FR2876415A1 - Controlling nitrogen oxide in an internal combustion engine with exhaust fume zone having nitrogen oxide catalyst/sensor comprises analyzing and measuring the difference in signal with the sensor, and regenerating the catalyst - Google Patents

Abstract

Measuring the time gradient/relative variation of the signal, if the sensor (15) does not exceeds a threshold. Catalyst model (31) is changed depends upon the evaluation of the signal. An independent claim is also included for a control equipment device for carrying out the above process.

Description

Field of the invention

  The present invention relates to a method for managing an internal combustion engine, the exhaust gas zone of which comprises a NOx nitrogen oxide storage catalyst and downstream of it a nitrogen oxide sensor.

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

  State of the art DE 198 43 879 A1 describes a method of managing an internal combustion engine whose exhaust gas zone comprises an NOx nitrogen oxide storage catalyst. In a first phase of operation in which the internal combustion engine works with stratified cylinder filling, in lean mode, NOx nitrogen oxides are stored in the NOx nitrogen oxide storage catalyst. In a second operating phase when the internal combustion engine is working with a homogeneous charge of the cylinders and a stoichiometric or rich mixture, the NOx nitrogen oxide storage catalyst is regenerated. Downstream of the NOx nitrogen oxide storage catalyst, a NOx nitrogen oxide sensor detects an increasing concentration of nitrogen oxides NOx in the exhaust gas during the storage phase. The increase in the signal comes from the passage of NOx nitrogen oxides as the storage capacity of NOx nitrogen oxide storage catalyst decreases.

  As soon as the concentration of nitrogen oxides NOx exceeds a predefined threshold, the regeneration phase begins. In other examples, the storage phase is changed to the regeneration phase when the mass flow rate of nitrogen oxides NOx or the integral of this mass flow rate in storage phase downstream of the catalyst accumulator of oxides of nitrogen. nitrogen NOx exceeds a predefined threshold. The mass flow rate of nitrogen oxides NOx downstream of the NOx nitrogen oxide storage catalyst can be deduced from the NOx nitrogen oxide storage catalyst signal, the mass flow rate of the exhaust gas obtained for example from from the measured mass flow of addition air and a constant coefficient which corresponds to the molar mass. A deficient signal from the NOx nitrogen oxide storage catalyst can either cause unnecessary regeneration of the NOx nitrogen oxide storage catalyst, or no longer provide it.

  Document DE 100 36 453 A1 describes a method of managing an internal combustion engine according to which the zone of the exhaust gases comprises an NOx nitrogen oxide storage catalyst. The storage change of the regeneration phase is based on the mass of NOx nitrogen oxides stored in the NOx nitrogen oxide storage catalyst. The mass flow rate of NOx oxides downstream of the NOx nitrogen oxide storage catalyst is calculated both by means of an NOx nitrogen oxide storage catalyst model or from the sensor signal of the NOx nitrogen oxide storage catalyst. nitrogen oxides NOx. By comparing the two mass flow rates, it is then possible to correct the model of the NOx nitrogen oxide storage catalyst.

  The NOx nitrogen oxide sensors currently known have in particular a signal shift which depends on the operating conditions of the NOx nitrogen oxide sensor and the internal combustion engine. In addition, NOx nitrogen oxide sensors may have a slope and / or linearity defect. A defective NOx nitrogen oxide sensor signal can cause the NOx nitrogen oxide storage catalyst to be unnecessarily regenerated or no longer provided. In addition, the reliability of the state diagnosis of NOx nitrogen oxide storage catalyst is no longer ensured.

  The object of the present invention is to develop a process for managing an internal combustion engine whose exhaust gas zone comprises an NOx nitrogen oxide storage catalyst and downstream after the oxide accumulator catalyst. NOx nitrogen, there is a nitrogen oxide NOx sensor. The invention also relates to a device for implementing the method, so that the method and the device offer a very high reliability.

  OBJECT OF THE INVENTION For this purpose, the invention relates to a process of the type defined above, characterized in that in a first step a first exploitation of the NOx nitrogen oxide sensor signal provided by the sensor is carried out. nitrogen oxides, and depending on the result of the first operation, a signal shift measurement of the NOx nitrogen oxide sensor signal in the NOx nitrogen oxide sensor signal is recovered in the second step, a second operation of the nitrogen oxide sensor signal NOx is carried out and, depending on the result of the second operation, the state of the catalyst is evaluated and / or the regeneration of the oxide storage catalyst is carried out NOx nitrogen.

  Both operations are planned in the storage phase of NOx nitrogen oxides.

  The method according to the invention makes it possible in a first step to quickly determine the offsets of the signals. In the second step, using the second operation of the NOx nitrogen oxide sensor signal, it is decided whether the state of the catalyst can be exploited and / or whether to start a regeneration of the accumulator catalyst. nitrogen oxides NOx.

  By determining the offset of the signal from the first step, the second operation can be accessed at the nitrogen oxide sensor signal NOx already corrected for the offset. This results in a very high reliability of the results of the operation on the basis of the NOx nitrogen oxide sensor signal, corrected.

  According to a development, during the first operation, it is checked whether the NOx nitrogen oxide sensor signal does not exceed a first threshold corresponding to the given upper limit of the concentration of NOx nitrogen oxides. As the nitrogen oxide sensor signal NOx exceeds the threshold, this means that the acceptable tolerance range of the NOx nitrogen oxide sensor signal has been exceeded. The NOx nitrogen oxide sensor signal can then be considered as defective. Under these conditions, erroneous diagnoses are avoided because NOx nitrogen oxide sensor signals are no longer reliable.

  According to another development, the first operation provides control of the NOx nitrogen oxide sensor signal to determine if a given measurement of a variation of this signal has exceeded a limit. If this is not the case, it can be assumed that the NOx nitrogen oxide storage catalyst still has sufficient storage capacity and that the NOx nitrogen oxide sensor signal moves within a permitted range to which determination of the derating of the signal is still possible.

  As a measure of the variation of the signal, for example, the gradient as a function of time of the NOx nitrogen oxide sensor signal is used. In addition or alternatively as a measure of the variation of the signal, it is possible to use a relative variation of the NOx nitrogen oxide sensor signal exploiting the place of a variation of the concentration of nitrogen oxides NOx, a variation in percentage of NOx nitrogen oxide sensor signal.

  The assessment of the state of the catalyst should be considered as overall. For example, the determination of the filling level of NOx nitrogen oxides can be done using a catalyst model and / or with the corrected NOx nitrogen oxide signal. In addition, the state of the catalyst can be exploited. The exploitation of the state of the catalyst can also be carried out using a model of catalyst and / or the signal of nitrogen oxides NOx, corrected. The operation concerns the determination of the filling level of NOx nitrogen oxides and / or for example the diagnosis of NOx nitrogen oxide storage catalyst. In the case of the diagnosis, it is possible to determine whether the NOx nitrogen oxide storage catalyst has a nitrogen oxide storage capacity that is still sufficient.

  Preferably, depending on the result of the second operation, the catalyst model is adapted. This means makes it possible to take account of the aging of the NOx nitrogen oxide storage catalyst in the catalyst model, which aging is reflected in particular by a reduction in the accumulation capacity.

  According to a development, before the first step, the NOx nitrogen oxide storage catalyst is re-generated to put it in a defined state.

  The device according to the invention for managing an internal combustion engine relates to a control apparatus for implementing the method.

  The control apparatus includes, in particular, signal operating means for performing the first and second operations, signal shift determining means, and a catalyst model. The control apparatus preferably comprises at least one electrical memory in which the steps of the method are recorded in the form of a computer program. Drawings The present invention will be described in more detail below with the aid of an exemplary embodiment of the method shown schematically in the accompanying drawings in which: FIG. 1 shows the technical environment in which the process is carried out; FIG. 2 shows timing diagrams of an NOx nitrogen oxides catalyst catalyst over time, and FIG. 3 shows a flow diagram of the process according to the invention. DESCRIPTION OF AN EMBODIMENT OF THE INVENTION FIG. 1 shows an internal combustion engine 10 whose intake zone 11 comprises an air sensor 12 and whose exhaust gas zone 13 is equipped with an nitrogen oxide storage catalyst NOx 14 and downstream of this NOx nitrogen oxide storage catalyst 14 there is a nitrogen oxide sensor 15.

  The air sensor 12 supplies an air signal msL to the control unit 20; the internal combustion engine 10 provides a rotational speed signal n and the nitrogen oxide sensor 15 provides a signal NOxS NOx nitrogen oxide sensor. The control apparatus 20 provides a fuel signal mK to the fuel metering device 21 associated with the internal combustion engine 10.

  The nitrogen oxide sensor NOxS signal NOx is applied to a signal operating means 25, a signal shift determining means 26 and an adder 27.

  A setpoint generator 28 provides the signal exploitation means 25 with a first and a second, a third and a fourth threshold S1, S2, S3, S4. A clock 29 provides a first and a second maximum time interval il, i2.

  The signal exploitation means 25 provides a signal shift determining release signal 30 by means of determining the offset of the signal 26 which transmits a decay signal OF to the adder 27.

  The signal exploitation means 25 provides an adaptation signal 32 to a catalyst model 31 and a regeneration release signal 34 to a regeneration control 33.

  A NO x NOx signal corrected by the adder 27 is provided both to the catalyst model 31 and the regeneration release signal 34.

  The catalyst model 31 provides a regeneration demand signal 35 to the regeneration control 33 and outputs a catalyst error signal 36. The regeneration control 33 provides a regeneration signal 37.

  FIGS. 2a-2d composing FIG. 2 show four chronograms of NOxS signal of NOx nitrogen oxide sensor as a function of time t. The timing starts at a start time t0. There is shown a first time interval 11 maximum between a first and a second time t1, t2 and a second maximum time interval i2 located between a third and a fourth time t3, t4. There is also shown a first and a second threshold S1, S3 NOxS NOxS sensor signal NOx nitrogen oxides.

  FIGS. 2a and 2c show that the NOxS signal NOx nitrogen oxide sensor has no OF signal shift. Figures 2b and 2d show the existence of an OF signal shift. However, in Figures 2c and 2d there is no first time interval there.

  Figure 3 shows a flow chart of the method of the invention. In this flow chart, in a first request 50 it is checked whether the NOx nitrogen oxide storage catalyst 14 can store NOx nitrogen oxides. If this is not the case, a first functional block 51 requests the regeneration and then the request or interrogation 50 is renewed. If this is the case, from the start time t0, the motor is operated. internal combustion 10 in lean mode according to the second functional block 50.

  Then, according to the third functional block 53, there is a first step 60 during which there is a first evaluation 61 of the NOxS signal NOx nitrogen oxide sensor.

  The second interrogation 54 determines whether the nitrogen oxide sensor NOxS signal NOx is less than or equal to the first threshold S1 and / or if a variation of the NOxS signal of NOx nitrogen oxide sensor is less than or equal to the second one. threshold S2. If this is the case, the signal offset OF in the fourth functional block 55 is determined. If this is not the case, according to a fifth functional block 56, a second evaluation 63 is carried out in a second step 62.

  In the third interrogation 57 following, it is checked whether the signal NOxS NOx NOxS sensor is greater than or equal to the third threshold S3 and / or if a NOxS signal NOxS signal NOxS signal is greater than or equal to the fourth threshold S4.

  If this is not the case, it returns to the fifth functional block 56. If this is the case, according to a sixth functional block 56, an adaptation of the catalyst model and / or a regeneration of the oxidation accumulator catalyst is carried out. NOx Nitrogen 14. Next, return to the first interrogation 50.

  The method according to the invention will be described below in more detail using the timing diagrams of FIGS. 2a-2d and the flowchart of FIG.

  The process according to the invention begins, for example, with the first interrogation 50 during which it is verified whether the NOx nitrogen oxide storage catalyst 14 is able to store NOx nitrogen oxides. The control is done for example in the catalyst model 31.

  If this is not the case, there will be, for example with the regeneration demand signal 35, a corresponding request for the regeneration of the NOx nitrogen oxide storage catalyst 14. This signal is applied to the regeneration control 33.

  As far as this is the case, according to the second functional block 52, the internal combustion engine 10 can switch to lean mode starting at the start time t0. The lean mode of the internal combustion engine 10 must generally be a mode of operation during which there is a gross mass flow rate of nitrogen oxides NOx which can no longer be totally converted into a catalyst, not shown, preferably a catalyst. three way.

  From the starting point t0, according to the third functional block 53, in a first step 60, the first evaluation 61 of the signal NOxS of NOx nitrogen oxide sensor is carried out in the signal operating means. 25. The signal operating means 25 can first check whether the NOxS signal NOx nitrogen oxide sensor has not exceeded the first threshold S1. Alternatively or additionally, the signal exploitation means 25 may also operate and verify the NO x NOxS sensor signal NO x vis-à-vis at least one signal variation measurement and determine whether this measurement of the signal variation does not exceed the second threshold S2.

  The measurement of the signal variation is, for example, the gradient as a function of time of the NOxS signal of NOx nitrogen oxide sensor. The gradient can be determined for example at least in the form of the difference quotient. The first operating means 61 can begin directly after the starting point t0. If necessary, a delay up to the first moment t1 is provided. The first operating means 61 is limited in time and the maximum duration can be predefined by the first time interval il.

  As an alternative to the exploitation of the gradient as a function of time, it is possible to determine, with a relative variation of NOxS signal NOx nitrogen oxide sensor, that instead of the concentration of nitrogen oxides NOx, it is possible to use a relative variation of NOxS NOx oxide sensor signal, for example in percentage.

  If the nitrogen oxide sensor NOxS signal NOx does not exceed the thresholds S1, S2, the signal operating means 25 provides the signal shift determining release signal 30. According to the fourth function block 55, it is then expected to determine the signal offset OF in the signal shift determining means 26. In the simplest case, the signal offset OF by the amplitude of the sensor signal NOxS can be considered. nitrogen oxides NOx taking into account the algebraic sign. Preferably, the means for determining the offset of the signal 26 contains a signal shift memory for permanently disposing of the signal offset OF, determined and having only to update it.

  The method according to the invention very briefly provides the signal derating OF which is subtracted in the adder 27 with respect to the signal NOxS NOx oxide sensor measured to obtain the NOx signal of oxides of NOx. NOx nitrogen. If there has been no change in the OF signal shift, the NOx signal of NOx nitrogen oxides also does not vary. The corrected NOx nitrogen oxide NOx signal is thus always available with very high accuracy.

  The method according to the invention is continued by the second step 62 in the fifth functional block 56 with the second operating means 63 of the NOxS signal NOx nitrogen oxide sensor.

  The second operating means 63 determines, by the third interrogation 57, whether the NOxS signal NOx nitrogen oxide sensor is greater than or equal to the third threshold S3 and / or at least one measurement of the variation of the signal NOxS signal sensor. nitrogen oxides NOx is greater than or equal to the fourth threshold S4.

  The exploitation of the variation of the NOxS NOx oxide sensor signal in the third interrogation 57 can again be based on the exploitation of the gradient over time, on a relative variation or on another measure of a variation. of signal.

  If necessary, the second operation 63 may also be limited in time. This limit may be predefined by the maximum duration given by the second time interval i2. FIGS. 2c and 2d show the case in which immediately after the start point t0 in the second interrogation 54 according to the first step 60, at least one threshold has been detected so that the second step 62 is directly passed. .

  Since the third interrogation 57 does not show a threshold exceeding, there is a return to the fifth functional block 56. If on the other hand, in the third interrogation 57 there is a threshold exceeding, then according to the sixth functional block 58, one can for example allow a catalyst model adaptation and / or request a regeneration of NOx nitrogen oxide storage catalyst 14.

  The catalyst model adaptation is released by the adaptation signal 32 supplied to the catalyst model 31. The regeneration can start with the regeneration release signal 34 applied to the regeneration control 33.

  The regeneration release signal 34 may be suppressed because the regeneration control 33 has the NOx signal NOx of nitrogen oxides, corrected so that the regeneration control 33 can determine on its own whether the regeneration of the accumulator catalyst Nitrogen oxides NOx 14 is required according to NOx signal of NOx oxides corrected.

  The regeneration signal 37 supplied by the regeneration control 33 can be used for example to determine the fuel signal mK and / or to influence in a non-detailed manner, the air supply of the engine intake zone 11 internal combustion engine 10 for example to use appropriate control of the internal combustion engine 10 to have an appropriate position of the exhaust gas to regenerate the nitrogen oxide storage catalyst NOx 14.

  Independently of the regeneration release signal 34 and the determination of a regeneration required in the regeneration control 33 using the corrected NOx NOx signal NOx, the regeneration request signal 35 provided is provided. by the catalyst model 31. The regeneration demand signal 35 may require regeneration independently of the other signals if the catalyst model 31 comes to the corresponding conclusion. By this signal, even if there is a fault in the nitrogen oxide sensor 15, it will be possible to properly regenerate the nitrogen oxide storage accumulator NOx 14.

  It is particularly advantageous to adapt the catalyst model 31 to the effective state of the NOx nitrogen oxide storage catalyst 14. The adaptation is released by the adaptation signal 32 provided by the signal operating means 25.

  The diagnosis of NOx nitrogen oxide storage catalyst 14 can be made in this case automatically in the catalyst model 31 for example using a registered model corresponding to a NOx nitrogen oxide storage catalyst 14 or by comparison between a novel NOx 14 nitrogen oxide catalyst and the current NOx 14 nitrogen oxide storage catalyst. If desired, the catalyst model 31 provides the catalyst error signal 36 which can be used, for example, to signal the need to replace the NOx 14 nitrogen oxide storage catalyst.

Claims (10)

  1) A method of managing an internal combustion engine (10) whose exhaust gas zone (13) comprises an NOx nitrogen oxide storage catalyst (14) and downstream thereof a sensor nitrogen oxide (15), characterized in that in a first step (60) is carried out a first operation (61) NOx nitrogen oxide sensor signal (NOxS) provided by the oxide sensor nitrogen (15), and depending on the result of the first operation (61), is recovered in the signal (NOxS) NOx nitrogen oxide sensor signal shift measurement (OF) of the signal (NOxS) NOx nitrogen oxide sensor, in the second step (62) following, a second operation (63) NOx nitrogen oxide sensor signal (NOxS) and depending on the result of the second operation (63), the state of the catalyst and / or the regeneration of the NOx nitrogen oxide storage catalyst (14) is evaluated.   2) Process according to claim 1, characterized in that the first operation (61) provides for a verification of the NOx nitrogen oxide sensor signal (NOxS) to determine if the latter does not exceed a first threshold (S 1 ) corresponding to a predefined upper limit of the concentration of nitrogen oxides NOx measured.   3) Process according to claim 1, characterized in that the first operation (61) provides for checking whether the signal (NOxS) NOx nitrogen oxide sensor does not exceed a second threshold (S2) of a measurement d a variation of this signal.   4) Method according to claim 3, characterized in that the measurement of the signal variation is the time gradient of the NOx nitrogen oxide sensor signal (NOxS).   5) Method according to claim 3, characterized in that the measurement of the variation of the signal is a relative variation of the signal (NOxS) NOx nitrogen oxide sensor.   6) Process according to claim 1, characterized in that one determines the state of the catalyst using a model of catalyst (31).   7) Process according to claim 6, characterized in that one adapts the model of catalyst (31) according to the second exploitation (63).   8) Process according to claim 1, characterized in that the NOx nitrogen oxide storage catalyst (14) is regenerated before the first step (60).   9) Device for implementing the method according to any one Claims 1 to 8,   characterized in that it comprises a control apparatus (20) for carrying out the method.   Apparatus according to claim 9, characterized in that the control apparatus (20) comprises signal operating means (25), signal shift determining means (26) and a catalyst model (31). ).