(19)
(11)EP 3 453 853 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
04.11.2020 Bulletin 2020/45

(21)Application number: 17792746.4

(22)Date of filing:  28.04.2017
(51)International Patent Classification (IPC): 
F01N 3/08(2006.01)
F01N 3/18(2006.01)
F01N 3/10(2006.01)
B01D 53/94(2006.01)
F01N 3/20(2006.01)
F01N 13/00(2010.01)
(86)International application number:
PCT/JP2017/016957
(87)International publication number:
WO 2017/191813 (09.11.2017 Gazette  2017/45)

(54)

EXHAUST GAS PURIFICATION SYSTEM FOR INTERNAL COMBUSTION ENGINE, AND EXHAUST GAS PURIFICATION METHOD FOR INTERNAL COMBUSTION ENGINE

ABGASREINIGUNGSSYSTEM FÜR VERBRENNUNGSMOTOR UND ABGASREINIGUNGSVERFAHREN FÜR VERBRENNUNGSMOTOR

SYSTÈME DE PURIFICATION DE GAZ D'ÉCHAPPEMENT POUR MOTEUR À COMBUSTION INTERNE ET PROCÉDÉ DE PURIFICATION DE GAZ D'ÉCHAPPEMENT POUR MOTEUR À COMBUSTION INTERNE


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 02.05.2016 JP 2016092375

(43)Date of publication of application:
13.03.2019 Bulletin 2019/11

(73)Proprietor: Isuzu Motors Limited
Tokyo 140-8722 (JP)

(72)Inventor:
  • NAGASHIMA Youhei
    Fujisawa-shi Kanagawa 252-0881 (JP)

(74)Representative: Miller Sturt Kenyon 
9 John Street
London WC1N 2ES
London WC1N 2ES (GB)


(56)References cited: : 
JP-A- 2009 510 333
JP-A- 2012 087 628
US-A1- 2009 272 101
JP-A- 2010 031 731
JP-A- 2015 098 869
US-A1- 2010 024 401
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    Technical Field



    [0001] The present disclosure relates to an exhaust gas purification system for an internal combustion engine and an exhaust gas purification method for an internal combustion engine.

    Background Art



    [0002] A selective reduction catalyst device (SCR) is provided as one of exhaust gas purification treatment devices in an exhaust passage of an internal combustion engine such as a diesel engine mounted on a vehicle (for example, see Patent Document 1). The selective reduction catalyst device (SCR) is a device that reduces and purifies NOx contained in exhaust gas with ammonia (NH3) generated by hydrolyzing urea water injected toward the exhaust gas from a urea water supply device provided in the exhaust passage on an upstream side by heat of the exhaust gas.

    Prior Art Document


    Patent Document



    [0003] Patent Document 1: JP-A-2013-515897

    [0004] US 2010/024401 discloses an exhaust gas purification apparatus for an internal combustion engine, in which an exhaust pipe is provided with a SCR catalyst (NOx catalyst) and an oxidation catalyst. A urea water adding valve and an exhaust gas temperature sensor are provided upstream of the SCR catalyst. A downstream NOx sensor is provided downstream of the SCR catalyst. The oxidation catalyst is provided with a catalyst temperature sensor. An ECU computes a temperature of the oxidation catalyst based on a detection value of the catalyst temperature sensor. Further, the ECU computes a temperature of exhaust gas flowing into the oxidation catalyst based on a detection value of the exhaust gas temperature sensor. The ECU detects ammonia flowing out from the SCR catalyst based on a differential temperature between the temperature of the catalyst and the temperature of the exhaust gas.

    Summary of Invention


    Problems to be Solved by Invention



    [0005] However, when a supply amount of the urea water from the urea water supply device becomes excessive, a generation amount of the ammonia may become excessive and a part of the ammonia may slip to a downstream side of the selective reduction catalyst device. If an ammonia slip amount can be calculated with high accuracy, the accuracy of failure diagnosis improves, and the urea water can be supplied from the urea water supply device without excess or deficiency in the reduction of NOx in the exhaust gas, but a good method of calculating the ammonia slip amount has not been proposed.

    [0006] An object of the present disclosure is to provide an exhaust gas purification system for an internal combustion engine and an exhaust gas purification method for an internal combustion engine in which the ammonia slip amount at an outlet of the selective reduction catalyst device can be calculated with high accuracy.

    Means for Solving Problems



    [0007] An exhaust gas purification system for an internal combustion engine according to an aspect of the invention is defined in claim 1.

    [0008] Further, an exhaust gas purification method for an internal combustion engine according to another aspect of the invention is defined in claim 9.

    Effect of Invention



    [0009] According to the exhaust gas purification system for an internal combustion engine and the exhaust gas purification method for an internal combustion engine of the present disclosure, the ammonia slip amount at an outlet of the selective reduction catalyst device group can be calculated with high accuracy.

    [0010] Further, by using the calculated value of the ammonia slip amount, the diagnostic accuracy of the purification rate of the selective reduction catalyst device group and the accuracy of the supply control of the urea water from the urea water supply device can be improved.

    [0011] Further, since it is not necessary to provide an ammonia concentration detection sensor at the outlet of the selective reduction catalyst device group, the cost can be reduced.

    Brief Description of Drawings



    [0012] 

    FIG. 1 is a diagram schematically showing a configuration of an exhaust gas purification system for an internal combustion engine according to an embodiment of the present disclosure.

    FIG. 2 is a diagram showing a relationship between an ammonia calorific value and an ammonia slip amount.

    FIG. 3 is a diagram showing a process of calculating the ammonia slip amount based on a first temperature.

    FIG. 4A is a diagram showing a relationship among the first temperature, an exhaust gas flow rate, and a first correction coefficient.

    FIG. 4B is a diagram showing a relationship among the first temperature, an upstream NOx concentration, and a second correction coefficient.

    FIG. 4C is a diagram showing a relationship among the first temperature, an upstream NOx flow rate, and a third correction coefficient.

    FIG. 4D is a diagram showing a relationship among the first temperature, an estimated ammonia storage amount, and a fourth correction coefficient.

    FIG. 4E is a diagram showing a relationship among the first temperature, a ratio R of nitrogen monoxide to nitrogen dioxide contained in the exhaust gas, and a fifth correction coefficient.

    FIG. 5 is a diagram showing a control flow of an exhaust gas purification method for an internal combustion engine according to the embodiment of the present disclosure.


    Description of Embodiments



    [0013] Hereinafter, an exhaust gas purification system for an internal combustion engine and an exhaust gas purification method for an internal combustion engine of an embodiment according to the present disclosure will be described with reference to the drawings. Incidentally, in the present embodiment, the number of selective reduction catalyst device configuring a selective reduction catalyst device group provided in an exhaust gas purification treatment device is one, but a plurality of selective reduction catalyst devices may be provided.

    [0014] As shown in FIG. 1, the exhaust gas purification system 1 for an internal combustion engine of the embodiment according to the present disclosure is a system including an oxidation catalyst device (DOC) 12, a particulate collecting device (CSF) 13, a urea water supply device 22, a selective reduction catalyst device 14 and an ammonia slip catalyst device (oxidation catalyst device (DOC)) 15 which are provided in an exhaust passage 11 of an engine (internal combustion engine) 10 in order from an upstream side (engine side).

    [0015] Exhaust gas G of the engine 10 passes through the devices 12 to 15 configuring the exhaust gas purification system 1, so that components to be purified, such as particulate matter (PM) and nitrogen oxides (NOx) contained in the exhaust gas G are purified, and purified exhaust gas Gc is discharged to the atmosphere via a muffler (not shown) or the like.

    [0016] In FIG. 1, the oxidation catalyst device 12 and the particulate collecting device 13 configure a first exhaust gas purification treatment device; a selective reduction catalyst device 14 and an ammonia slip catalyst device 15 configure a second exhaust gas purification treatment device.

    [0017] The oxidation catalyst device 12 is a device that oxidizes hydrocarbon (HC) and nitrogen monoxide (NO) contained in the exhaust gas G. Particularly, when the exhaust gas G is at a low temperature, as a ratio of nitrogen monoxide (NO) and nitrogen dioxide (NO2) contained in the exhaust gas G approaches 1:1, a NOx purification rate in the selective reduction catalyst device 14 on a downstream side increases, and thus nitrogen monoxide (NO) is oxidized to increase a proportion of nitrogen dioxide (NO2) in the oxidation catalyst device 12.

    [0018] The particulate collecting device 13 is a device that collects PM contained in the exhaust gas G. There is an upper limit to an amount (collection amount) of PM that can be collected in the particulate collecting device 13, and as the collection amount of PM approaches the upper limit, a differential pressure across the particulate collecting device 13 rises and the performance of the engine 10 is deteriorated. Therefore, a forced PM regeneration control of the particulate collecting device 13 is regularly performed so as to burn and remove the PM collected in the particulate collecting device 13.

    [0019] The selective reduction catalyst device 14 is a device that reduces and purifies NOx contained in the exhaust gas G with ammonia (NH3) which is generated by hydrolyzing urea water U injected toward the exhaust gas G from the urea water supply device 22 provided in the exhaust passage 11 on the upstream by heat of the exhaust gas G.

    [0020] The selective reduction catalyst device 14 can store ammonia in a supported catalyst and mainly reduces and purifies NOx contained in the exhaust gas G with the stored ammonia. However, there is an upper limit to an amount (storage amount) of ammonia that can be stored, and ammonia that exceeds the upper limit and cannot be stored any more is discharged to the exhaust passage 11 on the downstream side of the selective reduction catalyst device 14.

    [0021] Incidentally, the hydrolysis reaction of the urea water U to the ammonia in the selective reduction catalyst device 14 is performed based on a chemical formula such as "(NH2)2CO + H2O → NH3 + HNCO" (when the temperature of the exhaust gas G is extremely low), or "HNCO + H2O → NH3 + CO2" (when the temperature of the exhaust gas G is low). Further, the oxidation-reduction reaction of ammonia and NOx in the selective reduction catalyst device 14 is performed based on a chemical formula such as "NO + NO2 + 2NH3 → 2N2 + 3H2O", "4NO + 4NH3 + O2 → 4N2 + 6H2O", or "4NO2 + 4NH3 → 4N2 + 6H2O + O2".

    [0022] The ammonia slip catalyst device 15 is a device that oxidizes the ammonia discharged from the selective reduction catalyst device 14 on an upstream side to nitrogen (N2) or NOx. The oxidation reaction is performed based on a chemical formula such as "4NH3 + 5O2 → 4NO + 6H2O", "2NH3 + 2O2 → N2O + 3H2O", or "4NH3 + 3O2 → 2N2 + 6H2O". When the injection amount of the urea water U from the urea water supply device 22 is excessive, the amount of ammonia discharged from the selective reduction catalyst device 14 increases, the amount of NOx generated by oxidizing ammonia in the ammonia slip catalyst device 15 also increases, and thus the NOx purification rate of the exhaust gas purification system as a whole decreases.

    [0023] Further, the urea water supply device 22 is connected to a urea water storage tank 20 that stores the urea water U via a urea water supply pump 21. The urea water supply pump 21 is operated by a control signal from a urea water supply control device (DCU) 41 described later, so that a part of the urea water U stored in the urea water storage tank 20 is supplied to the urea water supply device 22 via the urea water supply pump 21. The urea water U supplied to the urea water supply device 22 is injected toward the exhaust gas G passing through the exhaust passage 11 by opening an injection valve (not shown) of the urea water supply device 22 by a control signal from the urea water supply control device 41.

    [0024] Further, an upstream temperature sensor for oxidation catalyst device 30 and a downstream temperature sensor for oxidation catalyst device 31 are respectively provided on an inlet side (upstream side) and an outlet side (downstream side) of the oxidation catalyst device 12; an upstream temperature sensor 33 is provided on an inlet side (upstream side) of the selective reduction catalyst device 14; and a downstream temperature sensor 34 (downstream temperature detecting device) is provided on an outlet side (downstream side) of the ammonia slip catalyst device 15.

    [0025] Further, an upstream NOx concentration sensor (upstream NOx concentration detecting device) 32 is provided in the exhaust passage 11 between the particulate collecting device 13 and the urea water supply device 22; and a downstream NOx concentration sensor (downstream NOx concentration detecting device) 35 is provided on the outlet side (downstream side) of the ammonia slip catalyst device 15.

    [0026] Further, an engine control device (ECU) 40 and the urea water supply control device (DCU) 41 are provided. The engine control device 40 is a device that controls an operating state of the engine 10 based on data such as detection values of the upstream temperature sensor for oxidation catalyst device 30 and the downstream temperature sensor for oxidation catalyst device 31, temperature of engine cooling water, atmospheric pressure, the temperature and flow rate of intake air flowing into the engine 10, and the flow rate of fuel injected into a cylinder (not shown) of the engine 10.

    [0027] The urea water supply control device 41 is a device that controls an operating state of the urea water supply pump 21 and the urea water supply device 22 based on data input to the engine control device 40 and then acquired from the engine control device 40, or data (for example, a detection value of the upstream temperature sensor 33, or the like) directly input to the urea water supply control device 41.

    [0028] In the exhaust gas purification system 1 for an internal combustion engine of the embodiment according to the present disclosure, the urea water supply control device (a control device that controls the exhaust gas purification system 1) 41 detects, by the downstream temperature sensor 34, first temperature T1 which is the temperature of the exhaust gas Gc which has passed through the second exhaust gas purification treatment device during supply of the urea water U from the urea water supply device 22; and calculates, from preset data, second temperature T2 which is the temperature of the exhaust gas Gc which has passed through the second exhaust gas purification treatment device in the same operating state of the engine 10 as when the first temperature T1 is detected and in a state where the supply of the urea water U from the urea water supply device 22 is stopped. As the preset data used for calculating the second temperature T2, for example, a control map (model) ("control map for T2" in FIG. 3) in which the second temperature T2 is set in accordance with the operating state of the engine 10, which is prepared in advance by experiments and stored in the urea water supply control device 41, is used.

    [0029] The urea water supply control device 41 calculates, based on the first temperature T1 and the second temperature T2, an ammonia calorific value C which is the amount of heat generated in the ammonia slip catalyst device 15 by oxidation of ammonia which is generated by hydrolysis from the urea water U supplied from the urea water supply device 22; and calculates an ammonia slip amount S from the selective reduction catalyst device 14 based on the ammonia calorific value C.

    [0030] Then, a urea water supply amount is calculated based on the calculated ammonia slip amount S, and the urea water is supplied with the calculated urea water supply amount. Alternatively, based on the calculated ammonia slip amount S, the urea water supply device 22 and the exhaust gas purification treatment device, particularly the selective reduction catalyst device 14 and the ammonia slip catalyst device 15, are subjected to failure diagnosis.

    [0031] Incidentally, the calculation of the ammonia calorific value C and the ammonia slip amount S is performed every time a control time set in advance by experiments or the like is elapsed during the operation of the engine 10 by the urea water supply control device 41. Further, the ammonia calorific value C is calculated by multiplying a difference ΔT (= T1 - T2) between the first temperature T1 and the second temperature T2 by a flow rate F of the exhaust gas Gc (C = ΔT × F). Further, the ammonia slip amount S is calculated based on the ammonia calorific value C by, for example, the following method. First, a control map (see FIG. 2) showing the relationship between the ammonia calorific value C and the ammonia slip amount S is prepared in advance and stored in the urea water supply control device 41. Then, the ammonia slip amount S is calculated by comparing the calculated ammonia calorific value C with the control map.

    [0032] According to such a configuration, the ammonia calorific value C generated by the oxidation of the ammonia slipping from the selective reduction catalyst device 14 by the ammonia slip catalyst device 15 on the downstream side is calculated based on a rise amount ΔT (= first temperature T1 - second temperature T2) of the exhaust temperature, and thus the calculation accuracy of the ammonia calorific value C can be improved. As a result, the calculation accuracy of the ammonia slip amount S also can be improved.

    [0033] Further, in the exhaust gas purification system 1 for an internal combustion engine, the urea water supply control device 41 calculates a total correction coefficient K based on the first temperature T1 (unit: degC), the flow rate F (unit: kg/h) of the exhaust gas G passing through the exhaust passage 11, an upstream NOx concentration Nud (unit: ppm) which is the detection value of the upstream NOx concentration sensor 32, an upstream NOx flow rate Nuf (unit: mg/s) calculated by converting the upstream NOx concentration Nud, an estimated ammonia storage amount Ns (unit: g) which is an estimated value of the amount of ammonia stored in the selective reduction catalyst device 14, and a ratio R of nitrogen monoxide (NO) to nitrogen dioxide (NO2) contained in the exhaust gas G flowing into the selective reduction catalyst device 14, and corrects the ammonia slip amount S based on the calculated total correction coefficient K.

    [0034] According to such a configuration, the ammonia slip amount S is corrected based on various parameters (T1, F, Nud, Nuf, Ns, R) related to the NOx purification rate in the selective reduction catalyst device 14, so that the calculation accuracy of the ammonia slip amount S can be further improved.

    [0035] Further, in the exhaust gas purification system 1 for an internal combustion engine, as shown in FIG. 3 and FIGS. 4A to 4E, the urea water supply control device 41 calculates the total correction coefficient K (= k1 × k2 ×k3 × k4 × k5) based on a first correction coefficient k1 calculated based on the first temperature T1 and the flow rate F of the exhaust gas G, a second correction coefficient k2 calculated based on the first temperature T1 and the upstream NOx concentration Nud, a third correction coefficient k3 calculated based on the first temperature T1 and the upstream NOx flow rate Nuf, a fourth correction coefficient k4 calculated based on the first temperature T1 and the estimated ammonia storage amount Ns, and a fifth correction coefficient k5 calculated based on the first temperature T1 and the ratio R of nitrogen monoxide to nitrogen dioxide.

    [0036] Incidentally, the "control map for k1" in FIG. 3 corresponds to FIG. 4A. Further, the "control map for k2" in FIG. 3 corresponds to FIG. 4B. Further, the "control map for k3" in FIG. 3 corresponds to FIG. 4C. Further, the "control map for k4" in FIG. 3 corresponds to FIG. 4D. Further, the "control map for k5" in FIG. 3 corresponds to FIG. 4E.

    [0037] According to such a configuration, the calculation accuracy of the total correction coefficient K for correcting the ammonia slip amount S can be improved.

    [0038] Further, in the exhaust gas purification system 1 for an internal combustion engine, the urea water supply control device 41 performs supply amount control of the urea water U by using the ammonia slip amount S calculated as described above. Regarding the supply amount control of the urea water U, there are the following two control methods depending on whether the detection value of the downstream NOx concentration sensor 35 is used.

    [0039] The method (first method) without using the detection value of the downstream NOx concentration sensor 35 is a method in which the urea water supply control device 41 corrects the supply amount of the urea water U from the urea water supply device 22 based on the ammonia slip amount S so that the ammonia slip amount S is not equal to or larger than a set threshold Sc set in advance by experiments or the like.

    [0040] Further, the method (second method) using the detection value of the downstream NOx concentration sensor 35 is a method in which the urea water supply control device 41 corrects the supply amount of the urea water U from the urea water supply device 22 based on the ammonia slip amount S, a downstream NOx concentration Ndd which is the detection value of the downstream NOx concentration sensor 35, and the estimated ammonia storage amount Ns which is the estimated value of the amount of ammonia stored in the selective reduction catalyst device 14 so that the ammonia slip amount S is not equal to or larger than the set threshold Sc.

    [0041] A correction amount is added to the supply amount of the urea water U every time the ammonia slip amount S becomes equal to or larger than a second set threshold Sc2 set in advance as a value smaller than the set threshold Sc, or every time the downstream NOx concentration Ndd becomes equal to or larger than a set threshold Nddc set in advance, or every time the estimated ammonia storage amount Ns becomes equal to or larger than a preset set threshold Nsc.

    [0042] Here, if the urea water supply control device 41 calculates the estimated ammonia storage amount Ns based on the ammonia slip amount S and a downstream NOx flow rate Ndf calculated by converting the downstream NOx concentration Ndd, the estimated ammonia storage amount Ns of the selective reduction catalyst device 14 can be calculated with high accuracy.

    [0043] A method of calculating the estimated ammonia storage amount Ns is, more specifically, a method of calculating the estimated ammonia storage amount Ns by subtracting an amount (set in advance by experiments or the like) of ammonia adhering to a wall surface of the exhaust passage (exhaust pipe) 11 between the urea water supply device 22, an amount (calculated based on the difference between the upstream NOx flow rate Nuf and the downstream NOx flow rate Ndf) of ammonia used for NOx purification in the selective reduction catalyst device 14, and the ammonia slip amount S from the amount of ammonia generated by hydrolyzing the urea water U injected from the urea water supply device 22.

    [0044] In either one of the two control methods described above, it is possible to optimize the supply amount of the urea water U from the urea water supply device 22 while suppressing the ammonia slip amount S from the selective reduction catalyst device 14. The method without using the detection value of the downstream NOx concentration sensor 35 has an advantage that the control time can be further shortened, while the method using the detection value of the downstream NOx concentration sensor 35 has an advantage that the control accuracy can be further improved.

    [0045] Further, in the exhaust gas purification system 1 for an internal combustion engine, the urea water supply control device 41 performs purification rate diagnosis (failure diagnosis) of the selective reduction catalyst device 14 by using the ammonia slip amount S calculated as described above. More specifically, the urea water supply control device 41 calculates a NOx purification rate P by the selective reduction catalyst device 14 based on the upstream NOx flow rate Nuf, the downstream NOx flow rate Ndf calculated by converting the downstream NOx concentration Ndd, and the ammonia slip amount S, and determines a failure in the selective reduction catalyst device 14 when the NOx purification rate P is equal to or lower than a determination threshold Pc set in advance by experiments or the like.

    [0046] Here, the downstream NOx concentration sensor 35 may detect not only the concentration of nitrogen oxides (NOx) contained in the exhaust gas G, but also the concentration of ammonia (NH3). Therefore, a concentration Ndft (= Ndf - S) of the nitrogen oxides (NOx) contained in the exhaust gas G which has passed through the ammonia slip catalyst device 15 is calculated by subtracting the ammonia slip amount S from the downstream NOx flow rate Ndf which is calculated by converting the detection value of the downstream NOx concentration sensor 35.

    [0047] That is, the NOx purification rate P is calculated using the following formula (1).



    [0048] Further, the determination threshold Pc may be set based on a control map (not shown) set in advance for each temperature and flow rate of the exhaust gas G passing through the selective reduction catalyst device 14, and may also be set as a value obtained by multiplying a diagnostic coefficient by the estimated value of the NOx purification rate of the selective reduction catalyst device 14 which is estimated according to the operating state of the engine 10.

    [0049] According to such a configuration, the NOx purification rate P of the selective reduction catalyst device 14 can be calculated with high accuracy, so that the accuracy of the purification rate diagnosis (determination of a failure) of the selective reduction catalyst device 14 can be improved.

    [0050] Next, FIG. 5 shows a control flow of the exhaust gas purification method for an internal combustion engine of the present disclosure based on the exhaust gas purification system 1 for an internal combustion engine. The control flow of FIG. 5 is shown as a control flow which is performed by calling from an advanced control flow at every preset control time according to the operating state of the engine 10, and then returning to the advanced control flow thereafter.

    [0051] When the control flow in FIG. 5 starts, in step S10, the first temperature T1 is detected, the first temperature T1 being the temperature of the exhaust gas Gc which has passed through the second exhaust gas purification treatment device; and the second temperature T2 is estimated, the second temperature T2 being the temperature of the exhaust gas Gc which has passed through the second exhaust gas purification treatment device in the same operating state of the engine 10 as when the first temperature T1 is detected and in a state where the supply of the urea water U from the urea water supply device 22 is stopped. After the control of step S10 is performed, the process proceeds to step S20.

    [0052] In step S20, the ammonia calorific value C which is the amount of heat generated in the ammonia slip catalyst device 15 by oxidation of ammonia is calculated based on the first temperature T1 and the second temperature T2 which are detected and estimated in step S10. The method of calculating the ammonia calorific value C has been described above, and the explanation thereof will be omitted here. After the control of step S20 is performed, the process proceeds to step S30.

    [0053] In step S30, the ammonia slip amount S from the selective reduction catalyst device 14 is calculated based on the ammonia calorific value C calculated in the step S20. The method of calculating the ammonia slip amount S has been described above, and the explanation thereof will be omitted here. After the control of step S30 is performed, the process is returned and the present control flow ends.

    [0054] Incidentally, in the control flow of FIG. 5, in a case of correcting the ammonia slip amount S with the total correction coefficient K, although not shown, first, the total correction coefficient K is calculated in parallel at any one of steps S10, S20, and S30. Then, after the step S30 ends, the process is not returned but proceeds to step S40 (not shown) so as to correct the ammonia slip amount S with the total correction coefficient K in step S40. After the control of step S40 is performed, the process is returned and the present control flow ends.

    [0055] As described above, an exhaust gas purification method for an internal combustion engine of the present disclosure based on the exhaust gas purification system 1 for an internal combustion engine is a method in which the exhaust passage 11 of the internal combustion engine 10 includes, in order from an upstream side: a urea water supply device 22; and an exhaust gas purification treatment device, the exhaust gas purification treatment device including: a selective reduction catalyst device group including at least one selective reduction catalyst device 14; and an oxidation catalyst device 15 arranged at a downstream side of the selective reduction catalyst device group, the exhaust gas purification method including: detecting a first temperature T1 which is a temperature of exhaust gas Gc which has passed through the exhaust gas purification treatment device during supply of urea water U from the urea water supply device 22; estimating a second temperature T2 which is a temperature of the exhaust gas Gc which has passed through the exhaust gas purification treatment device in a state where the engine 10 is in a same operating state as when the first temperature T1 is detected and the supply of the urea water U from the urea water supply device 22 is stopped; and calculating, based on the first temperature T1 and the second temperature T2, the ammonia calorific value C which is an amount of heat generated by the oxidation catalyst device 15 by oxidation of ammonia which has been generated from the urea water U supplied from the urea water supply device 22, and calculating an ammonia slip amount S from the selective reduction catalyst device group based on the ammonia calorific value C.

    [0056] According to the exhaust gas purification system 1 for an internal combustion engine configured as described above and the exhaust gas purification method for an internal combustion engine, the ammonia slip amount S at an outlet of the selective reduction catalyst device 14 can be calculated with high accuracy.

    [0057] Then, by using the calculated value of the ammonia slip amount S, the diagnostic accuracy of the purification rate of the selective reduction catalyst device 14 and the accuracy of the supply control of the urea water U from the urea water supply device 22 can be improved.

    [0058] Further, since it is not necessary to provide an ammonia concentration detection sensor at the outlet of the selective reduction catalyst device 14, the cost can be reduced.

    [0059] Incidentally, in the present embodiment, the exhaust gas purification treatment device is described based on the configuration having one selective reduction catalyst device 14, but the effects of the present disclosure described above can also be achieved when the exhaust gas purification treatment device is provided with two or more selective reduction catalyst devices 14.

    [0060] In this case, a temperature sensor or a NOx concentration sensor is further provided between the selective reduction catalyst devices 14, and it is preferable to correct the ammonia slip amount S by using the detection values since the calculation accuracy of the ammonia slip amount S can be further improved.

    Industrial Applicability



    [0061] The exhaust gas purification system for an internal combustion engine and the exhaust gas purification method for an internal combustion engine of the present disclosure is useful in that the ammonia slip amount in the outlet of the selective reduction catalyst device can be calculated with high accuracy.

    Description of Reference Numerals



    [0062] 

    1 exhaust gas purification system for internal combustion engine

    10 engine (internal combustion engine)

    11 exhaust passage

    14 selective reduction catalyst device

    15 ammonia slip catalyst device (oxidation catalyst device)

    22 urea water supply device

    32 upstream NOx concentration sensor (upstream NOx concentration detecting device)

    34 downstream temperature sensor (downstream temperature detecting device)

    35 downstream NOx concentration sensor (downstream NOx concentration detecting device)

    41 urea water supply control device

    T1 first temperature

    T2 second temperature

    C ammonia calorific value

    S ammonia slip amount

    Sc set threshold for ammonia slip amount

    P NOx purification rate

    Pc determination threshold for NOx purification rate

    F flow rate of exhaust gas

    Nud upstream NOx concentration

    Nuf upstream NOx flow rate

    Ndd downstream NOx concentration

    Ndf downstream NOx flow rate

    Ns estimated ammonia storage amount

    R ratio of nitrogen monoxide to nitrogen dioxide contained in exhaust gas

    K total correction coefficient

    k1 first correction coefficient

    k2 second correction coefficient

    k3 third correction coefficient

    k4 fourth correction coefficient

    k5 fifth correction coefficient

    U urea water

    G exhaust gas of engine

    Gc purified exhaust gas




    Claims

    1. An exhaust gas purification system (1) for an internal combustion engine (10), in which an exhaust passage (11) of the internal combustion engine includes, in order from an upstream side: a urea water supply device (22); an exhaust gas purification treatment device; and a downstream temperature detecting device (34), the exhaust gas purification treatment device including: a selective reduction catalyst device group including at least one selective reduction catalyst device (14); and an oxidation catalyst device (15) arranged at a downstream side of the selective reduction catalyst device group,
    wherein a control device (41) which controls the exhaust gas purification system is configured to:

    detect, by the downstream temperature detecting device, a first temperature (T1) which is a temperature of exhaust gas (Gc) which has passed through the exhaust gas purification treatment device during supply of urea water (U) from the urea water supply device;

    calculate, from preset data, a second temperature (T2) which is a temperature of exhaust gas (G) which has passed through the exhaust gas purification treatment device in a state where the engine is in a same operating state as when the first temperature is detected and the supply of the urea water from the urea water supply device is stopped; and

    calculate, based on a difference (ΔT) between the first temperature and the second temperature, an ammonia calorific value (C) which is an amount of heat generated by the oxidation catalyst device by oxidation of ammonia which has been generated from the urea water supplied from the urea water supply device, and calculate an ammonia slip amount (S) from the selective reduction catalyst device group based on the ammonia calorific value.


     
    2. The exhaust gas purification system (1) for an internal combustion engine (10) according to claim 1,
    wherein the control device (41) is configured to calculate a urea water supply amount based on the calculated ammonia slip amount (S) and supply the urea water (U) by the calculated urea water supply amount, or to perform failure diagnosis on the urea water supply device (22) and the exhaust gas purification treatment device based on the calculated ammonia slip amount.
     
    3. The exhaust gas purification system (1) for an internal combustion engine according to claim 1 or 2,
    wherein the exhaust passage (11) includes an upstream NOx concentration detecting device (32) at the upstream side of the urea water supply device (22), and
    wherein the control device (41) is configured to:

    calculate a total correction coefficient (K) based on: the first temperature (T1); a flow rate (F) of the exhaust gas passing through the exhaust passage; an upstream NOx concentration (Nud) which is a detection value of the upstream NOx concentration detecting device; an upstream NOx flow rate (Nuf) calculated from the flow rate of the exhaust gas and the upstream NOx concentration; an estimated ammonia storage amount (Ns) which is an estimated value of an amount of ammonia stored in the selective reduction catalyst device group; and a ratio (R) of nitrogen monoxide to nitrogen dioxide contained in exhaust gas flowing into the selective reduction catalyst device group; and

    correct the ammonia slip amount (S) based on the calculated total correction coefficient.


     
    4. The exhaust gas purification system (1) for an internal combustion engine according to claim 3,
    wherein the control device (41) calculates the total correction coefficient (K) based on:

    a first correction coefficient (k1) calculated based on the first temperature (T1) and the flow rate (F) of the exhaust gas (G);

    a second correction coefficient (k2) calculated based on the first temperature and the upstream NOx concentration (Nud),

    a third correction coefficient (k3) calculated based on the first temperature and the upstream NOx flow rate (Nuf),

    a fourth correction coefficient (k4) calculated based on the first temperature and the estimated ammonia storage amount (Ns), and

    a fifth correction coefficient (k5) calculated based on the first temperature and the ratio (R) of nitrogen monoxide to nitrogen dioxide.


     
    5. The exhaust gas purification system (1) for an internal combustion engine according to any one of claims 1 to 4,
    wherein the control device (41) is configured to:
    correct a urea water supply amount from the urea water supply device (22) based on the ammonia slip amount (S) so that the ammonia slip amount is not equal to or larger than a preset threshold.
     
    6. The exhaust gas purification system (1) for an internal combustion engine according to any one of claims 1 to 4,
    wherein the exhaust passage (11) includes a downstream NOx concentration detecting device (35) at the downstream side of the exhaust gas purification treatment device,
    wherein the control device (41) is configured to:
    correct a urea water supply amount from the urea water supply device (22) based on the ammonia slip amount (S), a downstream NOx concentration (Ndd) which is a detection value of the downstream NOx concentration detecting device, and the estimated ammonia storage amount (Ns) which is an estimated value of an amount of ammonia stored in the selective reduction catalyst device group so that the ammonia slip amount is not equal to or larger than a preset threshold (Sc).
     
    7. The exhaust gas purification system (1) for an internal combustion engine according to claim 6,
    wherein the control device (41) is configured to:
    calculate the estimated ammonia storage amount (Ns) based on the ammonia slip amount (S) and the downstream NOx concentration (Ndd).
     
    8. The exhaust gas purification system (1) for an internal combustion engine according to claim 6 or 7,
    wherein the control device (41) is configured to:

    calculate a NOx purification rate (P) by the selective reduction catalyst device group based on the upstream NOx flow rate (Nuf), a downstream NOx flow rate (Ndf) calculated by converting the downstream NOx concentration (Ndd), and the ammonia slip amount (S), and

    determine a failure in the selective reduction catalyst device group when the NOx purification rate is equal to or lower than a preset determination threshold (Pc).


     
    9. An exhaust gas purification method for an internal combustion engine (10) in which an exhaust passage (11) of the internal combustion engine includes, in order from an upstream side: a urea water supply device (22); and an exhaust gas purification treatment device, the exhaust gas purification treatment device including: a selective reduction catalyst device group including at least one selective reduction catalyst device (14); and an oxidation catalyst device (15) arranged at a downstream side of the selective reduction catalyst device group,
    the exhaust gas purification method comprising:

    detecting a first temperature (T1) which is a temperature of exhaust gas (Gc) which has passed through the exhaust gas purification treatment device during supply of urea water (U) from the urea water supply device;

    calculating, from preset data, a second temperature (T2) which is a temperature of exhaust gas (G) which has passed through the exhaust gas purification treatment device in a state where the engine is in a same operating state as when the first temperature is detected and the supply of the urea water from the urea water supply device is stopped; and

    calculating, based on a difference (ΔT) between the first temperature and the second temperature, an ammonia calorific value (C) which is an amount of heat generated by the oxidation catalyst device by oxidation of ammonia which has been generated from the urea water supplied from the urea water supply device, and calculating an ammonia slip amount (S) from the selective reduction catalyst device group based on the ammonia calorific value.


     


    Ansprüche

    1. Abgasreinigungssystem (1) für einen Verbrennungsmotor (10), bei dem ein Abgaskanal (11) des Verbrennungsmotors in der Reihenfolge von einer stromaufwärtigen Seite aus umfasst: eine Harnstoffwasser-Zuführvorrichtung (22); eine Abgasreinigungs-Behandlungsvorrichtung; und eine stromabwärtige Temperaturerfassungsvorrichtung (34), wobei die Abgasreinigungs-Behandlungsvorrichtung umfasst: eine selektive Reduktionskatalysatorvorrichtungs-Gruppe, die mindestens eine selektive Reduktionskatalysatorvorrichtung (14) umfasst; und eine Oxidationskatalysatorvorrichtung (15), die an einer stromabwärtigen Seite der selektiven Reduktionskatalysatorvorrichtungs-Gruppe angeordnet ist,
    wobei eine Steuervorrichtung (41), die das Abgasreinigungssystem steuert, konfiguriert ist, um:

    durch die stromabwärtige Temperaturerfassungsvorrichtung eine erste Temperatur (T1) zu erfassen, die eine Temperatur des Abgases (Gc) ist, das durch die Abgasreinigungs-Behandlungsvorrichtung während der Zuführung von Harnstoffwasser (U) von der Harnstoffwasser-Zuführvorrichtung hindurchgeströmt ist;

    aus voreingestellten Daten eine zweite Temperatur (T2) zu berechnen, die eine Temperatur des Abgases (G) ist, das durch die Abgasreinigungs-Behandlungsvorrichtung in einem Zustand hindurchgeströmt ist, in dem sich der Motor in einem gleichen Betriebszustand befindet, wie wenn die erste Temperatur erfasst wird und die Zuführung des Harnstoffwassers aus der Harnstoffwasser-Zuführvorrichtung gestoppt wird; und

    auf der Grundlage einer Differenz (ΔT) zwischen der ersten Temperatur und der zweiten Temperatur einen Ammoniak-Brennwert (C) zu berechnen, der eine Wärmemenge ist, die von der Oxidationskatalysatorvorrichtung durch Oxidation von Ammoniak erzeugt wird, das aus dem von der Harnstoffwasser-Zuführvorrichtung zugeführten Harnstoffwasser erzeugt wurde, und eine Ammoniakschlupfmenge (S) aus der selektiven Reduktionskatalysatorvorrichtungs-Gruppe auf der Grundlage des Ammoniak-Brennwerts zu berechnen.


     
    2. Abgasreinigungssystem (1) für einen Verbrennungsmotor (10) nach Anspruch 1,
    wobei die Steuereinrichtung (41) konfiguriert ist, um eine Harnstoffwasser-Zuführungsmenge auf der Grundlage der berechneten Ammoniakschlupfmenge (S) zu berechnen und das Harnstoffwasser (U) durch die berechnete Harnstoffwasser-Zuführungsmenge zuzuführen, oder um eine Fehlerdiagnose an der Harnstoffwasser-Zuführvorrichtung (22) und der Abgasreinigungs-Behandlungsvorrichtung auf der Grundlage der berechneten Ammoniakschlupfmenge durchzuführen.
     
    3. Abgasreinigungssystem (1) für einen Verbrennungsmotor nach Anspruch 1 oder 2,
    wobei der Abgaskanal (11) eine stromaufwärts gelegene NOx-Konzentrationserfassungsvorrichtung (32) an der stromaufwärts gelegenen Seite der Harnstoffwasser-Zuführvorrichtung (22) aufweist, und
    wobei die Steuereinrichtung (41) konfiguriert ist, um:

    einen Gesamtkorrekturkoeffizienten (K) zu berechnen auf der Grundlage von: der ersten Temperatur (T1) ; einer Durchflussgeschwindigkeit (F) des Abgases, das durch den Abgaskanal hindurchströmt; einer stromaufwärtigen NOx-Konzentration (Nud), die ein Erfassungswert der stromaufwärts gelegenen NOx-Konzentrationserfassungsvorrichtung ist; einer stromaufwärtigen NOx-Durchflussgeschwindigkeit (Nuf), die aus der Durchflussgeschwindigkeit des Abgases und der stromaufwärtigen NOx-Konzentration berechnet wird; einer geschätzten Ammoniak-Speichermenge (Ns), die ein geschätzter Wert einer Ammoniakmenge ist, die in der selektiven Reduktionskatalysatorvorrichtungs-Gruppe gespeichert ist; und einem Verhältnis (R) von Stickstoffmonoxid zu Stickstoffdioxid, das in dem Abgas enthalten ist, das in die selektive Reduktionskatalysatorvorrichtungs-Gruppe strömt; und

    die Ammoniakschlupfmenge (S) auf der Grundlage des berechneten Gesamtkorrekturkoeffizienten zu korrigieren.


     
    4. Abgasreinigungssystem (1) für einen Verbrennungsmotor nach Anspruch 3,
    wobei die Steuereinrichtung (41) den Gesamtkorrekturkoeffizienten (K) berechnet auf der Grundlage von:

    einem ersten Korrekturkoeffizienten (k1), der auf der Grundlage der ersten Temperatur (T1) und der Durchflussgeschwindigkeit (F) des Abgases (G) berechnet wird;

    einem zweiten Korrekturkoeffizienten (k2), der auf der Grundlage der ersten Temperatur und der stromaufwärtigen NOx-Konzentration (Nud) berechnet wird,

    einem dritten Korrekturkoeffizienten (k3), der auf der Grundlage der ersten Temperatur und der stromaufwärtigen NOx-Durchflussgeschwindigkeit (Nuf) berechnet wird,

    einem vierten Korrekturkoeffizienten (k4), der auf der Grundlage der ersten Temperatur und der geschätzten Ammoniak-Speichermenge (Ns) berechnet wird, und

    einem fünften Korrekturkoeffizienten (k5), der auf der Grundlage der ersten Temperatur und dem Verhältnis (R) von Stickstoffmonoxid zu Stickstoffdioxid berechnet wird.


     
    5. Abgasreinigungssystem (1) für einen Verbrennungsmotor nach einem der Ansprüche 1 bis 4,
    wobei die Steuereinrichtung (41) konfiguriert ist, um:
    eine Harnstoffwasser-Zuführungsmenge von der Harnstoffwasser-Zuführvorrichtung (22) auf der Grundlage der Ammoniakschlupfmenge (S) so zu korrigieren, dass die Ammoniakschlupfmenge nicht gleich oder größer als ein voreingestellter Schwellenwert ist.
     
    6. Abgasreinigungssystem (1) für einen Verbrennungsmotor nach einem der Ansprüche 1 bis 4,
    wobei der Abgaskanal (11) eine stromabwärts gelegene NOx-Konzentrationserfassungsvorrichtung (35) an der stromabwärts gelegenen Seite der Abgasreinigungs-Behandlungsvorrichtung aufweist,
    wobei die Steuereinrichtung (41) konfiguriert ist, um:
    eine Harnstoffwasser-Zuführungsmenge von der Harnstoffwasser-Zuführvorrichtung (22) auf der Grundlage der Ammoniakschlupfmenge (S), einer stromabwärtigen NOx-Konzentration (Ndd), die ein Erfassungswert der stromabwärtigen NOx-Konzentrationserfassungsvorrichtung ist, und der geschätzten Ammoniakspeichermenge (Ns), die ein geschätzter Wert einer in der selektiven Reduktionskatalysatorvorrichtungs-Gruppe gespeicherten Ammoniakmenge ist, zu korrigieren, sodass die Ammoniakschlupfmenge nicht gleich oder größer als ein voreingestellter Schwellenwert (Sc) ist.
     
    7. Abgasreinigungssystem (1) für einen Verbrennungsmotor nach Anspruch 6,
    wobei die Steuereinrichtung (41) konfiguriert ist, um:
    die geschätzte Ammoniakspeichermenge (Ns) auf der Grundlage der Ammoniakschlupfmenge (S) und der stromabwärtigen NOx-Konzentration (Ndd) zu berechnen.
     
    8. Abgasreinigungssystem (1) für einen Verbrennungsmotor nach Anspruch 6 oder 7,
    wobei die Steuereinrichtung (41) konfiguriert ist, um:

    eine NOx-Reinigungsrate (P) durch die selektive Reduktionskatalysatorvorrichtungs-Gruppe auf der Grundlage der stromaufwärtigen NOx-Durchflussgeschwindigkeit (Nuf), einer stromabwärtigen NOx-Durchflussgeschwindigkeit (Ndf), die durch Umwandlung der stromabwärtigen NOx-Konzentration (Ndd) berechnet wird, und der Ammoniakschlupfmenge (S) zu berechnen, und

    einen Fehler in der selektiven Reduktionskatalysatorvorrichtungs-Gruppe zu bestimmen, wenn die NOx-Reinigungsrate gleich oder niedriger als ein voreingestellter Bestimmungsschwellenwert (Pc) ist.


     
    9. Abgasreinigungsverfahren für einen Verbrennungsmotor (10), bei dem ein Abgaskanal (11) des Verbrennungsmotors in der Reihenfolge von einer stromaufwärtigen Seite aus umfasst: eine Harnstoffwasser-Zuführvorrichtung (22); und eine Abgasreinigungs-Behandlungsvorrichtung, wobei die Abgasreinigungs-Behandlungsvorrichtung umfasst: eine selektive Reduktionskatalysatorvorrichtungs-Gruppe, die mindestens eine selektive Reduktionskatalysatorvorrichtung (14); und eine Oxidationskatalysatorvorrichtung (15) umfasst, die an einer stromabwärtigen Seite der selektiven Reduktionskatalysatorvorrichtungs-Gruppe angeordnet ist,
    wobei das Abgasreinigungsverfahren umfasst:

    das Erfassen einer ersten Temperatur (T1), die eine Temperatur des Abgases (Gc) ist, das durch die Abgasreinigungs-Behandlungsvorrichtung während der Zuführung von Harnstoffwasser (U) von der Harnstoffwasser-Zuführvorrichtung hindurchgeströmt ist;

    das Berechnen, aus voreingestellten Daten, einer zweiten Temperatur (T2), die eine Temperatur des Abgases (G) ist, das durch die Abgasreinigungs-Behandlungsvorrichtung in einem Zustand hindurchgeströmt ist, in dem sich der Motor in einem gleichen Betriebszustand befindet, wie wenn die erste Temperatur erfasst wird und die Zuführung des Harnstoffwassers aus der Harnstoffwasser-Zuführvorrichtung gestoppt wird; und

    das Berechnen, auf der Grundlage einer Differenz (ΔT) zwischen der ersten Temperatur und der zweiten Temperatur, eines Ammoniak-Brennwerts (C), der eine Wärmemenge ist, die von der Oxidationskatalysatorvorrichtung durch Oxidation von Ammoniak erzeugt wird, das aus dem von der Harnstoffwasser-Zuführvorrichtung zugeführten Harnstoffwasser erzeugt wurde, und das Berechnen einer Ammoniakschlupfmenge (S) aus der selektiven Reduktionskatalysatorvorrichtungs-Gruppe auf der Grundlage des Ammoniak-Brennwerts.


     


    Revendications

    1. Système de purification de gaz d'échappement (1) pour moteur à combustion interne (10), dans lequel un passage d'échappement (11) du moteur à combustion interne comprend, dans l'ordre à partir d'un côté en amont : un dispositif d'approvisionnement en eau d'urée (22) ; un dispositif de traitement de purification de gaz d'échappement ; et un dispositif de détection de température en aval (34), le dispositif de traitement de purification de gaz d'échappement comprenant : un groupe de dispositifs de catalyseur de réduction sélective comprenant au moins un dispositif de catalyseur de réduction sélective (14) ; et un dispositif de catalyseur d'oxydation (15) disposé sur un côté en aval du groupe de dispositifs de catalyseur de réduction sélective,
    un dispositif de commande (41) qui commande le système de purification de gaz d'échappement étant configuré pour :

    détecter, par le dispositif de détection de température en aval, une première température (T1) qui est une température de gaz d'échappement (Gc) qui est passé à travers le dispositif de traitement de purification de gaz d'échappement durant l'approvisionnement d'eau d'urée (U) du dispositif d'approvisionnement en eau d'urée ;

    calculer, à partir de données préréglées, une seconde température (T2) qui est un température de gaz d'échappement (G) qui est passé à travers le dispositif de traitement de purification de gaz d'échappement dans un état où le moteur est dans un même état de fonctionnement que quand la première température est détectée et l'approvisionnement de l'eau d'urée du dispositif d'approvisionnement en eau d'urée est interrompu ; et

    calculer, sur la base d'une différence (ΔT) entre la première température et la seconde température, une valeur calorifique d'ammoniac (C) qui est une quantité de chaleur produite par le dispositif de catalyseur d'oxydation par l'oxydation de l'ammoniac qui a été produit à partir de l'eau d'urée approvisionnée du dispositif d'approvisionnement en eau d'urée, et calculer une quantité de perte d'ammoniac (S) du groupe de dispositifs de catalyseur de réduction sélective sur la base de la valeur calorifique de l'ammoniac.


     
    2. Système de purification de gaz d'échappement (1) pour moteur à combustion interne (10) selon la revendication 1,
    dans lequel le dispositif de commande (41) est configuré pour calculer une quantité d'approvisionnement en eau d'urée sur la base de la quantité de perte d'ammoniac (S) calculée et approvisionner l'eau d'urée (U) par la quantité d'approvisionnement en eau d'urée calculée, ou pour effectuer un diagnostic d'échec sur le dispositif d'approvisionnement en eau d'urée (22) et le dispositif de traitement de purification de gaz d'échappement sur la base de la quantité de perte d'ammoniac calculée.
     
    3. Système de purification de gaz d'échappement (1) pour moteur à combustion interne selon la revendication 1 ou 2,
    dans lequel le passage d'échappement (11) comprend un dispositif de détection de concentration de NOx en amont (32) au côté en amont du dispositif d'approvisionnement en eau d'urée (22), et
    le dispositif de commande (41) étant configuré pour :

    calculer un coefficient de correction totale (K) basé sur : la première température (T1) ; un débit (F) du gaz d'échappement passant à travers le passage d'échappement ; une concentration de NOx en amont (Nud) qui est une valeur de détection du dispositif de détection de concentration de NOx en amont ; un débit de NOx en amont (Nuf) calculé à partir du débit du gaz d'échappement et de la concentration de NOx en amont ; une quantité de stockage d'ammoniac estimée (Ns) qui est une valeur estimée d'une quantité d'ammoniac stockée dans le groupe de dispositifs de catalyseur de réduction sélective ; et un rapport (R) de monoxyde d'azote à dioxyde d'azote contenus dans le gaz d'échappement s'écoulant dans le groupe de dispositifs de catalyseur de réduction sélective ; et

    corriger la quantité de perte d'ammoniac (S) sur la base du coefficient de correction totale calculé.


     
    4. Système de purification de gaz d'échappement (1) pour moteur à combustion interne selon la revendication 3,
    dans lequel le dispositif de commande (41) calcule le coefficient de correction totale (K) sur la base de :

    un premier coefficient de correction (k1) calculé sur la base de la première température (T1) et du débit (F) du gaz d'échappement (G) ;

    un deuxième coefficient de correction (k2) calculé sur la base de la première température et de la concentration de NOx en amont (Nud) ;

    un troisième coefficient de correction (k3) calculé sur la base de la première température et du débit de NOx en amont (Nuf),

    un quatrième coefficient de correction (k4) calculé sur la base de la première température et de la quantité de stockage d'ammoniac estimée (Ns), et

    un cinquième coefficient de correction (k5) calculé sur la base de la première température et du rapport (R) de monoxyde d'azote à dioxyde d'azote.


     
    5. Système de purification de gaz d'échappement (1) pour moteur à combustion interne selon l'une quelconque des revendications 1 à 4,
    dans lequel le dispositif de commande (41) est configuré pour :
    corriger une quantité d'approvisionnement en eau d'urée à partir du dispositif d'approvisionnement en eau d'urée (22) sur la base de la quantité de perte d'ammoniac (S) de sorte que la quantité de perte d'ammoniac n'est pas supérieure ou égale à un seuil préréglé.
     
    6. Système de purification de gaz d'échappement (1) pour moteur à combustion interne selon l'une quelconque des revendications 1 à 4,
    dans lequel le passage d'échappement (11) comprend un dispositif de détection de concentration de NOx en aval (35) du côté en aval du dispositif de traitement de purification de gaz d'échappement,
    le dispositif de commande (41) étant configuré pour :
    corriger une quantité d'approvisionnement en eau d'urée du dispositif d'approvisionnement en eau d'urée (22) sur la base de la quantité de perte d'ammoniac (S), une concentration de NOx en aval (Ndd) qui est une valeur de détection du dispositif de détection de concentration de NOx en aval, et la quantité de stockage d'ammoniac estimée (Ns) qui est une valeur estimée d'une quantité d'ammoniac stockée dans le groupe de dispositifs de catalyseur de réduction sélective de sorte que la quantité de perte d'ammoniac n'est pas supérieure ou égale à un seuil préréglé (Sc).
     
    7. Système de purification de gaz d'échappement (1) pour moteur à combustion interne selon la revendication 6,
    dans lequel le dispositif de commande (41) est configuré pour :
    calculer la quantité de stockage d'ammoniac estimée (Ns) sur la base de la quantité de perte d'ammoniac (S) et la concentration de NOx en aval (Ndd).
     
    8. Système de purification de gaz d'échappement (1) pour moteur à combustion interne selon la revendication 6 ou 7,
    dans lequel le dispositif de commande est configuré pour :

    calculer une vitesse de purification de NOx (P) par le groupe de dispositifs de catalyseur de réduction sélective sur la base du débit de NOx en amont (Nuf), un débit de NOx en aval (Ndf) calculé par la conversion de la concentration de NOx en aval (Ndd), et la quantité de perte d'ammoniac (S), et

    déterminer un échec dans le groupe de dispositifs de catalyseur de réduction sélective quand la vitesse de purification de NOx est inférieure ou égale à un seuil de détermination préréglé (Pc).


     
    9. Procédé de purification de gaz d'échappement pour moteur à combustion interne (10) dans lequel un passage d'échappement (11) du moteur à combustion interne comprend, dans l'ordre à partir d'un côté en aval : un dispositif d'approvisionnement en eau d'urée (22) ; et un dispositif de traitement de purification de gaz d'échappement, le dispositif de traitement de purification de gaz d'échappement comprenant : un groupe de dispositifs de catalyseur de réduction sélective comprenant au moins un dispositif de catalyseur de réduction sélective (14) ; et un dispositif de catalyseur d'oxydation (15) disposé sur un côté en aval du groupe de dispositifs de catalyseur de réduction sélective,
    le procédé de purification du système d'échappement comprenant :

    la détection d'une première température (T1) qui est une température d'un gaz d'échappement (Gc) qui est passé à travers le dispositif de traitement de purification de gaz d'échappement durant l'approvisionnement de l'eau d'urée (U) du dispositif d'approvisionnement en eau d'urée ;

    le calcul, à partir de données préréglées, d'une seconde température (T2) qui est une température de gaz d'échappement (G) qui est passé à travers le dispositif de traitement de purification de gaz d'échappement dans un état où le moteur est dans un même état de fonctionnement que quand la première température est détectée et l'approvisionnement en eau d'urée du dispositif d'approvisionnement en eau d'urée est interrompu ; et

    le calcul, sur la base d'une différence (ΔT) entre la première température et la seconde température, d'une valeur calorifique d'ammoniac (C) qui est une quantité de chaleur produite par le dispositif de catalyseur d'oxydation par l'oxydation de l'ammoniac qui a été produit à partir de l'eau d'urée approvisionnée du dispositif d'approvisionnement en eau d'urée, et le calcul d'une quantité de perte d'ammoniac (S) du groupe de dispositifs de catalyseur de réduction sélective sur la base de la valeur calorifique d'ammoniac.


     




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    Cited references

    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description