DE4201136A1 - METHOD FOR MONITORING A CATALYTIC EXHAUST GAS PURIFICATION SYSTEM OF AN INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

The description relates to a process for monitoring a catalytic exhaust gas purifying system of an internal combustion engine, especially for motor vehicles, which makes it possible separately to monitor a pre-catalyser (1) belonging to the exhaust gas purifying system. Temperature sensors (4, 5, 6) at one or more points in the pre-catalyser (1) and their reading in an evaluation electronics system (8) facilitate the direct monitoring of the pre-catalyser so that compliance with even the strictest exhaust gas regulations, implying the use of an effective pre-catalyser, can also be monitored and ensured by operational monitoring in the vehicle.

Description

The present invention relates to a method for Monitoring a catalytic emission control system Internal combustion engine, especially in motor vehicles.

In the course of the increasingly strict regulations on the permissible emissions of pollutants in exhaust gases are the Exhaust gas cleaning systems in motor vehicles continue to grow improved. Systems are now widely used at which a first catalytic converter, a so-called Pre-catalyst is used close to the engine, which is particularly in the cold start phase of the vehicle quickly for a sufficient Implementation of pollutants can worry. This pre-catalyst usually becomes a larger catalytic converter downstream, a so-called main catalyst, which in Normal operation for a complete detoxification of the Exhaust gases, insofar as these have not already been implemented in the pre-catalytic converter be worried.

Of course it is desirable and in some countries it is prescribed the functionality of the catalytic Exhaust emission control system to monitor, so that the Pollutant emissions not increased unnoticed.

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

Since, as has now been found to comply with strict exhaust gas regulations the functionality of the Pre-catalyst is vital, too for this the possibility of monitoring is created. So far it has been assumed that the integral Monitoring the entire exhaust system or monitoring of the main catalyst is sufficient. Actually, however Pre-catalysts usually have a higher load than main catalysts, so that the functionality of the whole system is rather through the life of the pre-catalysts as the main catalyst is limited. The processes in the pre-catalyst are also much more transient and transient than in the main catalyze sator, because the pre-catalyst with its albeit small Heat capacity on temperature fluctuations of the exhaust gas like a Low pass filter works. With a suitable evaluation of the signals can therefore monitor pre-catalysts too much precise statements about its functionality and if necessary, even to obtain for engine control important data can be used.

Starting from WO 91/14 855 a method for monitoring a catalytic exhaust gas cleaning system of an internal combustion engine, in particular in motor vehicles containing at least one Pre-catalytic converter and at least one arranged at a distance from it neten main catalyst, which by an intermediate section the exhaust pipe is connected in series in terms of flow, the monitoring by means of temperature measurement on one or several points of the emission control system and evaluation of the Temperature measurements and / or their temporal courses and / or their correlation takes place, at least one further Temperature measurement takes place directly in the pre-catalyst and separately an evaluation and monitoring for the pre-catalyst is made. Through these measures, on the one hand, the Monitoring of the exhaust gas cleaning system particularly comprehensive, because also the most important in the cold start phase and because of the  the most sensitive part is closely monitored on the other hand, additional information about the Operating state of the engine obtained with great sensitivity will.

According to the reasons known from the prior art it makes sense to carry out at least two temperature measurements in the Perform pre-catalyst. This is not mandatory there u. U. Another arranged downstream in the exhaust system Temperature sensor can be used for evaluation, however, it makes sense to do it right in the pre-catalyst in two Areas to determine the temperature and according to the evaluate known methods.

It is also possible that at least one of the An integral temperature measurement in the pre-catalyst Temperature over at least part of the axial length of the Pre-catalyst determined. A temperature determined in this way alone allows a statement about the functionality of the Catalyst when compared to one on a new one Pre-catalyst temperature recorded at the appropriate Operating conditions is set. Aging pre-catalysts due to the thermal load so they may at the end of their lifespan no longer in their full range are catalytically active and thus exothermic reactions trigger, but only in a rear section. This would be due to a lower integral temperature of the Pre-catalyst when measuring over the axial length impact. It can also be convenient to take a measurement over the axial length with another temperature measurement in one combine certain area of the pre-catalyst and evaluate both measurements together.

As already explained in the prior art, it makes sense to Temperature measurements integrally over an approximately representative Part of the cross section of the pre-catalyst to perform  non-uniform temperature profiles across the cross-section wrong to evaluate. This is particularly the case with the Inflow conditions and the transient behavior of Pre-catalysts are particularly important.

In the event that in addition to the pre-catalyst Main catalyst is monitored by temperature measurements, it can be particularly cheap for both surveillance Temperature readings alternately from the same evaluation electronics feed 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 its engine control in of the evaluation electronics. So should for example the measured values for speed, engine temperature, Position of the throttle valve etc. of the evaluation electronics Data lines are fed.

Also the reverse connection, for the eventual utilization of the Monitoring results in the motor control can be useful be, for example, to initiate protective measures for the pre-catalyst against overheating.

A corresponding device according to the invention Monitoring a catalytic emission control system internal combustion engine controlled by an engine control, in particular in motor vehicles, contains at least one Pre-catalyst with at least one arranged therein Temperature sensor, at least one from the pre-catalyst an intermediate section of the exhaust pipe separated Main catalyst, which is also one or more Can contain temperature sensors and evaluation electronics, with which all temperature sensors are connected via measuring lines and which in turn with an indication of the function state of the exhaust gas cleaning system is connected. details  the device are based on an exemplary embodiment in the drawing explained. Two are preferred Temperature sensors in the pre-catalyst, one of which is a at least part of the axial length of the pre-catalyst integrally measuring temperature sensor.

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

A pre-catalytic converter 1 is connected upstream of a main catalytic converter 2 and connected to it via an intermediate section 3 of the exhaust pipe. Both the pre-catalyst 1 and the main catalyst 2 can each be one of two or more, which does not play a decisive role in the present invention. If there are several in each case, these can nevertheless be connected to a common evaluation electronics. Both pre-catalytic converter 1 and main catalytic converter 2 consist of known honeycomb bodies with a multiplicity of channels through which the exhaust gas can flow and contain the catalytically active substance in a ceramic coating. Pre-catalytic converter 1 and main catalytic converter 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 and are connected to evaluation electronics 8 via measuring lines 14 , 15 , 16 . The precatalyst preferably 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 catalyst 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 to be able to pass on evaluation results to the engine control 10 via leads 12 .

Method according to the invention and the associated device are also suitable for monitoring the fulfillment of operations strictest emissions regulations and to ensure that Malfunctions in the exhaust gas cleaning system early can be recognized and eliminated.

Claims (10)

1. A method for monitoring a catalytic exhaust gas cleaning system of an internal combustion engine, in particular in motor vehicles, containing at least one pre-catalyst ( 1 ) and at least one main catalyst ( 2 ) arranged at a distance therefrom which are connected in series through an intermediate section ( 3 ) of the exhaust gas line, the monitoring by means of temperature measurement ( 4 , 5 , 6 , 7 ) at one or more points of the exhaust gas cleaning system and evaluation ( 8 ) of the temperature measurement values and / or their temporal courses and / or their correlation, wherein at least one temperature measurement ( 4 , 5 , 6 ) takes place directly in the pre-catalyst ( 1 ), and an evaluation ( 8 ) and monitoring ( 9 ) is carried out separately for the pre-catalyst ( 1 ). 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 ( 6 ) of the temperature measurements ( 4 , 5 , 6 ) 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 ( 4, 5 ) of the temperature measurements ( 4 , 5 , 6 ) 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 ( 7 ) and their evaluation ( 8 ), characterized in that temperature measurements from the primary ( 1 ) and main catalyst ( 2 ) alternate for both monitors the same evaluation electronics ( 8 ) are supplied. 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 a catalytic exhaust gas purification system of an internal combustion engine controlled by an engine control ( 10 ), in particular in motor vehicles, containing at least one pre-catalyst ( 1 ) with at least one temperature sensor ( 4 , 5 , 6 ) arranged therein, at least one from the pre-catalyst ( 1 ) by an intermediate section ( 3 ) of the exhaust pipe, the main catalytic converter ( 12 ), which may also contain one or more temperature sensors ( 7 ), and evaluation electronics ( 8 ) with which all the temperature sensors ( 4 , 5 , 6 , 7 ) Measuring lines ( 14 , 15 , 16 , 17 ) are connected and which in turn is connected to a display ( 9 ) about the functional state of the exhaust gas cleaning system. 9. The device according to claim 8, characterized in that at least two temperature sensors ( 4 , 5 , 6 ) in the pre-catalyst ( 1 ) are present. 10. The device according to claim 9, characterized in that one of the temperature sensors ( 4 , 5 , 6 ) over at least part of the axial length of the pre-catalyst ( 1 ) measuring temperature sensor ( 6 ).