CN113574257A

CN113574257A - Method and device for regenerating a coated particle filter in the exhaust gas system of a motor vehicle operated with gasoline

Info

Publication number: CN113574257A
Application number: CN202080024281.8A
Authority: CN
Inventors: F·克莱纳; E·阿克莱特纳; H·库尼亚万; G·哈夫特; S·科洛德齐吉; P·罗达茨
Original assignee: Vitesco Technologies GmbH
Current assignee: Vitesco Technologies GmbH
Priority date: 2019-03-25
Filing date: 2020-03-17
Publication date: 2021-10-29
Anticipated expiration: 2040-03-17
Also published as: DE102019219892A1; CN113574257B

Abstract

The invention relates to a method for regenerating a coated particle filter in an exhaust system of a motor vehicle operated with gasoline, wherein the amount of secondary air introduced into the exhaust system is regulated, wherein the actual value for the regulation is provided by a sensor arranged downstream of the particle filter, and wherein the regulation is carried out such that an air coefficient existing downstream of the particle filter oscillates around a stoichiometric air coefficient. The invention further relates to a device for regenerating a coated particle filter in the exhaust gas system of a motor vehicle operated with gasoline.

Description

Method and device for regenerating a coated particle filter in the exhaust gas system of a motor vehicle operated with gasoline

Technical Field

The invention relates to a method and a device for regenerating a coated particle filter in the exhaust gas system of a motor vehicle operated with gasoline.

Background

Increasingly stringent emission limits to which the law is to be applied place ever higher demands on the exhaust gas system of the motor vehicle. To meet these requirements, different exhaust emission reduction strategies must be applied simultaneously. These different exhaust emission reduction strategies use different components, including the respective associated sensor devices.

In addition to reducing fuel consumption and thus CO₂Besides emissions, the reduction of gaseous emissions of CO, NOx and HC by means of one or more exhaust catalysts and the reduction of particulate emissions by means of particulate filters is an important development objective.

Particulate filters for diesel internal combustion engines, which are also often referred to as soot filters, have been used for a long time and have proven effective in practice.

Also knownIn the exhaust gas system of internal combustion engines operated with gasoline, particles are also produced, in particular in internal combustion engines having direct fuel injection systems, in which the fuel is introduced directly into the combustion chamber with high pressure and atomized very finely. Therefore, legislators also increase the limit value for particulate emissions for gasoline-operated internal combustion engines, which operate with direct fuel injection systems. Therefore, with the introduction of the hazardous substance standard Euro 6d, the maximum of 6x10 that is then applicable must be observed¹¹Limit value of individual particles/km.

The particle filters used for this purpose are essentially composed of a housing (so-called pot) and a monolithic structure (Monolith) inserted into the housing. The particle filter filters out the particles produced during combustion, mostly soot particles, from the exhaust gas. As long as the conditions present in the particle filter, such as, for example, increased temperature, oxygen in the exhaust gas, do not lead to a regeneration of the particle filter, the separated particles remain in the particle filter.

Temperatures above 550-. The higher the temperature, the faster the oxidation of the carbon black proceeds.

It is known to arrange a particle filter near the engine or in the floor of a motor vehicle. When the particle filter is arranged in the bottom plate, it is arranged, for example, at a distance of about 800 mm further from the engine than a particle filter arranged close to the engine. As a result, an exhaust gas temperature which is approximately 140 ℃ lower in the particle filter with the particle filter arranged in the base plate than in the particle filter arranged close to the engine is present in said particle filter.

Thus, the necessary regeneration temperature of the particle filter can only be reached in the "very high phase" of the WLPT (global light vehicle test protocol), in which there is a high driving speed, without heating measures in the exhaust gas system, in the presence of a floor arrangement of the particle filter. If the running is performed for a long time in the low speed range, the necessary particulate filter regeneration temperature of 600 c cannot be achieved.

To avoid these disadvantages, the applicant has developed a system in which secondary air is blown into the exhaust system upstream of the coated particle filter and the energy for warming up the particle filter is provided by the unburned components CO and HC by rich engine operation. The algorithm used here calculates the air ratio necessary for warming up the particle filter from the exhaust gas temperature upstream of the particle filter. The secondary air source is adjusted such that the air factor downstream of the particulate filter is in a lean range for ensuring soot oxidation in the particulate filter. With such a system, a particle filter temperature of approximately 800 ℃ can be achieved even in idle, which is significantly higher than the minimum temperature necessary for the regeneration of the particle filter.

In the case of a high thermal inertia of the exhaust gas system up to the floor particulate filter, the particulate filter is arranged at a distance from the engine, and the temperature necessary for the regeneration of the particulate filter can be reached at a later ignition time for the low-speed range without comfort loss. Since the heating measure must be much more powerful than for the purpose of rapidly reaching the ignition temperature ("light-off temperature") of the particle filter in the vicinity of the engine, a limiting factor is the detection of a misfire in the engine control. With the bottom plate arrangement of the particle filter, the particle filter regeneration temperature is reached without heating measures only by acceleration in the high speed range.

Since energy is required for warming up the particle filter by substoichiometric operation, 10% additional fuel consumption occurs during the regeneration of the particle filter. Since the particle filter is only warmed up and the thermal inertia of the exhaust gas turbocharger of the motor vehicle and of the catalyst close to the engine does not play a role, the additional consumption of fuel during regeneration is minimized. When the catalyst is heated for regenerating the particle filter by means of a delay in the ignition and lean operation (magerberreb), an additional consumption of 33% occurs without the temperature required for regeneration being reached. Furthermore, the nitrogen oxide conversion of the catalytic converter is deactivated as a result of lean-burn engine operation, as a result of which a large increase in nitrogen oxide emissions results.

In the case of regeneration of a particle filter with a secondary air heating, an increase in the nitrogen oxide emissions occurs. In substoichiometric operation of an internal combustion engine, NH is formed in a Pt/Rh catalyst₃NH of the catalyst₃In Pt/Rh-coated particle filters, in the event of an excess of oxygen, the particles are oxidized again to nitrogen oxides, so that an undesirable increase in nitrogen oxides occurs during regeneration.

Disclosure of Invention

The object of the present invention is to provide a method and a device with which the regeneration of a coated particle filter of an internal combustion engine can be carried out in a reliable manner without increased pollutant emissions.

This object is achieved by a method having the features specified in claim 1. Advantageous embodiments and refinements are specified in the dependent claims 2 to 16. The subject matter of claim 17 is a device for regenerating a coated particle filter in the exhaust system of a motor vehicle operated with gasoline.

In a method having the features specified in claim 1, the amount of secondary air which is conducted into the exhaust gas system of a motor vehicle which is operated with gasoline is regulated in order to regenerate a coated particle filter in the exhaust gas system, wherein the actual value for the regulation is provided by a sensor which is arranged downstream of the particle filter, and wherein the regulation is carried out in such a way that the air coefficient which is present downstream of the particle filter oscillates around a stoichiometric air coefficient (λ ═ 1).

According to one embodiment of the invention, the actual value is provided by a nitrogen oxide sensor arranged downstream of the particle filter.

According to another embodiment of the invention, said actual value is provided by a lambda sensor arranged downstream of the particulate filter.

According to another embodiment of the invention, said actual value is provided by an ammonia sensor arranged downstream of the particulate filter.

According to one embodiment of the invention, the secondary air quantity is increased if a change in the lambda value in the rich direction is detected.

According to one embodiment of the invention, the secondary air quantity is increased if an increase in the ammonia content in the exhaust gas is detected.

According to one embodiment of the invention, the secondary air quantity is increased if the calculated negative oxygen quantity extracted from the particle filter during the phase in which the secondary air injection is switched off is below a predetermined threshold value.

According to one embodiment of the invention, the secondary air quantity is reduced if a change in the lambda value in the lean direction is detected.

According to one embodiment of the invention, the secondary air quantity is reduced if an increase in nitrogen oxide emissions is detected.

According to one embodiment of the invention, the secondary air quantity is reduced if the oxygen quantity calculated during the active secondary air blowing phase exceeds a predetermined threshold value.

According to one embodiment of the invention, the respectively necessary secondary air quantity is provided by a secondary air source.

According to one embodiment of the invention, the secondary air source is an air pump.

According to one embodiment of the invention, the secondary air source is a scavenge pump.

According to one embodiment of the invention, the respectively necessary secondary air quantity is adjusted by a change in the rotational speed of the air pump.

According to one embodiment of the invention, the respectively necessary secondary air quantity is provided by an e-compressor.

According to one embodiment of the invention, the respectively necessary secondary air quantity is provided by a clock control of the secondary air valve or a variable opening cross section of the secondary air valve.

Drawings

The advantage of the invention is, in particular, that the invention enables regeneration of the particle filter even at low driving speeds without a loss in drivability. A further advantage of the invention is that the pollutant emissions, in particular nitrogen oxide emissions, which occur, are kept low. Further advantageous characteristics of the invention result from the following exemplary explanation thereof with the aid of the drawing. In which is shown:

figure 1 shows a sketch of a device for regenerating a coated particle filter in the exhaust system of a motor vehicle running on gasoline,

figure 2 shows a schematic view of a part of an exhaust system of a motor vehicle running on gasoline,

fig. 3 shows a first diagram for explaining a method for regenerating a particulate filter, and

fig. 4 shows a second diagram for explaining a method for regenerating a particle filter.

Detailed Description

Fig. 1 shows a schematic representation of a device for regenerating a coated particle filter in the exhaust system of a motor vehicle operated with gasoline.

The activated carbon container 1 connected to the fuel tank 5 belongs to the device shown in fig. 1. Fresh air is supplied to this activated carbon container 1 through an air filter 8. Further, the activated carbon container 1 is connected to a tank vent valve 4 via a scavenge pump 2. A pressure sensor 3 is positioned in the line between the scavenge pump 2 and the tank vent valve 4.

The mass flow flowing through the tank ventilation valve 4 is conducted upstream of the compressor 10 into the air path 9 of the motor vehicle and mixed there with the fresh air to be compressed, which is supplied to the air path 9 via a further air filter 7.

The compressor 10 is part of an exhaust-gas turbocharger which furthermore comprises a turbine 17 which is connected to the compressor 10 via a shaft which is outlined by a dashed line.

The mass flow compressed by means of the compressor 10 is supplied to a crankcase 15 of the motor vehicle via the charge air cooler 11 and the throttle 13 in the further course of the air path 9 and is injected there together with fuel into the combustion chamber of the motor vehicle, wherein the fresh air flow supplied via the air filter 7 and the mass flow flowing through the tank ventilation valve 4 belong to the aforementioned mass flow.

Between the charge air cooler 11 and the throttle 13, a pressure sensor 12 is arranged in the air path 9. Between the throttle 13 and the crankcase 15, a further pressure sensor 14 is arranged in the air path 9. The exhaust gases formed during the combustion process are supplied via an exhaust gas system 16 to a turbine 17 and are used in the turbine to drive a turbine wheel, which drives a compressor wheel provided in the compressor via a shaft. The exhaust gas output by the turbine 17 is fed via a three-way catalyst 18 and a four-way catalyst 19 with a particle filter to an exhaust gas end pipe, not shown, of the motor vehicle and is output via this to the environment.

For controlling the combustion process, an engine control unit 6 is provided, which provides an output signal 21 on the basis of an input signal 20 supplied thereto and stored operating software. The input signals 20 supplied to the engine control unit 6 are, in particular, sensor signals and data signals provided by a higher-level control unit. For example, pressure sensor signals, temperature sensor signals and accelerator pedal position signals belong to the sensor signals. In particular, the control signals for the injection valves and the tank ventilation valve 4 belong to the output signal 21 of the engine control unit 6.

The arrangement shown in fig. 1 also has a secondary air path 29 which leads from the scavenging pump 2 via the secondary air valve 24 upstream of the quaternary catalyst 19 into the exhaust gas system. Thus, in such an embodiment, a scavenge pump is used as the secondary air source. Downstream of the turbine 17, a plurality of sensors are arranged in the exhaust gas system. The differential pressure sensor 22 belongs to these sensors, wherein one connection of the differential pressure sensor is connected to the exhaust system upstream of the quaternary catalyst and the other connection of the differential pressure sensor is connected downstream of the quaternary catalyst. Furthermore, the control sensor 25 is the sensor mentioned, which is arranged downstream of the quaternary catalyst 19 in the exhaust gas system 16. The output signals of the sensors mentioned are supplied as input signals 20 to the engine control unit 6. The engine control unit 6 calculates its output signals 21 according to a stored algorithm, which are supplied as control signals to the actuators of the illustrated device.

In addition, these actuators comprise, in particular, a scavenging pump 2 and a secondary air valve 24, to which scavenging pump 2 and secondary air valve 24 corresponding control signals are supplied by the engine control 6, by means of which control signals the secondary air introduced into the exhaust gas system 16 is regulated.

In particular, the secondary air which is conducted into the exhaust gas system 16 is conditioned when a coated particle filter which is arranged in the exhaust gas system and is a constituent of the quaternary catalytic converter 19 is regenerated. In order to carry out such a regeneration of the particle filter, a control algorithm is stored in the engine control unit 6, which is controlled by evaluating the output signal of a control sensor 25, which is arranged downstream of the quaternary catalytic converter 19 and forms the actual value for the control, in such a way that the air coefficient λ prevailing downstream of the quaternary catalytic converter and thus downstream of the particle filter oscillates around the stoichiometric air coefficient λ ═ 1.

The control sensor 25 arranged downstream of the particle filter can be a nitrogen oxide sensor, a lambda sensor or an ammonia sensor, wherein each of these sensors can also be a combination sensor which, for example, performs the function of both the nitrogen oxide sensor and the ammonia sensor or the function of both the lambda sensor and the ammonia sensor.

In order to achieve the described oscillation of the air ratio around its stoichiometric value 1, the secondary air quantity is increased, for example, when a change in the lambda value in the rich direction is detected or when an increase in the ammonia content of the exhaust gas is detected. As an alternative, the following possibilities also exist, namely: when the calculated negative oxygen quantity extracted from the particle filter during the phase of cutting off the blowing of secondary air or reducing the secondary air quantity is below a predetermined threshold value, the secondary air quantity is increased.

In order to achieve the above-mentioned oscillation of the air ratio around its stoichiometric value 1, the secondary air quantity is reduced when a change in the lambda value in the lean direction or a rise in nitrogen oxide emissions or a calculated oxygen quantity present during the active secondary air injection phase exceeds a predetermined threshold value.

In the embodiment described with reference to fig. 1, a scavenging pump 2 is used as the secondary air source. Thus, the scavenging pump exerts a dual function. On the one hand it supports the venting process of the fuel tank 5. On the other hand, when the particulate filter is regenerated, it is used as a secondary air source.

As an alternative to the embodiment shown in fig. 1, an electrically operated air pump can also be used as secondary air source.

By suitable adjustment or variation of the rotational speed of the air pump and/or by suitable corresponding adjustment or variation of the throughflow cross section of the secondary air valve 24, a correspondingly necessary amount of secondary air can be introduced into the exhaust gas system.

An alternative possibility is to provide the respectively necessary secondary air quantity in the case of an e-compressor.

Fig. 2 shows a schematic representation of a part of an exhaust system of a gasoline-operated internal combustion engine, from which the principle operating principle of the invention can be seen. It can be seen from this illustration that a three-way catalyst 18 is arranged in the exhaust gas system 16 of the motor vehicle and a four-way catalyst 19 is arranged downstream of this three-way catalyst 18, this four-way catalyst comprising a coated particle filter having a three-way catalyst coating. It can also be seen from fig. 2 that the secondary air provided by means of the secondary air source 28 is conducted into the exhaust gas system 16 via a secondary air path 29 in which the secondary air valve 23 is arranged, and more precisely into the region between the three-way catalyst 18 and the four-way catalyst 19, i.e. upstream of the particle filter. Finally, fig. 2 shows that a control sensor 25 is arranged downstream of the four-way catalyst 19 and therefore downstream of the particle filter. The output signal of this control sensor 25 is used as an actual value for controlling the air ratio λ, which is carried out in such a way that the air ratio λ present downstream of the particle filter oscillates around the stoichiometric air ratio λ 1.

The quaternary catalyst is a coated particle filter with a three-way catalyst coating, the temperature in the quaternary catalyst being controlled by a model, wherein the fuel addition (anfetttung) upstream of the quaternary catalyst is calculated in such a way that a nominal temperature for the regeneration of the particle filter is reached.

Fig. 3 shows a first diagram for explaining the method for regenerating a particle filter according to the invention described above. In the graph, the time in s is plotted to the right and the curve of the nitrogen oxide emissions NOx in mg/km, the temperature T in DEG C, the carbon dioxide emissions CO in g/km is plotted upwards₂And the curve of the vehicle speed v in km/h and more precisely this is plotted for the case of regeneration of the particle filter with a lean air coefficient lambda and a retarded ignition timing (curve a), the case of conventional regeneration of the particle filter with injection of secondary air (curve b), the case of regeneration according to the invention of the particle filter with injection of secondary air (curve C) and the case of no regeneration of the particle filter (curve d). In particular, it can be seen from the curve shown that the high temperatures necessary for the regeneration have already been reached after a relatively short time in the regeneration according to the invention of the particle filter, which temperatures are reached despite a relatively low driving speed, and the nitrogen oxide emissions are significantly reduced compared to conventional regenerations with secondary air injection.

Fig. 4 shows a second diagram for explaining the method for regenerating a particle filter according to the invention described above. In this diagram, the time in s is plotted to the right and the change curves of I λ TWC (which is the air coefficient measured with a linear λ sensor with which the internal combustion engine has to be operated in order to reach the regeneration temperature in the quaternary catalyst), I λ GPF (which is the linear λ sensor signal of the NOx sensor after the quaternary catalyst or of an additionally arranged linear λ sensor), b λ GPF (which is the binary signal of the NOx sensor after the quaternary catalyst or of a binary λ sensor) and Fl (Fl is the secondary air quantity blown in front of the quaternary catalyst) in l/min are plotted upwards, and more precisely this is plotted for a conventional regeneration with secondary air injection (curve b) and a regeneration according to the invention with secondary air injection (curve c). It can be seen from these curves, in particular, that oscillations of the air ratio λ occur in the regeneration according to the invention.

In the present invention, as can be seen from the foregoing description, the secondary air amount is ascertained using the output signal of the conditioning sensor arranged downstream of the particulate filter as an actual value. As actual values, in particular the output signal of a nitrogen oxide sensor, a binary lambda sensor, a linear lambda sensor or an ammonia sensor can be used.

The switching on of the secondary air blowing can be carried out variably by means of one or more of the following criteria:

-a change in the binary lambda signal in the rich direction;

-a change in the linear lambda signal in the rich direction;

-an increase in ammonia emissions;

-a calculated negative oxygen quantity, which is extracted from the particle filter during the phase in which the secondary air blowing is switched off, when the negative oxygen quantity is below a predefined threshold value.

The shut-off of the secondary air blowing or the reduction of the secondary air quantity can be carried out variably by means of one or more of the following criteria:

-a change in the binary lambda signal in the lean direction;

-a change of the linear lambda signal towards lean;

-an increase in ammonia emissions;

-a calculated amount of oxygen to be delivered to the particulate filter during the active secondary air blowing phase when the amount of oxygen exceeds a pre-given threshold.

The respective necessary secondary air quantity can be adjusted by a change in the rotational speed of the scavenging pump serving as a secondary air source. This has a positive effect on low carbon monoxide and ammonia emissions.

Alternatively, the necessary secondary air quantity can be provided by a clocked secondary air valve, i.e. by opening and closing of the secondary air valve, to which the secondary air supplied by the scavenging pump is supplied in such a way that an air coefficient oscillating around the stoichiometric air coefficient exists downstream of the particle filter. However, a disadvantage which must be tolerated here is that higher emissions of carbon monoxide and ammonia occur than with the adjustment of the secondary air quantity by means of a change in the rotational speed of the scavenging pump or a change in the cross section of the secondary air valve.

In the invention described above, the air ratio for the coated particle filter is nevertheless adjusted, wherein the amount of secondary air blown into the exhaust gas system is adjusted using an adjustment sensor arranged downstream of the particle filter, and the fuel amount is not adjusted as is done when the air ratio for the three-way catalyst is conventionally adjusted.

The fuel quantity (lambda of the internal combustion engine) is used as a manipulated variable for a temperature model of the particle filter.

List of reference numerals

1 activated carbon container

2 scavenging pump

3 pressure sensor

4 oil tank ventilation valve

5 Fuel tank

6 Engine control mechanism

7 air filter

8 air filter

9 air path

10 compressor

11 charge air cooler

12 pressure sensor

13 throttle valve

14 pressure sensor

15 crankcase

16 waste gas system

17 turbine

18 three-way catalytic converter

19 particle filter

20 input signal

21 output signal

22 differential pressure sensor

23 Secondary air valve

24 secondary air valve

25 adjustment sensor

26 valve

27 pressure and temperature sensor

28 Secondary air Source

29 secondary air path.

Claims

1. Method for regenerating a coated particle filter arranged in an exhaust system of a motor vehicle operated with gasoline, characterized in that the amount of secondary air which is conducted into the exhaust system (16) is regulated, wherein the actual value for the regulation is provided by a regulation sensor (25) arranged downstream of the particle filter (19), and wherein the regulation is carried out such that the air coefficient prevailing downstream of the particle filter (19) oscillates around the stoichiometric air coefficient.

2. Method according to claim 1, characterized in that the actual value is provided by a nitrogen oxide sensor arranged downstream of the particle filter.

3. Method according to claim 1, characterized in that the actual value is provided by a lambda sensor arranged downstream of the particulate filter.

4. Method according to claim 1, characterized in that the actual value is provided by an ammonia sensor arranged downstream of the particle filter.

5. A method according to any one of claims 1 to 3, characterized in that the secondary air quantity is increased if a change in the lambda value in the direction of enrichment is detected.

6. The method according to claim 4, characterized in that the secondary air amount is increased if an increase in the ammonia content in the exhaust gas is detected.

7. Method according to any one of claims 1 to 3, characterized in that the secondary air quantity is increased if the calculated negative oxygen quantity extracted from the particle filter during the phase in which the secondary air blowing is switched off is below a predefined threshold value.

8. Method according to any of the preceding claims, characterized in that the secondary air quantity is reduced if a change of the lambda value in the lean direction is detected.

9. The method according to any one of claims 1 to 7, characterized in that the secondary air quantity is reduced if an increase in nitrogen oxide emissions is detected.

10. Method according to any one of claims 1 to 7, characterized in that the secondary air quantity is reduced if the calculated oxygen quantity present during the phase of active secondary air blowing exceeds a predefined threshold value.

11. Method according to any one of the preceding claims, characterized in that the respectively necessary amount of secondary air is provided by a secondary air source (2).

12. The method of claim 11, wherein the secondary air source is an air pump.

13. The method of claim 12, wherein the secondary air source is a scavenge pump.

14. Method according to claim 12 or 13, characterized in that the respectively necessary amount of secondary air is adjusted by a change in the rotational speed of the air pump.

15. Method according to any one of claims 1 to 10, characterized in that the respectively necessary amount of secondary air is provided by an e-compressor.

16. Method according to any one of claims 1 to 10, characterized in that the respective necessary secondary air quantity is provided by a clocked secondary air valve (24) or a variable opening cross section of the secondary air valve (24).

17. Device for regenerating a coated particle filter arranged in the exhaust gas train of a motor vehicle running on gasoline, characterized in that the device has an engine control (6) which is designed to control the method according to one of the preceding claims.