KR102605103B1 - Method for checking a scr system having at least two metering valves - Google Patents

Abstract

The present invention relates to a method for checking an SCR system comprising a transfer pump and two or more metering valves, where one metering valve is defective and the remaining metering valves are not defective. The following steps are carried out according to the invention. That is, the pressure (p _Ev, k, p Ev,k+1, p _{Ev,k+2) before metering supply (101, k, k+1} , _k +2) through one of the metering supply valves. ) and the pressure difference (Δp E, k, Δp) between the pressure (p _En,k , p _En,k+1 , p _En,k+2 ) after the metering supply ₍ k, k+1, k+2) _E,k+1 , Δp _E,k+2 ), and the metered volume of the reducing agent solution (ΔV _E,k , ΔV _E,k+1 , ΔV _E,k+2 ), for the one-side metered supply The metering supply ratio is calculated. Then, from the pressure difference between the pressure before metering through the other metering supply valve and the pressure after said metering, and the metered volume of the reducing agent solution, at least one additional metering supply ratio for said other metering supply valve is determined. It is calculated. Subsequently, a comparison is performed between the metering supply ratio of one metering supply valve and at least one metering supply ratio of one of the metering supply valves on the other side, wherein the metering supply ratio of the one metering supply valve is compared with the metering supply ratio of the other metering supply valve. If it differs from the metering supply ratio of the valve, it is recognized as defective.

Description

{METHOD FOR CHECKING A SCR SYSTEM HAVING AT LEAST TWO METERING VALVES}

The present invention relates to a method for checking an SCR system including two or more metering supply valves using comparison of metering supply ratios calculated during metering supply through each metering supply valve. Additionally, the present invention relates to a computer program that performs each step of the method when executed on a computer and a machine-readable storage medium storing the computer program. Finally, the invention relates to an electronic control device configured to carry out the method according to the invention.

Today, SCR catalytic converters are used specifically for the reduction of nitrogen oxides (NOx) in the exhaust gases of internal combustion engines in automobiles. DE 103 46 220 A1 describes the basic principles of SCR (selective catalytic reduction). Here, nitrogen oxide molecules on the surface of the SCR catalytic converter are reduced to elemental nitrogen in the presence of ammonia (NH3) as a reducing agent. The reducing agent is supplied in the form of urea water, which is separated from ammonia, also known commercially as AdBlue®. The transfer pump transfers the reductant solution from the reductant tank through a pressure line to one or more metering supply modules. The metering module includes a metering valve used to meter the reductant solution into the exhaust gas line upstream of the subsequent SCR catalytic converter. Control of metering and supply is carried out in an electronic control unit where metering and supply strategies for operation of the SCR system are stored.

In the so-called “volumetric mode” of the SCR system, the generally high precision of the transfer pump; It utilizes the property that, in the stationary state, a very accurately known mass of the reducing agent solution delivered through the transfer pump is discharged back from the system as a metered mass. Combined with relatively small tolerances in the mass of the reducing agent solution delivered via the transfer pump, a high mass accuracy is established on average. In volumetric mode, if the mass balance is disturbed, for example by a defect in the transfer pump or in the metering module, the metered mass can no longer be directly checked. In this case, there is a known method of monitoring the pressure using, for example, a pressure sensor.

Today, SCR systems often use multiple metering valves that are used to meter the reducing agent solution into the exhaust gas line, and these metering valves are usually assigned to different SCR catalytic converters. Typically, a plurality of metering valves are connected, via one or more common sections of pressure lines, to the same delivery pump, which supplies the reducing agent solution for all metering valves. Accordingly, the transported mass cannot be clearly assigned to only one metering valve.

DE 10 2012 218 092 A1 describes a method for monitoring the function of one or more metering supply valves. The reducing agent solution is metered in a clock-controlled manner by a transfer pump and one or more metering valves. In this case, the pressure is detected during control of the metering supply valve and evaluated by an adaptive filter. Subsequently, a comparison of the pressure values evaluated by the adaptive filter with expected comparison data is performed. Finally, based on the above comparison, defects in the metering valve and/or errors in the metered mass of the reducing agent solution are determined.

According to the invention, a method is presented for the inspection of an SCR system comprising a transfer pump and two or more metering valves, in particular a plurality of metering valves. The transfer pump transfers the reducing agent solution through a pressure line to two or more metering valves, which then meter the reducing agent solution into the exhaust gas line. Among two or more metering supply valves, one metering supply valve may be defective, and the remaining metering supply valves may not be defective. A “defective” metering valve means that the metering valve is defective or metering an incorrect volume or incorrect flow rate of the reducing agent solution.

The method herein includes the following steps.

The metering supply ratio is calculated for metering through one of the metering supply valves. For this purpose, the pressure difference between the pressure before and after the metering supply through the metering supply valve is calculated, and at this time, the pressure difference is applied to the proportional equation with the metered volume of the reducing agent solution as expressed in "Equation 1" below. do.

(Formula 1)

In the above formula, α is the metering supply ratio, Δp _E is the pressure difference during metering supply, and ΔV _E is the volume change during metering supply. The pressure difference during metered supply (Δp _E ) can be calculated as the difference between the pressure before metered supply (p _Ev ) and the pressure after metered supply (p _En ).

Additionally, the additional metering supply ratio for the other metering supply valve is calculated in the same way. Here too, the pressure difference between the pressure before and after the metering supply through the metering supply valve is calculated, and the pressure difference is applied in proportion to the volume of the reducing agent solution metered here. In this case, "Formula 1" applies correspondingly.

In this case, it should be borne in mind at the same time that only one metering supply of the reducing agent solution is carried out at any time through only one metering supply valve, because otherwise the respective volume changes and pressure differences would no longer be connected to one metering supply valve. This is because it cannot be allocated, and as a result, the metering supply ratio may be distorted. Metering strategies in which metering supplies are performed one after another will be explained later.

Subsequently, a comparison is performed between the metering supply ratio of the metering supply valve on one side and the metering supply ratio of at least one metering supply valve of one of the metering supply valves on the other side. In other words, the comparison is a direct comparison of two metering feed ratios for two different metering feed valves.

If the metering supply ratio of one metering supply valve deviates from the metering supply ratio of the other metering supply valve, that is, if the two metering supply ratios are different from each other, it is recognized as defective. The recognized fault is a “quantity error” and initially indicates that one of the two metering supply valves is faulty.

If the SCR system includes more than two metering valves, i.e., three or more, the above-described steps of the method can be repeated for the additional metering valves, thereby providing a complete metering valve for all metering valves in the SCR system. The above-described direct comparison of metering supply ratios can be performed. Preferably, direct comparison is performed according to a schema. In this case, especially in the current metering cycle, metering supply valves that have already been compared using our method and for which no defects have been detected are excluded from the repetition. As a result, not only time but also resources (especially reducing agent solutions) are saved. Optionally, if the fault has already been detected previously, the calculation of additional metering ratios for additional metering supply valves and their comparison can be omitted.

According to one aspect, the metering valve may be recognized as defective if the associated metering ratio is above an upper threshold or below a lower threshold, i.e. outside an acceptable range.

According to another aspect, when the SCR system includes three or more metering supply valves, if the metering supply ratio of one metering supply valve is different from the metering supply ratio of at least two of the other metering supply valves, the metering supply valve on one side may be perceived as having a defect. Thereby, a defective metering valve can be recognized with a sufficiently high probability for continued action.

Furthermore, additional metering ratios of the other metering valves can also be compared with each other, which can be used to more reliably recognize the defective metering valve. In this case, the metering ratios of all metering valves of the SCR system in particular can be calculated, compared and incorporated in this way.

Furthermore, the pressure ratio can be calculated from the transport ratio for metering supply and the metering supply ratio. The transfer ratio is calculated as the pressure difference between the pressure before and after the transfer of the reducing agent solution through the transfer pump, and then the pressure difference is applied to a proportional equation with the transferred volume of the reducing agent solution as expressed in "Equation 2" below. It is calculated by becoming.

(Formula 2)

In the above formula, γ is the transfer ratio, Δp _F is the pressure difference during transfer, and ΔV _F is the volume change during transfer. The pressure difference during transfer (Δp _F ) can be calculated as the difference between the pressure before transfer (p _Fv ) and the pressure after transfer (p _Fn ).

In addition, in Formula 3, the above-mentioned pressure ratio calculated by the metering supply ratio (α) and the transfer ratio (γ) ( ) is expressed. In this case, it is utilized that the transfer pump and the metering supply valves are connected to each other through at least a part of a common pressure line, and the reducing agent solution is transferred through this common pressure line. As a result, the pressure after delivery coincides with the pressure before metering (p _Fn = p _Ev ), and according to the volumetric principle, the delivered volume of the reducing agent solution corresponds to the metered volume (ΔV _F = ΔV _E ).

(Formula 3)

Pressure ratio ( ) is defined as the method of metering supply through the metering supply valve, expressed here. Since the metering supply valves share at least a portion of a common pressure line that conveys the reducing agent solution and creates pressure therein, the pressure ratio ( ) may be considered common for metering supplies through all metering supply valves of the SCR system.

The pressure ratio can be used as a prerequisite for comparison of metering supply ratios. The pressure ratio in a defect-free SCR system should be 1 for each metering supply through one of the metering supply valves. Comparison of metering supply ratios for each metering supply valve can only be performed if the pressure ratio deviates from unity. Thresholds may be provided to identify deviations from 1, and a deviation is identified if the pressure ratio falls below or above these thresholds. The pressure ratio or its deviation from 1 can be calculated in a simple way, for example by measuring pressure differences using a pressure sensor. However, defects in the transfer pump may also cause variations in the pressure ratio.

If the pressure ratios for the metering supply valves have already been calculated, a comparison of the metering supply ratios can advantageously be realized by comparing the pressure ratios for the respective metering supply valves. If the pressure ratio of one of the metering supply valves is different from the metering supply ratio of the other metering supply valve, one of the metering supply valves may be recognized as defective. Additionally, in this case, the metering supply valve whose pressure ratio deviates from 1 may be recognized as defective.

For the method herein, special metering strategies introduced below may be provided. Through these metering and dispensing strategies, interference effects that can lead to inaccurate metering and dispensing ratios during metering can be eliminated, or at least reduced. The following metering strategies can be partially or completely combined with each other.

In one metering strategy, the simultaneous metering demand for a plurality of metering valves can be divided into metering demands performed alternately and sequentially for the metering valves. In this way, it is achieved that metering through several metering and supply valves is not carried out simultaneously.

In another metering strategy, the metered volume of the reducing agent solution can be divided into several metering doses. As a result, the number of metering supplies performed increases, and the evaluable metering supply ratio increases accordingly.

In order to accurately calculate the pressure difference during metering supply, the pressure before metering supply and the pressure after metering supply must be sufficiently static. Therefore, preferably, a waiting time can be waited for the pressure to transition between two metering supplies carried out in succession not only through the same metering supply valve but also through different metering supply valves. The preferred waiting time is preferably greater than 200 ms, particularly preferably greater than or equal to 250 ms. Similarly, when calculating the pressure difference during transfer, the pressure before and after transfer must be sufficiently static. Therefore, a corresponding waiting time can be waited between transfer and metering.

When the transfer pump delivers reducing agent during metering, the pressure inside the pressure line fluctuates in a way that distorts the calculated metering ratio. Accordingly, it has been found to be desirable to discard the metering supply ratio calculated during the metering supply.

According to one aspect, to calculate the metering ratio, multiple metering is performed through the same metering and supply valve, and the metering and supply ratios can be averaged into an average metering and supply ratio. In this case, the sum of the pressure differences in multiple metering supplies can be applied in a proportional equation with the cumulative volume metered during these metering supplies. Finally, the average metering ratio can be used, in particular, for comparison of metering ratios, instead of the metering ratio for another method. In this way, measurement errors are minimized.

The metering supply ratio depends on the rigidity of the SCR system. Since the metering valves are hydraulically connected to each other, the stiffness is the same for all metering valves. To be able to compare metering ratios for different metering valves, the metering strategy can be selected such that the stiffness remains constant. However, stiffness can vary depending on the proportion of air dissolved in the reducing agent solution. Therefore, advantageously, the calculation of the metering supply ratios for several metering supply valves, in particular the average metering supply ratios, can be performed at very short time intervals between each other. Accordingly, the waiting time between successively performed meterings is not chosen to be too large, for example about 250 ms. Additionally, stiffness depends on the prevailing pressure level. For that reason, the metering supplies are preferably carried out within substantially the same pressure level. Likewise, the calculation of the conveying ratio can be performed at very short time intervals and within the same pressure level as the calculation of the metering supply ratio.

SCR systems are not air-free, especially at the beginning of the metering cycle, but usually contain air bubbles in the pressure lines. If the air bubbles are similarly washed out of the pressure line during metering supply, the metering supply ratio also changes as the pressure difference changes. Therefore, preferably, a configuration can be provided that does not calculate the metering ratios at the start of the metering cycle.

The computer program herein is specifically configured to perform the respective steps of the method herein when executed on a computer or control device. The computer program of the present application allows the method of the present invention to be implemented in a conventional control device without structural changes to the control device. For this purpose, the computer program herein is stored in a machine-readable storage medium.

By installing the computer program of the present application into a conventional electronic control device, an electronic control device configured to check an SCR system comprising two or more metering supply valves is obtained.

Embodiments of the invention are illustrated in the drawings and described in more detail in the description below.

Figure 1 is a schematic diagram of an SCR catalyst system comprising a plurality of metering valves, which can be checked by one embodiment of the method according to the invention.
Figure 2 is a graph showing control of the metering supply valve, control of the transfer pump, and pressure of the SCR system of Figure 1 over time.
Figure 3 is a flow chart of a first embodiment of the method according to the invention.
Figure 4 is a flow chart of a second embodiment of the method according to the invention.
Figure 5 is a flowchart of a third embodiment of the method according to the invention.

1 shows a schematic diagram of an SCR system 1 for one or more SCR catalytic converters (not shown). The SCR system (1) includes three metering supply modules (21, 22, 23), the first metering supply module (21) comprising a first metering supply valve (A), and the second metering supply module (22). ) includes a second metering supply valve (B), and the third metering supply module 23 includes a third metering supply valve (C). The metering supply modules (21, 22, 23) are connected to the transfer module (4) through the pressure line (3), which transfers the reducing agent solution from the reducing agent tank (5) into the pressure line (3). Includes a transfer pump (41). The pressure line (3) has a first section (31) which runs downstream of the common section (30) to the first metering supply module (21); a second section (32) leading to a second metering module (22); It is divided into a third section (33) leading to the third metering and supply module (23). The SCR system (1) operates in a volumetric mode in which the mass of reducing agent solution delivered via the transfer pump (4) is completely metered through the metering valves (A, B, C). Additionally, a pressure sensor 6 can be placed in the common section 30 of the pressure line 3 and measure the pressure p there. pressure sensor (6); a transfer module (4) including a transfer pump (41); and metering supply modules 21, 22, 23 including metering supply valves A, B, C; are connected to a common electronic control device 7 and controlled via this electronic control device.

In Figure 2, several metering supplies 101 are shown through one of the metering supply valves A, B or C, for example the first metering supply valve A (for convenience, only one metering supply is given a reference number as an example). Control (100) of the metering supply valve (A), including: Graph of control 140 of the delivery pump 41, comprising several pump strokes 141 (likewise, only one pump stroke is numbered) that causes the reducing agent solution to be delivered into the pressure line 3 is plotted over time t. In addition, the resulting pressure p, measured by the pressure sensor 6 in the pressure line 3, is also shown. If the pump head 141 is implemented, the pressure p rises strongly, and when the metering supplies 101 are implemented, it gradually decreases.

Based on the above graph, aspects of the metering strategy used are explained. In the metered supply strategy used here, the volume to be metered and supplied of the reducing agent solution is divided into several metered supplies (101). In addition, at the start of the metering cycle, several metering supplies (101), for example 100 metering supplies, of a total of 3 grams of reducing agent solution are waited for, and in this graph, among them, in some cases, the metering supply (101) present in the pressure line (3) Three metering cycles are shown where the bubbles were washed out.

In the graph, the three metering supplies used to calculate the metering supply ratio (α _A , α _B , α _C ) (see FIGS. 3 to 5) are indicated by reference numerals “k, k+1, and k+2”. there is. The metered volumes (ΔV _{E,k, ΔV E} ,k+1 and ΔV _{E,k+2) are displayed for each of the metered supplies (k, k+1} and _k+2 ). Between the two successive metering supplies (k, k+1), there is a waiting time (t _W ) of 250 ms during which the pressure (p) transitions, and then the pressure (p) is measured. When choosing the waiting time (t _W ), it should be borne in mind that it is not chosen too large, because otherwise the proportion of air dissolved in the reducing agent solution may fluctuate, thereby reducing the rigidity of the SCR system (1) and the resulting This is because the metering supply ratio (α _A , α _B , α _C ) also changes. As an example, the pressure before metering supply (k) (p _Ev,k ) and the pressure after metering supply (k) (p _En,k ) (which corresponds to the pressure before the next metering supply (k+1)) is shown, and at these pressures the pressure difference (Δp _E,k ) for the metering supply (k) is calculated.

When calculating the metering ratios (α _A , α _B , α _C ), they are averaged over several metering cycles 101 to reduce possible measurement errors. For this purpose, the sum of all pressure differences (ΔP _E ) and the sum of all metered volumes (ΔV _E ) are calculated. Then, from the above two values, the average metering supply ratio ( ) is calculated.

(Formula 1*)

The metering supply ratios (α _A , α _B , α _C ) are discarded.

The description given above in the description in relation to Figure 2 applies equally to each of the metering supply valves A, B and C. In particular, the same metering strategy is used for all metering valves (A, B and C), of course the metering strategies can also be matched. In addition, according to the metering strategy, simultaneous metering requirements for a plurality of metering supply valves (A, B and C) are performed alternately in succession for the metering supply valves (A, B and C). divided into fields.

3 shows a flow chart of a first embodiment of the method according to the invention suitable for the inspection of two metering supply valves. In this case, the two metering ratios (α _A and α B) of the two metering valves (A and _B ) of the SCR system 1 in Figure 1 are compared. The third metering valve C is not considered separately here, and the three metering valves A, B and C can be completely interchanged with each other in the method. Furthermore, in still other embodiments, the third metering supply valve (C) may be configured such that the first metering supply valve (A) or the second metering supply valve (B) is configured to provide a third metering supply valve (C), especially as described below when repeating the method herein. It can be engaged in such a way that it is replaced by the supply valve (C).

At the start, a measurement 200 of the pressure p _Ev,A is performed before the metering 201 to the first metering valve A. A metering supply (201) of the desired volume (ΔV _E,A ) of the reducing agent solution through the first metering supply valve (A) is carried out, followed by measurement of the pressure (p _En,A ) after the metering supply (201) ( 202) is executed. From the pressure before metering supply (201) (p _Ev,A ) and the pressure after metering supply (201) (p _En,A ), the pressure generated through the first metering supply valve (A) during metering supply (201) The difference (Δp _E,A ) is calculated (203). From the pressure difference (Δp _{E,A) calculated for the metering supply (201) through the first metering supply valve (A} ) and the volume (ΔV _E,A ) of the reducing agent solution metered during the metering supply (201), According to Formula 1 (see above), the metering supply ratio (α _A ) for the first metering supply valve (A) is calculated (210). As already explained in relation to Figure 2, steps 200 to 203 can be repeated and the sum of all pressure differences (Δp _E,A ) and the sum of all metered volumes (ΔV _E,A ) can be calculated, Instead of the metering supply ratio (α _A ), the average metering supply ratio can be calculated.

Then, a waiting time (t _W ) is waited before the measurement (220) of the pressure (p _Ev,B ) before the metering supply (221) through the second metering supply valve (B) is performed. Similarly, the metering 221 of the desired volume ΔV _E,B of the reducing agent solution through the second metering valve B is effected, and then the pressure after the metering 221 (p _En,B ). Measurements 222 of are carried out, from which the pressure difference Δp _E,B for the second metering supply valve B is calculated 223. In the same way, the metered supply ratio (α _B ) to the second metered supply valve (B) is determined by the metered volume (ΔV E,B) and the pressure difference (ΔV _E,B ) for the metered supply (221) of the second metered supply valve ( Δp _E,B ) is calculated from (230). Here too, steps 220 to 223 are repeated so that the already described averaging of the metering feed ratio α _B can be performed. In one embodiment, first the averaged metering ratio for the first metering supply valve (A) and then the averaged metering supply ratio for the second metering supply valve (B) are calculated as described above. In another embodiment, steps 200 to 203 and steps 220 to 223 are performed alternately in succession or in another order before the averaged metering ratios are calculated. It should be noted that in this case, steps 200 to 203 and steps 220 to 223 are not executed simultaneously.

Finally, a comparison 240 of the metering supply ratio (α _A ) of the first metering supply valve (A) and the metering supply ratio (α _B ) of the second metering supply valve (B) is performed. If the two metering supply ratios (α _A and α _B ) are different from each other, a defect 250 of one side (A or B) of the two metering supply valves, especially a supply amount error, is inferred. If the two metering supply ratios (α _A and α _B ) match each other, it is not recognized as a defect, and the method is repeated. In this case, in other embodiments, when repeating, the third metering supply valve (C) (or an additional metering supply valve, as the case may be) may be connected to the third metering supply valve (C) [or an additional metering supply valve (C), as the case may be. metering valve(s)].

Once recognized as defective (250), the two metering ratios (α _A and α _B ) of the two metering supply valves (A and B) are equal to the first upper threshold (S ₁ ) and the second lower threshold (S ₂ ). It is compared to (260). If the metering supply ratio (α _A ) of the first metering supply valve (A) exceeds the first threshold value (S ₁ ) or is below the second threshold value (S ₂ ), the first metering supply valve (A) It is perceived as defective (271). If the metering supply ratio (α _B ) of the second metering supply valve (B) exceeds the first threshold value (S ₁ ) or is below the second threshold value (S ₂ ), the second metering supply valve (B) perceived as defective (272). In still other embodiments, a unique pair of thresholds may be used for comparison 260 for each of the metering valves A and B.

4 shows a flow chart of a second embodiment for checking the three metering valves A, B and C of the SCR system 1 of FIG. 1. The same steps that can be referenced in the description of FIG. 3 are given the same reference numerals. In addition to the two metering ratios α A and _{α B} for the first metering valve A and the second metering valve B, whose calculations 210 and 230 have already been fully mentioned, in the same manner The metering supply ratio (α _C ) for the third metering supply valve (C) is calculated (350). For this purpose, measurement 340 of the pressure (p _Ev,C ) before metering supply 341 through the third metering supply valve C is performed. Similarly, the metering 341 of the desired volume ΔV _E,C of the reducing agent solution through the third metering valve C is effected, and then the pressure after the metering 341 (p _En,C ) Measurements (342) of are carried out, from which the pressure difference (Δp _E,C ) for the third metering supply valve (C) is calculated (343). Then, from the metered volume (ΔV _E,C ) and pressure difference (Δp _E,C ) for the metering supply (342) of the third metering supply valve (C), the metering supply for the third metering supply valve (C) The ratio (α _C ) is calculated (350). For this metering supply ratio (α _C ) also, averaging can be performed in the manner already described.

Now, in a comparison step 360, the three metering ratios (α _A , α _B and α _C ) are compared to each other. If the three metering supply ratios (α _A , α _B and α _C ) match each other, no defect is recognized and the method is repeated. However, if one of the metering ratios (α _A , α _B or α _C ) differs from the other two metering ratios, the relevant metering valve (A, B or C) is recognized as defective. More precisely, if the metering supply ratio (α A) for the first metering supply valve ( _A ) is different from the other two metering supply ratios (α _B and α _C ), the first metering supply valve (A) is defective. It is recognized as such (370). Similarly, if the metering supply ratio (α _B ) for the second metering supply valve (B) is different from the other two metering supply ratios (α _A and α _C ), the second metering supply valve (B) is considered defective. is recognized (371), and if the metering supply ratio (α _C ) for the third metering supply valve (C) is different from the other two metering supply ratios (α _A and α _B ), the third metering supply valve (C) is defective. It is recognized that there is (372).

In Figure 5, a flow chart of a third embodiment of the method according to the invention is shown, which is a variant of the first embodiment. The same reference numerals that may be referenced in the description of FIG. 3 indicate the same steps. At the start of the method herein, a measurement 400 of the pressure p _Fv prior to delivery 401 of the delivery pump 41 is performed. In order to transfer 401 the volume ΔV _F of the delivered reducing agent solution into the pressure line 3, the pump head 141 of the transfer pump 41 is executed. Subsequently, a measurement 401 of the pressure p _Fn after the transfer 401 is carried out. From the pressure before transfer (401) (p _F v) and the pressure after transfer (401) (p _Fn ), the pressure difference (Δp _F ) generated during transfer is calculated (403). From the pressure difference calculated for the transfer (Δp _F ) and the transferred volume of the reducing agent solution (ΔV _F ), the transfer ratio (γ) is calculated according to Equation 2 (404).

Subsequently, the metering supply ratio (α _A ) of the first metering supply valve (A) is calculated in the manner already described (210). The metering supply ratio (α _A ) of the first metering supply valve (A) is the pressure ratio ( ), it is compared with the transfer ratio (γ) previously calculated according to Equation 3. In the same way, the metering supply ratio (α _B ) of the second metering supply valve (B) is calculated (230), and similarly, the metering supply ratio (α _B ) and the transfer ratio (γ) of the second metering supply valve (B) are calculated (230). ) to pressure ratio ( ) is calculated (430). In the comparison step 440, the two pressure ratios ( and ) is checked to see whether one of them deviates from 1. The two pressure ratios ( and ) are all close to 1, then it is recognized that there is no fault in the SCR system 1 and the method is repeated (optionally with the involvement of additional metering valves). At least one of the two pressure ratios ( and/or ) If it deviates from 1, it is recognized as a supply quantity error within the SCR system (1). However, the feed amount error may also result from a defective transfer pump 41. Therefore, at least one of the two pressure ratios ( and/or ) deviates from 1, the two pressure ratios already calculated ( and ) Comparison 460 between them is performed. The two pressure ratios ( and ) are consistent with each other, and correspondingly, if both pressure ratios deviate equally from 1, it is recognized as a defect 470 of the transfer pump 41. The two pressure ratios ( and ) are different from each other, one of the two metering supply valves (A or B) must be defective, and in this case, the first pressure ratio ( ) deviates from 1, it is recognized that the first metering supply valve (A) is defective (471), and the second pressure ratio ( ) deviates from 1, it is recognized that the second metering supply valve (B) is defective (472).

Claims (14)

As a method for checking an SCR system (1) comprising one transfer pump (41) and two or more metering supply valves (A, B, C),
If one metering valve is defective and the remaining metering valves are not defective:
Among the metering supply valves, pressure (p _Ev,A, p Ev,k, _p Ev, _k ) before metering supply (201, 101, k, k+1, k+2) through one metering supply valve (A) ₊₁ , p _Ev,k+2 ) and pressure (p _En,A , p _En,k , p _En,k+1 , pressure difference between p _En,k+2 ) (Δp _E,A , Δp _E,k , Δp _E,k+1 , Δp _E,k+2 ), and
From the metered volume of reducing agent solution (ΔV _E,A , ΔV _E,k , ΔV _E,k+1 , ΔV _E,k+2 ),
Calculating a metering supply ratio (α _A ) for the metering supply valve (A) (210);
A pressure difference (Δp E,B) between the pressure (p _Ev,B ) before the metering supply (221) through the other metering supply valve (B) and the pressure (p _{En,B )} after the metering supply (221), and
From the metered volume of reducing agent solution (ΔV _E,B ),
Calculating at least one additional metering supply ratio (α _B ) for the other metering supply valve (B) (220);
Comparing the metering supply ratio (α A) of the one side metering supply valve ( _A ) with the metering supply ratio (α B) of at least one metering supply valve ( _B ) of the other metering supply valves (240) , 360); and
If the metering supply ratio (α _A ) of the one side metering supply valve (A) is different from the metering supply ratio (α B) of the other metering supply valve ( _B ), recognizing that there is a defect (250); How to check the SCR system. The method of claim 1, wherein the metering supply valves (A, B, C) have their metering supply ratios (α _A , α _B , α _C ) exceeding the first threshold value (S ₁ ) or the second threshold value ( A method for inspecting an SCR system, characterized in that if it falls below S ₂ ), it is recognized as defective (370, 371, 372). 2. The method of claim 1, wherein the SCR system comprises three or more metered supply valves (A, B, C) and at least one additional metered supply valve (C) to a non-metered supply ratio. (α _C ) is calculated (350), and one side metering supply valve (A, B, C) has its own metering supply ratio (α _A , α _B , α _C ) to the other side metering supply valves (A, B, A method for inspecting an SCR system, characterized in that it is recognized as defective (370, 371, 372) if it is different from at least two metering supply ratios (α _A , α _B , α _C ) of C). According to any one of claims 1 to 3,
For metering supply (201, 101, k, k+1, k+2),
metering supply ratio (α _A , α _B );
The pressure difference (Δp F) between the pressure (p _Fv ) before the transfer (401) of the reducing agent solution through the transfer pump (41) and the pressure (p _Fn ) after the transfer (401), and the transferred volume (ΔV _{F )} Calculated from (403) transport ratio (γ _A , γ _B ); pressure ratio ( , ) is calculated (410, 430),
Comparison 440 of the metering supply ratios (α _A , α _B ) is the pressure ratio ( , ) A method of checking an SCR system, characterized in that it is performed only when is out of 1. 5. The method of claim 4, wherein the comparison (440) of the metering supply ratios (α _A , α _B ) is performed by comparing the pressure ratios (440) for the respective metering supply valves (A, B). , ) is realized through comparison (460), and the pressure ratio of one side metering supply valve (A) ( ) is the pressure ratio of the other metering supply valve (B) ( ), an inspection method of the SCR system, characterized in that (471, 472) it is judged to be a defect in one side metering supply valve (A) or the other metering supply valve (B). 4. The method according to any one of claims 1 to 3, wherein in one metering strategy, simultaneous metering requirements for a plurality of metering valves are carried out alternately in succession for the metering valves (A, B). A method of inspecting an SCR system, characterized in that it is divided into metering supply requirements. The method according to any one of claims 1 to 3, wherein in one metering supply strategy, the volume to be metered and supplied of the reducing agent solution is divided into several metered supplies (k, k+1, k+2). , Inspection method of SCR system. The method according to any one of claims 1 to 3, wherein in the one metering supply strategy, there is a waiting time (t _W ) between two metering supplies (k, k+1; 201, 221) performed in succession. A method of inspecting an SCR system. The method according to any one of claims 1 to 3, wherein when the transfer pump (41) transfers the reducing agent (141) during the metering supply (101, k, k+1, k+2), the metering supply (101) , k, k+1, k+2) The metering supply ratio (α _A ) calculated for (k, k+1, k+2) is discarded. The method according to any one of claims 1 to 3, wherein for calculation (210, 230, 350) of the metering supply ratio (α _A , α _B , α _C ), the same metering supply valves (A, B, C) are used. Multiple metering and supply (k, k+1, k+2) are executed through, and the metering and supply ratio (α _A , α _B , α _C ) is the average metering and supply ratio ( ), an inspection method of an SCR system, characterized in that it is averaged. The method according to any one of claims 1 to 3, wherein the rigidity of the SCR system is taken into account in the metering supply strategy. A computer program stored on a machine-readable storage medium and configured to perform each step of the method according to any one of claims 1 to 3. A machine-readable storage medium storing the computer program according to claim 12. Electronic control device (7) adapted to check an SCR system (1) comprising two or more metering valves (A, B, C) using the method according to any one of claims 1 to 3.

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