Exhaust gas treatment for an internal combustion engine

Abstract

An internal combustion engine makes available exhaust gas which can be treated by means of a catalytic converter and a particle filter. A method for determining the particle load of the particle filter comprises steps of determining the storage capacity of the catalytic converter for oxygen and determining the particle load of the particle filter on the basis of the determined storage capacity in the controller.

Claims

1. A method for a particle filter for an exhaust gas of an internal combustion engine with a catalytic converter, the method comprising: determining a storage capacity of the catalytic converter for oxygen; and determining the particle load of the particle filter on the basis of the determined storage capacity, wherein the determination of the storage capacity of the catalytic converter for oxygen comprises: operating, in a first phase, the internal combustion engine with excess fuel relative to an amount of oxygen in order to reduce oxygen stored in the catalytic converter; following operating in the first phase, operating, in a second phase, the internal combustion engine with excess oxygen relative to an amount of fuel in order to permit the storage of oxygen in the catalytic converter; sensing oxygen contents of the exhaust gas upstream and downstream of the catalytic converter during the second phase; and determining the storage capacity on the basis of the oxygen contents of the exhaust gas sensed upstream and downstream of the catalytic converter during the second phase.

2. The method of claim 1, wherein the internal combustion engine is a spark ignition engine.

3. A control device for a particle filter for an exhaust gas of an internal combustion engine with a catalytic converter, wherein the control device comprises: a processing device for determining the particle load of the particle filter on the basis of the storage capacity of the catalytic converter for oxygen; wherein the processing device is configured to bring about regeneration of the particle filter if the determined particle load exceeds a predetermined threshold value, wherein the processing device is configured to determine the storage capacity of the catalytic converter for oxygen by operating, in a first phase, the internal combustion engine with excess fuel in order to reduce, if appropriate, oxygen stored in the catalytic converter; following operating in the first phase, operating, in a second phase, the internal combustion engine with excess oxygen in order to permit the storage of oxygen in the catalytic converter; sensing oxygen contents of the exhaust gas upstream and downstream of the catalytic converter during the second phase; and determining the storage capacity on the basis of the oxygen contents of the exhaust gas upstream and downstream of the catalytic converter during the second phase.

4. The control device of claim 3, wherein the regeneration comprises actuating the internal combustion engine in order to raise a temperature of the exhaust gas and to operate the internal combustion engine with excess oxygen.

5. A system for controlling an internal combustion engine, the system comprising: a particle filter and a catalytic converter for exhaust gas of the internal combustion engine; a first oxygen sensor for determining the oxygen content of the exhaust gas upstream of the catalytic converter; a second oxygen sensor for determining the oxygen content of the exhaust gas downstream of the catalytic converter; a first control device having a processing device configured to control combustion air ratio of the internal combustion engine as a function of one of the determined oxygen contents; and a second control device having a processing device configured to determine a particle load of the particle filter based upon a storage capacity of the catalytic converter, and to bring about regeneration of the particle filter if the determined particle load exceeds a predetermined threshold value, wherein the second control device is configured to determine the storage capacity of the catalytic converter for oxygen by operating, in a first phase, the internal combustion engine with excess fuel in order to reduce, if appropriate, oxygen stored in the catalytic converter; subsequent to operating in the first phase, operating, in a second phase, the internal combustion engine with excess oxygen in order to permit the storage of oxygen in the catalytic converter; and determining the storage capacity on the basis of the oxygen contents of the exhaust gas upstream and downstream of the catalytic converter during the second phase.

6. The system as claimed in claim 5, wherein the catalytic converter and the particle filter are embodied integrated with one another.

7. The method as claimed in claim 1, further comprising bringing about regeneration of the particle filter if the determined particle load exceeds a predetermined threshold value.

8. The method as claimed in claim 7, wherein regeneration of the particle filter comprises actuating the internal combustion engine in order to raise the temperature of the exhaust gas and to operate the internal combustion engine with excess oxygen.

9. The method as claimed in claim 1, wherein the particle load is determined based on a temperature of the exhaust gas.

10. The method as claimed in claim 1, further comprising receiving a sensed oxygen content of the exhaust gas upstream of the catalytic converter, receiving a sensed oxygen content of the exhaust gas downstream of the catalytic converter, and controlling a combustion air ratio of the internal combustion engine as a function of one of the sensed oxygen content.

11. The method as claimed in claim 1, wherein the particle load is determined based upon a space velocity of the exhaust gas.

12. The control device as claimed in claim 3, wherein the processing device is configured to determine the particle load of the particle filter based upon a temperature of the exhaust gas.

13. The control device as claimed in claim 3, wherein the processing device is configured to determine the particle load of the particle filter based upon a space velocity of the exhaust gas.

14. The control device as claimed in claim 3, wherein the processing device receives a sensed oxygen content of the exhaust gas upstream of the catalytic converter and a sensed oxygen content of the exhaust gas downstream of the catalytic converter, and controls a combustion air ratio of the internal combustion engine as a function of one of the sensed oxygen content.

15. The system as claimed in claim 5, wherein regeneration of the particle filter comprises actuating the internal combustion engine in order to raise a temperature of the exhaust gas and to operate the internal combustion engine with excess oxygen.

16. The system as claimed in claim 5, wherein the second control device is configured to determine the particle load of the particle filter based upon a temperature of the exhaust gas.

17. The system as claimed in claim 5, wherein the second control device is configured to determine the particle load of the particle filter based upon a space velocity of the exhaust gas.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The invention will now be described more precisely with reference to the appended figures, in which:

(2) FIG. 1 illustrates schematically a system for controlling an internal combustion engine; and

(3) FIG. 2 illustrates schematically a relationship between an oxygen storage capacity of a catalytic converter and a particle load of a particle filter of the system in FIG. 1.

DETAILED DESCRIPTION

(4) FIG. 1 shows a system 100 for controlling an internal combustion engine 105. The internal combustion engine 105 is preferably configured to drive a motor vehicle and is more preferably embodied as a spark ignition engine. A first control device 110 is configured to control the internal combustion engine 105, in particular an operating point of the internal combustion engine 105. For this purpose, it is possible to influence different components of the internal combustion engine 105, for example an injector 115 for injecting a predetermined quantity of fuel into a combustion chamber 120, an ignition device 125 for igniting a mixture of fuel and oxygen in the combustion chamber 120 at a predetermined time, an inlet adjustment means 130 for influencing an inlet time of air into the combustion chamber 120, an out adjustment means 135 for influencing an outlet time of exhaust gas from the combustion chamber 120 and, if appropriate, other components also. The control can be carried out on the basis of measured values at the internal combustion engine 105, for example a rotational speed of an output shaft 140, a temperature of a component of the internal combustion engine 105, or a mass of air which is let into the internal combustion engine 105 or the internal combustion engine 120.

(5) During the combustion of fuel and oxygen, which is contained in the air which has been let into the combustion chamber 120, an exhaust gas 145 is produced which can be treated and, in particular, purified, by means of the system 100. The system 100 comprises, in particular, a catalytic converter 150, which is preferably embodied as a three-way catalytic converter, and a particle filter 155 which is embodied integrated with the catalytic converter 150 in the illustrated embodiment. In other embodiments, the catalytic converter 150 and the particle filter 155 can also be connected in series, for example with respect to a direction of flow of the exhaust gas 145. The system 100 also comprises a first oxygen sensor 160 upstream of the catalytic converter 150, and a second oxygen sensor 165 downstream of the catalytic converter 150. Furthermore, a second control device 170 is provided which is configured to determine a particle load of the particle filter 155. The particles which have accumulated there are absorbed from the stream of exhaust gas 145 from the internal combustion engine 105. The second control device 170 is preferably connected to one or more sensors and/or to the first control device 110 in such a way that it is provided with a value for the oxygen storage capacity of the catalytic converter 150 and preferably also for the temperature of the exhaust gas 145 or the space velocity of the exhaust gas 145. The temperature can be detected by means of a dedicated temperature sensor 175 which can be mounted at different locations in the exhaust gas conduction system or can be obtained from the first control device 110 which can determine the temperature on the basis of the temperature sensor 175 or by means of the determination on the basis of a model. The space velocity of the flow of exhaust gas 145 is preferably also determined by the first control device 110 and made available to the second control device 110.

(6) The oxygen storage capacity of the catalytic converter 150 is preferably determined in that in a first phase, the internal combustion engine 105 is operated with excess fuel (<1) in order to reduce, if appropriate, oxygen stored in the catalytic converter 150 and in a subsequent second phase, the internal combustion engine 105 is operated with excess oxygen (<1) in order to permit the storage of oxygen in the catalytic converter 150, and the storage capacity of the catalytic converter 150 for oxygen is determined on the basis of the oxygen contents of the exhaust gas 145 upstream and downstream of the catalytic converter 150 during the second phase. These steps can alternatively be carried out by the first control device 110 or the second control device 170, for which purpose the oxygen sensors 160 and 165 are correspondingly connected to the first control device 110 or the second control device 170. It is also preferred that the first control device 110 controls the operating state of the internal combustion engine 105 as a function of at least one of the quantities of oxygen determined by means of the oxygen sensors 160, 165.

(7) The storage of particles from the stream of exhaust gas 145 through the particle filter 155 is a function of the particle load of the particle filter 155 and can additionally be dependent on the temperature and/or on the space velocity of the stream of exhaust gas 145. The second control device 170 is preferably configured to determine the particle load of the particle filter 155 and to compare it with a predetermined threshold value. If the determined load exceeds the threshold value, regeneration of the particle filter 145 can be brought about in that, in particular, the operating point of the internal combustion engine 105 is changed in such a way that the exhaust gas 145 has an increased temperature and/or a predetermined quantity of residual oxygen is located in the stream of exhaust gas 145. The execution of the regeneration can alternatively be controlled by the first control device 110 or the second control device 170. In a particularly preferred embodiment, the control devices 110 and 170 are embodied integrated with one another.

(8) FIG. 2 shows a qualitative relationship between an oxygen storage capacity of the catalytic converter 150 and a particle load of the particle filter 155 of the system 100 in FIG. 1. A time profile is plotted in the horizontal direction. An oxygen storage capacity 205 and a particle load 210 are plotted in the vertical direction, with different ordinate axes. A first profile 215 is illustrated with an interrupted line and relates to the oxygen storage capacity 205 of the catalytic converter 150, and a second profile 220 is illustrated with a dot-dashed line and relates to the profile of the particle load 210 of the particle filter 155. For the sake of better illustration, the profiles 215, 220 in FIG. 2 are plotted offset vertically.

(9) In a method 225, the oxygen storage capacity 205 of the catalytic converter 150 is determined in a first step 230 at a time t1. In addition, the temperature of the exhaust gas 145 and/or its space velocity can also be determined. In a second step 235, the particle load 210 of the particle filter 155 is determined by means of the second control device 170 on the basis of the information acquired in the first step 230. The determination can be carried out, for example, by means of a characteristic diagram, wherein individual values of the characteristic diagram have been determined in advance experimentally or analytically. In another embodiment, the particle load 210 is determined analytically on the basis of the oxygen storage capacity 205 and, if appropriate, the temperature and/or the space velocity of the stream of exhaust gas 145, for example in that a predetermined, if appropriate multi-parameter, function is used. The function can be specified, in particular, in a polynomial fashion. Other embodiments for the determination of the particle load 210 are also possible on the basis of the specified parameters.

LIST OF REFERENCE SYMBOLS

(10) 100 System 105 Internal combustion engine 110 First control device 115 Injector 120 Combustion chamber 125 Ignition device 130 Inlet adjustment means 135 Outlet adjustment means 140 Output shaft 150 Catalytic converter 155 Particle filter 160 First oxygen sensor 165 Second oxygen sensor 170 Second control device 175 Temperature sensor 205 Oxygen storage capacity 210 Particle load 215 Profile of the oxygen storage capacity 220 Profile of the particle load 225 Method 230 First step: Determining the oxygen storage capacity 235 Second step: Determining the particle load