KR102375062B1 - Method and device for sequential control of an exhaust gas control system - Google Patents

Abstract

The present invention relates, inter alia, to a method and apparatus for optimizing sequential control for a metering supply unit for an exhaust gas control system of an internal combustion engine having an SCR catalytic converter. From the section data and/or other additional data, the temperature i of the exhaust gas and/or the temperature j of the exhaust gas components at different locations in the exhaust gas control system is pre-calculated, in particular metering in relation to the boosting or emptying. Unit readiness is optimized. Thereby, optimization of the exhaust gas control system and reduction of harmful substances can be achieved. In addition, through the inclusion of this temperature prediction, a reduction in component load in sequential control can be achieved.

Description

Sequential control method and device of exhaust gas control system {METHOD AND DEVICE FOR SEQUENTIAL CONTROL OF AN EXHAUST GAS CONTROL SYSTEM}

The present invention relates to a method for sequentially controlling an exhaust gas aftertreatment component of an exhaust gas control system of an internal combustion engine, wherein the internal combustion engine is at least in an exhaust gas channel, as a component of an exhaust gas control system, an SCR catalytic converter in the exhaust gas channel and a metering supply unit having a metering supply valve, and an SCR system including a pressure boosting system, wherein the reducing agent is introduced upstream of the SCR catalytic converter in the flow direction of the exhaust gas through the metering supply unit for nitrogen oxide reduction In addition to the actual temperature using the control unit, temperature prediction for subsequent time points is also used.

The invention also relates to an apparatus for carrying out the method, in particular to an engine control unit or control unit.

In modern exhaust gas control systems, systems in which condition prediction is used to optimize exhaust gas aftertreatment are already known. DE 10 2004 005072 A1 states that for optimizing engine control functions and in particular exhaust gas aftertreatment functions or exhaust gas sensor functions, section data of a vehicle are used, for example in GPS data of a navigation system or vehicle telemetry data. This means that, on the one hand, in terms of reducing hazardous substances, or on the other hand, in terms of operational readiness, measurement accuracy or diagnostic functions, fuel consumption and additive consumption are as low as possible, and/or the maximum possible component protection (lifetime), and/or when the engine power is as high as possible or when the comfort is as high as possible. What is mentioned here is obviously the regenerative control of particulate filters or NOx storage catalytic converters, which must periodically restore the abatement effect of harmful substances through special operation of the engine. To this end, the engine must ensure that suitable conditions in relation to the temperature in the exhaust gas train, exhaust gas flow rate and mixture state (O ₂ content, reducing agent concentration such as CO or HC, etc.), for a certain period of time, the driver's accelerator pedal demand and the request of the auxiliary elements Regardless, it should be operated to be set according to engine power, rpm and torque. The task of such regeneration control is that under the use of information about the expected driving section of the vehicle, preferably, the engine operating point required by the section to be driven is advantageous in the exhaust gas condition required for the regeneration and lasts long enough as expected. By starting the playback, it can be optimized.

It is also known, according to DE 10 2007 027182 A1, that, for this purpose, preferably travel and section data of other vehicles, for example vehicles traveling ahead can also be intervened. Thereby, the accuracy or probability of prediction of the engine operating point may be increased.

In addition, according to DE 10 2008 008566 A1, a specific section and driving behavior for each driver are additionally recognized and assigned to be considered in the prediction of engine operation during current driving, so that prediction can be improved. In addition, this driver-specific data can be used and a corresponding response provided to the driver (DE 10 2008 041617 A1).

DE 10 2014 201304 A1 describes a method for determining, in the exhaust gas system of a combustion engine, an estimate of the temperature for a location located upstream of a component of the exhaust gas system having a heat capacity and exchanging heat with the exhaust gas wherein an estimate of the temperature of the location for a future point in time is determined, and the estimated value includes the temperature value for the location at the current point in time, the time interval from the current point in time to the future time, the characteristics of the exhaust gas, and the exhaust It is determined as a function of the gas flow rate and the properties of the component parts, which dictate the delay by which the temperature at that location responds to fluctuations in temperature and/or exhaust gas flow rate. The publication also claims a control device capable of determining said estimate for temperature. DE 10 2014 201304 A1 also states that the metering of the reducing agent in the SCR catalytic converter can also be optimized using this method.

The sequential control of the SCR system, i.e. the release of the boost pressure required for metering, and the shutdown of the system in case of low ambient temperature during non-essential metering preparation is substantially based on the actual value of the temperature sensor mounted in the exhaust gas train. do it with When the temperature upstream of the SCR catalytic converter approaches the temperature required for the chemical reaction, the release of the elevated pressure is allowed. This ensures that the metering readiness of the system is complete upon reaching the temperature required for the chemical reaction. If the temperature upstream of the SCR catalytic converter drops below the temperature required for the chemical reaction, at the same time there is a risk that the reducing agent may freeze in the system due to the low external temperature, the system is emptied. The reason is the connecting part (connector) between the transfer module and the pressure line. Unlike the transfer module and the pressure line, the connecting part cannot be heated. In addition, the portion has a relatively low degree of insulation, which increases the risk of freezing of the medium at the connection portion. During metering mode, the heated reducing agent transferred from the tank flows through the connector to prevent freezing.

However, when the temperature drops below the temperature required for the chemical reaction, metering is no longer required. This increases the risk of freezing, since the reducing agent no longer flows through the connector. If the reducing agent in the connector freezes and a metering request occurs again, an overpressure error may occur due to the resulting blockage of the pressure line. If the reducing agent in the connector freezes and the metering demand no longer occurs at the end of the driving cycle prior to shutting off the system, it may no longer be possible to empty the system by shutting off the pressure line. Thereby, damage to parts may occur due to the frozen reducing agent in the metering supply module. In addition, in the actual regeneration of the SCR system for passenger cars, known as DNOX5.x, heating of the transfer module is possible only through the control of the transfer and recirculation pumps. The pump can be controlled to full power only when the system is emptied. As soon as the temperature upstream of the SCR catalytic converter approaches this temperature again, emptying or heating of the system is stopped, since the system must be ready to meter again when the temperature required for the chemical reaction is reached again. .

DE 10 2004 061259 A1 discloses a method and apparatus for the detection of thawing in a metering device of an SCR catalytic converter, in particular for the reduction of nitrogen oxides in the exhaust gas stream of an internal combustion engine, wherein the reagent is dispensed using the metering device It is metered into the exhaust gas stream. In this case, the metering device is heated in at least one defrosting phase, and validation is performed following at least one defrosting phase, based on which it is directly checked whether the metering and feeding device has actually been defrosted. In this case, an estimate of the temperature is used for process optimization. Said temperature estimate is of course related to the temperature of the heating element in the metering device.

The object of the present invention is, on the one hand, to achieve an improvement in the temperature prediction in certain areas of the exhaust gas control system and, on the other hand, to avoid the above-mentioned disadvantages with associated problems, in particular with regard to the risk of freezing of the reducing agent in the metering system. It is to provide the optimal sequential control of the SCR system to help

It is also an object of the invention to provide a corresponding apparatus for carrying out the method.

A challenge with the method is that, using a temperature prediction unit, interval data and/or other additional data are evaluated, the temperature i of the exhaust gas at different locations in the exhaust gas channel and/or the exhaust gas mounted in the exhaust gas channel. Different component temperatures j of the control system components are predicted, and this predicted temperature value is solved by influencing the open-loop control or the closed-loop control of the exhaust gas aftertreatment component, in particular the sequential control of the SCR system. The inclusion of segment data including traffic information and inclusion of additional data from additional vehicle sensor devices for mobile data communication and/or prediction improves the accuracy of temperature prediction compared to the prior art. On the other hand, this solution prescribes a method of using temperature prediction for application in particular to the optimized sequential control of SCR systems. Inclusion of the temperature determined through prediction can prevent unnecessary operation of the component, thereby reducing the load and increasing the lifespan.

Through prediction of exhaust gas temperature and exhaust gas system components such as catalytic converters and sensors based on the future driving section, information on the thermal state of the components with a predetermined probability is provided to the engine control unit for subsequent engine operation. is provided on The use of this information for optimization of open-loop control and/or closed-loop control of exhaust gas aftertreatment components leads to improvements in the reduction of hazardous substances emissions, optimization of diagnostic processes and maximization of component lifespan, with as little fuel consumption as possible.

As in one preferred method variant, if the metering preparation of the metering unit of the SCR system is influenced by a predicted temperature value, in particular the sequential control can be efficiently carried out using the predicted temperature of the exhaust gas and of the exhaust gas system components. can be configured.

In a particularly preferred variant of the method, a configuration is provided wherein the timing of the boosting with the boosting system of the metering unit is influenced by one or more predicted temperature values. In this way, unnecessary boosting of the pressure can be avoided, for example, in the driving cycle in which the temperature of the SCR catalytic converter or the exhaust gas temperature upstream of the SCR catalytic converter required for the chemical reaction is not reached.

It is determined whether the chemically necessary temperature for optimal conversion of nitrogen oxides into harmless substances can be reached by the predicted exhaust gas temperature upstream of the SCR catalytic converter or based on the predicted temperature of the SCR catalytic converter or its parts. can be achieved if determined, and the boosting of the pressure is started only if the chemically required temperature can be reached within the applicable time interval T1. Therefore, the boosting is started only when it is actually needed.

In likewise another preferred method variant, in the sequential control of the SCR system, upon cancellation of the metering preparation of the metering unit, as soon as the temperature falls below the chemically necessary temperature for optimal conversion of nitrogen oxides into harmless substances, the SCR catalytic converter A configuration is provided in which it is determined whether the chemically required temperature can be reached again within the applicable time interval T2, either on the basis of the upstream predicted exhaust gas temperature or on the basis of the predicted temperature of the SCR catalytic converter or its parts. Through this evaluation, it can be determined whether emptying the system is significant and necessary, or rather it is desirable to maintain metering readiness.

In one method variant, if the time interval T2 is exceeded and expected, the booster system is evacuated and considerable energy is injected through heating before the temperature required chemically for optimal conversion of nitrogen oxides into harmless substances is again reached. and a configuration in which the pressure rises again is provided. In this way, an early shutdown of the system can be carried out for heating, when it can be recognized by prediction that the chemically required temperature will not be reached for a long time. This is advantageous during unnecessary metering preparation, especially when the ambient temperature is low, since the time in the heating mode can be increased. Thereby, the energy input into the system is increased and the risk of freezing of the reducing agent in the connector is reduced.

Alternatively, if the shortfall of the time interval T2 is predicted, the emptying process of the booster system is omitted. In this way, an uneconomical emptying of the system for heating can be avoided, for example if the temperature is only briefly below. In this case, a significant amount of energy input during the short period of time will not be able to be carried out.

These measures lead to reduced component load and longer life. At the same time, the power consumption of the SCR system is reduced by preventing unnecessary driving of the SCR components, which in turn has a positive effect on fuel consumption as well as reducing agent consumption and CO ₂ emission of the vehicle. In addition, system availability can be improved, since the point at which the required temperature for the chemical reaction is reached can be known, so that the initiation of the pressure boost can be optimized. By means of an early shutdown of the system for heating, the effectiveness of the heating mode can be increased, since the duration of the heating mode is prolonged. Accordingly, preferred uses of the method with the variant described above include the use of optimizing transfer and recirculation pumps in boosting systems, as well as sequential control of metering supply systems with non-heatable connection elements between the transfer module and the pressure line. And, the urea aqueous solution may be injected into the exhaust gas channel by the metering supply valve for the reduction of nitrogen oxides using the metering supply system. As explained at the outset, the disadvantages of such a system can be significantly reduced or even eliminated by the method variants described above.

A problem with the device is that the control unit comprises a temperature prediction unit, with which interval data and/or other additional data can be evaluated, whereby exhaust gases at different locations in the exhaust gas channel can be evaluated. The temperature (i) of and/or the different component temperatures (j) of exhaust gas control system components mounted in the exhaust gas channel can be predicted, using the predicted temperature values to control the exhaust gas aftertreatment components in open or closed loop This is solved by including an additional calculation unit and a comparison unit which can influence the control, in particular the sequential control of the SCR system, and which enables the execution of the method according to the method variants described above. The function and sequential control of the temperature prediction unit may be configured, at least in part, based on software. In this case, the control unit is a constituent part of the control unit dedicated to the metering supply unit, and may be implemented as an integrated constituent part of an upper engine control unit or as a separate unit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is explained in detail below with reference to the embodiments shown in the drawings.

1 is a schematic diagram of an internal combustion engine with an exhaust gas control system in which the method according to the invention can be applied;
2 is a schematic diagram illustrating the basic principle of the proposed temperature prediction.
3 is a graph showing a temperature change related to sequential control for a voltage increase.
4 is another graph of the temperature change in relation to the sequential control for shutdown of the system for the heating mode.

1 is a schematic diagram of an internal combustion engine 1 consisting of an engine block 10 and an exhaust gas channel 20, in which exhaust gas channel is implemented as a bandwidth lambda probe downstream of the engine block 10 in the flow direction of the exhaust gas The exhaust gas probe 30 and the catalytic converter 40 are disposed behind it. The lambda probe 30 enables lambda control and is used for balancing for diagnosis of the storage capacity of the catalytic converter. Downstream of the catalytic converter 40 is another exhaust gas probe 60 , for example a two-point lambda probe, which is used for the main control for catalytic converter diagnosis of the catalytic converter 40 and for breakthrough recognition. do. In the example shown, an SCR catalytic converter 70 for nitrogen oxide reduction is provided downstream of the first catalytic converter 40 in the exhaust gas channel 20 . Another exhaust gas probe 80 is used to monitor the exhaust gas value at the output of the exhaust gas control system.

The exhaust gas probes 30 , 60 , 80 are connected to a control unit 90 , in which normally a lambda control is implemented on the one hand and a diagnostic method relating to the monitoring of the functionality of the exhaust gas control system on the other hand. It can be designed as an engine control unit implemented in hardware or software.

In addition, a metering supply unit 50 is provided for nitrogen oxide reduction, by means of which, using the metering supply valve 51 and the pressure boosting system 52 , the reducing agent is supplied from the storage vessel tank 53 to SCR. It may be injected into the exhaust gas channel 20 upstream of the catalytic converter 70 . As the reducing agent, for example, an aqueous urea solution known on the market under the name AdBlue ^® is used.

According to the invention, exhaust gas temperatures 94.1 ... 94.3 and/or component temperatures 95.1 ... 95.3 at different locations in the exhaust gas channel are predicted. For further explanation of the invention, for example, in particular the temperature upstream of the SCR catalytic converter 70 (eg the exhaust gas temperature at position (2) 94.2) and/or the component temperature of the SCR catalytic converter 70 ( 3)(95.3) is noted.

The basic principle of the proposed temperature prediction is schematically illustrated in FIG. 2 . Exhaust gas temperature at different locations within the temperature prediction unit 91 also from the substantive interval data 92 , but also from other additional data 93 for improving the prediction of the operating point of the vehicle and engine, as mentioned at the outset. (i)(94.1...94.3) and/or component temperature (j)(95.1...95.3) are pre-calculated. The temperature prediction unit 91 is implemented as a component of the control unit 90 .

3 and 4 respectively show the typical temperature change 103 and the predicted temperature change 104 with respect to the sequential control for the metering supply unit 50 as a graph 100. As shown in FIG. Here, temperature 101 is plotted as a function of time 102, respectively.

3 shows a typical temperature change 103 (dotted curve) and the current state of the art in relation to the sequential control for step-up.

As soon as the temperature upstream of the SCR catalytic converter 70 reaches the applicable temperature threshold 105 , the boosting is started (time “start boosting” 107 ). The temperature threshold 105 is usually selected such that the pressure rise is terminated at the maximum possible temperature gradient before the temperature required for the chemical reaction (chemically required temperature 106) is reached. Thereby, as indicated by the conventional temperature change 103, the pressure increase can be performed even when the chemically required temperature 106 is not reached at all within the driving cycle, because the driving cycle has ended or has been blocked. (Point "End of Drive Cycle" (108)).

The predicted temperature change 104 (solid curve) in Fig. 3 shows the onset of the pressure increase based on the predicted temperature change through the prediction proposed by the present invention. In this case, through the prediction, as soon as the arrival of the chemically required temperature (the chemically required temperature 106) is predicted within the applicable time interval T1 (111) (the time point “the predicted arrival of the chemically required temperature 110 ) )"), the boosting is started (time point "Start boosting based on prediction" 109). Thereby, it starts only at the point in time when a voltage increase is actually needed.

4 shows, on the one hand, the current state of the art for sequential control for shutdown of the system for the heating mode. Thus, the conventional temperature change 103 (dotted curve) is a system as soon as the temperature upstream of the SCR catalytic converter is below the applicable temperature threshold 112 below the temperature threshold 105 set for boosting in the system. is emptied (time "shutdown of the system" 113). However, as shown in FIG. 4 , this is the time until the restart of the boosting (time “start of boosting” 107) to such an extent that, upon a temporary fall below the threshold, a significant amount of heat cannot be injected into the system by the heating mode. Even this brief can cause the system to shut down.

Predicted temperature change 104 of FIG. 4 illustrates a possible improvement through the use of predicted temperature change through prediction. The temperature upstream of the SCR catalytic converter 70 (eg the predicted exhaust gas temperature at position 2 94.2, see FIG. 1 ) is below the chemically required temperature 106 , and, therefore, is in preparation for metering. When there is no longer a need for this, an evaluation of the applicable time interval T2 115 may be performed until the temperature is reached (evaluation time 114), as suggested by the present invention. This can be done if there is sufficient time to empty the system, inject a significant amount of heat into the system through the heating mode, and raise the pressure again before reaching the chemically required temperature 106 again. If there is not enough time, the process can be stopped.

Claims (9)

A method for sequentially controlling an exhaust gas aftertreatment component of an exhaust gas control system of an internal combustion engine (1), wherein the internal combustion engine is at least in an exhaust gas channel (20), as a component of the exhaust gas control system, an exhaust gas channel (20) an SCR system comprising an SCR catalytic converter (70) in the inside, a metering supply unit (50) having a metering supply valve (51) and a boosting system (52), and for nitrogen oxide reduction, a metering supply unit (50) After the exhaust gas, a reducing agent can be introduced upstream of the SCR catalytic converter 70 in the flow direction of the exhaust gas through A method for sequential control of processed parts, the method comprising:
At least one of the interval data 92 and other additional data 93 is evaluated using the temperature prediction unit 91 , whereby the temperature i of the exhaust gas at different positions in the exhaust gas channel 20 . (94.1...94.3) and at least one temperature j (95.1...95.3) of different parts of the exhaust gas control system mounted in the exhaust gas channel 20 are predicted, these predicted temperature values being Affect the open-loop control or closed-loop control of exhaust gas after-treatment components;
Upon cancellation of the metering preparation of the metering unit 50, the predicted exhaust gas upstream of the SCR catalytic converter 70 as soon as the temperature 106 is below the chemically required temperature 106 for optimal conversion of nitrogen oxides into harmless substances. Based on the temperature or the predicted temperature of the SCR catalytic converter 70 or parts of the SCR catalytic converter 70, it is determined whether the chemically required temperature 106 can be reached again within the applicable time interval T2 115 become,
If the time interval T2 (115) is expected to be exceeded, then the boosting system (52) is evacuated and heated before reaching the chemically necessary temperature (106) again for optimal conversion of nitrogen oxides to harmless substances. A method for sequentially controlling exhaust gas after-treatment parts, characterized in that energy is input through and pressure is re-established. Method according to claim 1, characterized in that the metering readiness of the metering unit (50) of the SCR system is influenced by the predicted temperature. The exhaust gas aftertreatment component according to claim 1 or 2, characterized in that the timing of the pressure increase with the pressure boosting system (51) of the metering supply unit (50) is influenced by one or more predicted temperature values. of the sequential control method. 3. The conversion to harmless substances according to claim 1 or 2, based on the predicted exhaust gas temperature upstream of the SCR catalytic converter (70) or the predicted temperature of the SCR catalytic converter (70) or parts of the SCR catalytic converter (70). It is determined whether the chemically required temperature 106 can be reached for optimal conversion of nitrogen oxides, and the elevated pressure is such that the chemically required temperature 106 can be reached within the applicable time interval T1 111 . Sequential control method of exhaust gas after-treatment parts, characterized in that it starts only when delete delete Method according to claim 1 , characterized in that the boosting system ( 52 ) is not emptied if a failure of the time interval ( T2 ) ( 115 ) is predicted. 3. The method according to claim 1 or 2, wherein the method is used for optimizing the sequential control of the conveying and recirculation pumps in the boosting system (52) as well as the metering supply system with non-heatable connection elements between the conveying module and the pressure line. A method for sequential control of exhaust gas after-treatment parts used, wherein an aqueous urea solution can be injected into the exhaust gas channel (20) by a metering supply valve (51) for reduction of nitrogen oxides using the metering supply system. Device for sequential control of exhaust gas aftertreatment parts of an exhaust gas control system of an internal combustion engine (1) for carrying out a method according to claim 1 or 2, said internal combustion engine having one in an exhaust gas channel (20) at least one metering supply unit (50) having at least one SCR catalytic converter (70) and an exhaust gas control system, and a metering supply valve (51) and a boosting system (52), wherein the apparatus comprises: A reducing agent may be introduced upstream of the SCR catalytic converter 70 in the flow direction of the exhaust gas through the metering supply unit 50 , and the exhaust gas control system is configured to at least include the metering supply unit 50 and the SCR catalytic converter 70 . The function of sequential control of the SCR system is implemented, the exhaust gas after-treatment component comprising a control unit 90 that can also process temperature predictions for subsequent time points in addition to the actual temperature measured using the temperature sensor A sequential control device comprising:
The control unit 90 includes a temperature prediction unit 91 , by which the data of one of the interval data 92 and other additional data 93 can be evaluated, whereby the exhaust gas channel ( Temperature i (94.1...94.3) of the exhaust gas at different locations in 20) and temperature j (95.1...95.3) of different parts of the exhaust gas control system components mounted in the exhaust gas channel 20 characterized in that it comprises an additional calculation unit and a comparison unit, wherein the temperature of at least one of Sequential control of exhaust gas aftertreatment components.

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