DE102017213928B4 - Method and device for determining a condition of an exhaust gas treatment element for a motor vehicle - Google Patents

Abstract

Method for determining a condition of an exhaust gas treatment element (100) for a motor vehicle, comprising: - emitting microwaves (104) into a housing (102) of the exhaust gas treatment element (100) during a period (400) in which a temperature in the housing ( 102) is monotonically changed and the loading state of the exhaust gas treatment element (100) remains the same within predetermined limits, - Receiving microwaves (104) in response to the emission, - Determining a waveform (303, 402) of the received microwaves (104) in dependence changing the temperature, - determining the state of the exhaust gas treatment element (100) in dependence on the determined signal course (303, 402), wherein determining the state comprises: - dividing the period (400) into at least a first (405) and a second (406 ) Sub-period, - determining the signal profile (303, 402) during the first sub-period (405) to a first state of the exhaust gas treatment element (10 0), determining the waveform (303, 402) during the second sub-period (406) to determine a second state of the exhaust treatment element (100), wherein the first state and the second state are different from each other.

Description

The application relates to a method for determining a condition of an exhaust gas treatment element for a motor vehicle. The application further relates to a device which is designed to carry out a corresponding method.

Motor vehicles with gasoline or diesel internal combustion engines or gas engines require various components for exhaust aftertreatment in order to comply with the statutory emission limit values. These include, inter alia, the three-way catalyst, the diesel oxidation catalyst, the nitrogen oxide storage catalyst, the SCR catalyst (selective catalytic reduction), the diesel and Ottopartikelfilter and other systems. Several elements can also be combined, for example an SCR coating particulate filter (SDPF).

The DE 10 2015 001 231 A1 relates to a microwave-based device for the separate state recognition of the individual functions of a combined exhaust aftertreatment system and / or a spatial resolution by an asymmetric arrangement of the exhaust aftertreatment system.

It is desirable to provide a method for determining a condition of an exhaust gas treatment element for a motor vehicle, which enables a reliable determination. Furthermore, it is desirable to provide a device that allows reliable detection.

The invention comprises a method according to claim 1 for determining a condition of an exhaust gas treatment element for a motor vehicle as well as a corresponding device which is selected to perform the method.

In accordance with at least one embodiment, microwaves are emitted into a housing of the exhaust treatment element during a period of time. In the period, a temperature in the housing changes monotonously. The loading state of the exhaust gas treatment element remains the same within the specified time within predetermined limits. Microwaves are received in response to the broadcast. A signal curve of the received microwaves as a function of the changing temperature is determined. The state of the exhaust gas treatment element as a function of the determined signal profile is determined.

The exhaust gas treatment element is in particular a filter and / or a catalyst of an exhaust gas treatment system of the motor vehicle, also called exhaust gas aftertreatment system. For example, the filter is a particulate filter, in particular a soot particle filter. Alternatively or additionally, the exhaust gas treatment element is a catalyst, for example an oxidation catalyst, a three-way catalyst, a NOX storage catalyst, an HC adsorber for minimizing hydrocarbon emissions and / or a further element for treating exhaust gases of an internal combustion engine of the motor vehicle.

In order to determine the state of the exhaust gas treatment element, electromagnetic waves in the microwave range are coupled into the housing of the exhaust gas treatment element. The metallic housing represents an electrical cavity resonator. In response to the transmitted wave, a frequency spectrum is recorded either in reflection or in transmission. The properties of the spectrum change with a change in the dielectric constant in the housing. The change in the dielectric constant can be determined by a change in the conductivity and / or losses or a microwave attenuation and / or a change in the quality factor Q and / or a change in the resonant frequency and / or a phase change. If, for example, soot particles are deposited in a filter, a change in the received microwaves is also detectable.

Electromagnetic properties inside the enclosure are affected by material changes or material inputs. The incorporation of molecules or particles in the filter leads to a higher polarization and attenuation and thus to a higher half-width, lower frequency, quality factor Q and amplitude as well as a change in phase and transit time of the wave.

Even a higher temperature leads to lower frequencies due to the thermal expansion of the housing. However, this can be compensated with the aid of models, for example by means of software. Further measured variables can be combined for analysis with operating parameters of the vehicle, for example an ambient temperature, a humidity, a signal one gas sensor, such as a lamp sensor and / or a NOX sensor, a load state of a catalyst and / or filter.

In addition, the electrical conductivity of the substance that accumulates in the exhaust gas treatment element is dependent on the temperature. For example, in a particulate filter, the soot particles have an electrical conductivity that is thermally activated and increases with increasing temperature. Thus, with increasing temperature, the losses increase with the same soot loading in the resonance system. In the period in which the temperature changes monotonously, and the loading state remains about the same, this effect can be exploited, to determine the condition of the exhaust treatment element. For example, the load condition changes by no more than 0.5%, by no more than 1%, or by no more than 2% during the period. For example, the temperature increases monotonically during the period, for example, around 400 ° C. For example, the temperature drops monotonically during the period, for example, around 400 ° C.

The waveform is recorded during the time period, thus determining a temperature-dependent signal. The signal curve is characteristic for a specific state of the exhaust gas treatment element. For example, the signal characteristic is characteristic of a soot load of a particulate filter. Thus, it is possible to determine as a condition, for example, a soot loading of a filter. Due to the high number of data points during the period, high accuracy in determining the state is possible.

In accordance with at least one embodiment, the determined signal profile is compared with a predetermined reference profile. The condition of the exhaust treatment element is determined depending on the comparison. In particular, a plurality of reference curves are stored, which are each characteristic of different states of the exhaust gas treatment element. Thus, various states of the exhaust treatment element and the type of loading can be determined based on the characteristic temperature-dependent waveform.

In accordance with at least one embodiment, the predetermined reference curve is adapted to the aging curve of the exhaust gas treatment element. With increasing service life of the exhaust treatment element of the reference curve is redefined. Thus, effects in determining the condition of the exhaust treatment element that occur due to use of the exhaust treatment element can be considered.

In accordance with at least one embodiment, the determined signal profile is alternatively or additionally compared with a previously determined signal profile. The condition of the exhaust treatment element is determined depending on the comparison. By way of example, the previously determined signal profile is the predecessor signal profile determined directly before the determined signal profile. Thus, a relative comparison of the waveforms is possible.

Determining the condition includes determining a first condition of the exhaust treatment element and determining a second state of the exhaust treatment element. The first state and the second state are different from each other. For example, it is possible to determine a loading state as a first state and a functional state as a second state in a particulate filter. The functional state is, for example, a state as to whether the exhaust gas treatment element works as intended or malfunction occurs. Also for the functional state occur characteristic curves of the detected waveform, which indicate full functionality or certain errors.

The period is divided into at least a first and a second sub-period. The waveform is determined during the first sub-period to determine the first state of the exhaust treatment element. The waveform is determined during the second sub-period to determine the second state of the exhaust treatment element. For example, during the first sub-period, the first condition is a load with a first substance. In the second sub-period, the second condition is a load with another second substance. For example, it is possible to determine in a particulate filter, the loading of soot and additionally the loading of ash. The dependence of the electrical conductivity on the temperature of ash differs from the dependence of the electrical conductivity on the temperature of soot. For example, at higher temperatures, the increase in conductivity is greater with soot than with ash. In order to determine the loading of soot, for example, the first sub-period is placed so that it is in the range with higher temperatures than the second period.

For example, according to at least one embodiment, the determined signal profile is evaluated via at least one radio-frequency parameter, for example quality, frequency, half width, amplitude, phase and / or transit time and / or a further parameter. The evaluation takes place in temporally fixed or transient form, for example by means of algebra and / or statistics, for example by averaging, gradient formation and / or further mathematical functions.

In accordance with at least one embodiment, an internal combustion engine of the motor vehicle is switched off. The period is started after switching off the internal combustion engine. After switching off the internal combustion engine, the temperature of the exhaust gas treatment element decreases monotonically. Thus, the period is started after switching off the internal combustion engine at high temperatures and due to the switched-off internal combustion engine, the loading state of the exhaust gas treatment element remains the same. Alternatively or additionally, the period is started after a transient temperature change was detected with change in the loading state within the predetermined limits, for example at a Overrun, a load jump, or other modes that result in a sufficient temperature change with limited change in load.

In accordance with at least one further embodiment, a defined condition for the exhaust-gas treatment element is predetermined before the transmission and reception of the microwaves. The condition of the exhaust treatment element is determined depending on the predetermined condition. For example, a particulate filter is regenerated so that a load condition with soot of zero is specified as a defined condition. Thus, for example, a load condition of the particulate filter with ash can be determined very reliably.

Further advantages, features and developments emerge from the following, explained in conjunction with the figures examples. The same, similar and equivalent elements can be provided with the reference numerals.

• 1 eine schematische Darstellung eines Filters mit einer Vorrichtung gemäß einem Ausführungsbeispiel,
• 2 eine schematische Darstellung von Signalverläufen gemäß einem Ausführungsbeispiel,
• 3 eine schematische Darstellung von Signalverläufen gemäß einem Ausführungsbeispiel, und
• 4 eine schematische Darstellung von Signalverläufen.

Show it:

• 1 a schematic representation of a filter with a device according to an embodiment,
• 2 a schematic representation of signal waveforms according to an embodiment,
• 3 a schematic representation of signal waveforms according to an embodiment, and
• 4 a schematic representation of signal waveforms.

1 shows an exhaust gas treatment element 100 , The exhaust treatment element 100 is in particular part of an exhaust aftertreatment system of a motor vehicle. Exhaust gas from an internal combustion engine not explicitly shown is in the exhaust gas treatment element 100 introduced. In the exhaust treatment element 100 is an exhaust treatment module 101 arranged. The exhaust treatment module 101 For example, it is used to purify the exhaust gas of emissions. The exhaust treatment element 100 is for example a filter, in particular a particle filter such as a soot particle filter for diesel and / or Otto internal combustion engines. The filter module 101 is for example a channeled ceramic. Alternatively or additionally, the exhaust gas treatment element 100 a catalyst or a combination of a catalyst and a particulate filter. For example, the exhaust gas treatment element 100 a three-way catalyst, an oxidation catalyst, a NOX storage catalyst, an ammonia slip catalyst or other element to reduce emissions in the exhaust gas.

The method according to the invention will be explained in more detail below, in particular using the example of a particulate filter.

During operation, soot and ash are stored in the module 101 on. In the case of a certain loading state, the filter must be regenerated or cleaned, for example thermally burned free. The loading state can be determined well with high-frequency measurement technology, in particular with microwaves 104 , The microwaves are for example in a range between 300 MHz and some 100 GHz. In particular, according to the application, a frequency range of approximately 0.3 GHz to 10 GHz, for example from 1.5 GHz to 7 GHz, is used. Other frequency ranges are possible.

To send and receive microwaves 104 In the embodiment shown, a first and a second transmitting and receiving device 103 intended. These are, for example, each high-frequency antennas, which are coupled to a corresponding exciter, such as an oscillator. The coupling can be done electrically and / or inductively. The microwaves are received, for example, after transmission or after reflection.

According to further embodiments is only a single transmitting and receiving device 103 intended. This first sends the microwaves 101 out in the case 102 be reflected and subsequently again from the transmitting and receiving device 103 be received.

A device 110 is planned. The device 110 is for example part of an engine control of the motor vehicle. The device 110 Among other things, it is used to evaluate the received microwaves 104 ,

The conductivity of the soot load and the ash charge is thermally activated and thus increase with increasing temperature, the losses at the same soot loading in the resonance system.

2 shows this relationship using the example of a diesel particulate filter. A waveform 201 corresponds to an unloaded filter module 101 , Damping does not change significantly with increasing temperature.

The waveform 202 corresponds to a low constant filter loading with soot. As the temperature increases, so does the sensitivity of the signal to the soot loading. The damping is different depending on the temperature. The waveform 203 corresponds to a middle one constant filter loading and the waveform 204 with a comparatively high loading of the filter with soot.

The waveforms 202 . 203 and 204 Moreover, they are not linear in the entire temperature range but have different slopes. This behavior is dependent, for example, on the soot being examined and, for example, on the type of internal combustion engine.

3 shows a characteristic waveform 302 a soot loading at a changing temperature. In addition to the accumulation of soot it comes over the lifetime of the filter 100 also to a continuous load of ash. The ash has according to embodiments, the waveform 301 with increasing temperature. In particular, ash is not thermally regenerable. Ash (inorganic oxides) leads to the microwaves radiated into the filter 104 both to a different signal intensity and to a different temperature dependence than soot deposits.

The temperature-dependent signal course 302 for a pure soot loading differs from the temperature-dependent waveform 301 a pure ash load with the same load. These differ both in their absolute values and in their temperature dependence. The slope change of the signal course 301 is at a first temperature 304 , The slope change of the signal course 302 is at a second temperature 305 , The temperatures 304 and 305 are different from each other. In particular, the temperature 304 lower than the temperature 305 , Due to the different conductivity mechanisms of soot and ash, the change in pitch is due to the different temperatures 304 and 305 ,

In addition, there is a waveform 303 exemplified when soot and ash are present in equal amounts simultaneously. The temperature-dependent signal course 303 has characteristics of the waveform 301 and the waveform 302 on. From the waveform 303 can thus be deduced the amounts of both components. For example, the waveform 303 for this purpose compared with stored reference curves, for each of the soot and ash charge is known. For example, the reference curves are stored in a map.

Alternatively or additionally, it is possible to subdivide the signal profile or the period under consideration into a plurality of subperiods, as will also be described below in connection with FIG 4 explained. For example, in a first period when higher temperatures prevail, soot loading is determined because the effects of ash at higher temperatures are negligible. In a second period, in which lower temperatures prevail, the ash load is then determined.

4 shows exemplary waveforms 401 . 402 . 403 and 404 within a period 400 , With decreasing temperature and the resulting change in damping properties. For example, we at one time 407 the internal combustion engine switched off. Thus, the effect of the temperature-dependent conductivity can be used, for example.

The period 400 For example, it starts after the time 407 , The soot load and ash charge then remain constant and the temperature of the filter 100 takes off slowly. The signal 401 or. 402 . 403 or 404 the received microwaves will be during the period 400 recorded, ie in particular during the cooling phase of the filter 100 , Thus, the temperature-dependent signal 401 . 402 . 403 . 404 determined. In this case, the determined signal characteristic is characteristic of a loading state with soot and ash. The determined signal course 402 is a superposition of a pure soot loading, as by the waveform 403 shown and a pure ash charge as by the waveform 404 shown. Each course of the waveform 402 is thus characteristic of a certain loading state of the filter element 100 ,

Thus, it is possible to have both a continuous soot loading at shorter time intervals and an ash charge over the life of the filter element 100 to detect. For example, chemical models can be used for this, such as Arrhenius behavior. These can also be used in the evaluation.

The inventive method can also be used in transient operation, if in a short time high temperature differences on the filter element 100 present while the filter loading remains approximately constant. For example, in a downhill and overrun fuel cutoff or when driving uphill under heavy load occurs in the period 400 a sufficiently strong temperature change, wherein the loading state within this period 400 not changed significantly. For example, the load state changes within the time period 400 within preset limits, for example by no more than 1% or less.

According to embodiments, the period 400 in a first sub-period 405 and a second sub-period 406 divided. A subdivision into more than two part-time periods is possible. The first sub period 405 starts for example for time 407 , Higher temperatures prevail here than in the second half of the year 406 , The second sub period 406 closes, for example, to the first sub-period 405 on. In the first sub-period 405 is the change in the waveform 403 more significant than the change in the waveform 404 , The change in the electrical conductivity of the soot fraction is significantly greater than the ash content. Consequently, for example, from the cumulative waveform 402 in the first sub-period 405 Reliable on the soot loading of the filter element 100 shut down. From the course 402 in the second sub-period 406 can then be closed, for example, on the ash load.

The method according to the invention makes use of the temperature dependence of the microwave signal with constant loading of the exhaust gas treatment element 100 in order to infer a state such as an operating state and / or aging state of an exhaust gas catalytic converter, an exhaust gas filter or a catalytically coated filter. The age condition includes in particular a storage capacity and / or a poisoning condition.

According to exemplary embodiments, different sections of the received signal or different characteristic courses are utilized in order to be able to determine different catalyst and / or filter states as a function of temperature. For example, a gradient, a slope, a change in slope or other characteristic properties of the temperature-dependent signal curve is utilized to respond to different states of the exhaust gas treatment element 100 to be able to close.

Alternatively or additionally, different temperature ranges are investigated for different states. In particular, the method is performed after switching off the internal combustion engine during a subsequent cooling phase.

In normal driving operation, the method is distinguished, in particular in transient operation at high temperature, in a short time and at an approximately constant charge state of the catalyst and / or filter. The temperature differences can be both a cooling and a heating.

For example, the method is used to detect a loading state, a functional state and / or an aging state of a particulate filter, for example a diesel particulate filter or an Otto particle filter. For example, a soot load and / or an ash charge of the filter is determined.

For example, the method is alternatively or additionally used to detect a loading state, a functional state, and / or an aging state of a three-way catalyst, for example, a catalytic activity, an oxygen storage ability, and / or aging of the coating. Alternatively or additionally, the method is used to determine the loading state, the functional state and / or the aging state of a Dieseloxidationskatalystors, for example, a catalytic activity, a hydrocarbon storage capacity and / or aging of the coating.

For example, the exhaust gas treatment element 100 a three-way catalyst coating on a filter on or another type of catalyst. By means of the method according to the application it is possible to determine individual effects separately, for example an oxygen storage capacity, a soot charge and / or an ash charge.

For example, the method according to the application is used to determine a loading state, functional state and / or an aging state of a NOX storage catalytic converter (NSC, LNT), for example a catalytic activity, a NOX storage capability and / or aging of the coating. According to embodiments, the exhaust gas treatment element 100 a NOX storage catalyst coating on a filter. By means of the method according to the application it is possible to determine individual effects separately from one another, for example a NOX storage capacity, a soot charge and / or an ash charge.

Alternatively or additionally, the method according to the application according to exemplary embodiments is used to detect a loading state, a functional state and / or an aging state of an SCR storage catalytic converter, for example a catalytic activity, an ammonia storage capability, an ammonia storage and / or aging of the coating.

According to one embodiment, the exhaust gas treatment element 100 an SCR catalyst coating on a filter. By means of the method according to the application, individual effects can be determined separately from one another, for example an ammonia storage capacity, a soot charge and / or an ash charge.

The method according to the application is alternatively or additionally used in accordance with one embodiment to determine the loading state, the functional state and / or the aging state of a hydrocarbon adsorber, for example a catalytic activity, a hydrocarbon storage, a hydrocarbon storage capacity and / or aging of the coating.

According to one embodiment, the exhaust gas treatment element 100 a hydrocarbon adsorber coating on a filter. Individual effects can be determined separately from one another, for example a hydrocarbon storage capacity, a hydrocarbon storage, a soot charge and / or an ash charge.

The method according to the application can be used to calibrate a microwave measuring system for determining the state of the exhaust gas treatment element 100 be used. For example, during the ongoing operation of the internal combustion engine, the change in the dielectric constant with changing load is utilized to the loading state of the exhaust gas treatment element 100 to investigate. After switching off the engine at the time 407 and the resulting constant loading of the exhaust gas treatment element 100 and the monotonically reducing temperature, the loading state becomes independent of the varying dielectric constant in the exhaust gas treatment element 100 determined based on the temperature dependence of the electrical conductivity of the load. Thus, the loading state by means of the microwaves 112 based on two different methods. Thus, the system can be calibrated by means of the method according to the application. According to embodiments, the exhaust treatment element 100 , So for example, the catalyst, filters and / or adsorber shortly before turning off the engine, so shortly before the time 407 , In a defined state, that is, for example, a predetermined oxidation state, a predetermined NOX storage amount and / or a predetermined NH3 storage amount. Thus, for the period 400 a frame condition known and can be used to evaluate the waveform 401 be used to determine another condition can. For example, the time will be 407 selected after a particle filter has been regenerated. Thus, the loading state with soot is known and from the waveform 402 can reliably determine an ash load.

Claims (9)

A method of determining a condition of an exhaust treatment element (100) for a motor vehicle, comprising: - Sending microwaves (104) into a housing (102) of the exhaust treatment element (100) during a period (400) in which a temperature in the housing (102) monotonically changed and the loading state of the exhaust treatment element (100) within predetermined limits equal remains, Receiving microwaves (104) in response to the broadcast, Determining a signal curve (303, 402) of the received microwaves (104) as a function of the changing temperature, Determining the state of the exhaust gas treatment element (100) as a function of the determined signal profile (303, 402), wherein the determination of the state comprises: Dividing the time period (400) into at least a first (405) and a second (406) subperiod, Determining the signal profile (303, 402) during the first sub-period (405) in order to determine a first state of the exhaust-gas treatment element (100), - Determining the waveform (303, 402) during the second sub-period (406) to determine a second state of the exhaust gas treatment element (100), wherein the first state and the second state are different from each other. Method according to Claim 1 comprising: - comparing the determined signal curve (303, 402) with a predetermined reference curve, - determining the state of the exhaust gas treatment element (100) as a function of the comparison. Method according to Claim 1 or 2 , - comparing the determined signal profile (303, 402) with a previously determined signal course, - determining the state of the exhaust gas treatment element (100) in dependence on the comparison. Method according to one of Claims 1 to 3 comprising: - switching off an internal combustion engine of the motor vehicle, - starting the period (400) after switching off the internal combustion engine. Method according to one of Claims 1 to 4 comprising: predetermining a defined condition for the exhaust gas treatment element (100) before emitting and receiving the microwaves, - determining the state of the exhaust gas treatment element (100) in dependence on the given condition. Method according to one of Claims 1 to 5 wherein determining the condition comprises: determining a first loading condition of the exhaust treatment element (100) with a first substance; determining a second loading state of the exhaust treatment element (100) with a second substance different from the first substance. Method according to Claim 6 in which the first substance has a first dependence of the electrical conductivity on the temperature of the substance, and the second substance has a second dependence of the electrical conductivity on the temperature of the substance, the first and the second dependence being different from one another. Method according to one of Claims 1 to 7 in which determining the condition comprises: - determining a loading state of the exhaust gas treatment element (100), - determining a functional state of the exhaust gas treatment element (100). Device which is adapted to a method according to one of Claims 1 to 8th perform.

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