Method for regenerating a particle filter, and motor vehicle having a particle filter

Abstract

The invention relates to a method for regenerating a particle filter (74) in an exhaust system (60) of a motor vehicle (10) having an internal combustion engine (12). Here, for a temperature increase to a temperature (T) required for the regeneration of the particle filter (74), a sorption agent container (102) of a fuel tank (22) of the motor vehicle (10) is purged, and the fuel vapours (24) retained in the sorption agent container (102), in particular an activated carbon filter, are supplied directly or indirectly to the exhaust system (60) upstream of the particle filter (74). By means of an exothermic conversion of the fuel vapours (24) in the exhaust system (60) upstream of the particle filter (74), the exhaust-gas temperature (T) can be increased without the need for engine-internal measures for increasing the exhaust-gas temperature.

Claims

1. A method for regenerating a particle filter in an exhaust gas system of a motor vehicle, the motor vehicle having: an internal combustion engine that is operable with a fuel, an exhaust duct in which at least one catalytic converter and, downstream of the at least on catalytic converter, at least one particle filter is situated, a fuel tank, a sorption agent container that is in fluid-conducting connection with the fuel tank and contains a sorption agent, and a purge line that selectively connects the sorption agent container to the internal combustion engine or to the exhaust duct upstream from the particle filter, wherein, in order to heat the particle filter, supplying the fuel retained in the sorption agent container is supplied to the purge agent line, the method comprising: in a first purging mode, supplying the fuel retained in the sorption agent container to the combustion engine and burning that retained fuel in the combustion chambers of the internal combustion engine, and in a second purging mode used in overrun phases of the vehicle, in which the motor vehicle moves solely due to its excess kinetic energy, catalytically reacting the fuel retained in the sorption agent container in the at least one catalytic converter.

2. The method according to claim 1, further comprising initiating engine-internal measures for increasing the exhaust gas temperature.

3. The method according to claim 1, further comprising determining a loading state of the particle filter, and carrying out a purging operation of the sorption agent container when the need for regenerating the particle filter is established.

4. The method according to claim 3, further comprising determining an exhaust gas temperature in the exhaust duct, and wherein the purging operation of the sorption agent container is carried out when the exhaust gas temperature is below a first threshold temperature.

5. The method according to claim 4, wherein the purging operation of the sorption agent container is carried out only when the exhaust gas temperature is above a second threshold temperature.

6. The method according to claim 1, further comprising generating an air stream used for purging the sorption agent container by means of a pumping or suction action of the internal combustion engine.

7. The method according to claim 1, further comprising supplying a volume flow of fuel to the exhaust duct by a purging operation of the sorption agent container and controlling or regulating the volume flow by setting a mass or volume flow of the air conveyed through the sorption agent container.

8. The method according to claim 1, further comprising supplying a mass or volume flow conveyed through the sorption agent container and setting the volume flow by an opening time and/or an opening cross section of an actuating means situated in the purge line.

9. A motor vehicle, including: an internal combustion engine that is operable with a fuel, an exhaust gas system in which at least one catalytic converter and, downstream of the at least on catalytic converter, at least a particle filter is situated, a fuel tank, a sorption agent container that is in fluid-conducting connection with the fuel tank and contains a sorption agent, a purge line that connects the sorption agent container to the internal combustion engine and/or to the exhaust gas system upstream from the particle filter, and a control device that is configured for carrying out the method according to claim 1.

10. The motor vehicle according to claim 9, further comprising a three-way catalytic converter situated in the exhaust gas system, downstream from an outlet of the internal combustion engine and upstream from the particle filter.

11. The motor vehicle according to claim 9, further comprising a four-way catalytic converter having a particle filter with a three-way catalytically active coating situated in the exhaust gas system.

12. The motor vehicle according to claim 10, wherein the purge line opens into an exhaust duct of the exhaust gas system downstream from an outlet and upstream from the three-way catalytic converter.

13. The motor vehicle according to claim 9, wherein the sorption agent container is fluidically connected to a suction jet pump.

14. The motor vehicle according to claim 9, further comprising a purge blower for purging the sorption agent container situated at the sorption agent container.

15. The motor vehicle according to claim 11, wherein the purge line opens into an exhaust duct of the exhaust gas system downstream from an outlet and upstream from the four-way catalytic converter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is explained below in exemplary embodiments, with reference to the associated drawings. Identical components or components having an identical function are denoted by the same reference symbols in the various figures, which show the following:

(2) FIG. 1 shows a first exemplary embodiment of a block diagram of a motor vehicle according to the invention;

(3) FIG. 2 shows an alternative exemplary embodiment of a block diagram of a motor vehicle according to the invention; and

(4) FIG. 3 shows another alternative exemplary embodiment of a motor vehicle according to the invention in a block diagram illustration.

DETAILED DESCRIPTION OF THE INVENTION

(5) FIG. 1 shows a block diagram of a motor vehicle 10 according to the invention. The motor vehicle includes an internal combustion engine 12, a fuel supply system 20, an air supply system 40, an exhaust gas system 60, and a fuel vapor sorption system 100.

(6) The internal combustion engine 12 includes at least one combustion chamber, in the present case four, for example, combustion chambers 14, and is preferably a (spark-ignition) gasoline engine, but may also be an (auto-ignition) diesel engine. In the following example, the internal combustion engine 12 is designed as a gasoline engine that is spark-ignited by means of spark plugs. The internal combustion engine 12 is operable with a fuel 24 that is stored in a fuel tank 22 of the motor vehicle 10. The fuel tank 22 may be filled through a filling neck 26, and is equipped with a filling level sensor 28 for detecting the filling level. The fuel 24 is supplied by means of a fuel pump 30 to the internal combustion engine 12 via a fuel line 34 that branches off from the fuel tank 22; in the internal combustion engine the fuel is injected into the combustion chambers 14 of the internal combustion engine 12 by means of a fuel injection system 32.

(7) Fresh air 44 that is drawn in from the surroundings and provided to an inlet 16 that distributes the fresh air 44 over the combustion chambers 14 of the internal combustion engine 12 via an intake line 42 is supplied to the internal combustion engine 12 via the air supply system 40. In the illustrated example, the fresh air 44 is compressed by a compressor 48 of an exhaust gas turbocharger 46 to be able to operate the internal combustion engine 12 at a higher charge pressure than ambient pressure, and thus to operate with increased power. The compressor 48 is driven by a turbine 66 that is situated in the exhaust gas system 60 and is connected to the compressor 48 via a shaft. An adjustable throttle valve 50 by means of which the filling of the combustion chambers 14 may be controlled or regulated is situated in the intake line 42, downstream from the compressor 48. The air supply system 40 also has a return flow line 52 that branches off from the intake line 42 downstream from the compressor 48 and opens into the intake line 42 upstream from the compressor 48. A suction jet pump 54, whose function is explained in greater detail below in the description of the fuel vapor sorption system 100, is situated in the return flow line 52.

(8) Exhaust gas 62 of the internal combustion engine 12 is supplied via an outlet 18, in particular an exhaust manifold, to the exhaust gas system 60, where it undergoes catalytic aftertreatment. For this purpose, the exhaust gas system 60 includes an exhaust duct 64 in which the above-mentioned turbine 66 of the exhaust gas turbocharger 46 is situated, so that the exhaust gas 62 drives the turbine 66, and thus the compressor 48, with withdrawal of kinetic energy. The turbine 66 may be bypassed by means of a wastegate 68, the exhaust gas fraction that is led through the wastegate 68 being adjustable by a wastegate valve 70, in particular an electrically actuatable valve. To convert limited harmful exhaust gas components into harmless exhaust gas components, the exhaust gas system 60 has a catalytic converter 72, in particular a three-way catalytic converter. Exhaust gas catalytic converters are typically made up of a catalyst support that is provided with a catalytically active coating and through which the exhaust gas 62 may flow. The chemical composition of the catalytic coating determines which exhaust gas components are catalytically reacted. Oxidation catalytic converters catalyze the conversion of uncombusted hydrocarbons HC and carbon monoxide CO, reduction catalytic converters assist with the conversion of nitrogen oxides NO.sub.x, and three-way catalytic converters combine the functions of oxidation catalytic converters and reduction catalytic converters. In the present case, the illustrated catalytic converter 72 is a three-way catalytic converter. Situated downstream from the catalytic converter 72 is a particle filter 74 which retains the particles that occur during combustion of the fuel 24 in the combustion chambers 14 of the internal combustion engine 12 and prevents them from being emitted. In addition, the exhaust gas system 60 may have further components for exhaust aftertreatment, in particular a NO.sub.x storage catalytic converter or a catalytic converter for the selective catalytic reduction of nitrogen oxides. Situated in the exhaust duct 64, upstream from the catalytic converter 72, is a first lambda sensor 78 that measures an air-fuel ratio (referred to below as the air ratio), more precisely, the fraction of oxygen in the uncontrolled exhaust gas 62. The first lambda sensor 78 is used primarily for controlling the air-fuel mixture or the fuel fraction therein that is supplied to the internal combustion engine 12. Situated in the exhaust duct 64, downstream from the exhaust gas catalytic converter 72, is a second lambda sensor 80 that measures the air-fuel ratio (referred to below as the air ratio) or the fraction of oxygen in the exhaust gas 62 after passing through the catalytic converter 72. The function of the second lambda sensor 80, among other things, is to monitor the functioning of the catalytic converter 72. Both lambda sensors 78, 80 output a sensor signal in the form of a voltage as a function of the oxygen fraction in the exhaust gas 62. The lambda sensors 78, 80 may have designs, as broadband lambda sensors or jump lambda sensors, that are different from one another. The voltage signal of broadband lambda sensors is essentially proportional to the lambda value of the exhaust gas over wide ranges, while the voltage signal of jump lambda sensors, which ranges only about a lambda value of 10.03, shows a strong dependency on the lambda value. For a gasoline engine 12 with a downstream three-way catalytic converter 72, the internal combustion engine 12 in most operating points is controlled with a stoichiometric combustion lambda of one, since at this value the three-way catalytic converter 72 has its optimal conversion power for the three exhaust gas components HC, CO, and NO.sub.x. In this configuration the first lambda sensor 78 is often designed as a broadband lambda sensor, and the lambda sensor 80 is designed as a jump lambda sensor. The exhaust gas system 60 may include additional sensors not illustrated here, in particular a temperature sensor for detecting the exhaust gas temperature, the temperature of the catalytic converter 72, or the temperature of the particle filter 74.

(9) The fuel vapor sorption system 100 has a sorption agent container 102 in which a sorption agent 104 for sorption of fuel vapors, i.e., hydrocarbons, is present. In the present case, sorption is understood to mean any reversible binding, for example absorption, physical adsorption (physisorption), and/or chemical adsorption (chemisorption). The sorption agent 104 is preferably activated carbon, in particular an activated carbon filter, that binds fuel vapors by physical adsorption. The sorption agent container 102 is connected to the fuel tank 22 via a fuel vapor line 106. A purge line 108 branches off from the sorption agent container 102 and is divided into a first partial purge line 110 and a second partial purge line 112. The first partial purge line 110 opens into the return flow line 52 via the suction side of the suction jet pump 54. Downstream from the throttle valve 50, the second partial purge line 112 opens into the intake line 42 or directly into the inlet 16 of the internal combustion engine 12. An actuating means for adjusting, in particular limiting, the volume flow in the purge line 108 is situated in the shared section of the purge line 108. In the present example the actuating means is designed as a valve that is controllable via an electric motor, and that is also referred to below as a tank vent valve 116. A blocking means 118, 120 that is designed to allow flow only in the direction of the return flow line 52, or the intake line 42 or the inlet 16, respectively, is situated in the partial purge lines 110, 112, respectively. If the downstream pressure at the blocking means 118, 120 is greater than the upstream pressure or is greater than a predetermined pressure, the blocking means 118, 120 automatically close. The fuel vapor sorption system 100 may also include a diagnostic module that is in fluid-conducting connection with the sorption agent container 102 via two lines. The diagnostic module has an overpressure valve that is connected to the surroundings, and a pump (neither of which is illustrated). The diagnostic module is used on the one hand for pressure compensation of the sorption agent container 102 and the fuel tank 22, and on the other hand for monitoring tank leaks. In addition, a purge blower 122 via which the hydrocarbons retained in the sorption agent container 102 may be conveyed into the purge line 108 may be provided at the sorption agent container 102. There are basically two options: Firstly, the purge air may be conveyed through the sorption agent container 102 by means of the purge blower 122. Alternatively, the purge blower 122 may be situated in the area of the first blocking means 118 and may draw the hydrocarbons out of the sorption agent container 102. The (additional) blocking means 118 may thereby be dispensed with. The suction jet pump 54 may be dispensed with when a purge blower 122 is used. The introduction of the uncombusted hydrocarbons from the sorption agent container 102 into the exhaust duct 64 likewise takes place upstream from the turbine 66 of the exhaust gas turbocharger 46.

(10) The control device 90 controls, in a manner known per se, the operation of the internal combustion engine 12, in particular the supplied quantity of combustion air, via actuation of the throttle valve 50, and controls the supplied quantity of fuel via actuation of the fuel pump 30 and the fuel injection system 32. In addition, the control device 90 has a tank vent control module 92 that is configured to control the fuel vapor sorption system 100, and in particular to purge the sorption agent 104 with fresh air 44 from time to time in order to desorb the sorbed fuel vapors from the sorption agent 104, discharge them via the first partial purge line 110 or the second partial purge line 112, and supply them to the internal combustion engine 12.

(11) The fuel vapor sorption system 100 of the vehicle 10 illustrated in FIG. 1 may be operated in a loading mode and at least one purge mode, and has the following functions:

(12) In a loading mode the tank vent valve 116 is closed. Fuel vapors that evaporate from the fuel 24 in the tank 22 pass through the fuel vapor line 106 and into the sorption agent container 102, where they are adsorbed by the sorption agent 104 (activated carbon in this case). During this operation, the valve contained in the diagnostic module is continuously open in loading mode to allow pressure compensation between the fuel tank 22 or the sorption agent container 102 and the surroundings.

(13) In the purge mode of the fuel vapor sorption system 100, which includes a fired purge mode and an unfired purge mode, the tank vent valve 116 is controlled in such a way that it is at least occasionally open, wherein a free flow cross section and/or opening intervals is/are set by a signal of the tank vent control module 92. The purge mode may on the one hand be activated as a function of loading, for example when a predetermined operating period in the sorption operating mode has elapsed, and thus, a predetermined loading limit of the sorption agent 104 is presumably achieved. Alternatively or additionally, the purge mode may be activated independently of the loading when the operating point of the vehicle is favorable.

(14) The first, fired purge mode is used when the internal combustion engine 12 is fired, i.e., operated with the supply and combustion of fuel. The combustion air is compressed via the compressor 48 and supplied to the internal combustion engine 12. A portion of the compressed air branches off from the air intake line 42 downstream from the compressor 48, and is supplied once again upstream from the compressor 48 via the return line 52. If a sufficiently high pressure of 1000 mbar, for example, i.e., a charged operating point, is present in the line 42 or the inlet 16, the valve 120 situated in the line 112 closes, and the first check valve 118, situated in the first partial purge line 110, opens. If the tank vent valve 116 is now opened, purge air is drawn in by means of the suction jet pump 53, through the purge lines 108 and 110 via the compressed air stream that is returned in the line 52, and mixed with the combustion air. The fresh air 44 necessary for this purpose flows from the surroundings, across the overpressure valve of the diagnostic module, and into the sorption agent container 102 and discharges desorbed fuel vapor. The purge air loaded with the fuel vapor is drawn in via the suction jet pump 54 according to the Venturi principle due to the pressure difference in the intake line 42 upstream and downstream from the compressor 48, and the combustion air is admixed and supplied to the internal combustion engine 12 via the intake line 42 and the inlet 16. The fuel vapor together with the fuel 24 supplied via the injection system 32 is combusted in the internal combustion engine. The exhaust gas 62 is discharged via the exhaust gas system 60 and subjected to catalytic aftertreatment.

(15) The second, unfired purge mode is used in overrun phases of the vehicle, in which the motor vehicle 10 moves solely due to its excess kinetic energy, and the pistons and intake/exhaust valves of the internal combustion engine 12 are moved (dragged) by the rotating crankshaft or camshaft. In overrun phases, for fuel consumption and emission reasons the fuel supply to the internal combustion engine 12 from the fuel tank 22 is interrupted, and in gasoline engines the ignition is generally suspended. An overrun phase is typically recognized based on the pedal travel sensor signal, for example when the driver lets up on the accelerator in order to decelerate the vehicle. In such an unfired overrun mode of the motor vehicle 10, a low pressure is present in the intake line 42 downstream from the compressor 48 and in the return line 52, so that the first check valve 118 is closed, and the second check valve 120 situated in the second partial purge line 112 is open. If the tank vent valve 116 is now opened, air is drawn in via the second partial purge line 112 by means of the dragged internal combustion engine 12, and in turn flows in from the surroundings, across the overpressure valve of the diagnostic module, and into the sorption agent container 102, and discharges fuel vapor that is desorbed from the sorption agent 104. The purge air thus loaded with fuel vapor flows from the container 102 and through the purge line 108 and the partial purge line 112, and is mixed with the combustion air of the internal combustion engine 12. Since the internal combustion engine 12 is not operated fired, there is no combustion of the hydrocarbons in the engine. Instead, they are catalytically reacted in the downstream exhaust gas catalytic converter 72.

(16) During driving operation of the motor vehicle 10, the particles that arise during combustion of the fuel 24 in the combustion chambers 14 of the internal combustion engine 12 are retained by the particle filter 74 in the exhaust duct 64. Loading of the particle filter 74 is determined based on a differential pressure measurement, i.e., a comparison of the pressure in the exhaust duct 64 upstream from the particle filter 74 and downstream from the particle filter 74, or based on a balancing model stored in the control device 90. If the particle filter 74 has reached a loading level for which regeneration of the particle filter 74 is necessary to avoid a further rise in the exhaust back pressure due to exhaust back pressure that increases with the loading of the particle filter 74, in a regeneration phase the exhaust gas temperature T.sub.A or a temperature of the particle filter 74 is determined and compared to a first threshold temperature T.sub.S1 necessary for regeneration of the particle filter. If the exhaust gas temperature T.sub.A and/or the temperature of the particle filter 74 are/is below this first threshold temperature T.sub.S1, in an overrun phase of the internal combustion engine 12 the fuel vapors purged from the sorption agent container 102 are supplied to the internal combustion engine 12 and conveyed through the combustion chambers 14 and into the exhaust duct 64. An exothermic reaction of the fuel vapors on the three-way catalytic converter 72 occurs with the excess oxygen that is present In the exhaust duct 64 in an overrun mode. The particle filter 74 is heated to a regeneration temperature by the heat that is released during this exothermic reaction, as the result of which the soot particles retained in the particle filter 74 are oxidized with the oxygen that is present in the exhaust duct 64 in overrun mode, to form carbon dioxide.

(17) As an alternative to conveying the fuel vapor from the sorption agent container 102 via a suction jet pump or a pressure gradient, at the sorption agent container 102 the fuel vapor that is retained in the sorption agent container 102 or in the sorption agent 104 may also be conveyed by the purge blower 122 into the intake line 42 or into the exhaust duct 64 of the internal combustion engine 12.

(18) FIG. 2 illustrates one alternative exemplary embodiment of a motor vehicle 10 according to the invention. With essentially the same design and the same function as described for FIG. 1, instead of a three-way catalytic converter 72 and a particle filter 74, a four-way catalytic converter 76 is situated in the exhaust duct 64 of the internal combustion engine 12.

(19) FIG. 3 illustrates another alternative exemplary embodiment of a motor vehicle 10 according to the invention. With essentially the same design and the same function as described for FIG. 1, a third purge line 114 is provided that connects the sorption agent container 102 to the exhaust duct 64 upstream from the three-way catalytic converter 72.

LIST OF REFERENCE NUMERALS

(20) 10 motor vehicle 12 internal combustion engine 14 combustion chamber 16 inlet 18 outlet 20 fuel supply system 22 fuel tank 24 fuel 26 filling neck 28 filling level sensor 30 fuel pump 32 fuel injection system 34 fuel line 40 air supply system 42 intake line 44 fresh air 46 exhaust gas turbocharger 48 compressor 50 throttle valve 52 return flow line 54 suction jet pump 60 exhaust gas system 62 exhaust gas 64 exhaust duct 66 turbine 68 wastegate 70 wastegate valve 72 three-way catalytic converter 74 particle filter 76 four-way catalytic converter 78 first lambda sensor 80 second lambda sensor 90 control device 92 tank vent control module 100 fuel vapor sorption system 102 sorption agent container 104 sorption agent/activated carbon 106 fuel vapor line 108 purge line 110 first purge line 112 second purge line 114 third purge line 116 actuating means/tank vent valve 118 first check valve 120 second check valve 122 purge blower combustion air ratio/exhaust gas/air ratio T temperature T.sub.S1 first (upper) threshold temperature T.sub.S2 second (lower) threshold temperature