DE102005061876A1 - Method and device for controlling an exhaust aftertreatment system - Google Patents

Abstract

The invention relates to a method for controlling an exhaust gas aftertreatment system of an internal combustion engine with an engine block and at least one exhaust gas guide which has at least one catalytic converter and a downstream particle filter, the temperature in the exhaust gas guide and the temperature of at least one of its components being monitored and at least by means of at least one measuring device If the temperature is exceeded, a multi-level concept of measures is applied. The invention further relates to a device for controlling an exhaust gas aftertreatment system of an internal combustion engine with an engine block, a control unit interacting with a control device and at least one exhaust gas guide which has at least one catalytic converter and a downstream particle filter, for the temperature detection of which at least one temperature measuring device is provided, wherein in cascaded control loops are implemented in the control unit, by means of which countermeasures can be initiated if a maximum permissible component temperature is exceeded. DOLLAR A This enables consumption-optimized internal engine heating of the particle filter to be regenerated without the maximum permissible component temperature of the components in the exhaust gas duct being exceeded.

Description

State of technology

The The invention relates to a method for controlling an exhaust aftertreatment system an internal combustion engine with an engine block and at least one Exhaust system, having at least one catalyst and a downstream particle filter.

The The invention further relates to a device for controlling a Exhaust aftertreatment system of an internal combustion engine with an engine block, a cooperating with a control unit control unit and at least one exhaust system, the at least one catalyst and a downstream particle filter has, for the temperature detection at least one temperature measuring device is provided.

Become frequent Internal combustion engines, in particular diesel internal combustion engines with Exhaust after-treatment systems equipped with a particle soot filter or Diesel Particulate Filter (DPF). This is special no later than with the tightening the exhaust limits over EU VI also required. The use of particle filters provides is and is an efficient means of reducing particulates already introduced in series at various vehicle manufacturers. Of the in the filter attached soot must however, be burned discontinuously to the desired filtering effect to ensure.

to Regeneration of the diesel particulate filter are temperatures above the usual Exhaust gas temperatures necessary. Without additional measures, the particles oxidize at about 550 to 600 ° C. By combining the particulate soot filter with an oxidation catalyst (OXI-KAT), by catalytic coating of the filter and / or through an additive addition leaves lower the lower temperature threshold for the oxidation to below 500 ° C. Development goal is, however, on these additive-based systems to renounce.

In certain operating conditions the internal combustion engine may be the case that the regeneration uncontrolled fast or too slow. Especially with a Uncontrolled rapid burnup may be due to the highly exothermic Oxidation of the particles come to an undesirable heat release, the with steep, wandering temperature fronts in the filter and very high temperatures accompanied. Such states should be safely avoided or, if appropriate, appropriate activities controlled and controlled. Is regeneration too slow? from, must the regeneration measures be maintained for too long, resulting in increased fuel consumption Episode has. In addition, there is a risk that the operation of the internal combustion engine is interrupted or transferred to an operating state, the abort forces regeneration.

To avoid such conditions is in the writings DE-OS 10333441 A1 respectively. EP 1384868 A2 a method and a device for controlling an exhaust aftertreatment system, in particular a particulate filter, an internal combustion engine described. In this case, a desired value (LAS) for a lambda signal (L) or a change in a lambda signal (L) can be predetermined. An actual value for the lambda signal (L) or for the change of the lambda signal (L) is detected. Based on the comparison between the actual value and the setpoint value (LAS), a control signal for an actuating element, with which the reaction in the exhaust aftertreatment system can be controlled, is predetermined in such a way that the actual value approaches the desired value (LAS). With the control elements, the amount of oxygen in the exhaust gas can be influenced. Control elements may be an exhaust gas recirculation valve, a throttle flap, adjusting elements for influencing an exhaust gas turbocharger and / or a fuel metering system, which carries out a post-injection of a fuel into the internal combustion engine.

In Scripture EP 1364110 B1 a further method and a corresponding device is described in which a parameter is determined as a function of at least one operating characteristic of the internal combustion engine and at least one operating characteristic of the particle filter for controlling a regeneration process, which characterizes a future intensity of a reaction in the particle filter. When a threshold value is exceeded by the parameter, at least one measure is taken which reduces the oxygen concentration in the exhaust gas of the internal combustion engine, with the aim that the parameter does not reach the threshold value.

If the particle soot filter reaches a certain load and regeneration of the filter is not ensured because of the engine operating state, it is provided according to the prior art that the exhaust gas temperature is increased to such an extent that the particles burn rapidly. For this purpose, the concentration of hydrocarbons in the exhaust gas is increased, which are then reacted in an oxidation catalyst and lead to an increase in temperature. The increase in concentration in the exhaust system is usually carried out by a post-injection in the fuel metering system on the engine block or by direct metering of diesel fuel into the exhaust system, the metering is normally specified depending on the operating point. In connection with an increase in the concentration of hydrocarbons, an intake air throttling and a rail pressure reduction are also known. Further Also known are methods in which a late shift of the main injection and a remote post-injection are used.

Especially in the case of particle filters in underfloor position far from the engine limits the maximum permissible temperature exhaust manifold, Turbine and precatalyst the provided exhaust gas energy. Around the heating possible to represent efficiently, the internal engine intervention intake air throttling, late shift the main injection, modified pilot injection, and / or post-injection nevertheless applied as close as possible to the permissible temperatures become. To field influences or environmental influences and intercepting series tolerances, but is a safety margin to comply, which extends at least the necessary heat-up time and thus further increases fuel consumption.

task the invention is to provide a method for controlling the exhaust aftertreatment system, that's a safe and economical internal engine heating for regeneration of the particulate filter allows. It is a further object of the invention to provide a corresponding device provide.

Advantages of invention

The The object relating to the method is achieved in that by means of at least one measuring device, the temperature in the exhaust system and the Monitored temperature of at least one of its components and when the temperature is exceeded multi-level action concept is applied. In particular, with the proposed method in extreme environmental conditions, such as extreme ambient temperatures or extreme altitude, the Applied heating strategy for particle filter regeneration with less Safety distance are displayed. This allows a particularly secure and low-consumption internal engine heating.

In preferred embodiment is initially planned that in a first stage under normal conditions in a closed loop a control of the temperature is carried out by means of internal engine control variables, where the application is close to the permissible component temperature. This allows a particularly effective heating of the particulate filter. The time for regeneration is significantly shortened, which is advantageous in terms of fuel consumption.

When inner motor manipulated variable can a reduction in the intake air throttling and / or a post-injection with a closed or nearly closed throttle be carried out an exhaust gas recirculation. additional Facilities that would be required for heating are therefore not required.

at a temporally debounced overrun of maximum permissible Component temperature is a limit value control in a second stage carried out, which acts on the throttle valve of the exhaust gas recirculation and this in Steps or steadily opens. Advantageous Here is that an immediate lowering of the critical component temperature from manifold and possibly a turbocharger possible is without already the particle filter heating must be reduced. However, the prerequisite is that the exhaust gas recirculation during heating only minimally open or completely closed is what for many engine modifications but because of the risk of increased soot formation or combustion fluctuations is mandatory.

In preferred embodiment is a control intervention in the limit control to an operating point-dependent maximum Recirculation mass limited, which reduces the risk of increased soot formation and on the other hand for enough Torque reserves is advantageous.

Becomes if the maximum permissible component temperature continues to be exceeded over time in a next Stage another limit control performed on heating control sizes for the particulate filter can be achieved so that protective measures can be taken directly lowering the temperature in the exhaust system to Episode.

In preferred method variant can within the limit control at temperature exceeded reduces the post-injection amount of post-injection and / or a late shift the post-injection and / or a reduction of an intake air throttling and / or an early shift a main injection withdrawn become. With these measures is a significant reduction in the temperature of the components in the exhaust system possible.

When Emergency response is at a timely debounce exceeded the maximum allowed Component temperature in a final stage the entire internal engine activities aborted for particle filter heating. This safety shutdown prevents a destructive excess the maximum component temperature, if the previously performed control procedures no sufficient temperature reduction have caused.

For resetting, it is provided in a variant of the method that, if the maximum component temperature is undershot, the measures corresponding to the escalation stages of the measures concept to be gradually withdrawn.

In preferred embodiment is the critical component temperature by temperature measurement or monitored by modeling. In a modeling can also complex relationships, which are dependent on a large number of influencing factors become. From the real temperature increase taking into account an additional one Tolerance and a comparison of this value with that in a model calculated temperature increase can short-term temperature fluctuations or tolerance deviations the temperature sensors are detected, resulting in a less susceptible to temperature control contributes.

A particularly accurate temperature control can be achieved when the maximum permissible component temperatures the components in the exhaust system map-controlled be specified. With that you can For example, the various operating conditions of the internal combustion engine considered and thus controlling an optimal regeneration temperature for the particulate filter where other engine parameters can be taken into account.

The the object relating to the device is achieved in that in the control unit cascaded control circuits are implemented, by means of which when exceeded a maximum allowable Component temperature countermeasures can be introduced. This can be ensured that a heating of the Particulate filter can be safely displayed in the field and a lower one There is a risk of the heating being stopped. Such a heating stop is general to avoid, as only an undefined and incomplete Rußabbrand would be done and subsequently a clear detection of soot loading for safe Initiating the regeneration would be made much more difficult.

In preferred embodiment the control unit in a first stage, a control circuit for an engine inside Particle filter heating, in a second stage, a limit value control for an exhaust gas recirculation and in a third stage, another limit control for the particulate filter heating control quantities. With these escalation levels is an exact temperature control near the maximum allowed Component temperature of the components in the exhaust system possible.

is the control unit by means of at least one signal line with at least connected to a temperature sensor and the control unit for regulating the Nacheinspritzmenge by means of a signal line with a fuel metering system connected to the engine block, can be achieved that as internal engine measure especially in the first stage, the post-injection quantity regulated and at temperature can be reduced to the maximum component temperature.

A likewise preferred variant can provide that the control unit by means of at least one signal line with at least one throttle in the exhaust gas recirculation and / or by means of a further signal line with an intake air throttle connected is. Thus, on the one hand, an adjustability of the exhaust gas recirculation amount allows and, secondly, as a further internal motor measure, regulation of Intake air volume reached.

In Turbocharged internal combustion engines is in the exhaust system before the catalyst arranged an exhaust gas turbocharger, whereby the performance the internal combustion engine can be significantly increased.

To the Protection of exhaust gas turbocharger against overheating it is provided that the control unit by means of a signal line with a further temperature sensor in the exhaust system before is connected to the exhaust gas turbocharger. This is at a fuel burn in the exhaust manifold at the engine block of importance, since in this case extremely high temperatures on Exhaust gas turbocharger may arise.

When, the post injection assisting device, has the exhaust system at least one fuel metering device, which by means of a Signal line is connected to the control unit. This can additionally Fuel metered into the exhaust system become a rich mixture required for rapid heating adjust. The fuel metering unit can thus additionally as further manipulated variable in the be integrated cascaded temperature control.

has the control unit at least one Kennfeldeinheit to specify the maximum component temperature can, in this preferred embodiment Even complex operating parameters are taken into account. Especially in different load cases or operating phases of the internal combustion engine can be a variable specification be appropriate for the maximum component temperature.

In preferred embodiment can control the functions of the control loop and limit controls be executed in the control unit as software and / or hardware and at least partially be part of a higher-level engine control, wherein a program stored function for the control particularly simple as a subroutine in the entire engine control software integiert can be. this makes possible also inexpensive Software updates.

drawing

The Invention will be described below with reference to one shown in the figures embodiment explained in more detail. It shows:

1 schematically an internal combustion engine with an exhaust aftertreatment system, 2 a flowchart for controlling the exhaust aftertreatment system.

description the embodiments

1 schematically shows an internal combustion engine 1 with an exhaust aftertreatment system, the main components of which are an engine block 10 , a control unit cooperating with a control device 130 and an exhaust system 20 having. The exhaust system 20 has a catalyst in the embodiment shown 40 and a downstream particle filter 50 on. In addition, in the example shown in the exhaust system 20 to increase the performance of an exhaust gas turbocharger 30 intended.

To monitor the component temperature are temperature sensors at various points 70 . 80 . 90 . 100 intended. The first temperature sensor in the direction of flow 70 is located in front of the turbocharger 30 and above all serves to monitor the temperature of the exhaust gas turbocharger 30 and an exhaust manifold on the engine block 10 in front of the turbocharger 30 , With the temperature sensors 80 . 90 Can the temperatures in front of and behind the catalyst 40 or in front of the particle filter 50 be detected. The last in the flow direction of the exhaust gas temperature sensor 100 serves to monitor the exhaust gas temperature. All temperature sensors 70 . 80 . 90 . 100 are with appropriate signal lines 71 . 81 . 91 . 101 with the control unit 130 connected.

The control unit 130 is by means of a signal line 12 with a fuel metering system 11 on the engine block 10 connected. The fuel metering system 11 is usually controlled by a higher-level engine control, not shown here.

In addition, the internal combustion engine 1 an external exhaust gas recirculation 110 on, as the active component of an adjustable throttle 111 owns that via a signal line 112 with the control unit 130 connected is.

Supply air side has the internal combustion engine 1 an adjustable intake throttle 120 , by means of another signal line 121 also with the control unit 134 is in active connection.

In addition, it can be provided that in the exhaust system - in the example shown behind the exhaust gas turbocharger 30 A fuel metering unit 60 is arranged, by means of a signal line 61 with the control unit 130 connected is.

In an inventive embodiment are in the control unit 130 Cascaded control circuits implemented by means of which countermeasures can be initiated if a maximum permissible component temperature is exceeded. In a first stage is a control loop 131 intended for an internal engine particulate filter heating. In a second stage is a limit control 133 for exhaust gas recirculation 114 and in a third stage another limit value regulation 134 provided for the particulate filter Heizsteuerungsgrößen.

In a preferred embodiment, it is provided that the functions of the control loop 131 and the limit regulations 132 . 133 in the control unit 130 executed as software and / or hardware and are at least partially part of a higher-level engine control. In this case, the control unit 130 at least one characteristic unit for specifying the maximum component temperature, in which the maximum component temperature is stored operating point-dependent.

2 describes the method with reference to a flowchart. In the control unit 130 is provided that by means of at least one measuring device, the temperature in the exhaust system 20 and monitors the temperature of at least one of its components and a multi-step action concept is applied when the temperature is exceeded.

In a first stage, under normal conditions in the control loop 131 a regulation of the temperature carried out by internal engine control variables. As engine-internal manipulated variable is first a reduction of Ansauglufdrosselung (ALD) and / or a post-injection (NE) with closed or nearly closed throttle 111 the exhaust gas recirculation 110 intended. The component temperature (TB) is in a query 135 compared with the maximum permissible component temperature (Tmax). If the component temperature (TB) exceeds this for a certain minimum time, in the second stage, the limit value control 132 performed on the throttle 111 the exhaust gas recirculation 110 acts. This is the throttle 111 in the exhaust gas recirculation 110 open. This is already an immediate lowering of the critical component temperature of exhaust manifold and turbocharger 30 possible. However, the prerequisite is that the exhaust gas recirculation 110 during normal heating operation of the particulate filter 50 only minimally open or closed, otherwise the Risk of increased soot formation and also from combustion fluctuations may occur. The control intervention in the limit control 132 is therefore limited to an operating point-dependent maximum return mass.

In a new query 135 a repeated comparison is made between the component temperature (TB) and the maximum permissible component temperature (Tmax). If the maximum permissible component temperature continues to be exceeded over time, the next limit value control then becomes in a next stage 133 performed directly on the heating control sizes for the particulate filter 50 acts. In this case, if the temperature is exceeded, the post injection quantity (NE) is reduced and / or a retardation of the post injection (phi NE) and / or a reduction of an intake air throttling (ALD) and / or an early shift of a main injection (phi HE) are withdrawn.

In a final stage, if the maximum permissible component temperature continues to be exceeded by a certain amount of time, this is followed by a renewed query 135 determined, the entire internal engine measures for particulate filter heating aborted. This happens in an abort routine 134 ,

at Below the maximum component temperature, the activities according to the escalation levels of the action plan again gradually withdrawn become.

Advantageous in terms of debouncing it is when the critical component temperature monitored by temperature measurement or by modeling becomes. Short-term temperature fluctuations can then be detected as faults without having to resort to the measures described above must be reacted.

In practice, this cascaded control method, for example, leads to a variation of the exhaust gas recirculation (EGR) for an applied warm-up operation with intake air throttling (ALD), post-injection (EGR) causing, in addition to a known decrease of NOx in the exhaust gas, a steady decrease in the temperature after the exhaust gas turbocharger 30 takes place, which is particularly related to the increase in external exhaust gas recirculation. All other temperature profiles and the torque curve are initially unaffected.

With the method described and the device shown, a temperature monitoring and control can be realized, on the one hand overheating of the components in the exhaust system 20 safely prevented and on the other hand, a consumption-optimized internal engine heating of the particulate filter 50 allows for his regeneration.

Claims (20)

Method for controlling an exhaust aftertreatment system of an internal combustion engine ( 1 ) with an engine block ( 10 ) and at least one exhaust system ( 20 ) containing at least one catalyst ( 40 ) and a downstream particle filter ( 50 ), characterized in that the temperature in the exhaust system and the temperature of at least one of its components is monitored by means of at least one measuring device and a multistage action concept is applied when the temperature is exceeded. A method according to claim 1, characterized in that in a first stage under normal conditions in a control loop ( 131 ) a control of the temperature is carried out by means of internal engine control variables. A method according to claim 2, characterized in that as internal engine control variable, a reduction in the intake air throttling and / or a post-injection at a closed or nearly closed throttle valve ( 111 ) an exhaust gas recirculation ( 110 ) is carried out. Method according to one of claims 1 to 3, characterized in that at a temporally debounced exceeding the maximum allowable component temperature in a second stage, a limit value control ( 132 ) carried out on the throttle valve ( 111 ) of exhaust gas recirculation ( 110 ) acts. A method according to claim 4, characterized in that a control intervention in the limit control ( 132 ) is limited to an operating point-dependent maximum return mass. Method according to one of claims 1 to 5, characterized in that in a further temporally debounced exceeding the maximum allowable component temperature in a next stage, a further limit value control ( 133 ), which are based on heating control variables for the particulate filter ( 50 ) acts. Method according to claim 6, characterized in that within the limit value control ( 133 ) If the temperature is exceeded, the post injection quantity of the post injection is reduced and / or a retardation of the post injection and / or a reduction of an intake air throttling and / or an early shift of a main injection are withdrawn. Method according to one of claims 1 to 7, characterized in the event that the maximum permissible component temperature continues to be exceeded over time in a final stage, the entire internal engine measures for particle filter heating to be stopped. Method according to one of claims 1 to 8, characterized that falls below the maximum component temperature the measures according to the escalation levels of the action plan again gradually withdrawn become. Method according to one of claims 1 to 9, characterized that the critical component temperature through temperature measurement or monitored by modeling becomes. Method according to one of claims 1 to 10, characterized in that the maximum permissible component temperatures of the components in the exhaust system ( 20 ) are specified depending on the map. Device for controlling an exhaust gas post-combustion system of an internal combustion engine ( 1 ) with an engine block ( 10 ), a control unit cooperating with a control device ( 130 ) and at least one exhaust system ( 20 ) containing at least one catalyst ( 40 ) and a downstream particle filter ( 50 ), for whose temperature detection at least one temperature measuring device is provided, characterized in that in the control unit ( 130 ) Cascaded control circuits are implemented by means of which countermeasures can be initiated if a maximum permissible component temperature is exceeded. Apparatus according to claim 12, characterized in that the control unit ( 130 ) in a first stage a control loop ( 131 ) for an internal engine particulate filter heating, in a second stage a limit value control ( 133 ) for exhaust gas recirculation ( 110 ) and, in a third stage, another limit system ( 134 ) for the particulate filter heating control quantities. Apparatus according to claim 12 or 13, characterized in that the control unit ( 130 ) by means of at least one signal line ( 81 . 91 . 101 ) with at least one temperature sensor ( 80 . 90 . 100 ) and the control unit ( 130 ) for controlling the post-injection quantity by means of a signal line ( 12 ) with a fuel metering system ( 11 ) on the engine block ( 10 ) connected is. Device according to one of claims 12 to 14, characterized in that the control unit ( 130 ) by means of at least one signal line ( 112 ) with at least one throttle valve ( 111 ) in the exhaust gas recirculation ( 110 ) and / or by means of a further signal line ( 121 ) with an intake air throttle ( 120 connected is. Device according to one of claims 12 to 15, characterized in that in the exhaust ducts ( 20 ) in front of the catalyst ( 40 ) an exhaust gas turbocharger ( 30 ) is arranged. Device according to one of claims 12 to 16, characterized in that the control unit ( 130 ) by means of a signal line ( 71 ) with another temperature sensor ( 70 ) in the exhaust system ( 20 ) in front of the exhaust gas turbocharger ( 30 ) connected is. Device according to one of claims 12 to 17, characterized in that the exhaust system ( 20 ) at least one fuel metering device ( 60 ), which by means of a signal line ( 61 ) with the control unit ( 130 ) connected is. Device according to one of claims 12 to 18, characterized in that the control unit ( 130 ) has at least one characteristic unit for specifying the maximum component temperature. Device according to one of claims 12 to 19, characterized in that the functions of the control circuit ( 131 ) and the limit regulations ( 132 . 133 ) in the control unit ( 130 ) are executed as software and / or hardware and are at least partially part of a higher-level engine control.