Method for regenerating a particle filter

Abstract

The invention relates to a method for regenerating a particle filter in an exhaust system of an internal combustion engine, comprising at least the following steps: a) performing a first regeneration of the particle filter until a lower threshold value of a particle load of the particle filter is reached; b) performing a verification measurement, wherein the internal combustion engine is operated at a first operating point such that an exhaust gas having at least—an excess of oxygen or—an elevated first temperature is provided upstream of the particle filter; wherein, if an increase of a second temperature is detected downstream of the particle filter during or after step b), c) a second regeneration of the particle filter is initiated.

Claims

1. A method for regenerating a particle filter, which is located in an exhaust system of an internal combustion engine, comprising at least the following steps: a) performing a first regeneration of the particle filter until a lower limit value of a particle loading of the particle filter is reached; b) operating the combustion engine at a first operating point that is freely selectable by a user; c) performing a verification measurement, the combustion engine being operated at a second operating point, so that an exhaust gas having at least an oxygen excess or an increased first temperature is provided upstream of the particle filter; wherein step c) is initiated at a time interval after the end of the first regeneration in accordance with step a); and when an increase in a second temperature of the exhaust gas is ascertained during or after step c) downstream of the particle filter, the following step being performed: d) initiating a second regeneration of the particle filter.

2. The method as recited in claim 1, wherein, in step c), the combustion engine is operated at the second operating point without fuel injection.

3. The method as recited in claim 1, wherein the time interval is at least one second.

4. The method as recited in claim 1, wherein the time interval is at most five seconds.

5. The method as recited in claim 1, wherein the first regeneration in accordance with step a) is performed exclusively on the basis of a computation model.

6. The method as recited in claim 1, wherein, at least during steps a) and d), the combustion engine is operated in a way that at least limits the oxygen excess in the exhaust gas or a first temperature of the exhaust gas upstream of the particle filter.

7. The method as recited in claim 1, wherein: at least one temperature sensor for measuring a second temperature of the exhaust gas is configured downstream of the particle filter; and the combustion engine is operated at least during step c) in such a way that, upstream of the particle filter, the at least an oxygen excess in the exhaust gas or the first temperature increase of the exhaust gas is set as a function of the measured second temperature.

8. A motor vehicle comprising a combustion engine; an exhaust system, a particle filter, downstream of the particle filter, at least a temperature sensor in the exhaust system; a control unit for operating the combustion engine, the control unit being suited for implementing the method according to claim 1, so that, upstream of the particle filter, at least an oxygen excess in the exhaust gas or a first temperature of the exhaust gas is settable by the control unit as a function of the measured second temperature.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention, as well as the technical field are explained in greater detail in the following with reference to the figures. The figures show especially preferred exemplary embodiments; however, the present invention is not limited thereto. It should be noted in particular that the figures and, in particular the illustrated relative sizes are only schematic. The same reference numerals denote functionally equivalent subject matters.

(2) FIG. 1 shows a motor vehicle having an exhaust system;

(3) FIG. 2: shows a first temperature/oxygen/particle loading/time diagram; and

(4) FIG. 3: shows a second temperature/oxygen/particle loading/time diagram.

DETAILED DESCRIPTION OF THE INVENTION

(5) FIG. 1 shows a motor vehicle 14 having an exhaust system 2. Motor vehicle 14 includes a combustion engine 3 and an exhaust system 2; configured in exhaust system 2 along the direction of flow of exhaust gas 9, there initially being a catalytic converter 16, followed by a particle filter 1 and, downstream thereof, a temperature sensor 13 for measuring a second temperature 20 of exhaust gas 9. Motor vehicle 14 has a control unit 15 for operating combustion engine 3; as a function of first temperature 10 measured downstream of particle filter 1, control unit 15 setting an increased concentration of oxygen 21 in exhaust gas 21 and/or providing an exhaust gas 9 having an increased first temperature 10 upstream of particle filter 1. Control unit 15 also models the first and second regeneration of particle filter 1; combustion engine 3 then being operated at certain, corresponding operating points.

(6) FIG. 2 shows a first diagram, illustrating an exemplary profile of the temperature, oxygen, and particle loading over time. First temperature 10, second temperature 20, oxygen 21, and particle loading 6 of particle filter 1 are plotted on the vertical axis. Time 17 is plotted on the horizontal axis.

(7) At a zero point in time illustrated here (origin of the depicted diagram), a particle loading 6 increases with time 17. During this time 17, combustion engine 3 is operated at a second operating point 12 (selectable to possibly already be restricted); second temperature 20 of exhaust gas 9 being essentially constant here downstream of particle filter 1. A first regeneration 4 of particle filter 1 is initiated upon reaching an upper limit value 19. First regeneration 4 is accomplished by increasing first temperature 10 of exhaust gas 9 and/or by providing additional oxygen 21 in exhaust gas 9 upstream of particle filter 1 (by engine operation and/or via an inlet in the exhaust system). The profile of first temperature 10 and the concentration of oxygen 21 in exhaust gas 9 are shown in FIGS. 2 and 3, in each case on a common curve.

(8) In step a) of the method, a first regeneration 4 is performed until a particle loading 6 of particle filter 1 (computationally) reaches a lower limit value 5. Lower limit value 5 describes an upper limit of a particle loading 6 that may be placed in particle filter 1 following first regeneration 4.

(9) A verification measurement 7 follows in step b), during which combustion engine 3 is operated for a brief time 17 at a specific, first operating point 8. At this first operating point 8, a significantly increased quantity of oxygen 21 is provided in exhaust gas 9 upstream of particle filter 1 that would exothermically convert particles possibly still stored in particle filter 1. The thus induced conversion of the particles would result in an increase in second temperature 20 of exhaust gas 9 downstream of particle filter 1, which may be recorded by a temperature sensor 13.

(10) Here, no (significant) increase in second temperature 20 in exhaust gas 9 is measured as a result of verification measurement 7. It may, therefore, be inferred that first regeneration 4 in accordance with step a) was sufficient. In particular, it is inferred that the modeling of particle loading 6 of particle filter 1 and/or of first regeneration 4 was accurate enough.

(11) Following verification measurement 7, combustion engine 3 is operated at any second operating point 12.

(12) FIG. 3 shows exemplarily a second diagram having deviating profiles. In contrast to FIG. 2, verification measurement 7 establishes an increase in second temperature 20 in exhaust gas 9. It is thus inferred that, in spite of first regeneration 4, particle filter 1 continues to be loaded with particles. Thus, actually present, real particle loading 18 is greater than (modeled, thus computationally determined) particle loading 6. Therefore, in a step c) of the method, a second regeneration 11 of particle filter 1 is initiated, further reducing particle loading 6 of particle filter 1.

(13) Second regeneration 11 is essentially performed along the lines of first regeneration 4. Thus, at least for a short period, a first temperature 10 of exhaust gas 9 or a concentration of oxygen 21 is increased upstream of particle filter 1, thereby reducing particle loading 6 of particle filter 1.

REFERENCE NUMERAL LIST

(14) 1 particle filter 2 exhaust system 3 combustion engine 4 first regeneration 5 lower limit value 6 particle loading 7 verification measurement 8 first operating point 9 exhaust gas 10 first temperature 11 second regeneration 12 second operating point 13 temperature sensor 14 motor vehicle 15 control unit 16 catalytic converter 17 time 18 real particle loading 19 upper limit value 20 second temperature 21 oxygen