阅读说明：本技术 用于对内燃机进行废气后处理的方法 (Method for exhaust gas aftertreatment of an internal combustion engine ) 是由 D.康兹尔曼 G.施果伊 G.科纳蒂 J.泽勒 于 2019-06-05 设计创作，主要内容包括：本发明涉及具有进气路段和废气线路的内燃机的废气后处理用的方法。进气路段中布置电驱动的压缩机。废气涡轮增压器布置在进气路段和废气线路中。至少一个SCR催化器在废气线路中布置在废气涡轮增压器下游。在第一运行状态(B1)下SCR催化器的温度高于温度阈值,废气涡轮增压器以第一涡轮几何姿态运行,这引起进气管中第一空气压缩。在第二运行状态(B2)下SCR催化器的温度低于温度阈值,废气涡轮增压器以第二涡轮几何姿态运行(S04),这引起进气管中第二空气压缩,其在数值上低于第一空气压缩。在第二运行状态(B2)下运行(S05)压缩机使其在进气管中引起第三空气压缩,其与第二空气压缩一起产生总压缩,总压缩至少相应于第一空气压缩。(The invention relates to a method for exhaust gas aftertreatment of an internal combustion engine having an intake section and an exhaust gas line. An electrically driven compressor is arranged in the intake section. An exhaust gas turbocharger is arranged in the intake section and the exhaust gas line. At least one SCR catalyst is arranged downstream of the exhaust gas turbocharger in the exhaust gas line. In a first operating state (B1), in which the temperature of the SCR catalyst is above a temperature threshold, the exhaust gas turbocharger is operated with a first turbine geometry, which leads to a first compression of air in the intake tract. In a second operating state (B2) in which the temperature of the SCR catalyst is below the temperature threshold, the exhaust gas turbocharger is operated with a second turbine geometry (S04), which causes a second air compression in the intake pipe that is lower in value than the first air compression. Operating (S05) the compressor in a second operating state (B2) causes a third air compression in the intake pipe, which together with the second air compression produces a total compression which corresponds at least to the first air compression.)

1. Method for the exhaust-gas aftertreatment of an internal combustion engine (10) having an intake section (11) and an exhaust gas line (12), wherein an electrically driven compressor (20) is arranged in the intake section (11), an exhaust gas turbocharger (30) is arranged in the intake section (11) and in the exhaust gas line (12), and at least one SCR catalyst (40) is arranged downstream of the exhaust gas turbocharger (30) in the exhaust gas line (40), characterized in that,

-in a first operating state (B1), in which the temperature of the SCR catalyst (40) is above a temperature threshold, the exhaust gas turbocharger (30) is operated with a first turbine geometry, which leads to a first air compression in the intake section (11), and

-in a second operating state (B2), in which the temperature of the SCR catalyst (40) is below a temperature threshold, the exhaust gas turbocharger (30) is operated (S04) at a second turbine geometry, which leads to a second air compression in the intake section (11), which is lower in value than the first air compression, wherein operating (S05) the compressor (20) in the second operating state (B2) such that it leads to a third air compression in the intake section (11), which together with the second air compression leads to a total compression, which at least corresponds to the first air compression.

2. The method of claim 1, wherein the compressor (20) is operated in the second operating state (B2) such that the third air compression together with the second air compression produces a total compression that is greater than the first air compression.

3. The method according to claim 2, characterized in that the internal combustion engine (10) is operated (S07) in the second operating state (B2) with a higher injection quantity than in the first operating state (B1).

4. The method according to claim 3, characterized in that an electric recuperation system (70) is operated (S08) in the second operating state (B2) such that the torque output by the internal combustion engine (10) and/or the power output by the internal combustion engine (10) corresponds to the torque output by the internal combustion engine (10) and/or the power output by the internal combustion engine (10) in the first operating state (B1) after deduction of the torque consumption and/or the power consumption of the recuperation system (70).

5. The method according to any one of claims 2-4, characterized in that the internal combustion engine (10) is operated (S09) in the second operating state (B2) with a higher low-pressure exhaust gas recirculation rate than in the first operating state (B1).

6. The method as claimed in any of claims 2 to 5, characterized in that the internal combustion engine (10) is operated in the second operating state (B2) with the same combustion air ratio as in the first operating state (B1).

7. A computer program arranged to: performing each step of the method according to any one of claims 1 to 6.

8. A machine-readable storage medium on which a computer program according to claim 7 is stored.

9. An electronic control device (80) arranged to: exhaust gas aftertreatment of an internal combustion engine by means of a method according to any one of claims 1 to 6.

Technical Field

The invention relates to a method for exhaust gas aftertreatment of an internal combustion engine which, in addition to an exhaust gas turbocharger, also comprises an electrically driven compressor. Furthermore, the present invention relates to a computer program for implementing each step of the method, and a machine-readable storage medium storing the computer program. Finally, the invention relates to an electronic control device which is provided for carrying out the method.

Background

in order to comply with increasingly stringent exhaust gas legislation, it is necessary to reduce the nitrogen oxides in the exhaust gas of internal combustion engines, in particular diesel motors, for this purpose it is known to arrange in the exhaust gas circuit an SCR catalyst (Selective Catalytic Reduction) which reduces the nitrogen oxides contained in the exhaust gas of an internal combustion engine to nitrogen by means of a reducing agent, whereby the content of nitrogen oxides in the exhaust gas can be significantly reduced^®。

The SCR reaction in the SCR catalyst proceeds only with high efficiency at high local temperatures. Therefore, it is desirable to heat the SCR catalyst as quickly as possible after the internal combustion engine is started. This is done by the exhaust gas flowing into the SCR catalyst. If the internal combustion engine has a conventional exhaust gas turbocharger which drives a turbine in the exhaust gas line, it produces a cooling effect on the exhaust gas flow, which counteracts the desired rapid heating of the SCR catalyst.

Disclosure of Invention

The method is used for exhaust gas aftertreatment of an internal combustion engine having an intake section and an exhaust gas line. An electrically driven compressor, which may also be referred to as E-Charger or E-Booster, is arranged in the intake section. Exhaust gas turbochargers are arranged in the intake section and in the exhaust gas line. This means that the exhaust gas turbocharger has a turbine in the exhaust gas line, which turbine is connected via a shaft to a compressor in the intake section. The exhaust gas flow of the internal combustion engine drives the turbine. The rotational movement of the turbine is transmitted to the compressor by means of a shaft. This results in compression of the air in the intake section. The internal combustion engine furthermore has at least one SCR catalyst, which is arranged in the exhaust gas line. The SCR catalyst is located downstream of the exhaust gas turbocharger in the exhaust gas line.

The method provides a first operating state in which the temperature of the SCR catalyst is above a temperature threshold value and a second operating state in which the temperature of the SCR catalyst is below the temperature threshold value. The temperature of the SCR catalyst can be measured, for example, by means of a temperature sensor. In a first operating state, the exhaust-gas turbocharger is operated with a first turbine geometry. This causes a first compression of air in the intake section. The first operating state corresponds in particular to a conventional operating state of the internal combustion engine, and therefore a first turbine geometry (turbine ersteturbinegeometry) can be selected as a function of a conventional operating mode of the exhaust-gas turbocharger.

In a second operating state, the exhaust gas turbocharger is operated with a second turbine geometry. The change in turbine geometry may be accomplished, for example, by adjusting a Variable Turbine Geometry (VTG). The second turbine geometry is selected such that it causes a second air compression in the intake section that is lower in value relative to the first operating state. This means that it produces a boost pressure at the compressor outlet which is lower than the pressure produced by the first air compression. In addition to the exhaust-gas turbocharger, the electrically driven compressor is also operated in the second operating state. The electrically driven compressor is operated such that it causes a third air compression in the intake section, which third air compression together with the second air compression produces a total compression which corresponds at least to the first air compression. This results in a charging pressure at the intake port of the cylinder of the internal combustion engine which corresponds at least to the charging pressure which occurs in the first operating state.

The second operating state can be realized in particular by way of its digitization and calculation independently of the first operating state. For this purpose, different target values are set for the actuation of the variable turbine geometry and for the actuation of the electrically driven compressor than in the first operating state. No subsequent comparison with the first operating state is required.

The temperature threshold value may be selected such that the transition to the second operating state is carried out when a superordinate coordinator in the electronic control unit of the internal combustion engine requests a heating operation of the SCR catalytic converter. By changing the turbine geometry in the second operating state, a smaller enthalpy quantity is extracted by the turbine in the exhaust gas line than in the first operating state, so that the temperature drop caused by the turbine is reduced. The SCR catalyst is therefore loaded by the hotter gases and thus heats up more quickly.

The exhaust gas turbocharger contributes to an increase in the boost pressure of the internal combustion engine only to a lesser extent due to the change in the geometry of the turbine. But this can be compensated for by means of an electrically driven compressor.

preferably, the electrically driven compressor is operated in the second operating state such that the third air compression together with the second air compression produces a total compression which is greater than the first air compression. In this way, the reduction in the boost pressure due to the change in the turbine geometry is compensated for by means of the electrically driven compressor, but also even overcompensated, so that the boost pressure is increased compared to the first operating state. The additional boost pressure can be used actively in various ways in the sense of the whole system.

in one embodiment of the method, the internal combustion engine is operated in the second operating state with a higher injection quantity than in the first operating state, which can be achieved by filling the cylinder charge (zylinderfuelung) of the internal combustion engine with fresh air, which increases in accordance with an increase in the charging pressure.

In this embodiment, it is particularly preferred to operate the electric recuperation system in the second operating state such that, after deduction of the torque and/or power consumption of the recuperation system, the torque output by the internal combustion engine and/or the power output by the internal combustion engine corresponds to the torque output by the internal combustion engine and/or the power output by the internal combustion engine in the first operating state. Since the torque and/or the total power output by the motor (including the internal combustion engine and the recovery system) is unchanged compared to the first operating state, in this embodiment of the invention, the driver of a motor vehicle driven by the internal combustion engine, for example, does not perceive a change in the driving performance of the motor vehicle. The recuperation system can use the additionally obtained torque or the additionally obtained power to charge the battery of the motor vehicle. The electrical energy obtained and stored in this way can then be extracted again, for example from a battery, in order to drive an electrically driven compressor.

In a further embodiment of the method, the internal combustion engine is operated in a second operating state, which has a higher low-pressure exhaust gas recirculation rate than in the first operating state. This is also achieved in particular with maintaining the combustion air ratio of the first operating state. This can be achieved by mixing a larger amount of exhaust gas via the low-pressure exhaust gas recirculation line, while keeping the injection quantity of the cylinder charge constant. An increased exhaust gas recirculation rate in this way leads to a reduction in the original emissions of nitrogen oxides. Low-pressure exhaust gas recirculation is understood here to mean exhaust gas recirculation which is introduced upstream of the compressor of the exhaust gas turbocharger.

it can be provided that, by means of a coordinator function in the electronic control unit of the internal combustion engine, in particular based on a quality function (gutefull) that balances the primary emissions of nitrogen oxides and the desired charging of the battery, in the second operating state it is set that an additional boost pressure should be used in order to increase the injection quantity or to increase the low-pressure exhaust gas recirculation rate.

The computer program is provided to carry out each step of the method, in particular when the computer program runs on a computing device or an electronic control device. To this end, the computer program is stored on a machine-readable storage medium. By running the computer program on a conventional electronic control unit, an electronic control unit is obtained which is provided for carrying out an exhaust gas aftertreatment of the internal combustion engine by means of the method.

Drawings

An embodiment of the invention is illustrated in the drawings and will be described in detail in the following description.

FIG. 1 schematically illustrates an internal combustion engine system, exhaust after-treatment of which may be performed according to a method according to an embodiment of the invention;

FIG. 2 shows a flow diagram of a method for exhaust aftertreatment according to an embodiment of the invention.

Detailed Description

The internal combustion engine 10 shown in fig. 1 has an intake section 11 and an exhaust gas line 12 in one exemplary embodiment of the invention. A charge air cooling device 13 is arranged in the intake section 11. An electrically driven compressor 20 is arranged in the intake section 11 between the charge air cooling device 13 and a further cooling device 21. A first bypass 22 in the intake section 11 bypasses the further cooling device 21 and the electrically driven compressor 20. The first bypass can be opened and closed by means of a first bypass valve 23. The exhaust-gas turbocharger 30 is arranged such that its turbine is inserted into the exhaust-gas line 12 and is driven there by exhaust gas, and its compressor is inserted into the intake section 11 upstream of the further cooling device 21 and the bypass 22. The exhaust gas turbocharger 30 has a variable turbine geometry 31. An SCR catalyst 40 is arranged in the exhaust line 12 downstream of the exhaust gas turbocharger 30. The SCR catalyst has a temperature sensor 41. A high-pressure exhaust-gas recirculation line 50 branches off from the exhaust gas line 12 upstream of the exhaust gas turbocharger 30 and opens into the intake section 11 downstream of the charge air cooling device 13. The high-pressure exhaust gas recirculation line can be opened and closed by means of a high-pressure exhaust gas recirculation valve 51. A low-pressure exhaust-gas recirculation line 60 branches off from the exhaust gas line 12 between the exhaust gas turbocharger 30 and the SCR catalyst 40 and opens into the intake section 11 upstream of the exhaust gas turbocharger 30. The low-pressure exhaust gas recirculation line can be opened and closed by means of a low-pressure exhaust gas recirculation valve 61. An exhaust gas recirculation cooling device 62 is arranged in the low-pressure exhaust gas recirculation line 60 between the low-pressure exhaust gas recirculation valve 61 and the exhaust gas line 12. The second bypass 63 is able to bypass the exhaust gas recirculation cooling device 62. The second bypass may be opened and closed by means of a second bypass valve 64.

A Boost Recovery System (BRS) 70 is coupled to the internal combustion engine 10 via a driveline, not shown, and includes an electric motor, not shown. When the motor vehicle is braked, the recuperation system 70 can be used to feed back excess energy via the 48 volt vehicle circuit to the lithium ion battery or to directly operate an electrical consumer, such as in particular also an electrically driven compressor.

The components shown are controlled by an electronic control device 80. An embodiment of the method according to the invention is run as a computer program here. Which is shown in figure 2.

After the internal combustion engine 10 is started S01, the temperature of the SCR catalyst 40 is measured by means of the temperature sensor 41. If the temperature is already above a temperature threshold (which is the temperature at which the SCR catalyst 40 has reached good efficiency from here), the system is operated in a first operating state B1. This corresponds to the conventional manner of operation of the internal combustion engine 10 and other components of the system. In contrast, if it is recognized in step S02 that the temperature is lower than the temperature threshold, the heating operation is requested. For this purpose, the system changes to the second operating state B2. This second operating state is first digitized and calculated in step S03 by reading parameters relating to the operation of the electrically driven compressor 20, the turbine geometry of the exhaust gas turbocharger 30 and the low-pressure exhaust gas recirculation line 60 from a data record (Datensatz) which also contains data relating to the first operating state B1. The turbine geometry of the exhaust gas turbocharger 30 is adjusted by means of the variable turbine geometry 31 so that the next operation S04 of the exhaust gas turbocharger takes place with the turbine geometry, which causes a smaller air compression in the intake section 11 than the turbine geometry of the first operating state B1. It is then calculated how much additional compression is required in the intake section 11 in order to make the boost pressure greater than that of the first operating state B1. The compressor 20 is operated S05 to achieve this compression. For this purpose, the first bypass valve 23 is closed and the compressor 20 is electrically driven.

Now, the coordinator function S06 verifies based on the quality function: it is preferable to reduce the primary emissions of nitrogen oxides or to charge the battery during the current operation of the internal combustion engine 10. In order to charge the battery, a further operation S07 of the internal combustion engine 10 is carried out, which is achieved by filling the cylinder charge of the internal combustion engine 10, which is increased in accordance with the increase in the charging pressure (compared to the first operating state B1), with fresh air and by increasing the fuel injection quantity in the internal combustion engine 10. Furthermore, the recovery system 70 is operated S08 such that the torque output by the internal combustion engine 10 remains unchanged compared to the torque output by the internal combustion engine 10 in the first operating state B1 after deduction of the torque consumption of the recovery system 70. The recovery operation charges the battery. Conversely, if it is preferable to reduce the original emission of nitrogen oxides, the S09 low-pressure exhaust gas recirculation rate is increased by further opening the low-pressure exhaust gas recirculation valve 61 as compared to the first operating state B1. The coordinator may also be arranged to combine these two measures with each other, wherein steps S07 and S08 run simultaneously with step S09. The weighting (Gewichtung) between steps S07 and S08 and S09 is performed based on a quality function.

After all parameters of the second operating state B2 have been set in this way, a continuous test S10 is carried out, whether the temperature of the SCR catalyst 40 is still below the temperature threshold. If the temperature threshold is exceeded, no further heating operation is required. In step S11, all operating parameters are reset to the values of the first operating state B1. The method then ends in a final step S12.