METHOD FOR THE REGENERATION OF A SOOT PARTICLE FILTER

Abstract

The invention relates to a method for the regeneration of a soot particulate filter that is installed on the outlet side of an internal combustion engine, comprising the following steps: detecting a loading value of the soot particulate filter; measuring an operating temperature of the soot particulate filter; switching off a cylinder of the internal combustion engine; starting a supply of fresh air to the soot particulate filter via the switched-off cylinder; adjusting a cylinder valve so as to control the supply of fresh air; regenerating the soot particulate filter. The invention further relates to a control unit, to an internal combustion engine and to a motor vehicle for carrying out a method of this kind.

Claims

1. A method for the regeneration of a soot particulate filter that is installed on the outlet side of an internal combustion engine, comprising: ascertaining a load value of the soot particulate filter; measuring an operating temperature of the soot particulate filter; switching off a cylinder of the internal combustion engine; initiating a fresh air feed into the soot particulate filter via the switched-off cylinder adjusting a cylinder valve so as to regulate the fresh air feed; regenerating the soot particulate filter.

2. The method according to claim 1, further comprising heating up the soot particulate filter when the load has reached a first load value, if the operating temperature is below a first temperature value.

3. The method according to claim 2, whereby the fresh air feed is initiated when the first operating temperature of the soot particulate filter has been reached.

4. The method according to claim 1, whereby the cylinder valve is adjusted by means of an actuator that can be activated by a control unit.

5. The method according to claim 1, whereby the cylinder valve is adjusted by switching over to a separate control cam.

6. The method according to claim 5, whereby the control cam is configured in such a way that it brings about an elevated valve stroke, thus increasing the fresh air feed.

7. The method according to claim 1, whereby, during the regeneration of the soot particulate filter, an operating state requested by the driver is maintained by means of the active cylinders.

8. A control unit for operating an internal combustion engine of a motor vehicle, said control unit being configured to carry out a method according to claim 1.

9. An internal combustion engine with a control unit according to claim 8, whereby the internal combustion engine operates according to one of the following engine principles: gasoline engine, diesel engine and gas engine.

10. A motor vehicle with an internal combustion engine according to claim 9.

11. The method according to claim 3, wherein the first operating temperature of the soot particulate filter is above 450 C.

12. The method according to claim 11, wherein the first operating temperature of the soot particulate filter is 600 C.

Description

[0046] The embodiments of the invention will now be described by way of example, making reference to the accompanying drawing. The following is shown:

[0047] FIG. 1 a schematic sequence of an embodiment of the method according to the invention for the regeneration of a soot particulate filter;

[0048] FIG. 2 a schematic depiction of an internal combustion engine arrangement with a soot particulate filter arranged in its exhaust tract;

[0049] FIG. 3 an internal combustion engine with a switched-off cylinder, in which the method according to the invention can be carried out.

[0050] FIG. 1 shows the schematic sequence of a method according to the invention for the regeneration of a soot particulate filter. The method comprises Step 22: ascertaining a load value of the soot particulate filter, Step 23: measuring an operating temperature of the soot particulate filter, Step 24: switching off a cylinder of the internal combustion engine, Step 25: initiating a fresh air feed into the soot particulate filter via the switched-off cylinder, Step 26: adjusting a cylinder valve for regulating the fresh air feed, and Step 27: regenerating the soot particulate filter.

[0051] Step 29: heating up the soot particulate filter, is optionally provided. Step 29 is conditionally carried out when the load has reached a first value that corresponds to a regeneration value of the soot particulate filter.

[0052] As set forth here, the load value refers to a load value derived from a measurement or to a modeled load value of the soot particulate filter. A load value derived from a measurement is based, for example, on a pressure drop that is detected by means of two pressure sensors which are installed upstream and downstream from the soot particulate filter respectively, as seen in the flow direction. When the soot particulate filter is highly laden, the rising flow resistance increases the pressure drop (the pressure differential between the two pressure sensors). A load value can then be derived from this pressure differential.

[0053] In the case of a modeled load value, the ascertained operating states of the internal combustion engine serve as the basis for modeling a projected accumulation of soot over a given period of operation, taking into account the ascertained operating points or operating states. These two methods can also be combined with each other.

[0054] Step 25, initiating a fresh air feed into the soot particulate filter, can be conditionally carried out, namely, as a function of a given operating temperature of the soot particulate filter, which is preferably more than 450 C., especially above 600 C. The operating temperature of the soot particulate filter can be measured either directly by means of thermal measurements in or on the soot particulate filter or else indirectly by measuring the temperature of the exhaust gas that is flowing through the soot particulate filter. For this purpose, appropriate temperature sensors can be installed upstream from, downstream from, or else in the soot particulate filter.

[0055] FIGS. 2 and 3 show schematic depictions of an internal combustion engine in a motor vehicle that is suitable for carrying out the method according to the invention.

[0056] FIG. 2 schematically shows an internal combustion engine 1 having four cylinders 2 (see FIG. 3), each of which has an inlet valve 3 and an outlet valve 4. The fresh air feed is regulated by means of an intake pipe 5 with a throttle valve 6. The exhaust gas flows through an exhaust tract 7 in which an oxidation catalytic converter 8 and a particulate filter 9 are arranged consecutively as seen in the flow direction.

[0057] There are temperature sensors 10 upstream and downstream from the oxidation catalytic converter, whereas there are pressure sensors 11 upstream and downstream from the soot particulate filter 9.

[0058] Two alternatives are presented for the valve regulation. In this context, the inlet valve 3 is actuated by means of a camshaft control unit 12, and a control element 13 is shown for the inlet valve 4. The camshaft control unit 12 and the control element 13 constitute alternatives that can be realized alternatingly as well as in combination, that is to say, both the outlet valve 4 and the inlet valve 3 can be actuated by means of a control element 13, and conversely, the inlet valve 3 and the outlet valve 4 can be actuated by means of a camshaft control unit.

[0059] The engine is controlled by means of a control unit 14 (ECU) that is connected via signal lines to the throttle valve 6, to the camshaft control unit 12, to the control element 13, to the temperature sensors 10, to the pressure sensors 11 and to the gas pedal 15, by means of whose actuation a driver request (power demand) can be defined.

[0060] The internal combustion engine 1 is a component of a motor vehicle 100 and can also be integrated, for example, within the scope of a hybrid drive concept involving one or more electric motors.

[0061] The method presented above will now be carried out in the internal combustion engine 1 depicted in FIG. 2. The load value of the soot particulate filter 9 is ascertained by means of the pressure sensors 11, which determine a pressure drop or pressure differential between the inlet side and the outlet side of the soot particulate filter 9. A load value of the soot particulate filter 9 can be ascertained on this basis. As an alternative or in addition to this, the load value can also be modeled by the control unit 14 in that the soot particle load over a given period of time can be ascertained by detecting the operating points. In this manner, it is possible ascertain whether the load value has reached a regeneration value at which the soot particulate filter 9 has to be regenerated.

[0062] In parallel to this, the exhaust gas temperature or the operating temperature of the soot particulate filter 9 is measured by means of one or both temperature sensors 10 in that the exhaust gas temperature is measured. In alternative embodiments, it is also possible to install a measuring sensor directly on or in the soot particulate filter 9.

[0063] If the load value of the soot particulate filter corresponds to a regeneration value and if the operating temperature of the soot particulate filter corresponds to a regeneration temperature (for instance, above 450 C. or at 600 C.), then the actual regeneration process is initiated.

[0064] If the operating temperature does not correspond to the regeneration temperature, in other words, if the operating temperature is below the regeneration temperature, then the soot particulate filter 9 is heated up, either by means of external heating measures or else by means of heating measures effectuated by the engine (increasing the load point, additional fuel injection).

[0065] In order to start the regeneration procedure, one or more cylinders 2b are switched off. In FIG. 3, the switched-off cylinders 2b are marked with an X, while the outer cylinders 2a continue to be operated. Since the oxygen demand is lower for the regeneration than for the fuel combustion, the fresh air feed is adjusted by means of the cylinder valves (inlet valve 3 and/or outlet valve 4).

[0066] Within the scope of the method, an engine control unit 14 actuates the camshaft control unit 12 in such a way that a cylinder cam is activated which establishes a reduced opening cross section, thus diminishing the amount of fresh air.

[0067] As an alternative, this can be done by means of control elements 13 which correspondingly actuate either the inlet valve and/or the outlet valve. In this context, the control element 13 is likewise regulated by means of the control unit 14. In this operating state, the outer cylinders 2a continue to run in the normal mode of operation while the inner cylinders 2b run as fresh-air pumps, whereby the fresh air feed and thus the volume of oxygen are regulated by means of the cylinder valves 3, 4. The exhaust gas that has been enriched with additional fresh air is conveyed via the oxidation catalytic converter into the soot particulate filter 9, where the oxygen triggers and effectuates the soot combustion in the soot particulate filter 9.

[0068] By means of the control unit 14, a driver request (power demand) that has been selected prior to the regeneration is still maintained in that the power loss caused by the de-activation of the inner cylinders 2a is compensated for by a load increase of the two outer cylinders 2b. The regulation is thus carried out in such a way that the change in the operating state from normal operation over to regeneration operation does not affect the driver request and such a change is hardly noticeable. At the same time, increasing the load point of the two outer cylinders raises the temperature of the exhaust gas, as a result of which the soot particulate filter 9 can be additionally heated up which, in turn, promotes the burn-off of the soot accumulations.

[0069] In this process, the control unit 14 carries out the method according to FIG. 1. The internal combustion engine shown is especially configured as a gasoline engine with direct fuel injection and it is a component of the motor vehicle 100.

[0070] The person skilled in the art can derive other variants and embodiments of the invention on the basis of the claims.

LIST OF REFERENCE NUMERALS

[0071] 1 internal combustion engine [0072] 2 cylinders [0073] 2a outer cylinders [0074] 2b inner cylinders [0075] 3 inlet valve [0076] 4 outlet valve [0077] 5 intake pipe [0078] 6 throttle valve [0079] 7 exhaust tract [0080] 8 oxidation catalytic converter [0081] 9 particulate filter, soot particulate filter, gasoline particulate filter [0082] 10 temperature sensors [0083] 11 pressure sensors [0084] 12 camshaft control unit [0085] 13 control element [0086] 14 control unit [0087] 15 gas pedal [0088] 100 motor vehicle