment of an inventive method for determining lookup values for use in monitoring the operation of an exhaust aftertreatment system of a motor vehicle is shown in Fig. 4. In a first step S1 'it is determined whether the engine of the vehicle is running under station - close to operating conditions at a certain engine operating point or not. If this is the case, steps S2'-S4 'are performed corresponding to the above-mentioned steps S1-S3. If the comparison in step S4 'shows that the curve shape of the second curve C2 is similar to the curve shape of the first curve C1, a look-up value VN is generated for the motor operating point in question in step S5' based on measured values from the sensor and corresponding calculation values from the calculation model. . This process ends in step S6 ”. The above-mentioned steps S2'-S4 'can of course be performed simultaneously in real time.

As can be seen from the description above, the process steps according to Fig. 3 can be performed in combination with the process steps according to Fig. 4, in which case step S1 according to Fig. 3 is preceded by a step corresponding to step S1 'according to Fig. 4 and step S4 according to Fig. 3 is followed by a steps corresponding to step S5 * according to Fig. 4.

Computer program code for implementing * a method according to the invention is suitably included in a computer program which can be read into the internal memory of a computer, such as the internal memory of an electronic control unit of a motor vehicle which comprises an exhaust after-treatment system to be monitored. Such a computer program is suitably provided via a computer program product which comprises a data storage medium which can be read by an electronic control unit, which data storage medium has the computer program stored thereon. Said data storage medium is, for example, an optical data storage medium in the form of a CD-ROM, a DVD disc, etc., a magnetic data storage medium in the form of a hard disk, a floppy disk, a cassette tape, etc., or a memory of the ROM type. PROM, EPROM or EEPROM or a Flash memory.

An inventive computer program according to a first example includes computer program code for bringing a computer: a) to receive information from a sensor regarding the size of a parameter related to exhaust gases flowing out of an exhaust aftertreatment device included in an exhaust aftertreatment system of a motor vehicle, and determining a first curve C1 based on said information, this first curve C1 representing the measured magnitude of the parameter as a function of time during an evaluation period Tev; b) to calculate, based on a calculation model, values representing the size of the parameter or receive information about said values calculated based on a calculation model, and determine a second curve C2 based on the calculated values of the size of the parameter during the evaluation period Tev , this second curve C2 representing the calculated magnitude of the parameter as a function of time during the evaluation period Tev; c) comparing the second curve C2 with the first curve C1 to determine whether the curve shape of the second curve C2 is similar to the curve shape of the first curve C1 or not; and d) if it is determined by said comparison that the curve shape of the second curve C2 is similar to the curve shape of the first curve C1, to generate information regarding the function of the exhaust aftertreatment system based on the information from the sensor regarding the measured size of the parameter and the corresponding - the information concerning the estimated size of the parameter during the evaluation period TW.

The above-mentioned steps a) -c) can of course be performed simultaneously in real time. A computer program according to the invention according to a second example comprises computer program code for causing a computer to perform the following in a situation when it is determined that the vehicle's engine is running under stationary operating conditions at a certain engine operating point: a) receiving information from a sensor regarding the size of a parameter related to exhaust gases flowing out of an exhaust aftertreatment device included in an exhaust aftertreatment system of a motor vehicle, and determining a first curve C1 based on said information, this first curve C1 representing the measured size of the parameter as a function - tion of time during an evaluation period Tev; b) calculating, based on a calculation model, values representing the size of the parameter or receiving information on said values calculated based on a calculation model, and determining a second curve C2 based on the calculated values of the size of the parameter during the evaluation period Tev , this second curve C2 representing the calculated magnitude of the parameter as a function of time during the evaluation period Tev; c) comparing the second curve C2 with the first curve C1 to determine whether the curve shape of the second curve C2 is similar to the curve shape of the first curve C1 or not; and d) if it is determined by said comparison that the curve shape of the second curve C2 is similar to the curve shape of the first curve C1, to generate a reference value V. "for the engine operating point in question for use in monitoring the operation of the exhaust after-treatment system, on measured values from the sensor and corresponding calculation values from the calculation model regarding the size of the parameter during the evaluation period TSV.

The above-mentioned steps a) -c) can of course be performed simultaneously in real time.

Fig. 2 very schematically illustrates an electronic control unit 30 comprising an execution means 31, such as a central processing unit (CPU), for executing computer software. The execution means 31 communicates with a memory 33, for example of the RAM type, via a data bus 32. The control unit 30 also comprises data storage medium 34, for example in the form of a memory of the type ROM, PROM, EPROM or EEPROM or a Flash memory. The execution means 31 communicates with the data storage medium 34 via the data bus 32. A computer program comprising computer program code for implementing a method according to the invention is stored on the data storage medium 34.

The invention is of course not in any way limited to the embodiments described above, but a number of possibilities for modifications thereof will be obvious to a person skilled in the art, without departing from the basic idea of the invention as defined in the appended claims.

Claims (26)

10 15 20 25 30 35 530 674 23 PATENT REQUIREMENTS A method for monitoring the function of an exhaust after-treatment system (2) of a motor vehicle based on measured values from a sensor (11) regarding the size of a parameter related to exhaust gases flowing out of an exhaust after-treatment device, for example in the form of a catalyst or filter included in the exhaust after-treatment system, thereof: - that the method comprises the steps of: a) determining a first curve based on measured values from the sensor (11) regarding the size of the parameter during a certain time period, herein referred to as evaluation period; first curve represents the measured size of the parameter as a function of time during the evaluation period, b) determining a second curve based on values of the size of the parameter during the evaluation period calculated using a calculation model, this second curve representing the calculated size of the parameter as a function of time during the evaluation period, and c) compare the second curve with the first curve to determine whether the curve shape of the second curve is similar to the curve shape of the first curve or not; and - that information regarding the function of the exhaust after-treatment system (2) is generated based on measured values from the sensor (11) and corresponding calculation values from the calculation model regarding the size of the parameter during the evaluation period only if it is determined by said comparison that the curve shape of the second curve the first curve. Method according to claim 1, characterized in that information regarding the function of the exhaust aftertreatment system (2) is generated based on measured values from the sensor (11) and corresponding calculation values from the calculation model regarding the size of the parameter during the evaluation period only. 25 30 35 530 874 24 provided that it is determined that the vehicle's engine (1) runs under stationary operating conditions during the evaluation period. Method according to Claim 1 or 2, characterized in that the second curve is compared with the first curve by means of a curve comparison model or curve recognition model. Method according to claim 3, characterized in that said curve comparison model or curve recognition model is designed to compare the slope and / or the absolute value of the second curve at certain times during the evaluation period with the slope and / or the absolute value of the first curve at the corresponding curve. times to thereby determine whether or not the waveform of the second curve is similar to the waveform of the first curve. Method according to any one of claims 1-4, characterized in that: - measured values from the sensor (11) and corresponding calculation values from the calculation model regarding the size of the parameter during the evaluation period are evaluated to form a correspondence value representing the correspondence between said measurement values and calculation values; and - that information regarding the function of the exhaust after-treatment system (2) is generated based on this correspondence value. Method according to claim 5, characterized in that said correspondence value is formed so as to represent the correspondence between the average value of said measured values from the sensor (11) and the average value of said calculation values from the calculation model during the evaluation period or during a part thereof. Method according to claim 5 or 6, characterized in that information regarding the function of the exhaust after-treatment system (2) is generated by comparing said correspondence value with a look-up value, which has been stored linked to a 530 574 motor operating point corresponding to the motor operating point prevailing during the evaluation period and which has been generated based on one or more correspondence values previously determined for this motor operating point with the same motor (1) in the same way as the existing correspondence value and with the same sensor (11) and calculation model. A method according to any one of claims 1-7, wherein said sensor (11) is a temperature sensor arranged to measure the temperature of exhaust gases flowing out of the exhaust after-treatment device (5), characterized in that the first curve is fixed. is set based on measured values from the sensor regarding the magnitude of said temperature, and that the second curve is determined based on values of the magnitude of said temperature calculated by means of the calculation model. A method according to any one of claims 1-7, wherein said exhaust gas aftertreatment device (5) is a catalyst, for example an SCR catalyst, and said sensor (11) is a NOx sensor arranged to measure the NOx content of exhaust gases flowing out of the catalyst, characterized in that the first curve is determined based on measured values from the sensor regarding the magnitude of said NOx content, and that the second curve is determined based on values of the magnitude of said NOX content calculated by means of the calculation model. Device for monitoring the function of an exhaust after-treatment system of a motor vehicle based on measured values from a sensor regarding the size of a parameter related to exhaust gases flowing out of an exhaust after-treatment device, for example in the form of a catalyst or a filter included in the exhaust after-treatment system , characterized in that - the device (20) comprises calculation means (21) for calculating the size of the parameter based on a calculation model; and - that the device (20) comprises processing means (22) arranged to receive information from the sensor regarding the measured size of the parameter and information from the calculation means (21) regarding the calculated size of the parameter , the processing means (22) being arranged: a) determining a first curve based on the information from the sensor regarding the measured size of the parameter during a certain period of time, which is referred to herein as evaluation period, this first curve representing the measured size of the parameter which function of time during the evaluation period, b) determining a second curve based on the information from the calculation means (21) regarding the calculated size of the parameter during the evaluation period, this second curve representing the calculated size of the parameter as a function of time during the evaluation period , c) comparing the second curve with the first curve to determine h whether or not the curve shape of the second curve is similar to the curve shape of the first curve, and d) if it is determined by said comparison that the curve shape of the second curve is similar to the curve shape of the first curve, generating information regarding the function of the exhaust aftertreatment system based on the information from the sensor and the corresponding information from the calculation means (21) regarding the size of the parameter during the evaluation period. Device according to claim 10, characterized in that the processing means (22) is arranged to generate information regarding the function of the exhaust after-treatment system (2) based on the information from the sensor and the corresponding information from the calculation means (21) regarding the size of the parameter only during the evaluation period. provided that it is determined that the vehicle's engine (1) is running under stationary operating conditions during the evaluation period. 10 15 20 25 30 35 530 B74 27 Device according to claim 10 or 11, characterized in that the parameter is the temperature of exhaust gases flowing out of the exhaust after-treatment device, the sensor being a temperature sensor arranged to measure said temperature and the calculation medium (21) being arranged to calculate the magnitude of said temperature based on the calculation model. Device according to claim 10 or 11, characterized in that the parameter is the NOX content of exhaust gases flowing out of an exhaust after-treatment device in the form of a catalyst, for example an SCR catalyst, which is included in the exhaust after-treatment system, the sensor being a NOX sensor arranged to measure said NOX content and the calculation means (21) being arranged to calculate the magnitude of said NOX content based on the calculation model. A computer program readable to the internal memory of a computer in a motor vehicle comprising an exhaust after-treatment system and a sensor for measuring the magnitude of a parameter related to exhaust gases flowing out of an exhaust after-treatment device, for example in the form of a catalyst or a filters included in the exhaust aftertreatment system, the computer program comprising computer program code for bringing the computer: a) receiving information from said sensor regarding the measured size of the parameter during a certain time period, herein referred to as evaluation period, and determining a first curve based on said information, this first curve representing the measured size of the parameter as a function of time during the evaluation period; b) calculating, based on a calculation mode, values representing the size of the parameter or receiving information about said values calculated based on a calculation mode, and determining a second curve based on the calculation values of the size of the parameter during the evaluation period, this second curve representing the calculated size of the parameter as a function of time during the evaluation period; C) comparing the second curve with the first curve to determine whether or not the curve shape of the second curve is similar to the curve shape of the first curve; and d) if it is determined by said comparison that the curve shape of the second curve is similar to the curve shape of the first curve, generating information regarding the function of the exhaust aftertreatment system based on the information from the sensor regarding the measured size of the parameter and the corresponding the information regarding the estimated size of the parameter during the evaluation period. A method for determining look-up values for use in monitoring the operation of an exhaust after-treatment system (2) of a motor vehicle provided with a sensor (11) for measuring the magnitude of a parameter related to exhaust gases flowing out of an exhaust after-treatment. treatment device (5), for example in the form of a catalyst or filter, which is part of the exhaust after-treatment system, characterized in that: - the process comprises performing the following steps in a situation where it is determined that the vehicle's engine (1) is running under stationary operating conditions; at a certain motor operating point: a) determining a first curve based on measured values from the sensor (11) regarding the size of the parameter during a certain time period, which is referred to here as evaluation period, this first curve representing the measured size of the parameter as a function of time during evaluation period , b) determining a second curve based on values of the size of the parameter during the evaluation period calculated using a calculation model, this second curve representing the calculated magnitude of the parameter as a function of time during the evaluation period, and c) comparing the second curve with the first curve to determine whether the curve shape of the second curve is similar to the curve shape of the first curve or not; and - that a look-up value for the motor operating point in question is generated based on measured values from the sensor (11) and corresponding calculation values from the calculation model regarding the size of the parameter during the evaluation period only if it is determined by said comparison that the curve shape of the second curve is similar to the curve shape of the first curve. Method according to Claim 15, characterized in that the second curve is compared with the first curve by means of a curve comparison model or curve recognition model. Method according to claim 16, characterized in that said curve comparison model or curve recognition model is designed to compare the slope and / or absolute value of the second curve at certain times during the evaluation period with the slope and / or the absolute value of the first curve at the corresponding curve. times to thereby determine whether or not the waveform of the second curve is similar to the waveform of the first curve. Method according to any one of claims 15-17, characterized in that: - measured values from the sensor (11) and corresponding calculation values from the calculation model regarding the size of the parameter during the evaluation period are evaluated to form a correspondence value representing the correspondence between said measured values and corresponding calculation values during the evaluation period; and - that the reference value is generated based on this correspondence value. Method according to claim 18, characterized in that an initial look-up value for a certain motor operating point is generated based on an initial correspondence value determined for the motor operating point in question or based on the average value of several consecutive correspondence values determined at different times. for the engine operating point in question. 10 15 20 25 30 35 530 574 30 Method according to Claim 18 or 19, characterized in that the look-up value for a certain motor operating point is updated based on one or more subsequent correspondence values determined for the motor operating point in question. A method according to claim 20, characterized in that each subsequent correspondence value is caused to influence the magnitude of the look-up value to an extent which is caused to decrease as the accumulated operating time of the vehicle engine increases. Method according to any one of claims 18-21, characterized in that the respective correspondence value is formed so that it represents the correspondence between the average value of said measured values from the sensor (11) and the average value of said calculation values from the calculation model during the evaluation period or during some of it. 23. a device for determining look-up values for use in monitoring the operation of an exhaust after-treatment system of a motor vehicle provided with a sensor for measuring the magnitude of a parameter related to exhaust gases flowing out of an exhaust after-treatment device, for example in form of a catalyst or filter included in the exhaust after-treatment system, characterized in that: the device (20) comprises calculating means calculating the size of the parameter based calculation model; and - that the device (20) comprises processing means (22) arranged to receive information from the sensor regarding the measured size of the parameter and information from the calculation means (21) regarding the calculated size of the parameter, the processing means (22) being arranged to perform the following steps in a situation where the vehicle's engine is running under stationary operating conditions at a certain engine operating point: a) determine a first curve based on the information from the sensor regarding the measured size of the parameter during a certain period of time, which is referred to as evaluation (21) for a period, this first curve representing the measured magnitude of the parameter as a function of time during the evaluation period, b) determining a second curve based on the information from the calculating means ( 21) regarding the calculated size of the parameter during the evaluation period, this second curve representing the calculated the magnitude of the parameter as a function of time during the evaluation period, c) comparing the second curve with the first curve to determine whether the curve shape of the second curve is similar to the curve shape of the first curve or not, and d) if it is determined by said comparison that the curve shape of the second curve is similar to the curve shape of the first curve, generating a reference value for the motor operating point in question based on the information from the sensor and the corresponding information from the calculation means (21) regarding the size of the parameter during the evaluation period. A computer program readable to the internal memory of a computer in a motor vehicle comprising an exhaust after-treatment system and a sensor for measuring the size of a parameter related to exhaust gases flowing out of an exhaust after-treatment device, for example in the form of a catalyst or a filters included in the exhaust aftertreatment system, the computer program including computer program code to cause the computer to perform the following in a situation where it is determined that the vehicle's engine is running under stationary operating conditions at a certain engine operating point: a) receiving information from said sensor regarding the measured size of the parameter during a certain period of time, which is referred to herein as the evaluation period, and determining a first curve based on said information, this first curve representing the measured size of the parameter as a function of time during the evaluation period; b) calculating, based on a calculation model, values representing the size of the parameter or receiving information about said values calculated based on a calculation model, and determining a second curve based on the calculated values of the size of the parameter during the evaluation period. this second curve representing the calculated magnitude of the parameter as a function of time during the evaluation period; c) comparing the second curve with the first curve to determine whether the curve shape of the second curve is similar to the curve shape of the first curve or not; and d) if it is determined by said comparison that the curve shape of the second curve is similar to the curve shape of the first curve, generating a look-up value for the engine operating point in question for use in monitoring the operation of the exhaust aftertreatment system, the look-up value being generated based on values from the sensor (11) and corresponding calculation values from the calculation model regarding the size of the parameter during the evaluation period. A computer program product comprising a data storage medium readable by an electronic control unit (30), wherein a computer program according to claim 14 or 24 is stored on said data storage medium. An electronic control unit (30) comprising an execution means (33), a memory (33) connected to the execution means and a data storage medium (34) connected to the execution means, a computer program according to claim 14 or 24 being stored on said data storage medium (34) .