FR2834752A1 - METHOD AND DEVICE FOR DETERMINING AN INDOOR TEMPERATURE IN A CATALYST - Google Patents

Abstract

Method and device for determining an interior temperature in a catalyst. According to this method, which makes it possible to determine an internal temperature in a catalyst (13) located in an exhaust path of an internal combustion engine (1), a mass flow of exhaust gas entering the catalyst (13) is continuously read, and also continuously, the temperature of the incoming exhaust gas is read, subjected to low-pass filtering and outputted as a determined interior temperature, while in operation read mass flow values, a delay time is established and read temperature values are not subjected to low-pass filtering after the delay time has elapsed.

Description

inward and the other (126) outward.

  The invention relates to a method and a device for determining an internal temperature in a catalyst located in an exhaust path of a

internal combustion engine.

  With regard to catalysts, precise knowledge of the internal temperature is important, for example to prevent excessive heating. In addition, for example in the case of NOx storage catalysts, knowledge of the internal temperature under normal conditions is important and essential for determining the load level of the NOx storage catalyst and deducing therefrom whether it is necessary to proceed during the regeneration phase with a view to desullation. This then ensures the operating capacity of the catalyst in a sustainable manner. So far, to determine the interior temperature, for example, the temperature of the exhaust gases entering the catalyst has been subjected to low-pass filtering. The result of the low-pass filtering should correspond to the effective interior temperature in the catalyst. However, it has been found that, in the case of rapid changes in temperature of the incoming exhaust gases, which occur for example during abrupt changes in the mass flow rate passing through the catalyst, the result of the low-pass filtering only partially agrees with

  the variation over time of the effective internal temperature of the catalyst.

  If a relatively fast low-pass filter is used, the measured temperature obtained immediately after the rapid change in temperature of the exhaust gases entering the catalyst relatively agrees with the effective interior temperature of the catalyst, but, after the unwinding of the variation over time, the error between the measured temperature and the effective internal temperature grows more and more and can even be worth more than 100 C. If a relatively slow low pass filter is used, the measured temperature obtained immediately after the change in temperature of the incoming exhaust gases absolutely does not coincide with the effective interior temperature, but, during the course of the variation over time, a concidence is obtained

getting better and better.

  Starting from there, the present invention aims to provide a method for determining an internal temperature in a catalyst, located in an exhaust path of an internal combustion engine, by which the precision when determining the interior temperature can be increased and by which, especially also in the case of a rapid change in the temperature of the incoming exhaust gases, an accurate determination of the interior temperature of the catalyst is possible. There must also be further provided a device for determining an internal temperature in a catalyst, located in an exhaust path of an internal combustion engine, by means of which a

  precise determination of the indoor temperature is possible.

  To this end, the invention relates to a method for determining an interior temperature in a catalyst located in an exhaust path of an internal combustion engine, according to which, in a continuous manner, a mass flow of exhaust gas entering the catalyst is raised and, continuously, the temperature of the incoming exhaust gas is raised, subjected to low-pass filtering and output as a determined interior temperature, while depending on the measured mass flow values, a delay time is established and the measured temperature values are not subjected to low-pass filtering until the delay time has elapsed. It is each one after the other that the measured temperature values are subjected to low-pass filtering only once

the delay time has elapsed.

  Adjusting the delay as a function of the mass flow makes it possible to obtain that, even in the case of a rapid, for example abrupt, change in the temperature of the incoming exhaust gases, the determined interior temperature coincides with the effective interior temperature on the whole extent of the variation over time. There is therefore a concidence both immediately after the change in the temperature of the incoming exhaust gases and during the following

  of the variation over time.

  The delay time is preferably established so as to be all the smaller as the mass flow is high and so as to be all the greater as the mass flow is low. This is mainly motivated by the fact that, in the case of a high mass flow and therefore in the case of a high mass flow through the catalyst, the modification of the internal temperature in the catalyst follows more rapidly the modification of the incoming exhaust temperature only in the case of a

low massive flow.

  An essential advantage of the process according to the invention lies in the fact that the internal temperature in the catalyst, for example in a NOx storage catalyst or a catalyst-monolith, can be recorded in an extremely exact manner, even in the cases of rapid temperature changes

incoming exhaust gases.

  It may in particular be provided, according to the method according to the invention, that the delay time is established continuously as a function of the measured mass flow values. Therefore, the continuous adaptation of the delay time to the mass flow at the right moment is ensured, so that the temperature accuracy

  raised interior can be increased.

  In addition, according to the method according to the invention, the mass flow of the exhaust gases and the temperature of the incoming exhaust gases can each be recorded at constant respective time intervals. These are called constant "analysis intervals". This allows the method to be easily implemented. According to an advantageous development, the mass flow and the temperature of the incoming exhaust gases are recorded simultaneously. This results in a

  further simplification of the implementation of the method.

  In addition, the values recorded for the temperature of the incoming exhaust gases can be stored in a memory which re-delivers the values stored after the delay time has elapsed. The storage of the values in memory is carried out continuously one after the other and their reissue in output also one after the other. Thanks to such a memory, it is possible to use

  easily the process according to the invention.

  It may in particular be provided, according to the method according to the invention, that the memory is a first-in-first-out memory of variable length, the length thereof being adjusted as a function of the delay time. In the case of a first-in-first-out memory, the data appear at the memory output in the same order as they were entered in the memory entry. The use of such a first-in-first-out memory, which is commercially available today in the form of a ready-to-use component, allows the variable delay to be produced very simply, so that the process according to the invention can be

  implement in a simple way.

  A preferred development of the method in accordance with the invention resides in the fact that the first in-first out memory comprises a first and a second memory stage, the temperature values recorded being entered in the first memory stage, output data of the first memory stage being introduced into the second memory stage and the offset rate of the second memory stage being equal to n times the offset rate of the first memory stage, n being a natural number greater than 1. Thanks to this stepped structure , it is possible, for the same storage size of the first-in-first-out memory, to achieve greater delay times compared to a first-in-first-out memory comprising only one stage. Thus, the process according to

  the invention can be implemented in an economical manner.

  In particular, the first memory stage has at least n memory locations and outputs the second highest memory value among the values contained in the last n memory locations. Thanks to the measurement thus taken, there is an assignment of priority to the values of higher temperatures. This is particularly advantageous, since higher temperatures of the incoming exhaust gases have a greater influence on the interior temperature of the catalyst. This results in an improvement in the accuracy of the determined interior temperature of the catalyst. 11 is particularly advantageous, according to the method according to the invention, that the first-in-first-out memory also further comprises a third memory stage whose shift rate is m times the shift rate of the second memory stage, m being a natural number greater than 1 and output data from the second memory stage being introduced into the third memory stage. Thus, the adjustable delay time can further increase for the same memory size (more precisely the same number

memory locations).

  In particular, the second memory stage can comprise at least m memory locations and can output to the third memory stage the largest value among the values stored during the last m memory locations. Again, this results in a priority assignment to the higher temperatures of the incoming exhaust gases, temperatures whose influence on the internal temperature in the catalyst is greater than that of lower temperatures. This ultimately leads to more determination

  precise indoor temperature in the catalyst.

  A preferred development of the process according to the invention lies in the fact that a delay time shorter than the delay time hitherto provided for is established and then, among the temperature values whose delay corresponds at least to the time of shorter delay and at most the delay time hitherto expected, the largest value is sent to the low-pass filtering. This makes it possible to obtain a priority assignment to high temperature values with a shortening of the delay time, so that, advantageously, the precision of the determination of the

  interior temperature of the catalyst may be increased.

  Furthermore, according to the method according to the invention, a delay time longer than the delay time hitherto provided for can be established, while as temperature values whose delay is greater than the delay time. delay hitherto expected and smaller or equal to the longer delay time, a value is established each time which corresponds to the temperature value having the delay time hitherto established. It is thus advantageously guaranteed that no temperature value

  false is not subject to a delay and sent to low-pass filtering.

  According to the method according to the invention, the low-pass filtering is preferably a first-order low-pass filtering. Furthermore, for the same purpose of the invention, it also relates to a device for determining an interior temperature in a catalyst, located in an exhaust path of an internal combustion engine, the device comprising: a module for raising the mass flow of exhaust gas, which continuously records a mass flow of exhaust gas entering the catalyst, a module for raising the temperature of exhaust gas, which falls under a 'continuously the temperature of the incoming exhaust gases, a memory in which the measured temperature values are stored one after the other and are re-delivered at the output after a delay time, and a low-pass filter to which the temperature values delivered at the output are sent and which performs a low-pass filtering with a view to determining the internal temperature, the delay time being established, as a function of the values of fl ux mass relieoes, at

by means of a delay module.

  Providing the memory allows the values of the temperature of the incoming exhaust gases which are detected to be sent in a delayed manner to the low-pass filter, so that the determined interior temperature corresponds to a

  very precisely at the effective internal temperature in the catalyst.

  The delay module and the module for raising the mass flow of exhaust gases can be produced by means of a single module, so that the

  device can be arranged with a smaller footprint.

  According to a preferred development of the device according to the invention, the memory is produced in the form of a first in-first out memory with variable length. Given that the length of the first in first out memory is variable, the delay can also be set and adjusted in a variable manner and can thus be adapted to the mass flow values eVou to the temperature values of the gases incoming exhaust, so an extremely accurate determination

  indoor temperature is made possible.

  In addition, preferably, the first-in-first-out memory may comprise at least two memory stages, a first of the memory stages, in which the recorded temperature values are stored, having a first shift rate and introducing data of output to the second memory stage, which has a second offset rate which

  is n times the first offset rate, n being a natural number greater than 1.

  The staggered first-in-first-out memory arrangement and the different offset rates make it possible to achieve greater delay times for the same number of memory locations. Therefore, the device according to the invention is more economical to manufacture. An advantageous development of the device according to the invention lies in the fact that the first memory stage contains at least n memory locations and a selection module which, among the values contained in the last n memory locations of the first memory stage , enters the largest value in the second memory stage. Priority is thus assigned to high temperature values, which have a greater influence on the accuracy of determining the indoor temperature.

  of the catalyst, so that the accuracy of determination can be increased.

  The low-pass filter is preferably a first-order low-pass filter and can be implemented, as well as the modules described, in the form of software,

  hardware or a combination of the two.

  The invention is set out below in more detail by way of example with reference to the drawings. We see: in Figure 1, a schematic representation of an internal combustion engine, in Figure 2, a block diagram of part of the control device 4 shown in Figure 1, in Figure 3, a diagram sequence used to describe the process according to the invention, in FIG. 4, a graph which represents the temperature variation over time, in FIG. 5, another arrangement of the first-in-first-out memory represented in the figure 2, in FIG. 6, a schematic representation serving to expose an increase in the delay produced by means of the first in-first out memory and, in FIG. 7, a graph serving to expose a reduction in the delay imposed on the

  first in-first out memory means.

  FIG. 1 schematically represents an internal combustion engine 1, only being represented the constituent elements which are necessary for understanding the method according to the invention and the device according to the invention. The internal combustion engine has four cylinders 2 which are

  supplied with the desired carburanVair mixture via an intake path 3.

  To this end, there is provided in the intake route 3 a throttle valve 5 which can be controlled by means of a control device 4 and which serves to fix the mass air flow. Downstream in the intake path 3, there is provided a mass air flow meter 6 which measures the mass air flow and communicates it to the control device 4 via a line not designated by a particular benchmark. In addition, there is still arranged in the ad mission path 3 a fuel delivery device for which, by way of illustration, there is schematically indicated an injector 7. The injector injects the necessary fuel flow in accordance with the control and by means of the control device 4, in order to produce the desired carburanVair mixture. As an alternative to injection into the intake path 3, the fuel can also be introduced directly into the cylinder

  2 of the engine in the form of a direct injection.

  Furthermore, the internal combustion engine 1 comprises an exhaust path 8 comprising a main section 9 in which the exhaust gases from the cylinders 2 are discharged. In the main section 9, a temperature sensor 10 is used to measure the temperature of the exhaust gas, while downstream of the temperature sensor 10 in the direction of flow of the exhaust gas, there is provided a cooling loop 11 which is arranged in bypass with respect to the main section 9 and which can be placed in communication with this main section 9 of the exhaust route 8 by means of a butterfly of cooling loop 12 which can be controlled. The end of the cooling loop 11 opens, downstream of the bypass location in the direction of flow of the exhaust gases, into the main section 9 which

  for its part is connected to a NOx 13 storage catalyst.

  FIG. 2 shows in detail a part of the control device 4 which constitutes an exemplary embodiment of the device according to the invention and which is used to determine the interior temperature T-IN of the

NOx storage catalyst 13.

  The control device 4 includes an exhaust gas temperature reading module 14, an exhaust gas mass flow reading module 15, a first-in-first-out memory 16 at length

variable and a low pass filter 17.

  The first-in-first-out memory contains 24 locations or SZO-SZ23 memory cells which can each store one byte, the data being entered in the SZO memory location and the value of one of the SZO memory locations -SZ23 can be chosen as output delivery value. If the memory location SZ1 is chosen, the memory length is 2 bytes, while it is 24 bytes if the memory location SZ23 is determined. In the first in first out memory 16, the contents of the memory locations SZO-SZ22 are each shifted from one memory location to the right at a certain offset rate. It is thus possible to set a desired delay time by means of the length of the first-in-first-out memory 16. Instead of effectively shifting the contents of the memory locations to the right and thus passing them into memory in d 'other locations, it is of course also possible to shift, more precisely to modify, two pointers which indicate the address of the first and last memory locations. This variant of a prime memory

  in-out-out is often also called ring memory.

  In the example described, a length of 8 memory locations is first fixed, so that it is the memory location SZ7 which constitutes the output of the first in-first out memory 16. In addition, in in this case, a temperature value between O and 1,000 C is stored in the memory locations, so that, for a memory location size of 1 byte, it is possible to obtain a resolution in steps of 4 C. Of course, the storage size of the individual memory locations can be increased if desired.

  finer resolution of temperature values.

  To determine the internal temperature T-IN of the NOx storage catalyst 13, the temperature of the exhaust gas T-ST of the exhaust gases entering the catalyst 13 is detected continuously, being delayed by one prefixed duration, as a function of the mass flow of exhaust gases occurring at the right time (ie during detection), and then being sent to low-pass filtering. The result of the low-pass filtering then corresponds to the temperature

  interior of the NOx storage catalyst 13.

  The delay is chosen as much greater as the mass flow is smaller and is fixed all the smaller as the mass flow is large. In the first in first out memory 16, the delay can be easily adjusted by means of a modification

of its memory length.

  The process according to the invention will be described in detail in

link with figure 3.

  At a first step S1, the temperature T-ST of the exhaust gases entering the NOx storage catalyst 13 (therefore the temperature of the exhaust gases at the inlet end of the catalyst 13 which is situated on the side of the main section 8) and the AMF mass flow of the exhaust gases entering the

catalyst 13 are raised.

  To read the exhaust gas temperature T-ST, the temperature TEG of the exhaust gases leaving the cylinders 2 which is measured by means of the temperature sensor 10 and the EFP position of the cooling plug butterfly 12 are sent to the module. for raising the exhaust gas temperature 14. From these input quantities, the module 14 then determines the temperature T-ST of the incoming exhaust gases, the temperature T-ST being for example all the lower more exhaust goes through the loop

cooling 11.

  The mass flow of air LMF sent to the cylinders 2 is communicated by the mass flow meter of air 6 to the module for raising the exhaust gas mass flow 15, the module 15 then determining the mass flow of the exhaust gas AMF taking into account the flow of fuel mixed with this flow

AMF air mass.

  In step S2, the first in-first out memory 16 is read. Thus, in the embodiment described here, the content of the memory location SZ7 is output to the low-pass filter 17 as a delayed temperature T-V. Then, the contents of the memory location SZ7 are erased and the contents of the memory locations SZO-SZ6 are each shifted by one

memory SZ1-SZ7 to the right.

  In addition, the low-pass filter 17 also performs a low-pass filtering of the temperature values T-V which are sent to it and it outputs a filter value T-MDL which corresponds to the internal temperature T-IN in the catalyst of

NOx storage 13.

  At a third step S3, the length of the first-in-first memory 16 is fixed as a function of the mass flow of incoming exhaust gas AM F. as indicated schematically in FIG. 2 by the double arrow A. C ' This is how the memory location is thus determined, the memory value of which is output as the following. This length adjustment can be carried out by means of the module for raising the mass flow of exhaust gas 15 or by means of a separate delay module (not shown) to which the mass flow of

exhaust gas is sent.

  Then, the value of the determined temperature T-ST of the incoming exhaust gases is entered into memory 16 (therefore in its first location of

SZO memory).

  Once step S3 has been executed, the process continues at step S1, so that, continuously, the internal temperature T-IN in the NOx storage catalyst 13 is determined, more precisely modulated, as a function of the flow. mass of exhaust gas entering the catalyst 13 and the exhaust gas temperature. Preferably, a temperature value T-ST of the incoming exhaust gases and a mass flow value AFM of these incoming exhaust gases are determined at each step of the shift rate of the memory 16. Consequently, it is preferably choose an analysis rate that corresponds to the offset rate. The magnitude of the analysis rate and the offset rate is in particular determined in such a way that rapid changes in the temperature T-ST and / or the AFM mass flow are detected with the

  desired precision, and it can for example be worth 1 second.

  It is thus possible to very well determine the variation over time of the internal temperature T-IN in the case for example of an abrupt reduction in the mass flow of AMF exhaust gas and the rapid reduction, which results, from the exhaust gas temperature T-ST of the incoming exhaust gases, as well as

  this is clear from the graph in Figure 4.

  In the graph in Figure 4, time is plotted in seconds on the x-axis and

  the temperature is indicated in C on the y axis.

  At time T1, the AMF mass flow of the exhaust gases suddenly decreases. This immediately results in a marked reduction in the temperature of

  exhaust gas T-ST, as shown in Figure 4 by the curve K1.

  The temperature values T-V delivered at an output in a delayed manner by the memory 16 then manifest the behavior represented by the curve K2. Thanks to the low-pass filtering by means of the low-pass filter 17, there is the curve K3 for the variation over time of the determined interior temperature T-MDL. The curve K3 almost perfectly coincides with the variation of the effective internal temperature T-IN in the catalyst 13, which is shown as curve K4. Conidence therefore also occurs immediately after the sudden change in the mass flow of exhaust gas (immediately after

  time T1) until long after this abrupt change.

  Consequently, thanks to the process according to the invention, the internal temperature T-IN in the NOx storage catalyst can be determined in a remarkable manner, which constitutes a very important parameter for the

  operation of the internal combustion engine and in particular of the catalyst 13. FIG. 5 represents an alternative embodiment of the first memory

  input-first output 16. In this embodiment, the memory 16 comprises three memory stages 18, 19, 20 each comprising eight memory locations SZO-SZ7, SZ8-SZ15 and SZ16-SZ23, the first memory location SZO of the first memory stage 18 constituting the memory input. The second memory stage 19 further comprises, in addition to the memory locations SZ8-SZ15, a first comparison element 21 which compares the values stored in memory in the locations SZ6 and SZ7 and introduces the larger of the two values in the first location of second SZ8 memory

1 0 floor 1 9.

  Similarly, the third memory stage 20 includes a second comparison element 22 which compares the data values contained in the last two memory locations SZ14 and SZ15 and introduces the larger of the two values in the first location SZ16 of this third stage 20. The offset rates of the three memory stages are selected in such a way that the offset rate of the second stage is equal to n times the rate of the first stage and that the rate of the third stage is equal to m times the rate of second floor. n, m are whole numbers greater than 1. In the example described here, the first stage shift rate 18 is one second, the second stage rate 19 two seconds and the third stage rate

four seconds.

  The memory stages 18, 19, 20 are adapted to one another in such a way that, when all the stages are to be updated at step S2 after the output of the delayed temperature value TV (therefore every 4 seconds) ), it is first the updating of the third stage 20 which takes place. To do this, the contents of the last memory location SZ23 are erased and the contents of the previous locations SZ16 to SZ22 are shifted by one location to the right. It is then that by means of the second comparison element 22, the larger of the two values stored in the locations SZ14 and SZ15 of the second stage 19 is selected and introduced into the first location SZ16 of the third

floor 20.

  The calculation of the second memory stage 19 is then carried out, here again the content of the last location SZ15 being erased, then the data of the previous locations SZ8 to SZ13 being shifted by one location to the right. The maximum selection by means of the first comparison element 21 between the values stored in memory in the locations SZ6 and SZ7 of the first stage 18 follows and the larger of the two values is subsequently introduced in the

  first location SZ8 on the second floor.

  Then, the updating of the first memory stage takes place, the value of the last location SZ7 being erased and the data stored in memory in the first seven locations SZO to SZ6 being shifted by one location to the right. Then at step S3 follows the introduction of the new memory value

  in the first SZO location on the first floor 18.

  Every two seconds, it is first the described updating of the second stage 19, then the updating of the first stage 18 which are carried out. In the others

  not per second, only the described updating of the first stage 18 takes place.

  Thus, there is each time a delay of one second in the locations SZO to SZ7 of the first stage 18, while a delay is achieved every two seconds in the second stage 19 and that a delay of four seconds per

  memory location takes place in the third floor 20.

  This means that, the first location SZ8 of the second stage 19 contains a data value corresponding to a delay of eight seconds and corresponding to a delay of nine seconds, while, the second location SZ9 contains a data value corresponding to a delay of 10 seconds and a delay of eleven seconds. Thus, although the temporal resolution in the second stage 19 is lower than in the first, it is however, due to the maximum selection by means of the first comparator 21, the higher temperature value among the two values stored in memory locations SZ6 and SZ7 which is further delayed in the second stage 19. This is why, given that the influence of the temperature T-ST of the incoming exhaust gases is all the greater as the temperature value is greater, it is advantageously the temperature value which has the greatest influence on the precision of the interior temperature T-MDL determines the NOx storage catalyst which is further delayed in the second stage 19 As a result, a remarkable compromise is obtained between the lowest possible memory costs and the highest possible accuracy as regards the determination of the

  internal temperature in the catalyst 13.

  The temperature value contained in location SZ15 of the second stage 19 is then the temperature value corresponding to a delay of 22 or 23

seconds.

  As already indicated above, in the third memory stage 20, the shift rate is four seconds, so that the corresponding value in one of the locations SZ16 to SZ23 is each time valid for a four-second delay zone . This is how the data value deposited in front of location SZ16 is the corresponding data value for a delay of 24 to 27 seconds and that the data value in the last location SZ23 then corresponds to a delay of 52 to 55 seconds. . In FIG. 5, three pointers Z1, Z2, Z3 are furthermore shown by way of example, which each determine an adjustable length of the first in first out memory 16. The value stored in the designated memory location of a appropriately by pointer Z1 to Z3 is sent as the value of

  T-V temperature at low pass filter 17.

  The pointer Z1 points to the location SZI of the first stage 18. This corresponds to a delay of one second. The pointer Z2, on the other hand, points to the third location SZ10 of the second stage 19, so that the data value stored in this location SZ10 is the corresponding data value which is delayed by twelve or thirteen seconds. If the temperature value T-ST sent to memory 16 must be delayed by 51 seconds, it is the data value stored in location SZ22 which must be delivered in

  output, as indicated by the pointer Z3.

  Providing the first and second comparison elements 21, 22 is not absolutely necessary and only constitutes an advantageous embodiment of the first-in-first-out memory 16. The staged structure of the memory 16 can also be achieved without the two comparison elements 21 and 22, so that then, unlike the structure shown in FIG. 5, these are I data values stored in the last locations SZ7, S Z15 of the first and second stages 18 respectively, 19 which are introduced respectively in the first

  corresponding SZ8 or SZ16 location on the second or third floor 19, 20.

  With reference to FIG. 6, an advantageous way of proceeding will be explained for increasing the memory length of the first-in-first-out memory 16 and therefore of the delay time within the framework of step S3 described above with reference to in Figure 3, the three memory stages 18, 19 and 20 of Figure 5 being, for reasons of simplicity, shown side by side and the first and second

  comparison elements 21 and 22 not shown.

  It is assumed that due to the mass flow of exhaust gases entering the NOx storage catalyst 13 which varies, the delay must be increased, more precisely from the fourth location SZ3 (3 seconds) from the first stage 18 to the seventh replacement SZ14 (20 seconds) from the second stage 19. For this purpose, the value of the location SZ3 which was hitherto the last is copied in all the following locations up to and including the new location SZ14 and the indicator Z4, which initially indicated location SZ3, is shifted to location SZ14, as shown in FIG. 6. It is then the value contained in location SZ14 which is the new delivery value at the output of memory 16. It is thus advantageously possible to prevent the use of the data, contained in the slots SZ4 to SZ14 which were not used before the extension of the delay, which cannot be updated and may have a

  detrimental influence on the determination of the indoor temperature.

  With reference to FIG. 7, a particularly advantageous way of proceeding will be described for the case where, due to the mass flow passing through the NOx storage catalyst 13 which varies or the mass flow of the exhaust gases entering the catalyst. 13 which varies, the delay time of 20 seconds (location SZ14) must again be reduced to 3 seconds (location SZ4). In FIG. 7, in a manner analogous to FIG. 6, the three memory stages 18 to 20 are shown side by side, the comparison elements 20 and 22 not being indicated to simplify the representation. In addition, the first in first out memory 16 still contains a third element of

comparison 23.

  For reduction, the pointer (for output) Z4 pointing to location SZ14 is shifted to the fourth location SZ3 of the first stage 18, as shown in FIG. 6. In addition, the values stored in the memory locations SZ4 to SZ13 located between the new output delivery memory location SZ3 and the old SZ14 and also the values stored in this new output delivery memory location S Z3 and the old SZ14 are all compared with each other and the highest value among these is output as the delayed temperature value TV at the next step S2. For the rest, the process continues to proceed in the manner

  described above with reference to FIG. 3.

  By means of the maximum selection by means of the third comparison element 23, greater weight is given to the higher temperature, since higher temperature values have a greater influence on the accuracy with regard to the determination of the interior temperature of the

NOx storage catalyst 13.

  The comparison elements 21 to 23 described can be produced in the form of a computer hardware element, in the form of software or in the form of a combination of the two. It is the same for modules 14 and 15 and for the Ultra

  low pass 17, lequei is preferably a first order low pass filter.

Claims (16)

  1. Method for determining an internal temperature in a catalyst (13) located in an exhaust path of an internal combustion engine (1), according to which, in a continuous manner, a mass flow of gas exhaust entering the catalyst (13) is raised and, continuously, the temperature of the incoming exhaust gases is raised, subjected to low-pass filtering and output as a determined interior temperature, while as a function of the measured mass flow values, a delay time is established and the measured temperature values are not subjected to low-pass filtering until after the delay time.   2. Method according to claim 1, characterized in that the delay time   is established continuously based on the measured mass flux values.   3. Method according to any one of claims 1 and 2, characterized in   that the mass flow of the exhaust gases and the temperature of the incoming exhaust gases are each recorded at constant respective time intervals.   4. Method according to any one of claims 1 to 3, characterized in   what the mass flow and the temperature of the incoming exhaust gases are read simultaneously.   5. Method according to any one of claims 1 to 4, characterized in   that the readers of the temperature of the incoming exhaust gases are stored in a memory which re-delivers as output the values stored after expiration the delay time.   6. Method according to claim 5, characterized in that the memory is a variable variable length first-in-first-out memory, the length thereof   being set according to the delay time.   7. Method according to claim 6, characterized in that the first in-first out memory (16) comprises a first and a second memory stage (18, 19), the recorded temperature values being introduced into the first memory stage (18), output data from the first memory stage (18) being introduced into the second memory stage (19) and the offset rate of the second memory stage (19) being n times the offset rate   of the first memory stage (18), n being a natural number greater than 1.   8. Method according to claim 7, characterized in that the first memory stage (18) comprises at least n memory locations (SZ0, SZ1, SZ2, SZ7) and outputs the value to the second memory stage (19) the largest of the values contained in the last n memory locations (SZ6, SZ7).   9. Method according to any one of claims 7 and 8, characterized in   that the first-in-first-out memory (16) further comprises a third memory stage (20) whose shift rate is m times the shift rate of the second memory stage (19), m being a number natural greater than 1 and output data from the second memory store (19) being introduced into   the third memory stage (20).   10. Method according to claim 9, characterized in that the second memory stage (19) comprises at least m memory locations (SZ8, SZ9, SZ15) and outputs the largest value at the third memory stage   among the values stored during the last m memory locations.   11. Method according to any one of claims 1 to 10, characterized   in that a delay time shorter than the previously expected delay time is established and then among the temperature values whose delay corresponds at least to the shorter delay time and at most to the delay time until there expected, the value   the largest is sent to low-pass filtering.   12. Method according to any one of claims 1 to 11, characterized   in that a delay time longer than the hitherto expected delay time is established, while as temperature values the delay of which is greater than the hitherto expected delay time and smaller or equal to the longer delay time, a value is established each time which corresponds to the temperature value having the delay time hitherto established.   13. Device for determining an interior temperature in a catalyst (13), located in an exhaust path (8) of an internal combustion engine (1), the device comprising: a module for raising the mass flow exhaust gas (15), which continuously raises a mass flow of gas   exhaust entering the catalyst (13), a temperature raising module   ture of exhaust gases (14), which continuously records the temperature of the incoming exhaust gases, a memory (16), in which the values of temperature readings are stored one after the other and are redelivered at output   after a delay time, and a low-pass filter (17) at which the temperature values   ture delivered at the output are sent and which performs a low-pass filtering with a view to determining the interior temperature, the delay time being established, in function   tion of the measured mass flux values, by means of a delay module.   14. Device according to claim 13, characterized in that the memory (16) is produced in the form of a first-in-first-out memory of variable length. 15. Device according to claim 14, characterized in that the first-in-first-out memory comprises at least two memory stages (18, 19), a first of the memory stages (18, 19), in which the temperature values readings are stored, having a first offset rate and introducing output data into the second memory stage (19), which has a second offset rate which is equal to n times the first offset rate, n   being a natural number greater than 1.   16. Device according to claim 15, characterized in that the first memory stage contains at least n memory locations and a selection module (21, 22) which, among the values contained in the last n memory locations of the first stage from memory (18), enter the largest value in