WO2020109250A1

WO2020109250A1 - Exhaust gas cleaning assembly and motor vehicle

Info

Publication number: WO2020109250A1
Application number: PCT/EP2019/082463
Authority: WO
Inventors: Hong Zhang
Original assignee: Vitesco Technologies GmbH
Priority date: 2018-11-26
Filing date: 2019-11-25
Publication date: 2020-06-04
Also published as: DE102018220255A1

Abstract

The invention relates to an exhaust gas cleaning assembly (1) for a motor vehicle, comprising a nitrogen oxide storage (3). The exhaust gas cleaning assembly (1) is configured to obtain information regarding an exhaust gas composition of the exhaust gas downstream of the nitrogen oxide storage (3). The invention also relates to a motor vehicle comprising such an exhaust gas cleaning assembly (1) which is operatively connected to a combustion engine of the motor vehicle. With the aid of the proposed exhaust gas cleaning assembly (1), a better knowledge of the exhaust gas composition in the exhaust gas cleaning assembly (1) downstream of the nitrogen oxide storage (3) can be obtained, in particular for controlling and diagnosing the nitrogen oxide storage.

Description

description

Emission control device and motor vehicle

The present invention relates to an emission control system for a motor vehicle, which has a nitrogen oxide storage.

The present invention further relates to a motor vehicle which has such an exhaust gas purification arrangement which is operatively connected to an internal combustion engine of the motor vehicle.

Motor vehicles with exhaust gas purification arrangements are known in which a desorption by the nitrogen oxide store is controlled via an exhaust gas temperature or an absorber temperature of the nitrogen oxide store, which is also referred to as nitrogen oxide absorber. If the absorber temperature exceeds a certain threshold temperature, a combustion air ratio is switched from> 1 to 1, so that desorbed nitrogen oxide with HC / CO in N, H2O and CO2 is converted into a multi-way catalytic converter, especially a three-way catalytic converter. It is unknown whether a nitrogen oxide emission downstream of the exhaust gas cleaning arrangement, in particular a catalytic converter, already breaks through or not at the time of switching the combustion air ratio. The emission, especially the associated legal limit values, may therefore not be able to be complied with robustly.

The object of the invention is to provide an exhaust gas purification arrangement and a motor vehicle which are improved compared to the prior art. In particular, better knowledge of the exhaust gas composition is to be made possible or operation of the exhaust gas purification arrangement should also be made more efficient.

The object of the invention is achieved by an exhaust gas cleaning arrangement of the type mentioned at the outset, which is aimed to obtain information about an exhaust gas composition of the exhaust gas downstream of the nitrogen oxide storage.

A better knowledge of the exhaust gas composition in the exhaust gas purification arrangement downstream of the nitrogen oxide storage, which is thereby obtained, makes it possible to make the operation of the exhaust gas purification arrangement more efficient and, if necessary, to influence the exhaust gas composition in particular by adapting the operation, taking legal requirements into account.

Preferred embodiments of the invention are part of the dependent claims.

It is preferred that the exhaust gas purification arrangement is designed to control the operation of the nitrogen oxide store as a function of the information, in particular to control and diagnose the nitrogen oxide store. So instead of or in addition to a temperature, the exhaust gas composition can be used for control, which can be more reliable or simpler.

In the present sense, the term taxes is not necessarily to be understood only narrowly as the metrological term. Regulations can also be understood as taxes in the present case. Rather, the term control can generally be understood as the adaptation of the operation, in particular an activity, of the nitrogen oxide storage, taking into account the information obtained.

The activity of the nitrogen oxide storage can be a nitrogen oxide intake amount per time interval and / or a nitrogen oxide release amount per time interval. The more nitrogen oxide the nitrogen oxide store takes up per time interval, the less nitrogen oxide preferably contains the exhaust gas from which the nitrogen oxide was taken up. The more nitrogen oxide previously stored in the nitrogen oxide reservoir releases per time interval, the more nitrogen oxide preferably contains the exhaust gas into which the nitrogen oxide was released. The nitrogen oxide store is preferably designed with a multi-way catalyst function, in particular a three-way catalyst function. The nitrogen oxide storage is then preferably designed as a combined nitrogen oxide storage three-way catalyst. The nitrogen oxide store can not only store nitrogen oxide, but can also serve as a returnable catalyst.

It is preferred that the exhaust gas purification arrangement is arranged to determine a nitrogen oxide concentration in the exhaust gas downstream of the nitrogen oxide store as the information and to control the nitrogen oxide store with regard to its operation depending on the determined nitrogen oxide concentration. The information is particularly preferably determined as a measure of the activity of the nitrogen oxide storage. The exhaust gas makes it easy to draw a conclusion about the activity of the nitrogen oxide storage. If the nitrogen oxide intake quantity of the nitrogen oxide storage per time interval is high, a comparatively low nitrogen oxide concentration will be determined and vice versa. Accordingly, the operation of the nitrogen oxide store can be controlled, that is, high operation can be provided for a high nitrogen oxide concentration and low operation can be provided for a low nitrogen oxide concentration. This can save costs and energy. The control of the nitrogen oxide store is preferably proportional to the nitrogen oxide concentration.

It is generally preferred that the exhaust gas purification arrangement has a sensor downstream of the nitrogen oxide storage device which receives the information. Particular embodiments provide that the exhaust gas purification arrangement as the sensor has a nitrogen oxide sensor downstream of the nitrogen oxide storage, which determines a nitrogen oxide measurement result as the information. The nitrogen oxide measurement result is in a row preferably a nitrogen oxide concentration in the exhaust gas. The nitrogen oxide measurement result is preferably used in order to control the operation of the nitrogen oxide reservoir as a function of the specific nitrogen oxide concentration. If the nitrogen oxide sensor provides the nitrogen oxide measurement result, the activity of the nitrogen oxide storage does not have to be ascertained in a complicated manner directly on the basis of its performance data, which are unknown in vehicle operation due to aging, but can simply be determined in particular via the nitrogen oxide concentration in the exhaust gas.

The sensor, in particular the nitrogen oxide sensor, is preferably set up to continuously determine the information, in particular the nitrogen oxide measurement result. This enables permanent, uninterrupted control of the exhaust gas downstream of the nitrogen oxide store. In order to reduce a data volume provided by the sensor, it can alternatively be provided that the sensor is set up to determine the information at predetermined intervals, in particular with interruptions, preferably at a fixed interval of several seconds .

Preferably, the sensor, in particular the nitrogen oxide sensor, is arranged in the exhaust gas path after the nitrogen oxide storage device, which is integrated with a reusable catalytic converter, or is arranged after the nitrogen oxide storage device and a reusable catalytic converter, which is provided separately downstream. This allows both the nitrogen oxide measurement result, in particular the nitrogen oxide concentration, and lambda to be determined. Both catalysts can be optimally controlled with just one nitrogen oxide sensor.

The sensor, in particular the nitrogen oxide sensor, is preferably arranged in the exhaust gas path between the nitrogen oxide store and a multi-way catalytic converter. This allows the nitrogen oxide measurement result, especially that Determine nitrogen oxide concentration before the exhaust gas reaches the multi-way catalytic converter. This enables efficient control of the nitrogen oxide storage. In some embodiments, however, the nitrogen oxide sensor is arranged downstream of the reusable catalytic converter, in particular arranged at an outlet of the exhaust gas cleaning arrangement. Then the operation of the nitrogen oxide storage can be readjusted depending on the nitrogen oxide concentration of the exhaust gas released into the environment. Some embodiments provide a first nitrogen oxide sensor, which is located upstream of the multi-way catalyst, and a second nitrogen oxide sensor, which is located downstream of the multi-way catalyst. A nitrogen oxide removal rate of the exhaust gas aftertreatment device can be monitored particularly reliably because two nitrogen oxide sensors are present which can measure the nitrogen oxide concentration at different points along the exhaust gas path.

The sensor, in particular the nitrogen oxide sensor, is located immediately downstream of the nitrogen oxide reservoir. In this way, changes in the exhaust gas composition can be detected particularly promptly, which can be attributed in particular to the nitrogen oxide store.

Embodiments provide that the exhaust gas purification arrangement has a housing which encloses the exhaust gas path. The housing preferably radially encloses the exhaust gas path. The housing preferably provides an essentially cylindrical exhaust gas tunnel for the exhaust gas path. The nitrogen oxide storage device, the nitrogen oxide sensor and preferably further elements such as the reusable catalytic converter can be arranged in the housing. For example, all components of the exhaust gas cleaning arrangement can be provided and enclosed in a single compact component. Particularly preferably, the exhaust gas purification arrangement, which has the housing, forms a motor vehicle catalytic converter assembly, which preferably has the outlet of the exhaust gas purification arrangement, which preferably can be connected to an end pipe of the motor vehicle. A sensor housing of the sensor preferably penetrates the housing. In some embodiments, the sensor is arranged on an inner wall of the housing. So the sensor can be stably mounted on the housing.

The nitrogen oxide store is preferably set up to store nitrogen oxide from the exhaust gas up to a first temperature and to release it back to the exhaust gas from a second temperature which is higher than the first temperature. The first temperature and the second temperature are preferably operating temperatures of the exhaust gas purification arrangement. This ensures reliable operation of the nitrogen oxide storage. As an alternative to this, the nitrogen oxide store can be set up to release absorbed nitrogen oxide back into the exhaust gas by triggering an active regeneration. The nitrogen oxide store preferably has a TWC property, where TWC stands for three-way catalyst.

Embodiments provide that the exhaust gas purification arrangement has an internal control unit which is programmed to control the nitrogen oxide store with regard to its operation in dependence on the information. The exhaust gas cleaning arrangement can thus compactly control the operation without an external control unit. Alternatively, the exhaust gas purification arrangement has a circuit which can be connected to an external control unit in order to lead a data line to the outside for outputting the information and preferably a control line for controlling the nitrogen oxide store. For this purpose, the circuit for the control line and the data line can each have a control unit contact which can be connected to the external control unit in order to pass on the information from the sensor to the external control unit and to receive control signals for the nitrogen oxide store. The object of the invention is further achieved by a motor vehicle of the type mentioned at the outset, the exhaust gas purification arrangement being set up to obtain information about an exhaust gas composition of the exhaust gas downstream of the nitrogen oxide store.

The motor vehicle is preferably set up to control the operation of the nitrogen oxide storage as a function of the information. If one preferably controls the operation in dependence on the information, one can ensure that the cleaning performance of the exhaust gas cleaning arrangement is adequate in order to purify the exhaust gas with sufficient nitrogen oxide. In this way, it can in particular be prevented that the exhaust gas purification arrangement, in particular because of the upstream nitrogen oxide store, does too little or too much cleaning work. In this way, the motor vehicle can become more efficient and can work more economically.

It is particularly preferred that the motor vehicle is set up to adapt a combustion air ratio as a function of the information when a predetermined first threshold value information about the exhaust gas composition is obtained downstream of the nitrogen oxide storage, preferably after a cold start of the motor vehicle and during a catalyst heating phase. At this point in time, the nitrogen oxide store has preferably exceeded a predetermined first nitrogen oxide threshold value, which is dependent on the air mass flow. For this purpose, the sensor is preferably in particular the nitrogen oxide sensor is provided, which is located downstream of the nitrogen oxide reservoir in the exhaust gas path or integrated in the nitrogen oxide reservoir. It is preferred that the adaptation of the combustion air ratio comprises switching and regulating the combustion air ratio from> 1 to 1. Here, the nitrogen oxide and / or lambda signal from the nitrogen oxide measurement result of the sensor can be used for controlling the combustion air ratio, so that nitrogen oxide and NH ₃ are minimized after the nitrogen oxide storage. The predetermined first threshold value information is preferably a nitrogen oxide emission in the exhaust gas of more than 5 ppm, preferably more than 10 ppm.

In embodiments, it is provided that the motor vehicle is set up to increase the heating of the nitrogen oxide reservoir as a function of the information if predetermined second threshold value information about the exhaust gas composition is obtained downstream of the nitrogen oxide reservoir, preferably after a cold start of the motor vehicle and during a catalyst heating phase, and the nitrogen oxide storage, in particular the multi-way catalyst integrated in the nitrogen oxide storage, or a downstream downstream multi-way catalyst falls below a predetermined threshold temperature. The aim is then preferably to quickly heat the nitrogen oxide store, in particular the multi-way catalytic converter integrated in the nitrogen oxide store, or the downstream multi-way catalytic converter beyond the predetermined threshold temperature. The heating can be achieved by increasing the ignition angle and / or by increasing the electrical power in the case of an electrically heated catalytic converter, which can be adjacent to the nitrogen oxide store. The predetermined second threshold value information is preferably a nitrogen oxide emission in the exhaust gas of over 5 ppm, preferably over 10 ppm. A preferred predetermined threshold temperature is 150 ° C., preferably below 200 ° C. The first threshold value information and the second threshold value information are preferably the same. Some embodiments provide that the motor vehicle is set up to recognize the nitrogen oxide storage as defective on the basis of the information. In particular, the motor vehicle can be set up to add up nitrogen oxide emission values, in particular by integration over the time of a nitrogen oxide concentration from the sensor, multiplied by air mass flow past the sensor. It is preferred that the nitrogen oxide emission values are added up during the entire process from the cold start of the motor vehicle to after the desorption by the NO _x adsorber, that is to say the nitrogen oxide store, particularly until preferably 3 to 8 seconds after, in particular up to 1 second after. The motor vehicle can be set up to compare the total nitrogen oxide emission values with an emission threshold, which is preferably 100 mg and is dependent on a starting temperature of the internal combustion engine. If the sum of the nitrogen oxide emission values falls below the emission threshold, the motor vehicle can be set up to recognize the shortfall as an indication of a defective nitrogen oxide store. This means that maintenance measures can be requested quickly.

The motor vehicle preferably has a control unit which is programmed to carry out the above-mentioned steps if the motor vehicle is set up for these steps. With regard to the exhaust gas purification arrangement, the control unit is preferably an external control unit.

The motor vehicle is preferably a hybrid vehicle. Preferred hybrid vehicles include both an electric motor and the internal combustion engine, in particular a gasoline engine. Hybrid vehicles in particular can therefore benefit from the increased efficiency of the exhaust gas cleaning arrangement. However, the motor vehicle can also be a conventional motor vehicle that is operated exclusively by an internal combustion engine. Further possible configurations and possible advantages of the motor vehicle result analogously to the statements above with regard to the exhaust gas cleaning arrangement.

The invention is described below on the basis of a non-restrictive exemplary embodiment and with reference to the accompanying drawing, in which:

Fig. 1 shows a schematic cross section through an embodiment of the exhaust gas purification arrangement according to the invention along an exhaust gas path and an external control unit.

In the following detailed description of the embodiment example, in the accompanying drawings and in the appended claims, which define the scope of the invention, reference numerals have been inserted for readability, but should not have a restrictive effect.

Fig. 1 shows an exhaust gas purification arrangement 1 for a motor vehicle. The exhaust gas purification arrangement 1 is installed in a hybrid vehicle, which for simplification is not further presented. The hybrid vehicle has an electric motor, not shown, and an internal combustion engine, not shown, namely a gasoline engine. The gasoline engine is connected to an inlet 2 of the exhaust gas cleaning arrangement 1 in order to provide exhaust gas for cleaning to the exhaust gas cleaning arrangement 1. The exhaust gas purification arrangement 1 is therefore operatively connected to the internal combustion engine of the motor vehicle.

The exhaust gas cleaning arrangement 1 has a nitrogen oxide storage 3. In addition, a three-way catalytic converter function is implemented in the nitrogen oxide store 3. The exhaust gas cleaning arrangement 1 brings about a nitrogen oxide reduction in the exhaust gas.

The nitrogen oxide storage 3 is set up to nitrogen oxide from the exhaust gas up to a first temperature save and release it to the exhaust gas again at a second temperature that is higher than the first temperature. The exhaust gas cleaning arrangement 1 is set up to receive information about an exhaust gas composition of the exhaust gas downstream of the nitrogen oxide store 3.

It is provided that the exhaust gas purification arrangement 1 is further configured to control the operation of the nitrogen oxide storage 3 as a function of the information. This ensures that the exhaust gas cleaning arrangement 1 operates with an appropriate cleaning performance, taking into account an activity of the nitrogen oxide storage 3, for example a nitrogen oxide uptake from the exhaust gas or a nitrogen oxide emission into the exhaust gas.

In order to obtain the information, the exhaust gas purification arrangement 1 has a nitrogen oxide sensor 4 as a sensor which determines a nitrogen oxide measurement result, namely the nitrogen oxide concentration, in the exhaust gas as the information. The nitrogen oxide sensor 4 is set up to continuously determine the nitrogen oxide measurement result. The nitrogen oxide measurement result is then used to control the nitrogen oxide storage 3 with respect to its operation depending on the nitrogen oxide concentration in the exhaust gas. The nitrogen oxide sensor 4 is arranged in an exhaust gas path 5 between the nitrogen oxide storage 3, which in this exemplary embodiment also includes the three-way catalyst function, and an additional multi-way catalyst 6, which is a three-way catalyst 6 in the exemplary embodiment shown. In exemplary embodiments that are not shown, the additional three-way catalytic converter 6 is missing and the nitrogen oxide store 3 can take over its function completely with a multi-way catalytic converter integrated therein, in particular a three-way catalytic converter. Then the nitrogen oxide storage 3 is a combined nitrogen oxide storage three-way catalyst. In contrast, in the exemplary embodiment shown there is a two-stage three-way lysator treatment of the exhaust gas instead, in a first stage already in the nitrogen oxide storage 3 and in a second stage in the additional, downstream multi-way catalyst

6.

The nitrogen oxide sensor 4 is immediately downstream of the nitrogen oxide reservoir 3 in the exhaust gas path 5. The nitrogen oxide sensor 4 is also the three-way catalyst 6, which is provided in this embodiment in addition to the nitrogen oxide storage 3, upstream in the exhaust gas path 5. The exhaust gas thus flows through the exhaust gas path 5 first through the inlet 2, then passes through the nitrogen oxide store 3, the nitrogen oxide store 3 taking nitrogen oxide from the exhaust gas or supplying it, depending on the operation of the nitrogen oxide store 3, then flows past the nitrogen oxide sensor 4 arranged downstream of the nitrogen oxide store 3 , then flows through the three-way catalytic converter 6 and then flows further to an outlet 7, from which the cleaned exhaust gas leaves the exhaust gas path 5 of the exhaust gas cleaning arrangement 1.

An external control unit 8, which analyzes the nitrogen oxide measurement result of the nitrogen oxide sensor 4 and then controls the operation of the nitrogen oxide store 3 as a function thereof, is also provided in the motor vehicle. External means external to the exhaust gas purification arrangement 1, but internal to the vehicle.

More precisely, the external control unit 8 is set up to receive the nitrogen oxide measurement result from the nitrogen oxide sensor 4 and to control the nitrogen oxide storage 4 with regard to its operation as a function of the nitrogen oxide concentration of the exhaust gas. For this purpose, the control unit 8 is connected to the nitrogen oxide sensor 4 and the nitrogen oxide store 3 via cables. The exhaust gas cleaning arrangement 1 has a first control unit contact 9 in order to connect the nitrogen oxide storage 3 to the control unit 8. The exhaust gas purification arrangement 1 has a second one Control unit contact 10 to connect the nitrogen oxide sensor 3 to the control unit 8. In this way, the nitrogen oxide store 3 is set up in a controllable manner as a function of the information. A housing 11 radially encloses the exhaust gas path 5 and provides an exhaust gas tunnel between the inlet 2 and the outlet 7. The nitrogen oxide store 3, the nitrogen oxide sensor 4 and the three-way catalytic converter 6 are located in the exhaust gas tunnel. The external control unit 8 is arranged separately from the exhaust gas path 5.

The control unit 8 is further programmed to adapt a combustion air ratio as a function of the information when a predetermined first threshold value information about the exhaust gas composition is obtained downstream of the nitrogen oxide store 3 and the nitrogen oxide store 3 has exceeded a predetermined first nitrogen oxide threshold value. The control unit 8 then switches the combustion air ratio from> 1 to 1.

In addition, the control unit 8 is programmed to increase the heating of the nitrogen oxide storage 3 as a function of the information if a predetermined second threshold value information about the exhaust gas composition is obtained downstream of the nitrogen oxide storage 3 and the nitrogen oxide storage 3, in particular the three-way catalytic converter integrated in the nitrogen oxide storage, has a predetermined one Temperature falls below threshold.

The first threshold information and the second threshold information are both nitrogen oxide emissions of 10 ppm in the exhaust gas in this embodiment. The predetermined threshold temperature in this exemplary embodiment is an operating temperature of 200 ° C. The nitrogen oxide sensor 4 is set up to determine the first threshold value information and the second threshold value information. The motor vehicle is set up to increase the heating of the nitrogen oxide storage 3 by retarding the ignition angle in the internal combustion engine. Furthermore, the motor vehicle is set up to further reduce nitrogen oxide emissions through engine measures, in particular exhaust gas recirculation, in order to greatly reduce a nitrogen oxide breakthrough towards the outlet 7.

Finally, the control unit 8 is also programmed to recognize the nitrogen oxide storage 3 as faulty on the basis of the information, namely when nitrogen oxide emission values measured by the sensor 4 and added up by the control unit 8 fall below an emission threshold of 100 mg, for example. For this purpose, the nitrogen oxide emission values are added up by the control unit 8 via the sensor 4 over a period from a cold start of the motor vehicle to 1 second after the desorption from the nitrogen oxide store 3.

Claims

1. exhaust gas purification arrangement (1) for a motor vehicle, which has a nitrogen oxide reservoir (3),

characterized in that

the exhaust gas purification arrangement (1) is set up to receive information about an exhaust gas composition of the exhaust gas downstream of the nitrogen oxide store (3).

2. Exhaust gas cleaning arrangement (1) according to claim 1, characterized in that the exhaust gas cleaning arrangement (1) is set up to control the nitrogen oxide store (3) with regard to its operation as a function of the information.

3. Exhaust gas purification arrangement (1) according to claim 2, characterized in that the exhaust gas purification arrangement (1) is set up to determine a nitrogen oxide concentration in the exhaust gas downstream of the nitrogen oxide store (3) as the information and the nitrogen oxide store (3) with regard to its operation in To control depending on the specific nitrogen oxide concentration.

4. Exhaust gas purification arrangement (1) according to one of the preceding claims, characterized in that the exhaust gas purification arrangement (1) downstream of the nitrogen oxide store (3) has a nitrogen oxide sensor (4) which determines a nitrogen oxide measurement result as the information.

5. Exhaust gas purification arrangement (1) according to claim 4, characterized in that the nitrogen oxide sensor (4) is designed to continuously determine the nitrogen oxide measurement result.

6. Motor vehicle, which has an exhaust gas purification arrangement (1) according to claim 1, which is operatively connected to an internal combustion engine of the motor vehicle.

7. Motor vehicle according to claim 6, characterized in that the motor vehicle is set up to control the nitrogen oxide storage (3) with regard to its operation depending on the information.

8. Motor vehicle according to claim 6 or 7, characterized in that the motor vehicle is set up to adapt a combustion air ratio as a function of the information when a predetermined first threshold value information about the exhaust gas composition is obtained downstream of the nitrogen oxide store (3).

9. Motor vehicle according to one of claims 6 to 8, characterized in that the motor vehicle is set up to amplify a heating of the nitrogen oxide storage (3) depending on the information when downstream of the nitrogen oxide storage (3) a predetermined second Threshold lenwertinformation about the Exhaust gas composition is obtained and the nitrogen oxide storage (3) or a downstream downstream multi-way catalyst (6) falls below a predetermined threshold temperature.

10. Motor vehicle according to one of claims 6 to 9, characterized in that the motor vehicle is set up to recognize the nitrogen oxide storage (3) on the basis of the information as faulty.