CN102102565A - Method and device for on-board error diagnosis in operation of internal combustion engine of motor vehicle - Google Patents

Abstract

The invention relates to a method and device for "on-vehicle" fault diagnosis during the operation of an internal combustion engine. The method for "on-board" fault diagnosis includes the steps of: determining an emission reference value based on theoretical settings of an air path and a fuel path; determining a current emission value under a current operating condition; determining an index value, wherein the index value corresponds to the current emission a quotient of an integral of the value over a predetermined time interval and an integral of the emission reference value over the time interval; and generating a fault signal based on the index value.

Description

Method and device for "on-board" fault diagnosis during operation of an internal combustion engine

technical field

The invention relates to a method and a device for "on-board" fault diagnosis during operation of an internal combustion engine.

Background technique

Since the introduction of diesel particulate filters in motor vehicles, the analysis of soot emissions from internal combustion engines is increasingly carried out by estimating the soot load of the diesel particulate filter. Estimation of abnormal conditions in internal combustion engines that may lead to overloading of the diesel particulate filter, mainly for the prediction of overloading of the diesel particulate filter and for avoiding clogging due to soot particles when safely controlled regeneration is no longer possible caused by diesel particulate filter replacement. Another detrimental effect of increased particulate filter loading is the increase in back pressure beyond nominal, whereby both fuel economy and performance of the internal combustion engine are affected.

There is therefore a need to obtain information on the effect of faults in the operation of an internal combustion engine on the soot emissions of the internal combustion engine.

In addition, the "on-board" measurement of NOx emissions in the exhaust system of internal combustion engines opens up a series of new possibilities for control and fault diagnosis during operation of internal combustion engines. While sensors are currently used for fault diagnosis, there are also possible approaches for air path and fuel path recirculation adjustments.

At this time, a problem arises, that is, within the framework of "on-board" fault diagnosis, since the first driver can produce different results from the other driver according to his driving habits in terms of test driving from the same starting point to the same destination. A driver drives with different NOx emissions and different fuel consumption, so a limit on the NOx threshold is meaningless, eg a more aggressive driving style results in higher NOx emissions and more fuel consumption. In contrast, for regular test drive cycles, NOx emissions and fuel consumption do not depend on driving style, since this dependence is limited to acceptable variation between different test cycles by definition of the test cycle.

So far, in the state of the art, the application of "on-board" identification in terms of NOx emissions has not been studied in depth neither for "on-board" fault diagnosis nor for the control of the operation of the internal combustion engine.

Contents of the invention

The object of the present invention is to provide a method and device for "on-board" fault diagnosis during the operation of an internal combustion engine, which enable reliable "on-board" fault diagnosis in terms of soot emissions and/or _NOx emissions, And implement appropriate controls when necessary.

This object is achieved by the method according to the invention and by the device according to the invention.

A method for "on-board" fault diagnosis during operation of an internal combustion engine includes the following steps:

Determine the emission reference value based on the theoretical settings of the air path and the fuel path;

Determine current emission values under current operating conditions;

determining an index value, wherein the index value corresponds to the quotient of the integration of the current emission value over the predetermined time interval and the integration of the emission reference value over the time interval; and

A fault signal is generated based on the index value.

The invention is based, inter alia, on the idea of calculating an emission reference value, which may be a soot or _NOx emission reference value for an internal combustion engine, which to some extent represents a theoretical value for the emission level, where the emission reference The values are used for "onboard" fault diagnosis and, if necessary, also for emission control.

According to the invention, reference values for soot emissions (in mg/m ³ ) are calculated as a function of theoretical settings for air and fuel paths, so that vehicle dynamics (i.e. instantaneous corrections) to steady state are taken into account The effect of the calibration value.

According to an embodiment, the emission reference value is determined based on a reference value (F _exh,ref ) of the mass fraction burned in the exhaust gas. In addition, the current emission value under the current working condition can also be determined based on the value of the combustion mass fraction in the exhaust gas (F _{exh, ref} ).

For a given working condition, the concentration of soot generated during combustion mainly depends on the combustion mass fraction (F _exh ) in the exhaust. For reference values for soot emissions, a reference value for the mass fraction of combustion in the exhaust gas is calculated for the theoretical setup of the air path and the fuel path. More significant corrections to theoretical values due to aggressive or aggressive driving styles (i.e. larger deviations due to high-pass filtering of instantaneous corrections) and greater deviations between theoretical settings and measured values (especially concerning the air path), so the driving behavior should be taken into account in this case.

According to an embodiment, the emission control of the internal combustion engine is dependent on the fault signal.

According to another embodiment, the correction of the theoretical setting of the air path and/or the fuel path depends on the fault signal.

According to an embodiment, the theoretical setting of the air path is corrected for a first value range of the fault signal, and the theoretical setting of the fuel path is corrected for a second value range of the fault signal, wherein the second value range is lower than the first value Domains correspond to larger deviations of current emissions relative to emission reference values.

According to another aspect of the present invention, a method for "on-board" fault diagnosis during operation of an internal combustion engine is characterized in that the method includes determining emission reference values based on theoretical settings of air paths and fuel paths; determining current operating conditions The current emission value under; determining an index value, wherein the index value corresponds to the quotient of the integration of the current emission value over a predetermined time interval and the integration of the emission reference value over the time interval; and based on the index value Generate a fault signal, wherein based on the coordination of air and fuel path control, it is determined whether the theoretical setting of the air path and/or fuel path needs to be corrected. When there is a large soot emission deviation, the theoretical setting of the fuel path is corrected. When there is a relative For smaller soot emission deviations, the theoretical setting of the air path is corrected.

Furthermore, the invention relates to a device for "on-board" fault diagnosis during operation of an internal combustion engine, which device is designed to carry out the method according to the preceding claims. For preferred embodiments of the device reference is made to the above-described embodiments in relation to the method.

Further details of other embodiments of the invention are found in the description and in the respective dependent claims.

Description of drawings

Hereinafter, the present invention will be described in more detail according to preferred embodiments with reference to the accompanying drawings.

FIG. 1 is a schematic diagram illustrating a method for fault diagnosis performed using soot emission according to an embodiment;

Figure 2 is a schematic diagram illustrating a method for controlling soot emissions according to the present invention;

FIG. 3 is a schematic diagram illustrating a method for fault diagnosis performed using NOx emissions according to an embodiment;

FIG. 4 is a schematic diagram illustrating a method for controlling NOx emissions according to the present invention.

Detailed ways

Reference is first made below to FIGS. 1 and 2 , which show a possible embodiment of the method according to the invention for fault diagnosis or control of an internal combustion engine using soot emissions.

According to FIG. 1 , reference values for soot emissions (in mg/m ³ ) are calculated essentially as a function of the theoretical settings of the air path and/or fuel path.

As schematically shown in Fig. 1, for a given operating condition, the concentration of soot produced in the combustion process mainly depends on the combustion mass fraction (F _exh ) in the exhaust gas. Correspondingly, in order to determine the reference value of soot emission, it is necessary to calculate the reference value (F _exh,ref ) of the combustion mass fraction in the exhaust gas for the theoretical setting of the air path and the fuel path.

In the case of non-dynamic changes in the theoretical setting of the fuel path, the reference value of soot emission is mainly calculated based on the reference value (F _{exh, ref} ) of the combustion mass fraction in the exhaust gas, which is mainly determined by MAF and MAP reference values calculated without model-based air path control. Reference values for soot emissions are then estimated for internal combustion engine emissions in theoretical settings for the air path and fuel path.

For the purpose of "on-board" fault diagnosis, according to Fig. 1, the calculated current soot emission is integrated over a predetermined time interval and divided by the integral of the reference value of soot emission over a predetermined time interval. The choice of the time interval used here is very important for the time range of the pre-calibrated mass fraction in the DPF for the next operating cycle to ensure correct fault diagnosis.

The index value thus calculated will be compared with the OBD critical index value used for fault diagnosis (OBD critical index value, OBD="on-board diagnosis"), wherein the OBD critical index value corresponds to the OBD critical value (unit is gram The quotient of the integral of the soot emission reference value (unit: gram per operating cycle) per operating cycle). For the situation that the value exceeds the OBD critical index value, the fault information will be displayed and the fault signal will be output through fault diagnosis.

According to FIG. 2 , the deviation between the reference value of the soot level and the current value of the soot emission is used to generate a fault signal. This fault signal will be applied in the air and fuel path structure as follows:

The air and fuel routing control coordination determines whether the theoretical settings of the air routing and/or the fuel routing need to be corrected to bring the deviation between the reference value of the soot emission and the calculated value of the soot emission within an acceptable tolerance range.

Depending on the operating range of the internal combustion engine, the theoretical setting of the fuel path is corrected for larger soot emission deviations (ie in cases where fast dynamics are required). In the case of relatively small deviations in soot emissions and good tracking between the reference value and the current theoretical setting of the air path, the theoretical setting of the air path is corrected.

Alternatively, the soot fault signal can be applied directly in a closed loop ("closed loop") feedback control of the air path to control the regulation of the air path. When operation occurs at another operating point of the NOx soot correction curve, the feasibility of using this method of control is limited due to the link to the NOx emission value whose tolerance range is determined by the OBD threshold for NOx emissions. value to give.

Accordingly, if "on-board" control and/or monitoring of soot emissions is desired or necessary, models of any exhaust aftertreatment components may also be included for estimating soot emissions that would affect Soot levels in the exhaust (and at monitoring locations), such as any DPF catalyst element, which stores and converts soot particles from the air intake on the DPF inlet. Similarly, a model of the current soot emission can be used for the evaluation of the soot emission at the monitoring location, however in this case according to direct "on-board" measurements and/or suitable estimation algorithms. This can correspond to an estimation algorithm that is applied in relation to a reference value for soot emissions, however here the current measured values (MAF, MAP, exhaust lambda, intake lambda) of the air path and fuel path are required as base and apply it.

The method described above for "on-board" fault diagnosis with reference to FIG. 1 can also be used analogously for emission reference values for NOx emissions. In the following, a possible embodiment of a method for fault diagnosis and control of an internal combustion engine according to the present invention using NOx emissions will be described first with reference to FIGS. 3 and 4 .

Here, a reference value for NOx emissions is calculated based on estimating unburned NOx emissions, using a simplified order thermodynamic model of the exhaust aftertreatment components, and estimating downstream NOx emissions.

As shown in FIG. 3 , for a given working condition, the concentration of NOx produced in the combustion process is determined according to the combustion mass fraction (F _exh ) in the exhaust gas. Correspondingly, it is necessary to calculate the reference value (F _{exh, ref} ) of the combustion mass fraction in the exhaust gas for the theoretical setting of the air and fuel paths, so as to determine the reference value of the NOx concentration.

Reference values for soot emissions are then estimated for internal combustion engine emissions in theoretical settings for the air path and fuel path. In the case of a non-dynamic change in the theoretical setting of the fuel path, the reference value of the NOx concentration is mainly calculated based on the reference value (F _{exh, ref} ) of the mass fraction burned in the exhaust gas, which is mainly determined by different MAF and MAP reference values are calculated based on model-based air path control. A reference value for the NOx concentration is then estimated for internal combustion engine emissions in a theoretical setting for the air path and fuel path.

For "on-board" fault diagnosis purposes, according to FIG. 3 , the calculated current NOx emissions are integrated over predetermined time intervals and divided by the integration of the reference value of NOx emissions over predetermined time intervals. The choice of the time interval used here is very important for the time range of the pre-calibrated mass fraction in the DPF for the next operating cycle to ensure correct fault diagnosis.

For the situation that the value exceeds the OBD critical index value, the fault information will be displayed and the fault signal will be output through fault diagnosis. The index value thus calculated will be compared with the OBD critical index value used for fault diagnosis (OBD critical index value, OBD="on-board diagnosis"), wherein the OBD critical index value corresponds to the OBD critical value (unit is gram The quotient of the integral of the NOx emission reference value (in grams per operating cycle) per operating cycle). For the situation that the value exceeds the OBD critical index value, the fault information will be displayed and the fault signal will be output through fault diagnosis.

According to FIG. 4 , the deviation between the reference value of NOx emissions and the current value of NOx emissions is used to generate a fault signal. This fault signal will be applied in the air and fuel path mechanisms as follows:

The air and fuel routing controls coordinate to determine whether the theoretical settings of the air routing and/or the fuel routing need to be corrected to bring the deviation between the reference value of NOx emissions and the calculated value of NOx emissions within an acceptable tolerance range.

Depending on the operating range of the internal combustion engine, the theoretical setting of the fuel routing is corrected for larger deviations in NOx emissions (ie in cases where fast dynamics are required). In the case of relatively small deviations in NOx emissions and good tracking between the reference value and the current theoretical setting of the air path, the theoretical setting of the air path is corrected.

Alternatively, the NOx fault signal can be applied directly in a closed loop ("closed loop") feedback control of the air path to control the air path settings.

Accordingly, if "on-board" control and/or monitoring of NOx emissions is desired or necessary, models of any exhaust aftertreatment components that affect exhaust NOx emissions in-line (and at the monitoring location), such as any DPF catalyst element, which will store and convert NOx emissions on the intake on the DPF inlet. Similarly, a model of the current NOx emissions can be used, a model for the assessment of NOx emissions at the monitoring location, however in this case according to direct "on-board" measurements and/or a suitable estimation algorithm. This can correspond to an estimation algorithm that is applied in relation to a reference value for NOx emissions, but here needs to be based on current measurements of the air and fuel paths (MAF, MAP, Exhaust Lambda, Intake Lambda) and apply it.

Claims (10)

1. A method for "on-board" fault diagnosis during internal combustion engine operation, characterized in that the method comprises: Determine emission reference values based on theoretical settings for air and fuel paths; Determine current emission values under current operating conditions; determining an index value, wherein the index value corresponds to the quotient of the integration of the current emission value over a predetermined time interval and the integration of the emission reference value over the time interval; and A fault signal is generated based on the index value. 2. The method of claim 1, wherein the emission reference value is a reference value for soot emissions of the internal combustion engine. 3. The method of claim 1, wherein the emission reference value is a reference value for _NOx emissions of the internal combustion engine. 4. The method according to any one of the preceding claims, characterized in that the determination of the emission reference value is carried out on the basis of a reference value (F _{exh, ref} ) of the mass fraction burned in the exhaust gas. 5. The method according to any one of the preceding claims, characterized in that the determination of the current emission value is based on the value (F _exh,ref ) of the combustion mass fraction in the exhaust gas under the current operating conditions. 6. The method as claimed in any one of the preceding claims, characterized in that the emission control of the internal combustion engine is dependent on the fault signal. 7. The method according to any one of the preceding claims, characterized in that a correction of the theoretical setting of the air path and/or fuel path depends on the fault signal. 8. The method of claim 7, wherein the theoretical setting of the air path is corrected for a first value range of the fault signal, and corrected for a second value range of the fault signal The theoretical setting of the fuel path is corrected, wherein the second range of values corresponds to a greater deviation of the current emissions relative to an emissions reference value than the first range of values. 9. Device for "on-board" fault diagnosis during operation of an internal combustion engine, characterized in that the device is designed to implement the method as claimed in any one of the preceding claims. 10. A method for "on-board" fault diagnosis during operation of an internal combustion engine, characterized in that the method comprises: Determine emission reference values based on theoretical settings for air and fuel paths; Determine current emission values under current operating conditions; determining an index value, wherein the index value corresponds to the quotient of the integration of the current emission value over a predetermined time interval and the integration of the emission reference value over the time interval; and A fault signal is generated based on the index value, wherein it is determined based on air and fuel path control coordination whether the theoretical setting of the air path and/or the fuel path needs to be corrected, and when there is a large soot emission deviation, the theoretical setting of the fuel path is performed. Correction, the theoretical setting of the air path is corrected when there is a relatively small deviation from the soot emission.

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