FR2885387A1 - Exhaust gas treatment device diagnosis method for internal combustion engine, has determining diagnosis parameter, comparing parameter with threshold value and providing error signal when parameter exceeds threshold value - Google Patents

Abstract

The method involves measuring an exhaust temperature measure upstream of an exhaust gas treatment device (15). Another exhaust temperature measure is estimated based on a model of a catalytic support reaction. A diagnosis parameter is determined from the estimated and measured temperature measure. The diagnosis parameter is compared with a threshold value, and an error signal is provided when the parameter exceeds the threshold value. An independent claim is also included for a device for diagnosis of an exhaust gas treatment device in an exhaust area of an internal combustion engine.

Description

Field of the invention

  The invention relates to a method for the management or diagnosis of an exhaust gas treatment device installed in the exhaust zone of an internal combustion engine, this exhaust gas treatment device having at least one at least one catalytic effect layer and at least one particle filter function, in which, to increase the temperature of the exhaust gas treatment device, a reactive agent is introduced into the exhaust gas zone.

  The invention also relates to a device for implementing this method.

  State of the art DE 199 06 287 A1 describes a method of managing a particle filter of an internal combustion engine which is re-generated at regular intervals. The regeneration is based on a measurement of the state of charge of the particulate filter. Without conditioning the soot particles, they begin to oxidize from a temperature of the order of 550 C. The required ignition temperature of the particles can be obtained for example by introducing a reagent agent such as unburned hydrocarbons in the exhaust zone of the internal combustion engine which then reacts exothermically at the catalyst surface and increases the temperature of the exhaust gas.

  DE 44 26 020 A1 discloses a method of monitoring the operability of a catalyst installed in the exhaust zone of an internal combustion engine. The monitoring relates to the temperature rise produced by the exothermic conversion of the reducing components contained in the exhaust gas, at the level of the catalyst. Two temperature signals are determined; the first temperature signal corresponds to a measurement of the temperature downstream of the catalyst and the second temperature signal is obtained by calculation using a model.

  DE 101 13010 A1 discloses a method of diagnosing an exhaust gas treatment system installed in the exhaust zone of an internal combustion engine. According to this method, the temperature of the exhaust gases upstream and downstream of the exhaust gas treatment system is measured each time by means of a temperature sensor. The exhaust gas treatment system is considered to be non-defective if there is a foreseeable temperature rise in the temperature measured downstream of the exhaust gas treatment system when increasing the unburned hydrocarbon content in the exhaust gas system. exhaust gas from the internal combustion engine. The diagnosis is first made only as long as unburned hydrocarbons are introduced. In addition, the diagnosis is only made if the temperature measured upstream of the exhaust gas treatment system varies only negligibly during the introduction of unburned hydrocarbons for a certain period. The diagnosis is based on the predictable rise in exhaust gas temperature if the exhaust gas contains unburned hydrocarbons exothermically reacting at the catalyst surface.

  DE 101 08 720 A1 discloses a method of controlling an internal combustion engine which includes a particulate filter in an exhaust gas treatment system. This particulate filter is regularly regenerated. Starting from the operating variables or parameters of the internal combustion engine and / or the particulate filter, a characteristic quantity relating to the intensity of the exothermic reaction in the particulate filter is defined. If the characteristic magnitude exceeds a threshold value, steps are taken to reduce the oxygen content in the exhaust gas to reduce the rate of reaction in the particulate filter.

  Object of the invention The object of the present invention is to develop a simple and reliable method for diagnosing an exhaust gas treatment device installed in the exhaust zone of an internal combustion engine as well as a device for implementing this method.

  DESCRIPTION AND ADVANTAGES OF THE INVENTION For this purpose, the invention relates to a process of the type defined above, characterized in that a measurement of the temperature of the exhaust gas upstream of the gas treatment device is determined. exhaust and a measurement of the temperature in the exhaust gas treatment device, a diagnosis is made only if the temperature measurement of the exhaust gas upstream of the exhaust gas treatment device exceeds a lower limit given by the beginning of the catalytic conversion of the reactive agent on the catalytic layer and if the temperature measurement of the exhaust gas upstream of the exhaust gas treatment device is lower than an upper limit lower than the ignition temperature accumulated particles, using a model of the catalytic reaction is evaluated a measurement of the temperature in the exhaust gas treatment device e from the evaluated signal and the measured signal, at least one diagnostic value is determined which is compared with a threshold value and a fault signal is output if the diagnostic value exceeds the threshold value.

  The invention also relates to a device for carrying out this method and in particular a device comprising, upstream and downstream of the exhaust gas treatment device, a temperature sensor and a control device with a catalyst model, a comparator and a diagnostic magnitude determining means.

  The diagnostic method according to the invention of an exhaust gas treatment device installed in the exhaust gas zone of an internal combustion engine assumes that the exhaust gas treatment device comprises a Ca-Talytic effect and has a function of particle filter.

  The temperature rise of the exhaust gas treatment device required, for example, for the combustion of the accumulated particles is obtained by means of a reactive agent which is introduced into the exhaust gas zone and which reacts in such a manner exothermic on the catalytic layer.

  The method according to the invention allows not only a diagnosis of the efficiency of the catalytic layer of the exhaust gas treatment device but also the diagnosis of the introduction of the reagent agent. If, in case of introduction of reagent, the diagnostics value goes down, the predefined threshold, this corresponds to a faulty operation of the catalytic layer and a fault signal is emitted. If, on the other hand, when the reactive agent is not introduced, the diagnostic quantity exceeds the threshold value, which corresponds to an exothermic reaction on the catalytic layer, a fault signal is also emitted.

  According to one development, the diagnostic quantity is a measure of the efficiency of the catalytic effect layer.

  According to a development, the diagnostic quantity is determined from a difference of the evaluated temperature and the measured temperature. It is also intended to determine the diagnostic quantity as a measure of the thermal flow of the exhaust gas from the measured temperature and the evaluated temperature. According to one variant, the diagnostic quantity is determined as a measure of the amount of heat resulting from the integration of the heat flux obtained, or from the measured and evaluated temperature signals.

  According to another characteristic of the method, the diagnostic quantity is determined by forming the quotient of the measured temperature signal and the evaluated temperature signal and / or temperature differences and / or heat fluxes and / or heat amounts.

  According to another development, at least one threshold depends on at least one operating parameter of the internal combustion engine and / or at least one characteristic quantity of the exhaust gas. The operating parameters of the internal combustion engine are, for example, the air signal supplied by an air sensing means and / or the rotational speed and / or the fuel signal. As a characteristic quantity of the exhaust gases, for example, the temperature of the exhaust gases upstream of the exhaust gas treatment device and / or the mass flow rate of the exhaust gases is known.

  Preferably, a fault signal is emitted when the reagent is dosed if the diagnostic value falls below the threshold value.

  The device according to the invention for diagnosing an exhaust gas treatment device installed in the zone of the exhaust gases of an internal combustion engine comprises a control apparatus for carrying out the method defined above. above. This control apparatus preferably comprises at least one electrical memory containing the steps of the method in the form of a computer program.

  A development of the device according to the invention each time provides a temperature sensor upstream and downstream of the exhaust gas treatment device. The control apparatus includes a catalyst model, a comparator and a diagnostic magnitude determination means.

  Drawings The present invention will be described in more detail below with the aid of the accompanying drawings in which: - Figure 1 shows the technical background in which the process of the invention develops; - Figure 2 shows a flowchart; of a method according to the invention.

  FIG. 1 shows an internal combustion engine 10 whose suction zone 11 comprises an air sensor 12 and whose zone of the exhaust gases 13 comprises a device for assaying the reactive agent 14 as well as a device The exhaust gas treatment device 15 comprises a catalytic effect layer 16 and functions as a particulate filter 17.

  Upstream of the exhaust gas treatment device 15 there is a first temperature sensor 18 and downstream of the exhaust gas treatment device 15 there is a second temperature sensor 19.

  The air gripper 12 provides an air signal msL to the control apparatus 20 which receives the rotational speed signal N from the internal combustion engine 10; the first temperature sensor 18 provides a first temperature signal TvDPF-Mes and the second temperature sensor 19 provides a second temperature signal TnDPF-Mes.

  A means for determining an adjustment signal 31 of the control apparatus 20 provides the fuel metering device 30 associated with the internal combustion engine 10 with a fuel signal mK and the metering device 14 with the reactive agent 14. a dosing signal of the reagent msRea.

  The means for determining the adjustment signal 31 has the air signal msL as well as a torque signal mi. The air signal msL is also provided to a means for determining the exhaust gas mass flow rate 32 which further receives the fuel signal mK and an exhaust gas recycle signal agr. The means for determining the mass flow rate of exhaust gas 32 provides the mass flow rate of the exhaust gas vein msabg.

  The first TvDPF-Mes temperature signal is provided to a first selector 33 which further receives the evaluated signal provided by an exhaust gas temperature model 34, downstream of the exhaust gas treatment device 15.

  The exhaust temperature model 34 determines the signal evaluated upstream of the exhaust gas treatment device 15 starting from the fuel signal mK, the speed of rotation N and the mass flow rate of the fuel gas stream. msabg escape.

  The first selector 33 transmits a measurement of the temperature of the exhaust gas TvDPF upstream of the exhaust gas treatment device 15 to a release means 35. The release means 35 further receives the dosing signal from the reagent msRea, a first limit value G1 and a second limit value G2. The release means 35 emits a release signal 36 for the comparator 37.

  A catalyst model 40 provides an evaluated signal of the exhaust gas treatment device 15. The catalyst model 40 determines the signal evaluated from the measurement of the TvDPF exhaust gas temperature upstream of the exhaust gas treatment device. exhaust gas 15, the dosing signal of the reagent msRea and the mass flow rate of the exhaust gas vein msabg.

  The evaluated signal is provided both to a first diagnostic magnitude determination means 41 and also to a second diagnostic magnitude determination means 42. These two diagnostic magnitude determination means 41, 42 are further the second signal TnDPFmes provided by the temperature sensor 19, the mass flow rate of the exhaust gas vein msabg and the dosing signal of the reagent msRea.

  The first diagnostic magnitude determining means 41 provides a magnitude of the absolute diagnosis 43; the second diagnostic magnitude determining means 42 provides a relative diagnostic magnitude 44. The two diagnostic quantities 43, 44 are applied to a second selector 45 which transmits the two diagnostic quantities 43, 44 to the comparator 37.

  The comparator 37 further receives a threshold value 46 provided by a threshold value setting means 47. The threshold value setting means 47 determines the threshold value 46 as a function of the measurement of the gas temperature. exhaust TvDPF upstream of the exhaust gas treatment device 15, the mass flow rate of the exhaust gas vein msabg, the reagent dosing signal msRea and the air signal msL and the speed When the threshold is exceeded, the comparator 37 emits a fault signal F. FIG. 2 shows a flow chart of the method of the invention.

  The method according to the invention starts with a first functional block 50 with the beginning of the diagnosis. First, in a second functional block 51 is provided the dosing signal of the msRea reagent.

  In a third functional block 52, the measurement of the temperature of the exhaust gas TvDPF upstream of the exhaust gas treatment device 15 is then determined.

  In a fourth functional block 53 the evaluated signal of the exhaust gas treatment device 15 is then evaluated.

  In a fifth functional block 54 at least approximately the measured signal of the exhaust gas treatment device 15 is measured.

  In a sixth functional block 55 the magnitude of diagnosis 43, 44 is determined.

  In a next interrogation 56, the diagnostic magnitudes 43, 44 are checked to determine if they exceed the threshold value 46. Depending on the conditions, an overshoot of the threshold value 46 upwards or downwards leads to the transmission of the threshold value. A fault signal F. The method according to the invention executes as follows: The control device 20 determines the fuel signal mK supplied to the fuel metering device 30, for example as a function of the speed rotation (speed) of the internal combustion engine 10 and the position of the accelerator pedal of the vehicle, pedal not shown, and if necessary according to the air signal msL provided by the air gripping means 12 The position of the accelerator pedal corresponds to the set value represented by the torque signal mi.

  The exhaust gas treatment device 15, installed in the exhaust gas zone 13, has a particle filter 17. The particle filter must be regenerated from time to time to remove the accumulated particles. Regeneration is by combustion of particles that begin without conditioning the particles at temperatures above 550 C when there is oxygen.

  The starting temperature necessary for the combustion of the particles can be obtained for example by passive heating of the exhaust gas treatment device 15 by the temperature of the exhaust gas. In the example shown, the temperature increase in the exhaust gas treatment device 15 is automatically created. For this purpose, a catalytic effect layer 16 is provided which facilitates an exothermic reaction of a reactive agent with, for example, oxygen. As the simplest reactive agent is to use the fuel of the internal combustion engine 10. The catalytic effect layer 16 is preferably an integral part of the particulate filter 17. According to another development, the catalytic effect layer 16 is different from the Particle filter 17. In the extreme case, the catalytic effect layer 16 is a separate component, for example an oxidation catalyst.

  The reactive agent may be provided by means internal to the engine such as, for example, by deterioration of the combustion and / or by fuel post-injection. In the embodiment of FIG. 1, the reactive agent is introduced directly into the zone 13 of the exhaust gases by the reagent agent dosing device 14. The fixed msRea reagent dosing signal according to the second functional block 51, the amount of reagent agent to be assayed, regardless of the nature of its introduction.

  The diagnosis is based on capturing and exploiting the increase in temperature in the exhaust gas treatment device resulting from the catalytic exothermic reaction. Instead of directly measuring the temperature in the exhaust gas treatment device 15, according to the example shown, the temperature of the exhaust gas downstream of the exhaust gas treatment device 15 is measured. being at least approximately a measure of the temperature in the exhaust gas treatment device 15.

  When carrying out the diagnosis, it must be ensured that the temperature of the exhaust gases, upstream of the exhaust gas treatment device 15, is, on the one hand, greater than a minimum temperature for which the reaction the exothermic temperature just begins to occur and, on the other hand, this temperature must be below a maximum temperature at which the particles start to burn in the particulate filter 17. For the maximum temperature, it is necessary to take into account the temperature rise by the exothermic reaction which has already produced a rise in temperature. The minimum temperature is, for example, 400 ° C. and the maximum temperature, for example 500 ° C. The first limit value G1 supplied to the release means corresponds, for example, to the minimum temperature; the second limit value G2 corresponds to the maximum temperature. The two limit values G1, G2 can be modified according to the dosing signal of the reagent msRea or be completely modified. In the release means 35 it is checked whether the measurement of the temperature of the exhaust gas TvDPF upstream of the exhaust gas treatment device 15 provided by the first selector 33 is in the range limited by the two values G1, G2.

  The measurement of the temperature of the exhaust gas TvDPF upstream of the exhaust gas treatment device 15 is for example provided by an exhaust gas temperature model 34 which evaluates the temperature of the exhaust gas from at least one operating parameter of the internal combustion engine and / or a characteristic quantity of the exhaust gas. As an operating parameter of the internal combustion engine 10 there is, for example, the fuel signal mK and the rotational speed N. As a characteristic quantity of the exhaust gas, for example, the mass flow rate of the fuel gas stream is msabg exhaust provided by the means for determining the mass flow rate of exhaust gas 32.

  Alternatively, the temperature of the exhaust gas upstream of the exhaust gas treatment device 15 can be measured with the first temperature sensor 18 which provides the TvDPF-Mes temperature signal. The measurement of the temperature of the exhaust gas TvDPF transmitted to the third functional block 52 by the first selector 33 for the temperature of the exhaust gases, upstream of the exhaust gas treatment device 15, can be obtained as a function of the application, starting from the measurement or evaluation. The release signal 36 only occurs if the measurement of the exhaust gas temperature TvDPF, upstream of the exhaust gas treatment device 15, is within the temperature limits set by the limit values G1. , G2.

  It is necessary for the diagnosis that the temperature of the exhaust gas treatment device 15 or incidentally the temperature of the exhaust gas downstream of the exhaust gas treatment device 15 and which is at least approximately a measure of the temperature in the exhaust gas treatment device 15, both measured and also evaluated.

  The evaluation according to the fourth functional block 53 is done with the catalyst model 40 which evaluates the evaluated signal downstream of the exhaust gas treatment device 15 from the measurement of the exhaust gas temperature. TvDPF upstream of the exhaust gas treatment device 15 and preferably also the mass flow rate of the msabg exhaust gas stream and / or the msRea reagent dosing signal. In addition, input variables already described, or alternatively, the model may take into account exhaust gas treatment device measurements and / or the heat capacity of the exhaust gas treatment device 15 and and / or the heat capacity of the exhaust gas and / or the heat released to the environment and / or the heating capacity of the reactive agent and / or the ambient temperature and other quantities.

  The temperature measurement of the exhaust gas treatment device 15 provided in the fifth function block 54 is made with the second temperature sensor 19 which provides the temperature signal TnDPF-Mes; this signal is at least approximately a measure of the temperature in the exhaust gas treatment device 15.

  Then, according to the sixth functional block 55, the magnitudes of the diagnosis 43, 44 are determined. It is possible to provide an absolute diagnostic quantity that the first diagnostic value determination means 41 provides or a relative diagnostic quantity 44 that the second diagnostic value provides. means for determining the size of the diagnosis 42. The absolute diagnostic quantity 43 is, for example, a temperature difference, a heat flux or a quantity of heat determined from a heat flux. The relative diagnostic quantity 44 is preferably a dimensionless quantity. A relative diagnostic quantity 44 is, for example, the measured signal divided by the evaluated signal of the exhaust gas treatment device 15. The relative diagnostic quantity 44 may also be the measured signal divided by the evaluated signal of the processing device. The relative diagnostic quantity 44 may furthermore be the evaluated heat flux divided by the measured heat flow or the amount of heat evaluated divided by the amount of heat measured. The relative diagnostic quantity 44 thus corresponds in this case to the measurement of the efficiency of the catalytic effect layer 16.

  The second selector transmits either the absolute diagnostic value or the relative diagnostic quantity 43, 44 as a function of the application to the comparator 37 to be compared with the threshold value 46. The threshold value 46 is preferably a tolerance band in which the diagnostic quantity 43, 44 must be located. The threshold value 46 is set by the threshold value setting means 47, for example as a function of the measurement of the temperature of the exhaust gas TvDPF downstream of the device exhaust gas treatment system 15 and / or mass flow rate of the exhaust gas flow msabg and / or the dosing signal of the reagent msRea and / or operating parameters of the internal combustion engine 10 such as For example, the air signal msL and / or the speed of rotation N. The threshold value 46 of the absolute diagnostic value 43 corresponds, for example, to a minimum temperature and / or a temperature tolerance band, to a minimum voltage. minimum heat or a minimum amount of heat. The threshold value 46 of the relative diagnostic quantity 44 corresponds to a dimensionless number which translates the ratio corresponding to the relative diagnostic quantity 44.

  It is first assumed that the reagent is dosed with a dosing signal of the msRea reagent. The exceeding of the threshold value 46, which corresponds to a faulty operation of the catalytic effect layer 16, is observed in the comparator 37 which receives the release signal 36. This leads to the emission of the fault signal. F. The fault signal F is for example displayed or stored in a fault memory. Insofar as the threshold value 46 is exceeded, which corresponds to a satisfactory operation of the catalytic effect layer 16, the diagnosis ends without emission of a fault signal F. It is now assumed that there is no fault signal. no reagent dosage. In this case, the threshold value 46 is adapted to a low value and / or the limit values G1 and / or G2 are modified. The fault signal F is emitted if the threshold value 46 is exceeded; this is reported in that there has been exothermic reaction in the catalytic layer. With this diagnosis it can thus be seen that the reactive agent has arrived in the range of the exhaust gas 13 although this is not expected. This may for example arise from the fact that a reactive agent valve, not shown and which is part of the reagent dosing device 14 for example, is seized in the open position. The method according to the invention thus allows not only the diagnosis of the exothermic reaction in the catalytic effect layer 16 of the exhaust gas treatment device 15 but also the diagnosis of the introduction of the reagent agent.

Claims (12)

  1) A method of diagnosing an exhaust gas treatment device (15) installed in the exhaust gas zone (13) of an internal combustion engine (10), said gas treatment device exhaust system (15) having at least one catalytic effect layer (16) and at least one particulate filter function (17), in which, to increase the temperature of the exhaust gas treatment device (15), a reactive agent in the exhaust gas zone (13), characterized in that an exhaust gas temperature measurement (TvDPF) is determined upstream of the exhaust gas treatment device (15) and a measurement (TnDPF-Mes) of the temperature in the exhaust gas treatment device (15), a diagnosis is made only if the exhaust gas temperature measurement (TvDPF) upstream of the gas treatment device exhaust (15) exceeds a lower limit (G 1) given by the die purpose of the catalytic conversion of the reactive agent on the catalytic layer (16) and if the measurement of the exhaust gas temperature (TvDPF) upstream of the exhaust gas treatment device (15) is less than an upper limit (G2) lower than the ignition temperature of the accumulated particles, using a model of the catalytic reaction, a measurement (TnDPF-Mod) of the temperature in the gas treatment device is evaluated. (15) and from the evaluated signal and the measured signal (TnDPF-Mod, TnDPF-Mes) at least one diagnostic quantity (43, 44) is determined which is compared with a threshold value (46) and a fault signal (F) is output if the diagnostic value (43, 44) passes the threshold value (46).   2) Process according to claim 1, characterized in that the size of the diagnosis (43, 44) is a measure of the efficiency of the conversion of the reactive agent on the catalytic layer (16).   3) Method according to claim 1, characterized in that the magnitude of the diagnosis (43, 44) is a measure of the difference of the evaluated signal and the measured signal (TnDPF-Mod, TnDPF-Mes).   4) Method according to claim 1, characterized in that the magnitude of the diagnosis (43, 44) is a measurement of the thermal flow of the exhaust gas obtained from the measured temperature signal (TnDPF-Mes) and the temperature signal evaluated (TnDPF-Mod).   5) Process according to claim 4, characterized in that the diagnostic quantity (43, 44) is a measure of the amount of heat obtained by the integration of the determined thermal flux.   6) Method according to claim 1, characterized in that the diagnostic quantity (43, 44) is determined by forming the quotient of the measured temperature signal (TnDPF-Mes) and the evaluated temperature signal (TnDPF-Mod) and or differences in these temperatures and / or heat fluxes and / or amounts of heat.   7) Method according to claim 1, characterized in that the threshold value (46) depends at least on an operating parameter (msL, N) of the internal combustion engine (10) and / or at least one size characteristic (msabg, msRea, TvDPF) of the exhaust gas upstream of the exhaust gas treatment device (15).   Process according to Claim 1, characterized in that a fault signal (F) is emitted when the reagent is dosed if the diagnostic quantity (43, 44) falls below the threshold value (46). ).   9) Method according to claim 1, characterized in that when the dosing device of the reagent is turned off a fault signal (F) is emitted if the diagnostic quantity (43, 44) exceeds the threshold value.   Process according to Claim 1, characterized in that the reactive agent is introduced into the exhaust gas zone (13) upstream of the exhaust gas treatment device (15) by incomplete combustion of the fuel in the exhaust gas zone (13). the internal combustion engine (10) and / or at least one fuel post-injection and / or directly by the reagent dosing device (14).   11) Device for diagnosing an exhaust gas treatment device (15) fitted to an internal combustion engine (10) and which comprises at least one catalytic effect layer (16) and at least one particulate filter function (17), characterized in that it comprises a control apparatus (20) for carrying out the process according to one of claims 1 to 10.   Device according to claim 11, characterized by a temperature sensor (18, 19) installed respectively upstream and downstream of the exhaust gas treatment device (15) and the control device (20) comprises a model catalyst (40), a comparator (37) and a diagnostic magnitude determining means (41, 42).