DE10213660A1 - Control of diesel engine, determines volumetric flowrate from a second magnitude characterizing flow resistance of second component, e.g. silencer - Google Patents

Abstract

The volumetric flowrate (VS) is determined from a second magnitude (W2, F1, F2). This characterizes the flow resistance of a second component (120), e.g. an exhaust silencer, of the exhaust system. Independent claims are included for corresponding equipment and for a computer code product carrying out the determination for control purposes.

Description

State of the art

The invention relates to a method and a device for controlling an internal combustion engine, in particular one Internal combustion engine with an exhaust gas aftertreatment system, the preferably comprises a particle filter.

To improve emissions, vehicles, especially vehicles with diesel engines, with Particle filters equipped. To control such Exhaust aftertreatment systems and / or for monitoring the State of such exhaust gas aftertreatment systems usually evaluated a size that the Flow resistance of the exhaust gas aftertreatment system or individual components, such as the Particle filter, characterize. The control of the Filter loading with particle filters and the Regeneration monitoring is carried out with pressure sensors, since that Pressure drop across the filter allows conclusions to be drawn about those in the filter accumulated soot mass allows. The one to be measured Differential pressure across the filter also depends on Exhaust gas volume flow from.

In modern car engines with exhaust gas recirculation Usually an air mass sensor is available, the Measurement signal also for determining the exhaust gas volume flow can be used. Should this sensor be saved? or is there a system without exhaust gas mass sensor, is the Determination of the exhaust gas volume flow is not easy possible because this size is not measured directly or because it incurs enormous costs. With the The procedure according to the invention is precise control and / or regulation of the exhaust gas aftertreatment system without Air mass sensor possible.

The fact that in a method and an apparatus for Control of an internal combustion engine Flow resistance of a first component of the Exhaust aftertreatment system characterizing first size based on a first measurement and one Volume flow size is determined, the volume flow size starting from a second size that the Flow resistance of a second component of the Exhaust system characterized, determined is an accurate Control and / or regulation of the internal combustion engine, especially an exhaust gas aftertreatment system without the Use of an air mass sensor possible.

In a preferred embodiment for controlling the Internal combustion engine, this means that the first one used Size, in particular the loading condition of a Particulate filter characterized, starting from the Differential pressure across the particle filter and Exhaust gas volume flow is determined, the Exhaust gas volume flow based on the differential pressure over a further component of the exhaust gas aftertreatment system and known and / or easily identifiable second size, the corresponds to the first size for the first component, is determined.

In a preferred embodiment, as Volume flow size (VS) the exhaust gas volume flow used. Alternatively, other sizes that the Characterize exhaust gas volume flow.

It is particularly advantageous that the volume flow size (VS) on the basis of a second measured variable, which is the Differential pressure between the inlet and outlet of the second Characterized component and the second size that the Characterized flow resistance of the second component, is determined. As a rule, these quantities are recorded no further sensors required. Especially with the second size is a fixed size that in a map can be filed. One being special precise control means that the values depend on the Operating state of the internal combustion engine and / or of Environmental conditions are stored.

It is a particularly preferred embodiment the second component is a silencer. Alternatively, other components in the exhaust system can also be used be used. Requirement for using the Component is that they have the same exhaust gas mass flow is flowed through and that the flow resistance or a appropriate size is known and / or easily determined.

The first measurement variable is preferably the Differential pressure between the inlet and outlet of the first Component and / or by a quantity representing the differential pressure characterized. The second is preferred Measured variable around the differential pressure between inlet and outlet the second component and / or by a size that the Characterized differential pressure.

It is particularly advantageous if the first size that the Characterized flow resistance of the first component, based on the first measured variable and the volume flow variable is determined.

Further advantageous and expedient configurations and Further developments of the invention are in the subclaims characterized.

drawing

The invention is explained below with reference to the embodiments shown in the drawing. In the drawings Fig. 1 is a block diagram of a system for controlling an internal combustion engine, Fig. 2 is a flowchart illustrating the procedure of the invention, Fig. 3 is a flow diagram to illustrate a further embodiment and Fig. 4 is a block diagram of the inventive apparatus.

Description of the embodiments

In Fig. 1 the essential elements of an exhaust aftertreatment system of an internal combustion engine are shown. The internal combustion engine is designated 100. It is supplied with 105 fresh air via a fresh air line. The exhaust gases of internal combustion engine 100 reach the environment via an exhaust pipe 110 . An exhaust gas aftertreatment system 115 is arranged in the exhaust gas line. This can be a catalyst and / or a particle filter. Furthermore, it is possible for several catalysts to be provided for different pollutants or combinations of at least one catalyst and one particle filter.

A silencer 120 is usually arranged behind the exhaust gas aftertreatment system 115 .

Furthermore, a control unit 170 is provided, which comprises at least one engine control unit 175 and an exhaust gas aftertreatment control unit 172 . The engine control unit 175 applies control signals to a fuel metering system 180 . The exhaust gas aftertreatment control unit 172 applies control signals to the engine control unit 175 and, in one embodiment, an actuating element 185 , which is arranged in the exhaust gas line upstream of the exhaust gas aftertreatment system or in the exhaust gas aftertreatment system.

Furthermore, various sensors can be provided which supply the exhaust gas aftertreatment control unit and the engine control unit with signals. At least a first sensor 194 is provided, which delivers signals that characterize the pressure PU of the ambient air. A second sensor 177 provides signals that characterize the state of the fuel metering system 180 . Sensors 182 a and 182 b provide signals that characterize the state of the exhaust gas upstream of the exhaust gas aftertreatment system. Sensors 192 a and 192 b provide signals that characterize the state of the exhaust gas after the exhaust gas aftertreatment system and before the silencer 120 .

Sensors 182 a and 192 a, the temperature values TV and / or TN and / or sensors 182 b and 192 b, which record pressure values PV and / or PN, are preferably used.

Furthermore, sensors can also be used that the chemical compositions of the exhaust gas and / or Characterize fresh air. This is, for example. Lambda sensors, NOX sensors or HC sensors.

The exhaust gas aftertreatment control unit 172 is preferably acted upon with the output signals of the sensors 182 a, 182 b, 192 a, 192 b and 194 . The output signals of the sensor 177 are preferably applied to the engine control unit 175 . It is also possible to provide further sensors, not shown, which characterize a signal relating to the driver's request or other environmental or engine operating states.

In the embodiment shown, a compressor 106 is arranged in the intake line 105 and a turbine 108 in the exhaust line 110 . The turbine is driven by the exhaust gas flowing through and drives the compressor 106 via a shaft, not shown. The amount of air that the compressor compresses can be controlled by suitable control.

The line 110 for an exhaust gas recirculation line 102 is also connected to the intake line 105 . An exhaust gas recirculation valve 104 is arranged in the exhaust gas recirculation line 102 and can also be controlled by the control unit 175 .

In the illustrated embodiment, both are Exhaust gas recirculation and a controllable exhaust gas turbocharger intended. According to the invention, only one can also be used Exhaust gas recirculation and only a controlled one Exhaust gas turbocharger can be provided.

It is particularly advantageous if the engine control unit and the exhaust gas aftertreatment control unit is a structural one Form unity. But it can also be provided that these are designed as two control units that are spatially separated from each other.

The procedure according to the invention is described below on Example of a particle filter that is particularly useful for direct injection internal combustion engines is used described. However, the procedure according to the invention is not limited to this application, it can also be used for other internal combustion engines with one Exhaust gas aftertreatment system can be used. In particular can it be used in exhaust aftertreatment systems, where a catalyst and a particle filter are combined are. Furthermore, it can be used in systems that are only equipped with a catalyst.

On the basis of the sensor signals present, the engine control 175 calculates control signals for the application of the fuel metering system 180 . This then measures the corresponding amount of fuel in internal combustion engine 100 . Particles can form in the exhaust gas during combustion. These are taken up by the particle filter in the exhaust gas aftertreatment system 115 . In the course of the operation, corresponding amounts of particles accumulate in the particle filter 115 . This leads to an impairment of the functioning of the particle filter and / or the internal combustion engine. It is therefore provided that a regeneration process is initiated at certain intervals or when the particle filter has reached a certain loading state. This regeneration can also be called a special operation.

The loading state is recognized, for example, on the basis of various sensor signals. On the one hand, the differential pressure between the inlet and the outlet of the particle filter 115 can be evaluated. On the other hand, it is possible to determine the loading condition on the basis of different temperature and / or different pressure values. Furthermore, other variables can be used to calculate or simulate the loading condition. A corresponding procedure is known, for example, from DE 199 06 287.

If the exhaust gas aftertreatment control unit detects that the particle filter has reached a certain loading state, the regeneration is initialized. There are various options for regenerating the particle filter. On the one hand, it can be provided that certain substances are supplied to the exhaust gas via the control element 185 , which then cause a corresponding reaction in the exhaust gas aftertreatment system 115 .

It is usually provided that the loading state is determined based on different sizes. By The different are compared with a threshold States recognized and dependent on the recognized loading state the regeneration initiated. As a size that the Characterized loading state, is preferably the Flow resistance of the particle filter used. The Flow resistance is essentially based on the Pressure difference across the particle filter and the volume flow, that flows through the particle filter.

If the internal combustion engine does not include an air mass meter, see above the volume flow that flows through the particle filter, cannot be easily determined. With the following The procedure described is a determination of the Exhaust gas volume flow and thus an exact loading and Regeneration monitoring of a particle filter also at Internal combustion engines without air mass meter, such as for example with truck engines.

According to the invention, it is provided that the exhaust system after the diesel particle filter comprises an absolute pressure sensor in order to determine the pressure drop across the silencer 120 . Starting from the known flow resistance of the muffler, the exhaust gas mass flow through the muffler can be determined. Since both the muffler and the particle filter are traversed by the same exhaust gas volume flow, the flow resistance of the particle filter is determined based on the differential pressure across the particle filter and the exhaust gas volume flow determined in this way.

According to the invention, it is therefore provided that in a first step 200 the differential pressure DP2 between the inlet and outlet of the silencer is detected. For this purpose, it can be provided that a differential pressure sensor is used, or that an absolute pressure sensor 192 b, which detects the pressure PN upstream of the silencer, and a second absolute pressure sensor 194 , which detects the pressure PU downstream of the silencer, are used. The pressure behind the silencer usually corresponds to the atmospheric pressure PU, which is already recorded and evaluated by the control unit for other purposes.

In a second step 210 , the flow resistance W2 of the silencer is determined. In a simple embodiment it is provided that a fixed value is read out of a memory. In a particularly advantageous embodiment, it is provided that this value W2 is determined on the basis of various operating parameters such as, for example, the engine speed N and the load, or a variable that characterizes the load, such as the injection quantity.

In a next step 220 , starting from the flow resistance W2 and the differential pressure DP2, the exhaust gas volume flow VS is determined by the silencer according to the following formula.

VS = DP2 / W2

In the subsequent step 230 , the differential pressure DP1 is then determined via the particle filter as in step 200 , that is to say one differential pressure sensor or two absolute pressure sensors 182 b and 192 b can be used.

In the subsequent step 240 , the flow resistance W1 of the particle filter is then determined on the basis of the differential pressure DP1 and the volume flow VS according to the following formula.

W1 = DP1 / VS

The flow resistance W1 of the particle filter is used for Control and / or monitoring of the particle filter.

It when the volume flow size VS for further controls and / or diagnostic tasks, especially for the exhaust system and / or to control the Exhaust gas recirculation rate is used.

In the embodiment described in FIG. 2, depending on the embodiment, a constant or a flow resistance W2 of the muffler which is dependent on the operating state, in particular the speed and the injected fuel quantity, is assumed. An increase in accuracy is possible by using an additional temperature sensor.

In the embodiment shown in FIG. 3, the exhaust gas volume flow V2 is simulated by simulating the muffler through a pipe through which it flows. The equation applies to the volume flow VS:
VS = F1.F2.DP2 'of various factors F1, F2 and DP2'. Size F1 is one or more temperature-dependent parameters, which are preferably stored in a map depending on the temperature of the exhaust gas. The factor F2 essentially contains geometric parameters of the silencer, which can be determined experimentally. The size DP2 'is a size essentially determined by the differential pressure across the silencer.

The embodiment of FIG. 3 essentially differs from the embodiment of FIG. 2 in that steps 210 and 220 are replaced by step 300 . In step 300 , the exhaust gas volume flow VS is determined using the specified formula. The sizes F1 and F2 characterize the flow resistance of the silencer. In contrast to the embodiment of FIG. 2, the flow resistance is not determined directly, but the exhaust gas volume flow is preferably formed by multiplying several factors F1, F2 and DP2 '.

In Fig. 4a and 4b, the two embodiments are shown in block diagram. In the embodiment according to FIG. 4a, two sensors are provided which determine the pressure before and the pressure after the silencer. These can also be replaced by a differential pressure sensor. A first signal setting means 301 provides a signal PV, which characterizes the pressure PV upstream of the silencer, and a second signal specification means 302 provides a signal PN, which characterizes the pressure downstream of the silencer. Furthermore, a third signal setting means 303 supplies a quantity QK which characterizes the quantity of fuel QK to be injected, and a fourth signal setting means 304 supplies a signal relating to the rotational speed of the internal combustion engine.

In the first, second and fourth signal setting means it is preferably sensors, the third Signal specification is preferably the control unit, where the amount of fuel to be injected is internal Size. Alternatively, the other sizes internally in the control unit, starting from others Operational parameters. Furthermore, it is possible that other operating parameters are taken into account become.

The signal relating to the fuel quantity QK to be injected and the speed reach a characteristic diagram 310 , at the output of which the flow resistance W2 of the muffler is applied. The output signals PV and PN arrive at a subtractor 315 , which outputs the differential pressure DP2 via the silencer as the output variable. The two variables DP2 and W2 arrive at a division point 320 , at the output signal of which the exhaust gas volume flow VS is present.

This means that the flow resistance of the muffler is stored in the characteristic diagram 310 as a function of various operating parameters. Starting from the differential pressure, which is measured by means of sensors, and the flow resistance W2 of the muffler, the exhaust gas volume flow is then calculated by division.

In the embodiment according to FIG. 4B, in addition to the first and second signal specification, a fifth signal specification 305 , which specifies a constant variable F2, and a sixth signal specification 306 , which supplies a temperature signal T, are provided. The output signals PV and PN of the first and second signal specifications arrive at a subtractor 315 , which outputs the differential pressure DP2 as an output variable via the silencer. The output signal of the subtraction point 315 arrives at a characteristic diagram 340 , on which a variable DP2 'dependent on the differential pressure is applied. The output signal T of the sixth signal specification 306 reaches a connection point 350 via a characteristic curve 330 , in which the temperature dependence of physical quantities of the exhaust gas volume flow is stored. The output signals of the two maps are multiplicatively linked in node 350 . The output signal of the node 350 arrives at a node 360 , at the second input of which the output signal F2 of the fifth signal specification 305 is present.

Basically, this block diagram forms the above formula to. The volume flow VS is based on a first Factor F1, a second factor F2 and one from Differential pressure across the silencer dependent size DP2 ' calculated by multiplication. The factor F1 is taken into account one or more temperature-dependent parameters that preferably in a map and / or in a or several characteristics depending on the temperature of the exhaust gas are filed. The factor F2 essentially includes Geometric characteristics of the silencer, which in the are essentially constant.

Realizations are of particular importance in the form of a computer program with program code means and in the form of a computer program product with program code Means. The computer program according to the invention has Program code means to complete all steps of the perform the inventive method if that Program on a computer, in particular a control device for an internal combustion engine of a motor vehicle becomes. In this case, the invention is represented by an in program stored in the control unit, so that this control unit provided with the program in the same The invention represents how the method for its Execution the program is suitable. The invention Computer program product has program code means that are stored on a computer-readable data medium in order to to carry out the method according to the invention if that Program product on a computer, especially one Control device for an internal combustion engine of a motor vehicle is performed. In this case, the invention realized by a disk so that the The inventive method can be carried out if that Program product or the data carrier in a control unit for an internal combustion engine, in particular of a motor vehicle is integrated. As a data carrier or as Computer program product can in particular be an electrical one Storage medium are used, for example Read-only memory (ROM), an EPROM or an electrical one Permanent storage such as a CD-ROM or DVD.

Claims (9)

1. Method for controlling an internal combustion engine, a first variable (W1) characterizing the flow resistance of a first component ( 115 ) of an exhaust gas aftertreatment system being determined on the basis of a first measured variable (DP1) and a volume flow quantity (VS), characterized in that the volume flow quantity ( VS) is determined on the basis of a second variable (W2, F1, F2) which characterizes the flow resistance of a second component ( 120 ) of the exhaust system. 2. The method according to claim 1, characterized in that the volume flow size (VS) the exhaust gas volume flow characterized. 3. The method according to any one of the preceding claims, characterized characterized that starting from a second measurement (DP2), which is the differential pressure between the inlet and outlet of the characterized second component, and the second size (W2, F1, F2), the flow resistance of the second Component characterizes the volume flow size (VS) is determined. 4. The method according to any one of the preceding claims, characterized in that the second component ( 120 ) is a silencer. 5. The method according to any one of the preceding claims, characterized in that the first measured variable (DP1) characterizes the differential pressure between the inlet and outlet of the first component ( 115 ). 6. The method according to any one of the preceding claims, characterized characterized that starting from the first measurement (DP1) and the volume flow size (VS) the first size (W1), the the flow resistance of the first component characterized, determined. 7. Device for controlling an internal combustion engine, a first variable (W1) characterizing the flow resistance of a first component ( 115 ) of an exhaust gas aftertreatment system being determined on the basis of a first measured variable (DP1) and a volume flow variable (VS), characterized in that means are provided which determine the volume flow size (VS) on the basis of a second size (W2) which characterizes the flow resistance of a second component ( 120 ) of the exhaust system. 8. Computer program with program code means to all Steps of any of claims 1 to 11 perform when the program is on a computer in particular a control device for an internal combustion engine, is performed. 9. Computer program product with program code means based on a computer-readable data carrier are stored in order to Method according to any one of claims 1 to 11 perform when the program product on a computer in particular a control device for an internal combustion engine, is performed.