DE4201136C2 - Method for monitoring a catalytic exhaust gas cleaning system of an internal combustion engine - Google Patents

Description

The present invention relates to a method for Monitoring of catalytic exhaust gas purification location of an internal combustion engine, in particular Motor vehicles.

In the course of the increasingly strict regulations about the permissible emissions of pollutants The exhaust gas cleaning systems are used for exhaust gases Motor vehicles continue to improve. In the meantime systems are often used in which a first catalytic converter, a so-called pre-catalytic converter gate, is used close to the motor, particularly in the Cold start phase of the vehicle quickly enough adequate implementation of pollutants. The This pre-catalyst is usually a larger one downstream catalytic converter, a so-called ter main catalyst, which in normal operation for egg ne complete detoxification of the exhaust gases as far as possible these are not already implemented in the pre-catalyst, worries.

Of course it is desirable and in some countries your even prescribed the operability of the monitor catalytic emission control system, so that the pollutant emissions do not go unnoticed increases.

This is already known, in particular from WO 91/14 855 and WO 91/14 856, a catalyst with temperature sensors during operation watch.

From WO 91/14855 it is also known that for monitoring the functionality temperature measurements in a catalytic emission control system can, the measured values themselves, differences between temperature measured values, and / or their temporal behavior can be used for monitoring. From this document it is also known that such measured values with data from the Motor electronics can be linked to increase the accuracy of the monitoring.

For exhaust systems with a main catalyst is also from DE-OS 26 43 739 known to measure temperatures at several points in an exhaust gas cleaning system and the measured values and / or their temporal courses and / or their correlation to Determine the catalytic activity.

There, as it turned out, to halts function of strict exhaust gas regulations Ability of the pre-catalyst is of crucial importance is the possibility of a Surveillance to be created. So far one is of it assumed that the integral monitoring of the ge entire exhaust system or monitoring the Main catalyst is sufficient. Actually, however Pre-catalysts usually have a higher load than main catalyst sators, so that the functionality of the whole Sy rather by the life of the pre-catalysts than the main catalysts is limited. They are too Processes in the pre-catalyst much more transient and more unsteady than in the main catalyst, because the pre-catalyst sator with its albeit low heat capacity on temperature fluctuations of the exhaust gas like a Low pass filter works. With a suitable evaluation of the Si gnale can therefore monitor pre-catalysis to very precise statements about its functions ability and possibly even to obtain important data for the engine control the.

To solve the task therefore serves starting from WO 91/14 855 a method for transferring monitoring of a catalytic exhaust gas cleaning system Internal combustion engine, especially in motor vehicles testify containing at least one pre-catalyst and at least one spaced apart Main catalyst, which is replaced by an intermediate cut the exhaust pipe in terms of flow are switched, the monitoring using Temperature measurement at one or more points in the Exhaust gas cleaning system and evaluation of the tempera tower measurements and / or their temporal courses and / or their correlation takes place, whereby at least at least a temperature measurement directly in the pre-catalytic converter Tor takes place and an off separately for the pre-catalyst evaluation and monitoring is carried out. By these measures will, on the one hand, monitor the Exhaust gas cleaning system particularly comprehensive, as well the most important in the cold start phase and because of the mo the most sensitive part near the gate is monitored, on the other hand, additional information about the operating state of the engine with great sensitivity be won.

According to be from the prior art known reasons, it makes sense to at least two tem temperature measurements in the pre-catalyst. This is not mandatory because u. U. another downstream in Exhaust system arranged temperature sensor with for Evaluation can be used, however it seems sensible to be in the pre-catalyst in two be range to determine the temperature and accordingly evaluate the known methods.

It is also possible that at least one of the Temperature measurements in the pre-catalyst an integra le temperature over at least part of the axial Length of the pre-catalyst determined. Already one of them average temperature alone allows a statement about the functionality of the catalytic converter if it ins Ratio to one on a new pre-catalyst taken temperature at appropriate operating conditions is set. Pre-catalysts age reason of thermal stress, so that it is more possible at the end of their lifespan no longer in their entire area are catalytically active and therefore exo trigger thermal reactions, but only in one rear section. This would be characterized by a low gere integral temperature of the pre-catalyst at egg measurement over the axial length. Cheap it can also be a measurement over the axial length with another temperature measurement in a be matched area of the pre-catalyst to combine and evaluate both measurements together.

As already explained in the prior art, it is sensible, integral temperature measurements via an et wa representative part of the cross-section of the pre-cataly sators to perform over the cross section un uniform temperature profiles not wrong This is particularly the case with the inflow conditions conditions and the transient behavior of pre-catalysis especially important.

In the event that in addition to the pre-catalyst Main catalyst through temperature measurements above is guarded, it can be particularly cheap for both Monitoring the temperature readings alternate to selectively supply the same evaluation electronics in order to avoid unnecessary components.

Basically it is for the correct interpretation of the Temperature readings advantageous, including data on the Operating states of the internal combustion engine from it Motor control in the evaluation electronics with ver evaluate. For example, the readings for Speed, engine temperature, position of the throttle valve pe etc. of the evaluation electronics via data lines be directed.

Also the reverse connection to the eventual Utilization of the monitoring results in the mo Gate control can be useful, for example Initiation of protective measures for the pre-catalytic converter against overheating.

A corresponding device according to the invention for monitoring catalytic exhaust gas cleaning system of a controlled by an engine control Internal combustion engine, especially in motor vehicles gene, contains at least one pre-catalyst with min  at least a temperature sensor arranged in it, at least one of the pre-catalytic converter by an intermediate main section of the exhaust pipe Talysator, which also has one or more temperature can contain sensors, and evaluation electronics, with which connects all temperature sensors via measuring lines which are and which in turn with an advertisement about ver the functional state of the exhaust gas cleaning system is bound. Details of the device are given on hand of an embodiment in the drawing tert. Two temperature sensors are preferred Pre-catalyst, one of which is at least one part of the axial length of the pre-catalyst inte temperature sensor can be grim.

An embodiment of the invention is in the Drawing shown in the direction of the exhaust is indicated by an arrow.

A pre-catalytic converter 1 is connected upstream of a main catalytic converter 2 and is connected to it via an intermediate section 3 of the exhaust line. Here, the pre-catalyst 1 as well as the main catalyst 2 can be one of two or more, which does not play a decisive role for the present invention. If several are available, they can still be connected to a common evaluation electronics. Both the pre-catalyst 1 and the main catalyst 2 consist of known honeycomb bodies with a large number of channels through which the exhaust gas can flow and contain the catalytically active substance in a ceramic coating. Pre-catalyst 1 and main catalyst 2 can preferably have metallic carrier bodies made of structured sheet metal layers, but ceramic honeycomb bodies are also possible.

According to the invention, temperature sensors 4 , 5 , 6 are arranged in the pre-catalyst, which are connected via measuring lines 14 , 15 , 16 to an electronic evaluation unit 8 . Preferably, the precatalyst has at least two of the three temperature sensors 4 , 5 , 6 shown , for example a front temperature sensor 4 , and a rear temperature sensor 5 , both of which measure integrally over a representative part of the cross-sectional area in their area. In addition or as an alternative to one of the two temperature sensors 4 , 5 measuring in cross-sectional areas, a longitudinal temperature sensor 6 integrally measuring over at least part of the axial length of the pre-catalytic converter 1 can be present.

If the main catalytic converter 2 is also to be monitored, it can also have temperature sensors 7 , which are connected to the evaluation electronics 8 via measuring lines 17 . The evaluation electronics 8 is connected to a display 9 , which can be a control lamp, a measuring instrument or the like, the storage in the broadest sense also being used for later diagnosis or acoustic warning signals and the like. In addition, the evaluation electronics 8 can be connected to the engine control 10 via data lines 11 , 12 , in order to obtain information on the operating state of the engine via feed lines 11 for evaluating the temperature measurements and, on the other hand, via derivations 12, evaluation results to the engine control 10 to be able to pass on.

Method according to the invention and the associated Devices are suitable for monitoring the operation of the Compliance with the strictest emissions regulations and to ensure that malfunctions in the Ab gas cleaning system recognized early and eliminated can be.

Claims (10)

1. A method for monitoring the functionality of a catalytic exhaust gas cleaning system of an internal combustion engine, in particular in motor vehicles, comprising at least one pre-catalytic converter ( 1 ) and at least one main catalytic converter ( 2 ) arranged at a distance therefrom, which are connected in series in terms of flow through an intermediate section ( 3 ) of the exhaust pipe, wherein Monitoring by temperature measurement by means of temperature sensor (s) (e.g. 4, 5, 6, 7 ) at one or more points in the exhaust gas cleaning system and evaluation of the temperature measurement values and / or their temporal courses and / or their correlation to determine the catalytic activity , wherein at least one temperature measurement (for example 4, 5 and / or 6 ) takes place directly in the pre-catalyst ( 1 ) and an evaluation ( 8 ) and monitoring ( 9 ) in evaluation electronics ( 8 ) separately for the pre-catalyst ( 1 ). is made. 2. The method according to claim 1, characterized in that at least two temperature measurements ( 4 , 5 , 6 ) in the pre-catalyst ( 1 ). 3. The method according to claim 1 or 2, characterized in that at least one of the temperature measurements determines an integral temperature over at least part of the axial length of the pre-catalyst ( 1 ). 4. The method according to claim 1 or 2, characterized in that at least one of the temperature measurements determines an integral temperature over an approximately representative part of the cross section of the pre-catalyst ( 1 ). 5. The method according to any one of the preceding claims, wherein the main catalyst ( 2 ) is monitored by temperature measurements and their evaluation, characterized in that for both monitors temperature measurements from the primary ( 1 ) and main catalyst ( 2 ) alternately the same evaluation electronics ( 8 ) be fed. 6. The method according to any one of the preceding claims, characterized in that the evaluation electronics ( 8 ) are also supplied with data on the operating state of the internal combustion engine from the engine control ( 10 ) (11). 7. The method according to any one of the preceding claims, characterized in that the monitoring results from the evaluation electronics ( 8 ) of the motor controller ( 10 ) are supplied ( 12 ). 8. Device for monitoring the functionality of a catalytic emission control system of an internal combustion engine controlled by an engine control ( 10 ), in particular in motor vehicles, containing at least one precatalyst ( 1 ) with at least one temperature sensor arranged therein (e.g. 4 , 5 and / or 6 ), at least one main catalytic converter ( 12 ) which is separated from the pre-catalytic converter ( 1 ) by an intermediate section ( 3 ) of the exhaust pipe and which can also contain one ( 7 ) or more temperature sensors, and evaluation electronics ( 8 ) with which all temperature sensors ( 4 , 5 , 6 and / or 7 ) are connected via measuring lines ( 14 , 15 , 16 and / or 17 ) and which in turn is connected to a display ( 9 ) of the functional state of the exhaust gas cleaning system. 9. The device according to claim 8, characterized in that at least two temperature sensors (z. B. 4 , 5 and / or 6 ) are present in the pre-catalyst ( 1 ). 10. The device according to claim 9, characterized in that one of the temperature sensors ( 4 , 5 or 6 ) is a temperature sensor over at least part of the axial length of the pre-catalyst ( 1 ).