CN107542563A

CN107542563A - Fault Identification is carried out in SCR system by means of ammonia fill level

Info

Publication number: CN107542563A
Application number: CN201710500625.8A
Authority: CN
Inventors: F.米科利斯; A.沃洛诺; M.通多
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2016-06-28
Filing date: 2017-06-27
Publication date: 2018-01-05
Anticipated expiration: 2037-06-27
Also published as: KR20180002057A; CN107542563B; DE102016211575A1

Abstract

The present invention relates to the method that Fault Identification is carried out in the SCR system for internal combustion engine in a motor vehicle, SCR system has two SCR catalysts and two NOx sensors.Methods described includes：First SCR catalyst is heated to following temperature, can be about zero by the maximum ammonia fill level that the first SCR catalyst stores for the temperature；Adjust the ammonia fill level for setting defined in the first SCR catalyst；Measure the nitrous oxides concentration of the upstream of SCR catalyst and the nitrous oxides concentration and the summation that forms of ammonia density in the downstream by SCR catalyst；Draw the comparison of the actual ammonia fill level of the second SCR catalyst and the desired ammonia fill level of the second SCR catalyst when there is ammonia sliding；Failure at least one SCR catalyst in two SCR catalysts is identified according to the comparison of the actual ammonia fill level of the second SCR catalyst when there is ammonia sliding and desired ammonia fill level.

Description

Fault Identification is carried out in SCR system by means of ammonia fill level

Technical field

It is used for the present invention relates to a kind of when there is ammonia sliding by means of ammonia fill level with two SCR catalysts The method that Fault Identification is carried out in SCR system.In addition, the present invention relates to a kind of computer program, the computer program its Each step of methods described is performed when being run on calculator, and the present invention relates to a kind of machine readable storage medium, should Storage medium stores the computer program.Finally the present invention relates to a kind of electronic controller, the electronic controller to be set up For performing methods described.

Background technology

SCR（SCR）It is in current wide-scale distribution, the waste gas for making the combustion motors in motor vehicle Nitrogen oxides（NOx）The technology of reduction.In SCR system, AdBlue will be commercially also served as^®And known urine Element-water-solution by jet module at least one SCR catalyst injected upstream into exhaust system.From the urea-water- The ammonia separated in solution is at the SCR catalyst with SCR and reaction of nitrogen oxides generation element Nitrogen.

Multiple SCR catalysts are used due to the introducing of stricter emission regulation, the SCR catalyst is to same Waste gas works.In the situation of the efficiency deficiency for making SCR catalyst that the discharged nitrous oxides in the exhaust system reduce Descend the detection method, it is specified that with vehicle itself（Generally realized in electronic controller）Carry out Fault Identification.For this reason, Continuously monitored in the implementation during normal operation of the vehicle.For common detection method, at least one cloth is used Put the nitrogen sensor in the upstream of the SCR catalyst and the nitrogen sensing at least one downstream for being arranged in the SCR catalyst Device.For single SCR catalyst, two NOx sensors are enough to be used in calculating the efficiency of the SCR system simultaneously And discharged nitrous oxides are monitored simultaneously.

The SCR system expanded in same exhaust system multiple（n）The way of SCR catalyst is according to tradition with n+ Premised on 1 NOx sensor, for by means of pin-point（Pin mark type）Strategy come obtain it is at least one without or Less preferably play the SCR catalyst of function.Correspondingly, it can targetedly repair either to change and or less preferably not play work( Can SCR catalyst, and preferably play the SCR catalyst of function or the SCR system then remains unaffected.But, The use of the pin mark type strategy is not necessarily to during normal operation the vehicle, because herein only to the efficiency It is monitored just enough.For in the case of the SCR catalyst of function or is not less preferably played, than if passing through Signal lamp on instrument board alarms to driver, and the vehicle is such as reached maintenace point by subsequent driver.Tieed up in maintenace point During repairing, using the pin mark type strategy being previously mentioned in detection method, work(or is not less preferably played for acquisition is described The SCR catalyst of energy.

The content of the invention

Methods described is related to the SCR system of the combustion motors in motor vehicle.Here, the SCR system is common at one There are two SCR catalysts successively arranged in exhaust system.Waste gas first passes around the first SCR catalyst and then continues to lead Give the second SCR catalyst so that two SCR catalysts work to the waste gas.In addition, the SCR system has two NOx sensor, the NOx sensor are equally arranged in this exhaust system.First NOx sensor cloth Put in the upstream of described two SCR catalysts, and can there measure and exhaust-gas treatment is being carried out by the SCR catalyst Nitrous oxides concentration before.Second nitridation nitrogen sensor arrangement is in the downstream of described two SCR catalysts and can be at that In measurement summation for being made up of nitrous oxides concentration and ammonia density after exhaust after-treatment is carried out by the SCR catalyst, Wherein described ammonia density and the ammonia occurred when ammonia fill level exceedes maximum ammonia fill level slide（Ammoniak- Schlupf）It is consistent.

It the described method comprises the following steps.First SCR catalyst is heated to following temperature first, for the temperature Almost can be zero by the maximum ammonia fill level that first SCR catalyst stores for degree.This is than if under It is accomplished to state mode：The temperature dependency of the maximum ammonia fill level shows and therefrom obtained down as characteristic curve Temperature is stated, the characteristic curve is less than the limiting value of defined for the temperature.Especially this temperature arrives in 400 DEG C In the range of 600 DEG C.It is noted that the temperature of second SCR catalyst is preferably kept into alap degree so that Second SCR catalyst can store ammonia loading almost corresponding with normal operation.It is preferred that pass through the SCR catalyst Upstream hot-fluid, such as first SCR catalyst is added by the heating for the waste gas in the internal combustion engine Heat.Compared with also only meeting with the second SCR catalyst of less hot-fluid, due to thus causing for first SCR catalyst Higher heat exchange and easily reach desired temperature difference.

Then, the ammonia fill level for setting defined in first SCR catalyst is adjusted.The ammonia fill level of defined （Ammoniak-Füllstand）In the maximum ammonia fill level by that can be stored in second SCR catalyst and also On the summation formed when former with the ammonia fill level of the reaction of nitrogen oxides.Can correspondingly it contemplate, not described The ammonia amount for being used to reduce nitrogen oxides in one SCR catalyst is stored in second SCR catalyst completely.

Then measure the nitrous oxides concentration of the upstream of the SCR catalyst and the downstream by the SCR catalyst The summation that nitrous oxides concentration and ammonia density are formed.Traditional NOx sensor has laterally sensitive relative to ammonia density Property, thus the NOx sensor in the downstream by being arranged in the SCR catalyst is enabled in particular to measure by the nitrogen oxygen The summation that compound concentration and the ammonia density are formed.Especially by the summation signals that the sensor measures relative to desired nitrogen The change of oxide concentration may originate from the ammonia density consistent with the sliding of the ammonia of second SCR catalyst.The ammonia sliding Show following ammonia amount, this ammonia amount passes through the SCR catalyst, without participating in the reduction.It is preferred that urged from described two SCR Change the actual ammonia loading that the second SCR catalyst described in when the ammonia sliding occur is obtained in the ammonia density in the downstream of device. It can provide in another aspect, be obtained from the characteristic curve for second SCR catalyst and the ammonia cunning occurring The desired ammonia loading of second SCR catalyst described in during shifting（Ammoniak-Füllmenge）.

In further process, during the analysis phase, implement the 2nd SCR catalysis described in when the ammonia sliding occur The comparison of the actual ammonia loading of device and desired ammonia loading.Finally, identify on basis of the comparison described The failure at least one SCR catalyst in two SCR catalysts.If here it is preferred, in particular, that there is the ammonia The actual ammonia loading of second SCR catalyst described in during sliding is different from desired ammonia loading, then identifies described Failure in two SCR catalysts,.

Alternatively, can methods described the nitrogen oxides implemented at the beginning for the upstream of the SCR catalyst it is dense The measurement of degree and for described two SCR catalysts downstream nitrous oxides concentration measurement.Here, described two SCR Catalyst converter works in normal operation.If the nitrous oxides concentration in the downstream of described two SCR catalysts and desired nitrogen Oxide concentration is not consistent, then identifies the failure in the SCR system.If here it is preferred, in particular, that as described Identify the failure in the SCR system like that and extraly when there is ammonia sliding described in the second SCR catalyst Actual ammonia loading and desired ammonia loading is consistent, then identifies the failure in first SCR catalyst.

It can provide in another aspect, faulty catalyst converter is repaired or changed on the basis of methods described Afterwards, the distance of the motor-driven vehicle going defined and/or time and then methods described is implemented again.Thus also to described Two SCR catalysts have a case that failure is this in the identical time and rare taken in.Alternatively, can implement again Also the analysis phase is changed during methods described, so as to cover bigger fault spectrum（Fehlerspektrum）.

The computer program is configured for：Especially implement the side when it is being implemented on calculator or controller Each step of method.The computer program can implement methods described in traditional electronic controller, without entering to it Change in row structure.Therefore, the computer program is stored in the machine readable storage medium.

The electronic controller is obtained by the way that the computer program is loaded on traditional electronic controller, the electricity Sub-controller is configured for implementing Fault Identification in the SCR system.Here, the electronic controller can not only be car Itself controller and also can be outside controller, such as diagnostor, the controller of the outside is carrying out failure knowledge It is connected during not with the SCR system and controls methods described.

Brief description of the drawings

Embodiments of the invention are shown in the drawings and are explained in detail in the following description.Wherein：

Fig. 1 schematically shows SCR system, and the SCR system includes two SCR catalysts and three NOx sensors simultaneously And Fault Identification can be implemented by means of traditional method；

Fig. 2 schematically shows SCR system, and the SCR system includes two SCR catalysts and two NOx sensors simultaneously And by means of Fault Identification can be implemented in the present inventive method；

Fig. 3 shows a kind of flow chart of embodiment in the present inventive method；And

Fig. 4 shows the chart of the temperature dependency of the ammonia fill level of SCR catalyst, it is described in the present inventive method one The temperature dependency can be used in kind embodiment.

Embodiment

Figure 1 illustrates a kind of common SCR system 100 of the unshowned combustion motors in motor vehicle, the SCR systems System has the first SCR catalyst 101 and the second SCR catalyst 102, and tradition can be used for above-mentioned two SCR catalyst Method identify failure.Described two priorities of SCR catalyst 101 and 102 are arranged in exhaust system 120, wherein described first SCR catalyst 101 is arranged to closer to jet module 130, and the jet module is by urea-water-solution in described two SCR The injected upstream of catalyst converter 101 and 102 is into the exhaust system 120.In addition, the SCR system 100 includes the first nitrogen oxides Sensor 110, first NOx sensor are arranged between the jet module 130 and first SCR catalyst 101 And the nitrogen oxidation of the waste gas before exhaust after-treatment is carried out by the SCR catalyst 101 and 102 can be measured there Thing concentration NOx__{Before processing}.In addition, the SCR system 100 includes the second NOx sensor 111, second nitrogen oxides sensing Device is arranged in the downstream of second SCR catalyst 102 and can measured there by described two SCR catalysts The nitrogen concentration NOx_ of waste gas after 101 and 102 progress exhaust after-treatments_{After processing}.The SCR system also extraly includes the 3rd nitrogen Oxide sensor 112, the 3rd NOx sensor are arranged in first SCR catalyst 101 and urged with the 2nd SCR It can measure between change device 102 and there useless after exhaust after-treatment is carried out by first SCR catalyst 101 The nitrous oxides concentration of gas.Three NOx sensors 110,111 and 112 and the jet module 130 that are previously mentioned with Electronic controller 140 is connected and controlled by the electronic controller.

In the method for being traditionally used for carrying out Fault Identification, the sum at first NOx sensor 110 is obtained The actual difference of nitrous oxides concentration at 3rd NOx sensor 112, or obtain the 3rd nitrogen oxidation The actual difference of nitrous oxides concentration at thing sensor 112 and described second NOx sensor 111, and will It is compared with desired difference.If at least one difference and corresponding desired difference in the actual difference It is worth inconsistent, then to be inferred in the SCR catalyst 101 or 102 that is formed therebetween failure.

Fig. 2 shows the SCR system 200 of the unshowned combustion motors in motor vehicle, and the SCR system equally includes first The SCR catalyst 202 of SCR catalyst 201 and second, can be by means of described by the present invention's for above-mentioned two catalyst converter A kind of embodiment of method identifies failure.Described two SCR catalysts 201 and 202 are correspondingly successively arranged in exhaust system In 220, wherein first SCR catalyst 201 is arranged to closer to jet module 230 as previously described. But, SCR system 200 herein shown only include being arranged in jet module 230 and first SCR catalyst 201 it Between the first NOx sensor 210 and be arranged in second SCR catalyst 202 downstream the second nitrogen oxides sensing Device 211.Described two SCR catalysts 210 and 211 and the jet module 230 are connected and at least with electronic controller Controlled during Fault Identification is carried out by the electronic controller.In another embodiment, the electronic controller energy Enough it is outside equipment, the equipment of the outside is connected during Fault Identification is carried out with the SCR system 200.

First NOx sensor 210 measures to be located after waste gas is carried out by the SCR catalyst 101 and 102 The nitrous oxides concentration NOx_ of waste gas before reason_{Before processing}, and second NOx sensor 211 according to it relative to ammonia The horizontal sensitivity of concentration measures by useless after exhaust after-treatment is carried out by described two SCR catalysts 101 and 102 The nitrogen concentration NOx_ of gas_{After processing}With ammonia density NH_{After 3_ processing}The summation signals of composition.Fig. 2 SCR system 200 therefore the SCR systems with Fig. 1 Differing only in for system has lacked the 3rd NOx sensor 112.

Implement by a kind of the of method for being used to carry out Fault Identification in SCR system 200 described above of the present invention Example as flow chart figure 3 illustrates.It is dense to the nitrogen oxides at first NOx sensor 210 in the first step Spend NOx__{Before processing}With the nitrous oxides concentration NOx_ at second NOx sensor 211_{After processing}Implement measurement 300.If The nitrous oxides concentration NOx_ after exhaust after-treatment is carried out by described two SCR catalysts 201 and 202_{After processing}With from described Nitrous oxides concentration NOx__{Before processing}Different with the desired numerical value obtained in the conversion ratio of described two SCR catalysts, that is just known The failure not haveing in 301 SCR systems 200.That is, at least one SCR catalyst in described two SCR catalysts 201 or 202, there are the two SCR catalysts that there is functional fault and/or at least one reduce in the case of rare Conversion ratio.If not identifying the failure in 301 SCR systems 200, terminate 302 methods describeds.

Otherwise, the combustion motors conversion 303 of the motor vehicle of stopping is existed into idle running and then in another step 304 combustion motors are run in the operating point of defined.Then wait always, until first NOx sensor Nitrous oxides concentration NOx_ at 210_{Before processing}With the nitrous oxides concentration NOx_ at second NOx sensor 211_{After processing} It is identical.First SCR catalyst 201 is then heated 306 and arrives following temperature T, for the temperature, described first The maximum ammonia fill level NH of SCR catalyst 201_{3_ maximum fill levels}Almost it is zero.The temperature of first SCR catalyst is used for this The characteristic curve 400 of correlation is spent, as illustrated in Figure 4.In such an embodiment, the temperature（T）About 500 ℃.Then by the urea-water-solution injection 306 into the exhaust system 220.

Therefore, the ammonia fill level NH in first SCR catalyst 201_{3_ fill levels}Increase to the numerical value of defined always. This defined numerical value is in the maximum ammonia fill level NH of second SCR catalyst 202_{3_ maximum fill levels}With described first On the ammonia amount reacted in SCR catalyst 201 when the nitrogen oxides reduces.As a result, by all in the nitrogen oxidation The ammonia reacted when thing reduces not at first SCR catalyst 201 hands to second SCR catalyst 202.Due to height In the maximum ammonia fill level NH of second SCR catalyst_{3_ maximum fill levels}Ammonia fill level NH_{3_ fill levels}, described second Occurs ammonia sliding at SCR catalyst 202, not stored ammonia amount passes through this SCR catalyst for ammonia sliding 202, the reduction without participating in the nitrogen oxides.

If reach the ammonia fill level NH of defined_{3_ fill levels}, then on the one hand first nitrogen oxides is sensed again Nitrous oxides concentration NOx_ at device 210_{Before processing}And the nitrous oxides concentration by second NOx sensor 211 NOx__{After processing}With ammonia density NH_{After 3_ processing}The summation signals of composition implement measurement 308.The ammonia density NH_{After 3_ processing}Institute can be attributed to State the ammonia sliding occurred at the second SCR catalyst.Therefore, once the summation signals are obtained by the ammonia sliding occurred Improve, then obtain the ammonia fill level NH actual when there is the ammonia sliding_{3_ is actual}.On the other hand, urged from the 2nd SCR Change and the ammonia fill level NH desired when there is the ammonia sliding is obtained in the characteristic curve 500 of device_{3_ is expected}, wherein described first The maximum ammonia fill level NH of second SCR catalyst_{3_ maximum fill levels}As reference.

In comparing 311, during the analysis phase, when will occur the ammonia sliding at second SCR catalyst 202 Actual ammonia fill level NH_{3_ is actual}With desired ammonia fill level NH_{3_ is expected}Compareed.If the actual ammonia filling Horizontal NH_{3_ is actual}With desired ammonia fill level NH_{3_ is expected}Difference, then identify the event in 320 second SCR catalysts 202 Barrier.As further step 321, faulty second SCR catalyst 202 is repaired or changed.If the reality The ammonia fill level NH on border_{3_ is actual}With desired ammonia fill level NH_{3_ is expected}It is consistent, then the 2nd SCR catalysis is not can determine that Failure at device 202.But because in the failure measured in identifying the SCR system 200 in 300, it can set Think, first SCR catalyst 201 is faulty.Correspondingly, 330 first SCR catalysts are identified in this case Failure in 201.Herein, as further step 331, faulty first SCR catalyst 201 is repaired or Change.

In order to exclude all faulty this rare situation of described two SCR catalysts 201 and 202, identifying first During failure in 320 second SCR catalysts 202, time and/or distance as defined in the motor-driven vehicle going 340.Then from Methods described is repeated at the beginning.Provide in another embodiment, change the analysis phase when repeating methods described.

Fig. 4 shows the maximum ammonia fill level NH_{3_ maximum fill levels}The characteristic curve 400 depending on temperature T.This In embodiment, the maximum ammonia fill level of second SCR catalyst 202 on 401 is being put when temperature is 500 DEG C NH_{3_ maximum fill levels}It is not different with zero.It is noted that the temperature where the point 401 depends on used SCR catalyst simultaneously And such as it may be about in another embodiment as 450 DEG C.

Claims

1. the SCR system for internal combustion engine in a motor vehicle（200）The middle method for carrying out Fault Identification, the SCR system tool There are two SCR catalysts（201；202）With two NOx sensors（210；211）, one of NOx sensor （210）It is arranged in described two SCR catalysts（201；202）Upstream, an and NOx sensor（211）It is arranged in The downstream of described two SCR catalysts, the described method comprises the following steps：

- by the first SCR catalyst（201）Heating（306）To following temperature（T）, can be by described for the temperature One SCR catalyst（201）The maximum ammonia fill level of storage（NH_{3_ maximum fill levels}）About zero；

- tune is set（307）First SCR catalyst（201）The ammonia fill level of middle defined（NH_{3_ fill levels}）, the ammonia of defined Fill level, which is in, is used for the second SCR catalyst（202）Maximum ammonia fill level（NH_{3_ maximum fill levels}）On；

- measurement（308）The SCR catalyst（201；202）Upstream nitrous oxides concentration（NOx__{Before processing}）And by described SCR catalyst（201；202）Downstream nitrous oxides concentration（NOx__{After processing}）And ammonia density（NH_{After 3_ processing}）The summation of composition；

- during the analysis phase, will the second SCR catalyst described in when ammonia sliding occur（202）Actual ammonia fill level （NH_{3_ is actual}）With when there is ammonia sliding described in the second SCR catalyst（202）Desired ammonia fill level（NH_{3_ is expected}）Carry out Compare（311）；

- according to the second SCR catalyst described in when ammonia sliding occur（202）Actual ammonia fill level（NH_{3_ is actual}）With it is pre- The ammonia fill level of phase（NH_{3_ is expected}）Comparison（311）To identify（320；330）Described two SCR catalysts（201；202）In At least one SCR catalyst in failure.

2. the method as described in claim 1, it is characterised in that if the second SCR catalyst described in when ammonia sliding occur （202）Actual ammonia fill level（NH_{3_ is actual}）With desired ammonia fill level（NH_{3_ is expected}）It is different（311）, then identify （320）Second SCR catalyst（202）In failure.

3. the method as described in claim 1, it is characterised in that at the beginning to the SCR catalyst（202；203）Upstream Nitrous oxides concentration（NOx__{Before processing}）And by described two SCR catalysts（201；202）Downstream nitrous oxides concentration （NOx__{After processing}）And ammonia density（NH_{After 3_ processing}）The summation of composition implements measurement（300）, two of which SCR catalyst（201；202） Worked in normal operation, and if by described two SCR catalysts（201；202）Downstream nitrous oxides concentration （NOx__{After processing}）And ammonia density（NH_{After 3_ processing}）The summation of composition is not consistent with desired nitrous oxides concentration, then identifies（301） The SCR system（200）In failure.

4. the method as described in claim 3, it is characterised in that if identified（301）The SCR system（200）In event Barrier and the second SCR catalyst described in when ammonia sliding occur（202）Actual ammonia fill level（NH_{3_ is actual}）With it is desired Ammonia fill level（NH_{3_ is expected}）It is consistent（311）, then identify（330）First SCR catalyst（201）In failure.

5. the method as any one of preceding claims, it is characterised in that repairing or changing（321；331）There is event The catalyst converter of barrier（201；202）Afterwards, the motor-driven vehicle going（340）The distance of defined and/or time and then repeat Methods described.

6. the method as described in claim 5, it is characterised in that change the analysis phase when repeating methods described.

7. the method as any one of preceding claims, it is characterised in that the 2nd SCR described in when ammonia sliding occur is urged Change device（202）Actual ammonia fill level（NH_{3_ is actual}）From described two SCR catalysts（201；202）Downstream ammonia density （NH_{After 3_ processing}）Middle acquisition（309）.

8. the method as any one of preceding claims, it is characterised in that the 2nd SCR described in when ammonia sliding occur is urged Change device（202）Desired ammonia fill level（NH_{3_ is expected}）From for second SCR catalyst（202）Characteristic curve （500）Middle acquisition（310）.

9. computer program, the computer program is configured for：Implement the side as any one of claim 1 to 8 Each step of method.

10. machine readable storage medium, stored in the machine readable storage medium based on described in claim 9 Calculation machine program.

11. electronic controller, the electronic controller is configured for：By means of as any one of claim 1 to 8 Method implements Fault Identification in the SCR system.