METHOD AND COMPUTING UNIT FOR OPERATING A COMBUSTION ENGINE WITH A PARTICLE FILTER

Abstract

A method (200) for operating a combustion engine (120) with a particle filter (130) is disclosed, wherein an exhaust gas flow of the combustion engine (120) is passed through the particle filter (130), a particle concentration in the exhaust gas flow is measured (220) downstream of the particle filter (130) and the combustion engine is operated at least depending on the measured particle concentration downstream of the particle filter.

Claims

1. A method (200) for operating a combustion engine (120) with a particle filter (130), the method comprising: passing an exhaust gas flow of the combustion engine (120) through the particle filter (130), measuring (220) a particle concentration in the exhaust gas flow downstream of the particle filter (130), and operating the combustion engine based on the measured particle concentration downstream of the particle filter.

2. The method (200) according to claim 1, wherein the combustion engine (120) is operated in such a way that a loading of the particle filter (130) with particles increases (245) if the measured particle concentration exceeds a predetermined first threshold value (230) or that the loading of the particle filter decreases (235) if the measured particle concentration is below a second predetermined threshold value (240).

3. The method (200) according to claim 2, wherein the first threshold value and/or the second threshold value are determined as a function of at least one emission-relevant parameter (210) selected from group consisting of engine temperature, outside temperature, ambient pressure, composition of the atmosphere, season, fuel quality, aging, defects and driving behavior.

4. The method (200) according to claim 1, wherein the loading of the particle filter is adjusted by adjusting a composition of the exhaust gas flow upstream of the particle filter.

5. The method (200) according to claim 4, wherein the composition of the exhaust gas flow is shifted to the detriment of oxidizing components, if the measured particle concentration is above the first threshold value and/or is shifted in favor of the oxidizing components if the measured particle concentration is below the second threshold value.

6. The method (200) according to claim 1, further comprising measuring a particle concentration upstream of the particle filter.

7. The method (200) according to claim 1, wherein the particle concentration describes a number of particles and/or a particle mass, each based on a predeterminable exhaust gas volume or a predeterminable driving distance.

8. The method (200) according to claim 1, wherein at least one particle concentration is measured with respect to at least one range of a particle size distribution (220).

9. The method (200) according to claim 1, wherein the combustion engine comprises a machine with compression ignition and/or a machine with external ignition.

11. A non-transitory, computer-readable medium containing instructions that when executed by a computer cause the computer to control a combustion engine (120) with a particle filter (130) to pass an exhaust gas flow of the combustion engine (120) through the particle filter (130), measuring (220) a particle concentration in the exhaust gas flow downstream of the particle filter (130), and operate the combustion engine based on the measured particle concentration downstream of the particle filter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Further advantages and embodiments of the invention result from the description and the enclosed drawing.

[0051] The invention is represented in the drawing based on an exemplary embodiment and is described below with reference to the drawing.

[0052] FIG. 1 shows a vehicle, which is set up to carry out an advantageous design of a method according to the invention, in the form of a greatly simplified block diagram.

[0053] FIG. 2 shows an advantageous embodiment of a method according to the invention in the form of a simplified flowchart.

DETAILED DESCRIPTION

[0054] In FIG. 1, a vehicle 100, which is set up to carry out an advantageous design of a method according to the invention, is shown. The vehicle 100 comprises a combustion engine 120, a fuel preparation device 110, a particle filter 130, a control unit 140 and a first particle sensor 145 arranged upstream of the particle filter in an exhaust system of the vehicle 100 and a second particle sensor 147 downstream of the particle filter.

[0055] The first particle sensor 145 and the second particle sensor 147 are connected in a data-conducting or date-transmitting manner to the control unit 140, which in turn is connected to the combustion engine 120 and the fuel preparation device 110 in a data-conducting manner.

[0056] The fuel preparation device 110, which includes, for example, a turbocharger for compressing air, a fuel pump and an injection pump, is set up to supply the combustion engine with an air-fuel mixture and to adjust its composition and quantity depending on the signals received from the control unit 140.

[0057] The combustion engine 120, which comprises, for example, a petrol or diesel engine, is designed to burn the air-fuel mixture provided by the fuel preparation device 110 and thereby convert at least part of the released combustion enthalpy into mechanical work. The resulting exhaust gas is emitted by the combustion engine 120 into the exhaust system of the vehicle 100, so that the exhaust gas flows through the particle filter 130 on its way into an atmosphere surrounding the vehicle 100.

[0058] The particle filter 130 is set up to retain particulate components of the exhaust gas at least partially, so that the exhaust gas leaving the particle filter 130 is depleted of the particulate components in the particle filter compared to the exhaust gas entering the particle filter 130. The particle filter 130 comprises, for example, a suitable filter material, for example a porous material of ceramic or metallic type for this purpose. Such filter materials retain the particulate components of the exhaust gas by the particles interacting mechanically with the filter material, in particular by colliding. In connection with such a mechanical interaction and/or alternatively thereto, adhesion forces may occur (for example electrostatic or chemical bonds, in particular van der Waals forces) which prevent particles from being further transported through the filter material once in the filter.

[0059] In principle, all known devices for the detection of particles in a fluid flow can be considered as particle sensors. For example, such particle sensors work on the basis of scattered light, light extinction or laser diffraction. Also sensors which are based on laser-induced or light-induced incandescence (LII), condensation particle counting (CPC) or high-voltage processes (escaping current, electrostatic method), can be used for this purpose. However high voltage methods cannot measure PN directly. In such cases, the measurement signal can be converted into the particle number PN by means of a raw emissions model.

[0060] In some embodiments of the particle filter 130, electrodes for retaining the particulate exhaust gas components may also be provided. In such systems, particles present in the exhaust gas are pushed towards the electrodes by electrostatic and/or electrodynamic interactions and deposited there. In such electrostatic precipitators, the particle size distribution of the separated particles can be influenced by changing the potential applied to the electrodes.

[0061] FIG. 2 illustrates a method 200 which is used to control the loading of a particle filter 130. In a parameterization step 210, a first threshold value in the form of a maximum particle concentration, which is not to be exceeded downstream of the particle filter 130, and a second threshold value in the form of a minimum particle concentration, which is not to be undercut downstream of the particle filter, are determined. The first and second threshold values can also be the same and in this sense form a setpoint for the control. In a measuring step 220, a particle concentration downstream of the particle filter 130 is measured. In particular, the second particle sensor 147 arranged downstream of the particle filter 130 can be used for this purpose.

[0062] The measured value of the particle concentration is transmitted to the control device and can be stored there in a step 225, in particular together with other variables, for example a current load requirement, a current engine temperature, a current outside temperature, the time of day and/or season, the weather and the like.

[0063] In a comparison step 230, it is checked whether the measured particle concentration is below the minimum concentration. If this is the case, a control step 235 causes the exhaust gas flow upstream of the particle filter 130 to experience an increase in the proportion of oxidizing components. In addition, the fuel preparation device 110 can be controlled by means of the control unit in such a way that the composition of the air-fuel mixture is changed in favor of air or at the expense of fuel. As a result, the exhaust gas mixture downstream of the combustion engine 120 becomes leaner and more residual oxygen or other oxidizing compounds are available, which oxidize some of the particles deposited in the particle filter 130 and thus remove them from the particle filter 130. In other words, a filter cake in the particle filter 130 is burned off in this way at least partially. This reduces the back pressure of the exhaust system against which the combustion engine 120 must work, which increases the usable degree of effectiveness of the combustion engine 120.

[0064] If, on the other hand, it is determined in the comparison step 230 that the particle concentration does not exceed the second threshold value, it is checked in a further step 240 whether the maximum particle concentration is exceeded. If this is the case, in a control step 245 influencing of the exhaust gas composition follows in such a way that fewer oxidizing components are permitted. For this purpose, for example, the composition of the air-fuel mixture provided by the fuel preparation device 110 can be changed in favor of fuel or at the expense of air. Another possibility is control of the combustion engine 120, for example to change ignition timings. As a result, for example, it can be achieved that the combustion of the air-fuel mixture is more complete or less complete. In addition, the exhaust gas temperature can be influenced in this way. Overall, intervention in the control of the combustion engine 120 and/or the fuel preparation device 110 is carried out in such a way that the filter cake is built up in the particle filter 130, the loading of the particle filter 130 thus increases, if the first threshold value is exceeded.

[0065] If, on the other hand, the first threshold value is not exceeded, the method 200 returns to the measurement step 220.

[0066] It is understood that certain steps can be swapped with each other or combined into a common step without changing the way the method 200 works. For example, the two comparison steps 230 and 240 can be swapped with each other or combined into a single comparison step, just as the two control steps 235 and 245 can be combined into a single control step if the associated comparison steps are carried out together.

[0067] The data stored in step 225 can be used to determine the minimum and/or maximum particle concentration. For example, the minimum particle concentration can be increased if only a few particles are measured downstream of the particle filter 130 over a longer period of time in order to reduce the filter efficiency and thus positively influence the consumption behavior of the combustion engine 120. If, on the other hand, a high particle concentration is detected downstream of the particle filter 130 over a longer period of time, it can be assumed that some influencing factors are in an unfavorable range and therefore greatly increased particulate emissions are to be expected in the future, for example after a break in operation in which the engine temperature drops. In such a situation, it is advantageous if the filtration efficiency is increased as a precaution, for example to safely ensure compliance with legal requirements.

[0068] It may also be advantageous to lower the first threshold value when the second threshold value is increased. This is particularly useful if the first threshold value is very close to a legally prescribed limit value. If the second threshold value is increased, the filtration efficiency regularly decreases as a result, which can then lead to increased particulate emissions downstream of the particle filter 130 in the event of changing load requirements. In order to be able to safely comply with the legal limit values, a safety margin should therefore be provided in the case of a reduced filtration efficiency in order to increase the filtration efficiency in a timely manner if the particle concentration increases due to dynamic changes in the operating state of the combustion engine 120. The parameterization step 210 can therefore be designed in such a way that with increased fuel efficiency (less filter loading), the loading of the filter is rebuilt faster if necessary than with the filtration efficiency already set high (high filter loading).

[0069] Advantageously, a loading parameter can be calculated dynamically, which maps the current loading state of the filter and thus the expected filtration efficiency. In particular, a difference between particle concentrations measured upstream and downstream of the particle filter 130 can be included in this calculation of the loading parameter. If no particle sensor 145 is provided upstream of the particle filter 130, the calculation can also be made on a numerical model which, for example, uses data from the control unit to model a current particle concentration upstream of the particle filter 130. Further data, for example engine and/or outside temperatures, differential pressure across the particle filter, lambda values in the exhaust system and the like, can be included in the calculation of the loading parameter or in the modeling of the particle concentration upstream of the particle filter 130.