Method for operating a system for supplying an air mass flow to a burner

Abstract

Method for operating a system (40) for supplying an actual air mass flow (ms55,ist) to a burner (43), wherein an exhaust gas is generated in the burner (43) and is fed to a catalytic converter (37) of an internal combustion engine (10) for its conditioning, wherein the catalytic converter (37) is designed in particular as a three-way catalytic converter, wherein a pump (58) conveys air between an air inlet (46) in the system (40) and the burner (43), and a sensor arrangement (47) in the flow of the exhaust gas serves to set an - in particular stoichiometric - air-fuel ratio in the burner (43), characterized in that in order to quantitatively adjust the actual air mass flow (ms55,ist) to the burner (43), the pump (58) is operated in a pilot-controlled manner in a step (S1).

Description

Prior ArtIt is known that the use of three-way catalysts is necessary to achieve emission limit values. Such emission limit values are determined, for example, by the EU exhaust gas standard EU6. These three-way catalysts make possible a conversion of the relevant gaseous pollutants, such as nitrogen oxide NOx, hydrocarbons HC and carbon monoxide CO, into harmless products, such as nitrogen N2, water H2O and carbon dioxide CO2. In order for the catalytic reactions required for this to proceed, the temperature in the catalyst, the so-called light-off temperature, must typically exceed 300° C. to 400° C. Once this temperature is reached, the catalyst converts the relevant pollutants almost completely. In order to achieve this state as quickly as possible, so-called internal-engine catalyst heating measures are already used. By means of these internal-engine catalytic converter heating measures, the efficiency of the internal combustion engine (in particular a spark ignition engine) is changed by late ignition angles, for example, in such a way that the exhaust gas temperature and the so-called enthalpy input into the catalytic converter are increased. Intelligent injection strategies (e.g. multiple injections) simultaneously ensure stable combustion. With the test cycles valid up to now (NEDC, FDP 75), which all begin with an extended idling phase, a fast light-off temperature with low emissions could thus be ensured.In addition to these internal engine catalyst heating measures, external catalyst heating measures have also been studied in the past. These include, for example, electrically heatable catalytic converters, but also so-called exhaust gas burners, as are known, for example, from the published patent applications DE 41 32 814 A1 and DE 195 04 208 A1.In connection with previously applicable exhaust gas standards, it was nevertheless possible, despite the ever more stringent requirements in the past, to adhere to these requirements solely by internal combustion catalyst heating measures. For this reason, the aforementioned external catalytic converter heating measures, such as the electrically heatable catalytic converter or the exhaust gas burner, or burners for short, have not yet been able to pass through the market. With the introduction of the determination of emissions determined during real road driving (real driving emissions, RDE), driving situations in which the conversion of various exhaust gas constituents by the above-mentioned three-way catalytic converters alone by internal engine catalytic converter heating measures is rather not possible gain higher significance. These so-called RDE boundary conditions also include, for example, the so-called urban spontaneous cold departure of a motor vehicle, which can proceed with a high engine load in combination with a very short idling phase that previously occurred. Such real driving conditions bring the known internal engine catalyst heating to its limits, in particular if at the same time further reduced emission limit values are to be expected, which must be complied with. This is expected, for example, for the EU exhaust gas standard EU7. In connection with these requirements, a so-called exhaust gas burner turns out to be an extremely effective measure. By means of such an exhaust gas burner it is possible to bring a three-way catalytic converter extremely quickly to the light-off temperature mentioned, at which the pollutants are converted very early.Embodiments of the InventionAccording to a first embodiment of the invention, a method for operating a plant for supplying an air mass flow to a burner is provided, wherein an exhaust gas is generated in the burner and is supplied to a catalytic converter of an internal combustion engine for the conditioning thereof (heating, operating temperature). The catalytic converter is designed in particular as a three-way catalytic converter, wherein a pump delivers air between an air inlet into the plant and the burner. In the flow of the exhaust gas, a lambda probe serves to set an-in particular stoichiometric-air-fuel ratio in the burner.It is provided here that for quantitative adjustment of the air mass flow to the burner, the pump is operated in a pilot-controlled manner in one step.This control circuit for the air pump on the basis of an air mass flow measurement value-in particular an HFM air mass flow measurement value (HFM: hot film air mass flow meter)-has the advantage of compensating for the possibility of dynamic effects which occur during operation of the burner, as a result of which a high quality of the air quantity supply can be ensured at all times.According to a further aspect of the invention, it is provided that, for the - in particular approximate - reaching or setting of the desired air-fuel ratio in the burner, in one step a mass (actual air mass) of the air determined by means of a sensor element is compared with a setpoint air mass or an actual air mass flow determined by means of the sensor element is compared with a setpoint air mass flow.According to a further aspect of the invention, it is provided that, in the case of a deviation of the determined mass (actual air mass) of the air from a setpoint air mass or of an actual air mass flow determined by means of the sensor element from a setpoint air mass flow, a pilot control is changed, in particular in order to reduce a deviation (correction of the pilot control). This has the advantage that in particular a more accurate air-fuel ratio is set.Furthermore, it is provided that long-term changes-for example of the individual components of the device-or effects of tolerances of the individual components-are determined and are taken into account by an adaptation value in the quantitative setting of the air mass flow. Long-term changes are understood to mean, for example, changes occurring over a plurality of operating phases or longer operating periods. For example, due to wear of an impeller for conveying air, less air can be conveyed than a setpoint value it provides, or a bearing of the pump can "engage" over time and therefore become somewhat smoother than at the beginning of use and the conveying of air can thereby be increased. This can be corrected by adaptation values which are repeatedly (from time to time). A high adaptation value can indicate, for example, a fault in a measurement of a mass flow with an air mass flow meter, in particular a hot-film air mass flow meter, or problems in a delivery rate of the pump.According to a further aspect of the invention, an embodiment of an air pump regulator is provided as a PID regulator, wherein a control difference is determined from the setpoint air mass flow and the actual air mass flow determined by means of the sensor element, and a control factor of the pump consists of a proportional component, an integral component and a differential component.According to a further aspect, it is intended that the adaptation value is formed in parallel with the integral part according to the same principle.According to a further aspect of the method, it is provided that the adaptation value is stored in a nonvolatile memory of the control unit.According to a further aspect of the method, it is provided that the integral portion of the air pump regulator is initialized with the aid of the stored adaptation value when the control unit is started up. In particular, the initialization advantageously takes place to relieve the air pump regulator.It is provided in particular that a learning range of the adaptation is learned only at defined operating points of the combustion operation, in particular in a steady-state operation. This has the advantage that it is avoided with respect to the integral portion that the integral portion is not adapted in the case of short-term effects.According to a further aspect, it is provided that a running readiness-in particular a start-of the adaptation is formed as a function of at least one of the input parameters mentioned below: an exhaust gas back pressure, a dynamics of the exhaust gas back pressure, an ambient temperature, an ambient pressure, a dynamics of the air, an air mass flow.According to a further aspect, it is provided that the option value is used for diagnosing individual components in an air duct of the burner.Furthermore, a computer program is provided which is designed to execute all the steps of one of the methods or to be programmed in such a way that it executes a method when it is executed on a computer. A machine-readable storage medium is disclosed on which the computer program is stored or on which the computer program is stored. A control device is disclosed which is designed to carry out all steps of one of the methods or to be programmed for application in a method.The invention is explained in more detail below with reference to the figures: FIG. 1 shows a schematic illustration of a system comprising an internal combustion engine, an exhaust system, an exhaust burner system and an intake device for supplying the internal combustion engine with air, FIG. 2 shows a structure of a regulator of a pump, FIG. 3 shows a schematic sequence of the method.FIG. 1 shows a device 10, which is in particular a motor vehicle. This device 10 has an internal combustion engine 13 which is supplied with air via an intake device 16. This intake device 16 has an air inlet 19. In the supply of air to the internal combustion engine 13, there is furthermore a sensor arrangement 22, which can have a sensor element-for example a hot film air mass meter-or at least one further sensor element, and subsequently a valve 25, which is typically designed as a so-called throttle valve. The valve 25 is followed by a sensor arrangement 26 which has, for example, a pressure sensor. The air inlet 19 typically leads into a so-called box 28 (air filter box), so that the introduced air initially flows through the air inlet 19 and then flows through an air filter, not designated in any more detail here.The intake device 16 has an intake pipe 31 in which the sensor arrangement 22 is arranged. The valve 25 is also arranged in this intake pipe 31. The exhaust gases or combustion gases generated by the internal combustion engine 13 are introduced into an exhaust system 34. The exhaust gases first flow past a sensor arrangement 27-embodied as a lambda probe-in order to then be introduced into the following parts of the exhaust system 34. Parts of this exhaust system 34 are here, for example, a first catalytic converter 37, a second catalytic converter 38 and a petrol particle filter 39, through which exhaust gas flows in this sequence. After the first catalytic converter 37, the exhaust gases flow past a sensor arrangement 41-constructed as a lambda probe. After passing through the gasoline particle filter 39, the converted exhaust gases are discharged into the environment (arrow) or, depending on the exhaust system system, flows through this further exhaust gas aftertreatment system.In FIG. 1, the plant 40 for supplying air to a burner 43 is furthermore illustrated. This plant 40 also has an air inlet 46 which constitutes an inlet to a box 49. An air filter can also be arranged in this box 49. The boxes 28, 49 can also be designed as a box, as is symbolically represented by the dashed rectangle around both boxes 28, 49, without further designation. Accordingly, such a combined box can also have only one air inlet, which combines the two air inlets 19, 46. In addition, such a box can also have a single air filter, which is representative of the two air filters mentioned above. The air passing through the air inlet 46 into the box 49 then enters an intake pipe 52, in which a sensor arrangement 55, which can have a sensor element-for example a hot film air mass meter-or at least one further sensor element-is likewise arranged. The sensor arrangement 55 can be designed, for example, as a sensor element for detecting pressure. If this sensor arrangement 55 is part of a so-called hot film measuring probe, for example, this can serve, in addition to the air mass flow, as a whole, to determine the pressure, temperature and humidity of the air. The incoming air then passes a pump 58 and is supplied by this pump 58 to a valve 61 (shut-off valve). As the name already states, this valve 61 serves to shut off the air supply to the burner 43. the device 10 shown here also has a control unit 70, which is designed as a so-called engine control unit (engine control unit). The control device 70 is connected to individual components of this device 10 via signal lines, which are not designated in more detail here. These signal lines are used for communication between the individual components and the control device 70.The burner 43 is in operation and is supplied with fuel via a fuel supply unit 44-for example, designed as an injector. By supplying or delivering air by means of the pump 58-the open valve 61 is here illustrated by the schematically illustrated open flap (valve closure V 61)-by the system 40 for supplying air, a fuel-air mixture can then be formed in the burner 43, which mixture is ignited and burned by an ignition unit 45-for example embodied as a spark plug. The exhaust gas discharged from the burner 43 flows past a sensor arrangement 47, designed as a lambda probe, and is introduced into the exhaust system 34 via an individually designed introduction path and heats the catalytic converter 37 in a particularly quick manner. The device 10 shown here also has a control unit 75, which is designed as a so-called burner control unit (Burner Control Unit). The control device 75 is connected to individual components of this device 10 via signal lines, which are not designated in more detail here. The two control units 70, 75 exchange signals via signal lines, not shown, and are thus able to communicate with one another.The system shown in FIG. 1 offers the possibility, compared to conventional secondary air systems, of very precise control of the air mass or the actual air mass flow ms55 through the use of the sensor arrangement 55. For this purpose, during the operation of the burner 43, the pump 58 is initially operated via a pilot control of the control unit 75. In the control unit 75 of the burner 43, the actual air mass m55,istmeasured or determined by the sensor arrangement 55 is compared with the setpoint air mass m55,sot, or the actual air mass flow ms55,ist is compared with the setpoint air mass flow ms55,sot. In the event of a deviation, the pilot control of the pump 58 is corrected accordingly in order to adjust the desired setpoint air mass flow m55,sollor the setpoint air mass flow ms55,sollby means of an air pump regulator 86.In FIG. 2, the air pump controller 86 is shown, which is implemented as a PID controller. It can be arranged, for example, in the control device 75 of the burner 43. In this case, e(t) is a control difference between the setpoint air mass m55,solland the measured air mass m55,istor between the setpoint air mass flow ms55,solland the measured or determined air mass flow ms55,ist. This control difference e(t) is applied as an input to an amplifier kp, an integrator 80 and a differentiator 83.An adaptation value is formed in parallel with the integral part ki of the air control according to the same principle. For this purpose, this is stored in a nonvolatile memory of control device 75. The I-component of the air pump regulator 86 can be initialized with the aid of the stored adaptation value when the control unit 75 is started up, so that the air pump regulator 86 is relieved.The I-component partially adjusts its value even in the case of short-term effects during operation of the burner 43. It can therefore be helpful if the learning range of the adaptation is "learned" only at defined operating points of the combustion operation. Above all, against the background that the aim of the adaptations represents the compensation of tolerances and long-term changes. For this purpose, the adaptation is ready to run as a function of the following input parameters: exhaust gas back pressure, dynamics of the exhaust gas back pressure, ambient temperature, ambient pressure, dynamics of the air, air mass flow.The adaptation value can be used for the diagnosis of individual components of the exhaust gas burner system. Thus, a high adaptation value can indicate, for example, an error in the mass flow measurement using the sensor arrangement 55 or problems in the delivery rate of the pump 58.Furthermore, a computer program 90 is disclosed which is designed to execute all the steps of one of the methods or to be programmed in such a way that it executes a method when it is executed on a computer (control unit 75). In addition, a machine-readable storage medium 93 is disclosed on which the computer program 90 is stored or on which the computer program 90 is stored for application in a method.The control device 75 is designed to execute all steps of one of the methods or is programmed for use in a method.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 41 32 814 A1

[0002] DE 195 04 208 A1

[0002]

Claims

Method for operating a plant (40) for supplying an actual air mass flow (ms55,ist) to a burner (43), wherein an exhaust gas is generated in the burner (43) and this is supplied to a catalytic converter (37) of an internal combustion engine (10) for conditioning the latter, wherein the catalytic converter (37) is designed in particular as a three-way catalyst, wherein a pump (58) delivers air between an air inlet (46) into the plant (40) and the burner (43), and a sensor arrangement (47) serves to set an - in particular stoichiometric - air-fuel ratio in the burner (43) in the flow of the exhaust gas, characterized in that the pump (58) is operated in a pre-controlled manner in a step (S1) for a quantitative setting of the actual air mass flow (ms55,ist) to the burner (43).Method according to Claim 1, characterized in that, in order to - in particular approximately - achieve / set the desired air-fuel ratio in the burner (43), in a step (S2), an actual air mass flow (ms55,ist) determined by means of a sensor element (55) is compared with a setpoint air mass flow (ms55,ist).Method according to Claim 2, characterized in that, in the case of a deviation of the ascertained actual air mass flow (ms55,ist) ascertained by the step (S2) from a setpoint air mass flow (ms55,sot), pilot control is changed in a step (S3), in particular in order to reduce a deviation.Method according to Claim 3, characterized in that - in particular long-term - changes or effects of tolerances - in particular of the elements involved in the setting of the actual air mass flow (ms55,ist) - are determined and are taken into account by an adaptation value in the quantitative setting of the actual air mass flow (ms55,ist).Method according to Claim 4, characterized in that an air pump regulator (86) is designed as a PID regulator, wherein a control difference (e(t)) is determined from the setpoint air mass flow (ms55,soll) and the actual air mass flow (ms55,soll) determined by means of the sensor element (55), and a control factor (u(t)) of the pump (58) is determined from a proportional component (kp), an integral component (ki) and a differential component (kd).Method according to Claim 5, characterized in that the adaptation value is formed in parallel with the integral component (ki) on the same principle.Method according to one of Claims 4 to 6, characterized in that the adaptation value is stored in a nonvolatile memory of the control unit (75).Method according to Claim 7, characterized in that the integral proportion (ki) of the air pump regulator (86) is initialized with the aid of the stored adaptation value when the control unit (75) is started up, in particular for relieving the load on the air pump regulator (86).Method according to one of Claims 4 to 8, characterized in that a learning range of the adaptation is learned only at defined operating points of the combustion operation.Method according to one of Claims 4 to 9, characterized in that a ready-to-run state of the adaptation is formed as a function of at least one of the input parameters mentioned below: - exhaust gas back pressure, - dynamics of the exhaust gas back pressure, - ambient temperature, - ambient pressure, - dynamics of the air, - air mass flow.Method according to one of Claims 4 to 10, characterized in that the adaptation value is used for the diagnosis of individual components in an air duct.A computer program (90) adapted to perform all the steps of any of the methods of any of claims 1 to 11 or programmed to perform a method of any of claims 1 to 11 when executed on a computer.Machine-readable storage medium (93) on which the computer program (90) according to Claim 12 is stored or on which the computer program (90) according to Claim 12 is stored for application in a method of Claims 1 to 11.A controller (75) configured to perform all the steps of any of the methods of any of claims 1 to 11 or programmed for use in a method of any of claims 1 to 11.

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