Method For Operating An Exhaust Gas Cleaning System Arranged In The Exhaust Line Of An Internal Combustion Engine, And Exhaust Gas Cleaning System

Abstract

A method for operating an exhaust-gas purification system which is arranged in the exhaust system of an internal combustion engine, and an exhaust-gas purification system, are described. In the method, a combination of electrical catalytic converter heating measures with internal combustion engine catalytic converter heating measures is implemented, whereby particularly fast and inexpensive heating of a catalytic converter is achieved. The corresponding exhaust system preferably has, in an exhaust-gas flow direction, firstly a support catalytic converter and then a heated catalytic converter.

Claims

1. A method for operating an exhaust-gas purification system arranged in an exhaust system of an internal combustion engine and having a heated catalytic converter for preheating a catalytic converter to bring the catalytic converter to its light-off temperature before a starting of the internal combustion engine, the method comprising: electrically heating the heated catalytic converter before the starting of the internal combustion engine; operating the internal combustion engine, before the starting thereof, as an air pump; thereafter starting the internal combustion engine; and bringing the catalytic converter above the light-off temperature of the catalytic converter before the starting of the internal combustion engine by way of the internal combustion engine being controlled, during its air pump operating mode, such that air is drawn back into a combustion chamber and/or air is discharged into an intake tract.

2. The method of claim 1, wherein the internal combustion engine is controlled, during the air pump operating mode, such that there is an increased valve overlap between outlet valves and inlet valves.

3. The method of claim 1, further comprising: reducing an intake pipe pressure during the air pump operating mode and of the internal combustion engine.

4. The method of claim 1, further comprising: reducing a rotational speed of the internal combustion engine during the air pump operating mode.

5. The method of claim 1, further comprising: closing a throttle flap of the internal combustion engine further during the air pump operating mode.

6. The method of claim 1, wherein the heated catalytic converter preheats a three-way catalytic converter.

7. An exhaust-gas purification system arranged in an exhaust system of an internal combustion engine, the exhaust-gas purification system comprising, in an exhaust-gas flow direction: a support catalytic converter; and a heated catalytic converter positioned after the support catalytic converter, the heated catalytic converter for preheating a catalytic converter in order to bring the catalytic converter to its light-off temperature before a starting of the internal combustion engine, the exhaust-gas purification system configured to execute a method comprising: electrically heating the heated catalytic converter before the starting of the internal combustion engine; operating the internal combustion engine, before the starting thereof, as an air pump; thereafter starting the internal combustion engine; and bringing the catalytic converter above the light-off temperature of the catalytic converter before the starting of the internal combustion engine by way of the internal combustion engine being controlled, during its air pump operating mode, such that air is drawn back into a combustion chamber and/or air is discharged into an intake tract.

8. The exhaust-gas purification system of claim 7, wherein the internal combustion engine is controlled, during the air pump operating mode, such that there is an increased valve overlap between outlet valves and inlet valves.

9. The exhaust-gas purification system of claim 7, wherein the method further comprises: reducing an intake pipe pressure during the air pump operating mode and of the internal combustion engine.

10. The exhaust-gas purification system of claim 7, wherein the method further comprises: reducing a rotational speed of the internal combustion engine during the air pump operating mode.

11. The exhaust-gas purification system of claim 7, wherein the method further comprises: closing a throttle flap of the internal combustion engine further during the air pump operating mode.

12. The exhaust-gas purification system of claim 7, wherein the heated catalytic converter preheats a three-way catalytic converter.

Description

DESCRIPTION OF DRAWINGS

[0024] FIG. 1 is a highly schematic illustration of an exemplary exhaust-gas purification system; and

[0025] FIG. 2 is a highly schematic block diagram of an internal combustion engine with an exemplary exhaust-gas purification system.

[0026] Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

[0027] In the present case, the aim is to achieve fast heating of a catalytic converter 3, which may, for example, be a three-way catalytic converter that is arranged in the exhaust system 4 of an internal combustion engine 6. A heated catalytic converter 2, which is configured as an electrically heated honeycomb body, serves for rapid heating of the catalytic converter 3. The system furthermore has a support catalytic converter 1, which is likewise configured as a honeycomb body.

[0028] By contrast to the prior art, in which, in a flow direction, the heated catalytic converter is arranged first and is followed by the support catalytic converter, it is the case in the solution described here that, in the exhaust-gas flow direction, the support catalytic converter 1 is arranged first and is followed by the heating catalytic converter 2, which has an electrical connection 7. The exhaust gas therefore flows firstly into support catalytic converter 1 and then into the heated catalytic converter 2. This arrangement offers the advantage that the catalytic converter system can be heated at two points. The internal combustion engine heats the support catalytic converter 1, and the heated catalytic converter 2 heats the downstream catalytic converter (three-way catalytic converter).

[0029] In the present case, the aim is to bring the catalytic converter to its light-off temperature as quickly as possible, in order that, during the starting of the internal combustion engine as combustion motor, the catalytic converter can already perform the desired pollutant conversion. For this purpose, electrical catalytic converter heating measures (with the aid of the heated catalytic converter 2) are combined with internal combustion engine catalytic converter heating measures. The corresponding procedure is illustrated schematically in FIG. 2.

[0030] The procedure is such that the internal combustion engine is operated as an air pump until it is started. For this purpose, the internal combustion engine, with the injection deactivated, is cranked by an electric machine, for example by a belt-type starter generator, or is driven by an electric motor in a P1-P4 hybrid configuration. In addition to the electric heating of the heated catalytic converter 2, the internal combustion engine 6 is controlled, during the air pump operating mode thereof, such that air is drawn back into the combustion chamber and/or air is discharged into the intake tract. This may be implemented by various measures individually or jointly, for example by virtue of the throttle flap in the air intake channel 5 being closed further, by way of a corresponding valve adjustment of the outlet valves and inlet valves so as to result in an increased valve overlap, and/or by way of a reduction of the rotational speed of the internal combustion engine 6 during the air pump operating mode thereof. In any case, a temperature increase is achieved as a result, such that rapid and inexpensive heating of the catalytic converter is achieved overall.

[0031] In some examples, assuming a light-off temperature of the catalytic converter of 300° C., this light-off temperature will be reached before the starting of the internal combustion engine, for example within 15 seconds before the start, wherein the internal combustion engine is operated as an air pump during this period.

[0032] A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.