DE19753006C2 - Procedure for the assessment of exhaust gas limit value violations and for the assessment of the quality of exhaust gas relevant components in low emitting motor vehicles while driving - Google Patents

Description

The present invention relates to a method for assessing Emission limit violations and for the quality assessment of exhaust-relevant components low emitting motor vehicles while driving according to the characteristics of the Claim 1.

The increasing air pollution has led to the fact that the Pollutant emissions have been limited and increasingly limited, as from the Fonts 1) to 3) of the enclosed list of publications can be seen. To the Test procedures were used to guarantee reproducibility and comparability Developed. The disadvantage is that many countries have different test methods, Have set ratings and limits. Another big problem is that the test cycles and test conditions used are only a part of those in reality can map driving conditions that occur.

The current limit for methane-free hydrocarbons (NMHC) is in the USA at 0.25 g / mile and applies to both the certification process and the Endurance run over 50,000 miles. For the endurance run over 100,000 miles is a higher one Value of 0.41 g / mile allowed. With the model year 1999 the Limit values and require compliance with 0.125 g / mile for the non-methane Organic gas (NMOG).

The introduction of the ULEV (Ultra-Low-Emission Vehicles) category began in the US state California in 1997, but will only be available for larger sales from 2000 Mandatory. ULEV requires compliance with a limit of 0.04 g / mile at NMOG.

In Europe, an HC limit value (EURO III) for petrol cars of 0.2 g / km is to be introduced in 2000 be introduced, which will be reduced to 0.1 g / km in 2005 (EURO IV).  

The limit values for ULEV and presumably for EURO III and IV can only be set by the Use of new on-site measuring techniques are observed and controlled. Indeed are those to be recorded in the warm operating state of the motor vehicle Concentrations so low that the measurement signals from natural noise could be suppressed.

Various methods are known from the prior art known for exhaust gas measurement. In this way, the vehicle can be tested on a dynamometer Drive through the specified test cycle, the CVS Measurement method (constant volume sampling) is used (see Document 5). During the test cycle, the exhaust gases are exposed to ambient air diluted and collected in bags. From the speed of the fan and from the The temperature of the gas determines the mass of the exhaust gas. From the funded The gas mass and the measured concentration of the pollutant in the exhaust gas is the The pollutant mass of the respective component is calculated on the corresponding one Test length related and the emission values are shown in grams of pollutant per km.

An emission measurement method while driving was described in publication 4).

Nowadays the direct emission is not measured while driving. In the However, the USA has the On-Board Diagnostic (OBD) II system for Passenger cars, which requires that all emission-related components, such as Lambda sensor, fuel system, secondary air system, exhaust gas recirculation, Tank ventilation and the detection of misfires are monitored. However, the pollutant concentrations are not measured, but indirectly suitable sensor signals correlated.

It is up to the manufacturer of the motor vehicle, how he does it in detail Surveillance is undertaken, however, when certain limits were set Technologies ran out. There is only one limit for the three-way catalytic converter for HC, compliance with which is indirectly determined by the oxygen storage behavior of the Catalyst is monitored. For this purpose, the measurement signals of two lambda probes are pre- and compared behind the catalyst and the signal ratio with that Correlation behavior for hydrocarbons correlated.  

It is currently not foreseeable whether this two-probe technology is also suitable for Catalyst monitoring in ULEV and EURO III / IV Otto cars is suitable.

This technique does not provide any information about the immediate HC emissions. In Motor vehicles with ever lower emission limit values seem the most immediate Detecting the pollutant concentration to be the cheaper way.

The only method for component monitoring today is the OBD method, even if no immediate emission measurements can be achieved with it. Some techniques for Fulfillment of the OBD requirements are little or none Extra costs associated with the emissions-relevant component to be monitored. That is true on general electrical monitoring (circuit continuity), the analysis of sensor signals used anyway (plausibility check of measured values e.g. the Lambda probe voltage) but also for the monitoring of Misfires. Monitoring the most important component, the However, the catalyst takes place only indirectly and only taking into account the HC concentration.

The latest motor vehicles with new ones Emission control technologies, alternative fuels, with preheating of the catalytic converter etc. emitted HC concentrations move when the vehicle is in perfect condition in the warm operating condition by approx. 10 ppm. The greatest risk of aging is among those emission-relevant components, the catalyst exposed. The increase in Emission of pollutants with a thermally pre-aged catalytic converter (e.g. 40 hours at 110 ° C) is approx. 30 ppm. The pollutant emission is therefore on average 40 ppm while driving. For a limit catalytic converter that meets the specified ULEV limit at 0.040 (for 50,000 miles) or 0.055 grams per mile (for 100,000 miles), the average value of 60-70 ppm applies during the Drive when all other components are in order. (The ones just mentioned Aging effects in the catalytic converter can also be caused by very high-speed driving behavior Road traffic occurs under natural conditions.)

It is an object of the invention to make subtle changes in pollutant emissions among the To record conditions of driving operation in vehicles with low emissions and to check the quality of exhaust-relevant components.

This task will solved according to the invention by the features of claim 1. Closer Explanations of the invention can be found in the drawings.

Here, FIG. 1 shows the measured emission of pollutants in the exhaust path downstream of the catalyst, determined with precision measuring instruments. The detection of increases of an average of 20-30 ppm is possible, but involves a high level of measurement effort.

Fig. 2 shows the pollutant emissions during the cold start of a ULEV motor vehicle (very low emitting vehicle). Apart from an increased emission in the cold start phase, the HC concentration is very low. The measurable concentrations during the cold start phase, in the first 40-80 seconds after the start, are high compared to the later low level of pollutant emissions. They may amount to several 1,000 ppm. This means that they can be measured more cheaply than the lower concentrations during later warm operation.

Capturing this phase has the following key advantage:

Errors in the exhaust system are particularly drastic in this phase.

Fig. 3 illustrates the change in the cold start parameters in aged catalyst. In addition to the extension of the emission time of increased HC concentration, is related to the higher catalyst temperature necessary, also the absolute amount increases the emission of pollutants. Loss of active positions in the catalytic converter reduces the conversion efficiency.

Of course, other effects can also lead to increased pollutant emissions, so a defect in the preheating of the catalytic converter or problems in the internal combustion engine etc. Ultimately, it does not matter which components to comply with the limit values to cause the error. The errors must then be evaluated by the diagnostic data available anyway or by further investigation be identified and corrected.  

The shape and size of the cold start peak can drive even the latest Motor vehicles, e.g. B. ULEV, reflect well.

It is advisable:

• - the coordinates of the maximum,
• - the absolute size of this maximum point in the peak,
• - the duration of the peak and
• - The area (integral) of the cold start peak

to be recorded in the on-board microcomputer.

Fig.

4 shows the representation of the cold start parameters that measure and evaluate. Every motor vehicle gets an individual one when leaving the production plant or the specialist workshop Map that is formed from several cold starts as an average. The four above Parameters are stored in the microcomputer of the motor vehicle. Each additional Cold start phase is compared with this old motor vehicle-specific map the changes that have occurred are determined. Exceed the changes, such as increasing the absolute level of pollutant emissions, shifting the Time of the maximum within the peak or broadening of the total Area of the emission (i.e. longer heating phase) the predetermined limit, see above an alarm message must be reached when the previously entered limit values are reached to be triggered.  

bibliography

/ 1 / Commission of the European Community: Proposal for a Council Directive amending Directive 70/220 / EEC on the approximation of the laws of the Member States relating to measures to prevent air pollution from motor vehicle emissions
/ 2 / Schäfer, F .: Statutory regulations on pollutants and limitation of consumption in car combustion engines MTZ 52 (1991) 7/8
/ 3 / Stern, AC: University of North Carolina, History of Air Pollution Legislation in the United States, (1982), pp. 52-57
/ 4 / DE 198 21 136 A1 (not pre-published)
/ 5 / Federal Environment Agency: Motor vehicle emissions, limit values, regulations, measurements, Berlin 1989

Claims (4)

1.Procedure for assessing compliance with exhaust gas limit values and for assessing the quality of exhaust-relevant components in motor vehicles with a low emission level, during which the following parameters are measured and evaluated via a gas analyzer located directly in the exhaust gas stream during the cold start phase of the motor vehicle:

• - the maximum concentration of the measured exhaust gas component,
• - the duration of the cold start phase,
• - the temporal position of the emission maximum,
• - the area of pollutant emissions.

2. The method according to claim 1, characterized in that the measured exhaust gas components hydrocarbons, carbon monoxide or Are nitric oxide. 3. The method according to claim 1, characterized in that each Motor vehicle in quality control in the manufacturing plant or in a Specialist workshop goes through the cold start phase several times, the during the Tests in the fault-free condition of all exhaust-relevant components data of the Parameters stored in the on-board microcomputer and each later cold start process newly measured data of the parameters with the, at the parameters saved in the last quality control are compared, with a parameter change in the event of a violation of the limit value Warning message is triggered. 4. The method according to any one of claims 1 to 3, characterized in that the Relationship between the concentration curve of the measured Exhaust component during the cold start phase and the emission during the later driving must be determined.