FR2916802A1 - METHOD FOR DIAGNOSING A REAGENT AGENT DOSING SYSTEM AND DEVICE FOR CARRYING OUT THE METHOD - Google Patents

Abstract

A method for diagnosing a DV IV reagent assay device (14), comprising a continuously opening DV metering valve and a reagent IV injector, wherein the reactive agent pressure is sensed in the reagent path (13) between the dosing valve DV and the reagent injection valve IV.After the closure of the dosing valve DV, the reactive agent pressure p is monitored when arrival of a rise in pressure (31) and a fault signal F is provided if the rise in pressure (31) is not detected.The diagnostic method according to the invention makes it possible to detect a leak in the path of reagent (13) as well as blocking the reagent injector (IV) in the open position.

Description

Field of the Invention: The present invention relates to a method of

  diagnosis of a reagent dosage device having a continuously opening metering valve and a reagent injector, wherein the reagent pressure is sensed in the reagent path between the valve dosing unit and the reagent injection valve. The invention also relates to a device for implementing the diagnostic method of the type defined above. The invention further relates to a program for a control apparatus and a program product for a control apparatus. State of the art: DE 10 2004 056 412 A1 describes a method and a device according to which a pressurized reactive agent is injected into the exhaust gas of an internal combustion engine, upstream of the cleaning device of the internal combustion engine. exhaust gas. This device comprises a catalyst and / or a particulate filter. The reagent dosing device is provided with a safety valve, a continuously adjusting metering valve, a reagent injector and a pressure sensor located therein. in the reagent path between the metering valve and the reagent injector. The pressure sensor monitors the reagent pressure by comparing it to a threshold. A specially set control of both the safety valve and the metering valve allows predefining different operating states leading to different reactant pressures. The threshold values are predefined according to the selected operating situation. In the event of a defect in the metering device which results in a difference between the reactant pressure and the expected pressure, there is a risk of an insufficient conversion rate in the exhaust gas cleaning device. an excess of reactive agent. In the event of a difference between the reactive agent pressure and the expected pressure, a fault signal will be obtained asking the user of the internal combustion engine to check the dosing device.

  DE 101 59 849 A1 also discloses a process and apparatus for spraying a reactive agent under pressure in the exhaust gas of an internal combustion engine upstream of the SCR catalyst. As a reactive agent, fuel is provided which functions as a reducing agent, in particular for the NO 2 components contained in the exhaust gas. The reactive agent that would be fuel, that is to say in particular hydrocarbons, can be provided generally for an exothermic reaction that can be supported for example by a catalytically active surface. The heat energy released can be used for heating the exhaust gas or directly for heating a component of an exhaust gas cleaning device. OBJECT OF THE INVENTION The object of the present invention is to develop a method for diagnosing a reactive agent dosing device provided in particular for introducing a reactive agent into the zone of the exhaust gases, preferably of a internal combustion engine as well as a device for carrying out the dosing method, enabling the diagnosis of the reactive agent injector of the reagent agent dosing device. DESCRIPTION OF THE INVENTION AND ADVANTAGES OF THE INVENTION For this purpose, the invention relates to a diagnostic method of the type defined above, characterized in that after the closure of the metering valve, the pressure of reactive agent is monitored with respect to the arrival of a rise in pressure and in that a fault signal is provided if the rise in pressure is not detected. The diagnostic method according to the invention is based on the consideration that after closure of the metering valve there will be in the reagent path between the metering valve and the reagent injector an increase of pressure due to the pressure wave generated by the closure of the reagent injector; this pressure wave can be used for diagnosis. When such a rise in pressure is not detected after the closing of the do-wise valve, a fault signal will be emitted which will for example be displayed or stored in a memory.

  The diagnostic method according to the invention increases the safety of the reagent dosage device, especially if the reagent is easily flammable, such as for example fuel. A leak in the reagent path may be detected. The diagnostic method according to the invention further ensures the proper functioning of the reagent agent dosing device by detecting a possible reactive agent injector which would be seized in the open position. An injector of reactive agent seized in the open position can not form a correct sputtering cone during the emission of reagent, so that the expected effect will not be obtained. According to one development, the diagnostic method provides a check to determine whether the reactant pressure exceeds a higher threshold. The upper threshold may, for example, be predefined in a fixed manner and this upper threshold will be determined by tests.

  According to an advantageous development, the upper pressure threshold is obtained from a reference pressure to which an increase in pressure is added. As a reference pressure, it is possible, for example, to use an average value of the pressure obtained for an at least partially open metering valve or a peak pressure value obtained for an at least partially or green metering valve. The diagnostic device according to the invention for the implementation of the diagnostic method relates first of all to a control apparatus designed in a special way and comprising means for implementing the diagnostic method. The diagnostic apparatus includes in particular a means for determining the reference pressure, a threshold fixing means and a comparator for comparing the reactive agent pressure and the upper pressure threshold. The control apparatus preferably comprises at least one electrical memory in which the process steps are recorded in the form of a control device program. The control device program according to the invention provides for carrying out all the steps of the diagnostic method according to the invention when this method is executed in a control apparatus. The control device program product according to the invention, with a program code stored in memory on a support that can read a machine, performs the diagnostic process according to the invention if the program takes place in a control device. Drawings: The present invention will be described hereinafter in more detail with the aid of embodiment examples shown schematically in the accompanying drawings in which: - Figure 1 shows the technical environment in which the diagnostic process according to Figure 2a shows a dosing signal, Figure 2b shows a dosing valve control signal, and Figure 2c shows the pressure of the reagent respectively as a function of time. DESCRIPTION OF EMBODIMENTS FIG. 1 shows an internal combustion engine 10 whose exhaust gas range zone 11 comprises a reactive agent injector IV and, downstream thereof, after the injector reactive agent IV, an exhaust gas cleaning device 12. The reactive agent injector IV is connected by a reactive agent path 13 equipped with a pressure sensor 14 to a dosing valve DV preceded by a safety valve SV, itself connected to a pump 15. The pressure sensor 14 supplies the control apparatus 20 with a reactive agent pressure p. The reactive agent pressure p is applied in the control apparatus 20 to both a reference value determining means 21 and a comparator 22. The means for determining a reference value 21 and the comparator 22 as well as a control device 23 receive a dosing signal sD. The means for determining the reference pressure 21 determines a reference pressure s-Ref which is supplied to a threshold value setting means 24; the latter, starting from the reference pressure s-Ref and a pressure increase dp, sets a higher threshold of pressure p-Lim and supplies it to the comparator 22 which can emit a fault or error signal F. The controller 23 includes a pulse width modulator PWM providing an s-DV metering valve control signal for controlling the metering valve DV. The controller 23 further provides a safety valve control signal s-SV for controlling the safety valve SV and a pump control signal sP for controlling the pump 15. The pump 15 sets the reagent at pump pressure pP.

  Figure 2a shows the dosing signal s-D as a function of time ti; the dosing signal s-D starts at a first instant ti 1 and ends at a second instant ti2. Fig. 2b shows the s-DV metering valve control signal as a function of time ti; between the two instants tif, ti2, there is a permanent signal variation due to the pulse width modulated signal generated by the pulse width modulator PWM. Figure 2c shows the pressure signal p as a function of time ti. Starting from the initial pressure p-S before the first instant ti 1, a pressure oscillation 30 starts at the first instant ti 1 and ends at the second instant ti2; at the second time t12, there will be a pressure increase 31 followed by a pressure drop 32. The pressure oscillation 30 has a mean value of pressure p-MW and a pressure peak value p-SW. The pressure increase 31 is up to a maximum pressure p-Max. Figure 2c shows the upper pressure threshold p-Lim located below the maximum pressure p-Max. Starting from either the peak pressure value p-SW or the average pressure value p-MW, the pressure increase dp set by the threshold fixing means 24 is recorded and will be added to either the value pressure peak p-SW is at the average value of pressure p-MW to obtain the upper threshold of pressure p-Lim. FIG. 2c also shows the opening pressure p-0 of the reactive agent injector IV. The diagnostic process according to the invention is carried out in the following manner: The exhaust gases of the internal combustion engine contain troublesome components such as, for example, nitrogen oxides and particles. The function of the exhaust gas cleaning device 12 is to reduce as much as possible the content of giant components. The exhaust gas cleaning device 12 comprises for example at least one catalyst such as, for example, an oxidation catalyst and / or an NOx nitrogen oxide storage catalyst and / or an SCR catalyst and, where appropriate , a particulate filter. The exhaust gas cleaning device 12 may require a minimum temperature that must be exceeded in order to perform the exhaust gas cleaning function. For example, a reaction on a catalytically effective surface will take place optimally for example in a certain temperature window. In addition, it may be necessary to have a minimum temperature to allow regeneration of at least one component of the exhaust cleaning device 12. For example, a particulate filter requires a start temperature for start the combustion of the particles. This temperature can be between 450 ° C. and 650 ° C. A NOx oxide nitrogen storage catalyst requires a higher temperature during the regeneration. In particular, for the regeneration of sulfur poisoning, very high temperatures of up to 800 ° C are required. An increase in the temperature of the exhaust gases makes it possible to introduce the reagent into the gas zone. exhaust 11; this reactive agent reacts on a catalytically active surface by an exothermic reaction with the oxygen contained in the exhaust gas. The reactive agent may also be introduced to allow a chemical reaction in the range of the exhaust gas 11.

  The reactive agent is for example fuel, which avoids having to separately transport a reactive agent in the vehicle. Due to the easy flammability of the fuel and in particular fuel vapors, strict safety requirements must be respected.

  For this reason, the safety valve SV must first be completely opened or completely closed by the safety valve control signal s-SV. The flow rate of the reagent can be adjusted with the downstream DV metering valve using the s-DV metering valve control signal. The dosing valve DV is continuously regulated and preferably there is provided a clocked operation set by the pulse width modulator or PWM pulse duration; this modulator controls the DV dosing valve in a fast chronological order, which gives an average opening. The corresponding s-DV metering valve control signal is shown in FIG. 2b. The reagent IV injection valve is preferably made as a check valve having an opening pressure p-0 that the reagent pressure p should exceed. The opening pressure p-0 is for example 2.5 bar so that the reagent IV injection valve opens above a mean reactive agent pressure p of 2.5. bars and closes again below the reagent pressure p = 2.5 bars. The reagent IV injection valve forms a spraying cone, of defined shape, which ensures a desired spatial distribution of the reagent in the exhaust zone 11 with droplets as small as possible and which can be distributed correspondingly over the entire section of the exhaust zone 11. According to Figures 2a-2c, before the first instant tif, it is assumed that there is no reagent dosage; the dosing valve DV and / or the safety valve SV, preferably the two valves DV, SV, are closed. At the latest at the first instant tif, the control signal of the safety valve s-SV opens the safety valve SV so that the reagent can be supplied to the dosing valve DV at the pressure pP of the pump 15. At the first instant, the metering valve DV will be set at a mean aperture by the pulse width modulated s-DV metering valve control signal; this opening results in a predefined coefficient of dosing of reactive agent in the zone of the exhaust gases 11. The pump pressure pP must for this purpose be greater than the opening pressure p-0 of the injection valve. reactive agent IV so that the reagent reagent dosing valve IV can open. Due to the dynamic processes at the reagent IV injection valve, which oscillate between an open state and a closed state, the pressure sensor 14 gives a reactive agent pressure p according to FIG. 2c oscillating between the two instants tif and ti2 around the average value p-MW of the pressure. The average value p-MW of the pressure as well as the peak pressure value p-SW are respectively below the opening pressure p-0 of the reactive agent injector IV although the value of their pressure point, not shown, periodically exceeds the opening pressure p-0 in the reagent injector IV to allow the opening of the reagent injector IV. Since the opening pressure p-0 is not stationarily supplied, the reagent injector IV oscillates between the open state and the closed state in a fast-successional manner. At the end of the dosing with removal of the dosing signal s-D, at the second time t12, the s-DV dosing valve control signal closes the valve. Due to the transition between the dynamic conditions in the reactive agent path 13 and the quasi- stationary state after the dosing cutoff or the closing of the dosing valve DV, there will be at the second instant ti2 the rise in pressure 31 caused mainly by the pressure wave emitted by the reagent IV injector after closing.

  The pressure rise 31 at the end of the dosing is used according to the invention to diagnose the reagent dosage device which comprises at least the DV dosing valve, the IV reagent injector and the pressure sensor 14 in the reactive agent path 13 between the dosing valve DV and the reagent injector IV.

  The diagnosis provides a comparison between the reactive agent pressure p and the upper value of the pressure threshold p-Lim. In the simplest case, there is a greater value of the predefined pressure threshold p-Lim at which the reactive agent pressure p is compared in the comparator 22 from the second instant ti2; this instant is recognized by the comparator 22 due to the cut-off of the s-D signal. The fixed upper value of the pressure threshold p-Lim is set at a value below the maximum predictable pressure p-Max, which is determined experimentally. According to an advantageous development, the upper value of the pressure threshold p-Lim is related to a reference pressure s-Ref at which the threshold fixing means 24 adds the pressure increase dp to arrive at the upper value of the threshold of p-Lim pressure. As reference pressure s-Ref, it is possible to use, for example, the average value p-MW of the pressure that the means for determining the reference pressure determines from the known instants ti 1, ti2 over a part of the time interval. between the first and the second instant ti 1, ti2 or during the entire time interval. Alternatively, the s-Ref reference pressure of the p-SW peak pressure value which occurs in part of the time interval or in the whole time interval can be used. Linking the upper value of the pressure threshold p-Lim to a reference pressure s-Ref allows adaptation of the upper value p-Lim of the pressure threshold. A variation which occurs if necessary for the maximum pressure p-Max as a function of the quantity of reagent dosed, and which can be linked to a variation of the average value p-MW of the pressure, can be taken into account. with such means so that the diagnostic method according to the invention provides reliable diagnostic results in an extended dosage range.

  Insofar as the pressure increase 31 of the upper value p-Lim of the pressure threshold at the second instant ti 2 or just after it is not reached, the comparator 22 supplies the fault signal F. This signal will be displayed or saved in a non-detailed memory. The fault signal F indicates that the reactant path 13 leaks, or that the reagent injector IV is seized in the open position. In both cases, it will no longer be possible to guarantee the desired effect of the introduction of reactive agent into the zone of the exhaust gases 11, for example to allow a chemical reaction or the heating of the exhaust gas or the device for cleaning the exhaust gases 12 and in the event of a leak in the reactive agent path 13,

  depending on the characteristics of the reactive agent, there will even be a potential risk which must be detected in time with the diagnostic method according to the invention.

Claims (5)

  1) A method for diagnosing a reagent agent dosing device (DV, IV, 14), comprising a continuously opening dosing valve (DV) and a reagent injector (IV), wherein captures the reagent pressure (p) in the reagent path (13) between the metering valve (DV) and the reagent injection valve (IV), characterized in that after the closure of the metering valve (DV) is monitored the reactant pressure (p) when the arrival of a pressure rise (31) and a fault signal (F) is provided if the rise in pressure (31) is not detected. 2) A method of diagnosis according to claim 1, characterized in that the monitoring provides a control to determine whether the reactive agent pressure (p) exceeds a higher threshold pressure (p-Lim). 3) A method of diagnosis according to claim 2, characterized in that the upper pressure threshold (p-Lim) is obtained from a reference pressure to which is added a pressure increase (dp). 4) A method of diagnosis according to claim 3, characterized in that as a reference pressure is used an average pressure value (p-MW), obtained while the metering valve (DV) is at least partially open. 5) A method of diagnosis according to claim 3, characterized in that as reference pressure, the pressure peak value (s-SW) obtained when the metering valve (DV) is at least partly open is used. .6) Device for diagnosing a reactive agent dosing device (DV, IV, 14), characterized in that a specially designed control apparatus (20) is provided which comprises means (21, 22 , 23, 24) for performing the diagnostic method according to one of the preceding claims. 7) A diagnostic device according to claim 6, characterized in that the control apparatus (20) comprises a reference pressure determining means (21), a threshold setting means (24) and a comparator (22) for comparing the reactive agent pressure (p) with the upper pressure threshold (p-Lim). 8) A diagnostic device according to claim 7, characterized in that the reactive agent dosing device (DV, IV, 14) introduces a reactive agent into the exhaust gas zone (11) of a combustion engine. internal combustion (10). 9) Controller program that performs all the diagnostic steps according to one of claims 1 to 5, when the program is executed in a control apparatus (20). 10) A control device program product having program code recorded on a machine-readable medium for carrying out the diagnostic method according to one of claims 1 to 5 when the program is executed in a control apparatus (20). 30