MXPA00001082A - Device for analysing exhaust emissions from motor vehicles - Google Patents

Abstract

The invention relates to a device for analysing the most important environmentally relevant substances such as CO,HC and NO in exhaust fumes from motor vehicles, based the principle of IR gas absorption. Measuring signals and a reference signal are picked up along an optical measuring distance (special steel tube) using an infrared source and a detector and a measuring value is determined by forming quotients. The OBM system consists of modular components such as a removal device, an exhaust gas processor, an analysis device and an evaluation unit which are integrated into the construction of the motor vehicle. Vibratory conditions in the motor vehicle are compensated by a robust design structure and correction of temperature drift by forming a first derivation and adjustment of the signal height by electronically adjustable amplification regulation. Other correction options are calibration of the zero line with ambient air during switching operations in addition to the creation of a range of tolerance around the noise signals in the detector. The measuring system is to be fitted in the future in all motor vehicles as an addition to the existing OBD (On board Diagnosis) system. Retrofitting devices can be used for older vehicles.

Description

DEVICE FOR THE ANALYSIS OF MOTOR VEHICLE EXHAUST EMISSIONS 1. Introduction Exhaust gases from passenger and freight vehicles cause numerous environmental contaminations. Due to the introduction of limiting steps for the limitation of exhaust emissions, the manufacturers of motor vehicles were forced to reduce the emissions of individual vehicles, for example by the continuous development of engines and exhaust gas systems. . A deterioration of the behavior of the exhaust gas through the service life of the vehicle, which increases gradually due to an increase in emission due to aging, partly due to the failure of the components of the exhaust system and the reduction of the exhaust gas, it may be the reason why these limitation regulations are not maintained. Usually it is procured by means of regular exhaust gas investigations, to guarantee a state of emission comparable with the original state. Here it is disadvantageous that a defect in an exhaust gas investigation is first recognized when high emissions must already be avoided. In the first few seconds of engine operation, when the catalytic converter has not yet reached its operating temperature, the reduction of harmful vapor from the exhaust gas by the catalytic converter is negligible, since the engine in the cold phase produces approximately 70% its total emission, it would be desirable a decrease of the harmful material already in that phase, that the investigation of the current exhaust gas can not encompass from plane. 2. State of the Art A new application for the reduction of the expulsion of harmful material is the On Board Diagnose (OBD). By this is meant a system for emission control by monitoring the capacity of the individual components important for the emission of exhaust gas from a passenger or cargo vehicle by means of sensors. In the United States, a first form of the OBD for passenger vehicles has already existed for a long time (OBD I law), which since the 1995 models is applied in the form of steps by the following OBD II law. While the OBD I law only refers to the control of the operation of the functionality of the components, which are in conjunction with an electronic motor control, the OBD II requires the verification of all the construction parts related to the emission. The verification of the catalyst, the lambda probe, the fuel system, the secondary system, the return of the exhaust gas, the air in the tank and the recognition of the combustion state are all required. In the determination of the fault or the failing function of a component, a sealing lamp is pre-lit on the armature and a fault code is stored. The function recognized as with failure must be located as accurately as possible, described and the information stored, so that when reading in the repair shop in a normal cutting position a quick identification and repair of the fault is made. Another law represents the use of an "On-Board-Measureraent" (OBM). The systems for the direct analysis of emission in motor vehicles are known in many ways. Only by way of example are the open German writings cited; 32 32 416; 3339 073; 36 08 122, 37 16 350, 39 32 838, 40 05 803, 41 24 116, 42 35 225; 43 07 190, the patents 43 19 282 Cl, the North American Patents 4, 803 052 and 5 281 817, as well as other applications GB 2 264 170 A, EP 0 196 993 A2, and WO 94/09266, In these documents will be made reference in the following explanation without describing the individual details. The requests / l / and 12 / refer in a narrow sense to neighboring fields of application and therefore will be treated in that way. This describes the patent / l / an infrared measuring device, which verifies the operating status of the catalyst so that, observes the catalyst laterally and by means of an opening determines the gas atmosphere prevailing in the catalyst. In / 2 / a fast-acting measuring device is represented, which by means of a rear connection of several infrared cells allows a temporary solution in 0.1-0.3 seconds. Both sources give no indication for the continuous measurement of the ejection of material after the catalyst in the exhaust system. From the sources of the literature it can be known that momentarily no system is in a position to capture during the cold phase and in continuous operation the actual emission, to characterize all the deviations and isolate the fault. 3. Description of the opposing / opposing patents Future vehicles will have an integrated OBM system for the analysis of the exhaust gas. Here, certain fractions of the exhaust gas will be analyzed. By comparing the course of momentary concentration with nominal knowledge lines, a fault in the combustion system can be detected. Then a warning will be given, and for that type of car a "good" course will be given in case a long, repeated and clear course lasts., Maintained long indicates a long time, repeated indicates that the overshoot does not present a once, but many times and of course it indicates that the concentration of the window width of the tolerance band has been abandoned. These criteria serve for the security of the analysis. and take care, I do not know of any false communication. Figure 1 shows by way of example how the concentration of harmful material is influenced by faults in the combustion system, here intermittent or ignition distributor (1). The measurement of the exhaust gases is made difficult by the oscillating conditions in the vehicle. On the one hand it must contain a measurement system, with all the limits of tolerance and exigency in force for a vehicle and on the other hand the properties of the exhaust gas are strong such as pressure, humidity, temperature and amount of flow, which influence in the concentration measurement. in the solution of this problem, robust construction parts, microscopic system techniques are required both for the evaluation of the exhaust gas and for the measurement of the components of the exhaust gas. A device for the analysis of the exhaust gas of motor vehicles is known from DE 196 05 053 Al. In this device, however, as in the other equipment for measuring documents, problems arise in the application. Due to the agitations that occur in the vehicle the measuring system must be built very stable and thus be insensitive to carbon black, dust and aerosol alloys. However, it must achieve a high power of solution, since the concentrations to be measured of the constituent parts of the exhaust gas, such as carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxide (NO) are very low in Otto vehicles equipped with catalytic converter. In the present invention, an OBM system is applied as the method of the analysis of the exhaust gas the process of the absorption by the gas of the infrared radiation. The invention starts from the basic thought that to achieve the necessary separation a long optical path is necessary. The bucket can then be placed in a motor vehicle, if it is to be integrated into the construction of the car. 4. Technical Structure of the Measurement System Figure 2 shows the main installation of the OBM system in a car as well as the most important components of the combustion system. The motor (2) as an internal combustion machine produces exhaust gas, in the catalyst (3) the transformation of the harmful materials into less poisonous substances is carried out. The tap position (4), the preparation of the exhaust gas (5) in the analysis device (6) in the exhaust system (7), as well as the data line (8) for joining the indicator unit ( 9) with the analysis device (6) form the OBM system in the motor vehicle or 'automobile. The intake or removal of exhaust gas from the exit of the motor vehicle takes place behind the catalytic converter, since this is the only way to give an opinion on the state of the combustion system and the catalyst. The exhaust gas preparation is represented as a gas course plan in Figure 3. The exhaust gas is cleaned of carbon black and particles with a changeable exhaust gas filter (11). A magnetic valve (12) serves for switching between the exhaust gas and the calibration gas (see part 7). The gas measuring pump (13) forces the gas to be measured through a pressure reducer (14) and a flow meter (15) to the analysis device (6). The analysis of the exhaust gas takes place in accordance with the principle of gas absorption of infrared radiation in the analysis device (cuvette). This consists of an infrared source (transparent piston) whose radiation finds a measuring head through a measuring section (cuvette). The cuvette may consist of a highly reflective straight tube or several tubes with mirror heads, which reflect the radiation. Two pyroelectric measuring sensors, which are equipped with different optical filters and generate a signal dependent on the measured and reference gas, are placed on the measuring head. The formation of the quotients of this signal diminishes the transstorm influences of temperature, pressure, fouling, aging) on the measurement signal. The use of the pyroelectric principle requires a source of radiation with pulses. An electrical pulse in the radiation source avoids decomposable mechanical components (Chopper). The robustness of the measuring system is increased because, the cuvette, measuring section consists of stainless steel. In case the device or parts fail due to dirt, it is advantageous that the device is modularly structured and the individual components, for example the filter, can be easily changed. 5. Installation of subsequent equipment for the analysis of exhaust gas in old motor vehicles. In older motor vehicles, in which no OBD or OBM system has yet been installed in the vehicle by the manufacturer, the engine operating efficiency and the exhaust gas treatment can not be verified outside the exhaust gas investigation . Therefore, there should be the possibility of later equipment. The disadvantage of installing systems later OBD are the multiple measurement values, for which there is no space or connections in the electronic system. Therefore, the installation of an On-Board measurement system is favorable. In Figure 4, such a modular rear OBM installation system is presented. The exhaust gas intake is made with a withdrawal probe (16), which is fixed at the exhaust end. The gas is purified in an exhaust leak preparation, dried and then pumped to the analysis device (6). The indicator unit (9) in the reinforcement table then shows information on the status and operation of the OBM system. The placement of the rear equipment apparatus in the motor vehicle is shown in Figure 5. Here the withdrawal probe (16) is fixed at the exhaust end. The analysis device (6) and the gas preparation (17) can be placed in the space of the chest. The indicator unit (9) can as an air grille be hung or otherwise put on the armor board. 6. Measurement of cold start and adsorption failure. In the cold start phase, 70% of the total emissions of the engine are given, see Figure 6. With the on-board measurement system these emissions are also measured. By means of these values it is possible to switch a case of adsorption failure (10 s, Figure 2) to capture the emissions of cold start in the way of the exhaust gas by the measurement of the exhaust gas the possibility is obtained, of driving the lack of adsorption to the optimal points in time in the path of the exhaust gas or introduce desorption. The desorption of the active carbon retaining hydrogen particles is then carried out, when the catalyst has reached a temperature, at which a satisfactory conversion is ensured. Since the measuring system only needs a small energy expenditure, it can be started before the cold start phase. The control can for example be carried out by a seat sensor or a sensor of the ignition connection, it can also be connected through the adsorption layer HC (10) in the exhaust gas path, 7. Calibration of the null line The principle of gas adsorption of infrared radiation has long been known. The problems, which this measurement principle has under changing environmental conditions, are presented in point 3. The correction of the measurement by different procedures is described below. The most frequent problem is the displacement of the zero point, that is, in the measurement of the gas without load, the measurement value obtained is not zero or zero. The solution to this problem is a frequent calibration of the system with ambient air according to the following method. The magnetic valve (12) in the preparation of the exhaust gas (5, 17) is automatically switched after a predetermined time or due to an influx measured from the outside, so that the air from outside reaches the analysis device (6) In the outdoor air, the concentrations of CO, HC and NO are so low that they can be considered as null gases with sufficient accuracy. By means of a mathematical comparison, the zero or zero line is corrected. This results in that along with the null line in general also the sensitivities reach their correct value again and with this the system shows reproducible values again. Figure 7 shows the effect of that correction on the null line. You see the null line (18) displaced by the temperature influx, as well as the measurement curve again correct (19) after the calibration. This process with an interruption for the indication of the emission does not have any noteworthy influence on the capacity of verification of the measurement, because in that way the objective is not the absolute continuity of the observations, but the recognition of failures in the exhaust gas system. S. Adjustment of the sensitivity of the measurement signals with the help of the C02 concentration of the outside air. The procedure described in point 7 for the calibration of the null line has the advantage that a continuous sensitivity adjustment can disappear, since in this procedure the correct corrections also occur for the sensitivity point (and thus for all the others) . However, it is also possible to control the sensitivity according to the following procedure; The C02 content of the atmosphere has an average value of 350 ppm worldwide (in clean air, outside the cities). This constant fact can be used for the control of the sensitivity, since this concentration is well suited to the regions of measurement of the constituent parts to be considered in the exhaust gas stream. CO, HC but mainly DO NOT precisely have absorption bands weaker than C02, but for that peak or peak values in the concentration. According to the Lambert-Beerschen equation, therefore, the same cuvette length, practically the same cuvette, can be used. If the exhaust gas analysis device (6) receives the addition of unloaded external air, after having made the determination of the null line that has been described, the system must indicate the average concentration of C02. It is then possible, with sufficient security, to start from it, which also applies to other channels for measuring the sensitivity point. It is disadvantageous in the method described above that the local concentration of C02 strongly oscillates due to external influences. Especially in centers of population accumulation, caused by traffic on the streets, the concentration of C02 is very high.

Figure 8 shows the concentration of carbon dioxide in the outside air during a measurement path. After the adjustment of the null point by synthetic air (20) the route is made through a small community- (21) with a relatively constant C02 concentration. The route through a large city (22) with crosses and traffic lights increased greatly, with strongly oscillating C02 concentrations. The measurement in a quiet town (23) presents approximately the concentration of natural C02. 9. Sensitivity adjustment for the C02 concentration in the exhaust gas. As a possible way out of the difficulty presented in point 8, which is produced by the oscillation of the natural concentration of C02, it is recommended to observe the concentration of C02 in the exhaust gas stream of the motor vehicle. This value is relatively stable during the combustion process, so that this concentration can be used as a comparison value for the adjustment of the sensitivity of the individual measurement channels. Due to the high concentration of C02 (12% vol) in the exhaust gas, the arrangement of the jet passage of C02 in the measuring cuvette must be made in any other way than for the other polluting gases. Basically should the optical path for the CO measurement? be essentially shorter than for CO, NO and HC polluting gases. 10. Correction of the displacements of the null line of the measurement signals caused by temperature oscillations, by means of a software technique filter. Normally, a measurement value is obtained by forming the quotient from the signal for the components of the harmful or polluting substances (measurement signal) and the reference signal. The courses of the signals of the measurement signal and the reference signal present a great similarity. Therefore, the quotient procedure can be modified, as long as a certain tolerance field is fixed around the signal course and within that region the quotient "one" is established. This results in a zone or region for the zero concentration, and only that tolerance is abandoned, a concentration corresponding to the values of the determined authentic ratios will be indicated. Note: the correspondence of the zero concentration with the quotient "one" is not necessarily necessary, but the best measurement result is achieved. 11. Compensation of the Temperature Flow by the Observation of the Dynamics of the Signal Courses. Since extreme dynamic conditions (very rapid variations in the system, compared to the pulse time of the radiation) prevail in the motor vehicles according to experience, the oscillations caused by the slow oscillations of the temperature of the radiation can be differentiated. the authentic measurement signals, this is generated by the exhaust gas. For correction, the first derivative of the concentration course must first be formed according to time. The first derivation covers only genuine jump functions, which, for example, occur when accelerating in the vehicle. Figure 9 shows a specific measurement value course. The first derivation (25) was formed from the original measurement signal of the HC contaminating components (24). It is clearly seen that the oscillations of the measurement signal (26) caused by the temperature influences tend to zero in the derivation (25). If the positions of the jump functions have been found from the first derivation with respect to time, then the points with hop properties can be clearly recognized. If such an authentic jump function is presented, this raises the average value clearly from the tolerance band defined above with a width allowed from the differential curve, then it must start from this point to the authentic concentration curve for the evaluation. When the first derivative moves back to the zero point, the zero or zero line returns as a stable line without variation from the software technical filter. If during the tour has been considered either an absolute null line, without tipping, because no jump function has been presented and the tipping caused by the temperature has been neglected, or either when presenting authentic dynamic jump functions, for example when existing gases, change gear speed, brakes etc, according to the first derived the signals originally measured, which have been gained from the course of the concentration. 12. Adjustment of the original signal quantities in the channels of the IR gas analyzer Another correction method consists of the subsequent determination of the signal heights by an tronically adjustable amplification regulation. Since the reference band in the absorption of infrared gas is established in such a way that no basic absorption is made in its band, the measurement signal of the reference channel of the infrared detector should always have the original magnitudes. However, due to influences of temperature and aging, this signal is significantly affected by motor vehicles. To compensate for the tipping caused by the temperature of the signals, there is the possibility of observing the reference signal by the installation -regulation-control- measuring the system itself continuously. If the reference signal deviates around a previously defined value from the value originally set for the first calibration, all signals are carried by means of an tronically adjustable amplification regulation at the height of the original signal. Figure 10 shows the original course of the reference signal (27), the course weakened by aging or action of the temperature (28) as well as by the course of the signal (29) adjustable by the tronic amplification. Through this measure the total region of signal dynamics remains. Indication of the Figures Figure 1 course of the concentration of polluting material in an intermittent ignition. 1. flashing. Figure 2 Main installation of the OBM system in the vehicle 2 engine 3 catalytic converter 4 intake position 5 exhaust gas preparation 6 analysis device 7 ejection device 8 data conduit 9 indicator unit 10 HC adsorption capture Figure 3 gas course plan for waste gas preparation 11 exhaust gas filter 12 magnetic valve 13 measuring gas pump 14 pressure reducer 15 flow meter through Figure 4 Main installation in a retrofit 16 Retraction probe 17 exhaust gas preparation Figure 5 Positioning of the rear equipment in the chest space Figure 6 cold start measurement Figure 7 zero line corrector 18 null line displaced by the action of temperature 19 corrected measurement curve Figure 8 Carbon dioxide concentration in the outside air. 20 adjustment by synthetic air 21 travel by small community 22 travel by large city 23 measurement in a quiet village Figure 9 Derivation as a correction function 24 original measurement signal 25 first derivation 26 measurement signal oscillation caused by temperature. Figure 10 Correction of signal height 27 original course of reference signal 28 for aging weakened course 29 Corrected signal course Literature / l / United States Patent System for monitoring exhaust gas composition Patent Number 5, 475, 223, Date of patent 12 Dec 1995. / 2 / Document published DE 196 05 053 Al; On Board Diagnose / OBD / Procedure and Device in micrometer bar for continuous measurement of pollutant content from motor vehicles.

Claims (15)

1. CLAIMS 1. A device for the analysis of substances harmful to the environment found in the exhaust gas of motor vehicles, such as carbon monoxide, hydrocarbons and nitrogen monoxide, with at least one sensor, which considers the qualitatively, and that is disposed in a measurement section separated from the exhaust gas system, characterized in that, a pumping system is provided, which forces to the sensor zero point adjustment position, the exhaust gas changing from the exhaust gas system and ambient air from the atmosphere through the measurement section.
2. 2. The device according to claim 1, characterized in that, the sensor works in accordance with the method of absorption of the infrared gas.
3. The device according to claim 2, characterized in that the measuring section consists of a stainless steel bowl with an optical path length of at least 50 cm.
4. 4. The device according to claim 2 or 3, characterized in that the sensor has a micro-radiator-halogen, which is surrounded by a transparent piston that acts as a black body. The device according to one of claims 2 to 4, characterized in that the sensor simultaneously receives the light from the radiation source in accordance with the principle of measuring channel / reference channel and from the signals forms a quotient for Obtaining a measurement value. The device according to one of claims 1 to 5, characterized in that the pumping system has an exhaust gas filter regenerable by heating, a magnetic valve and a pump. The device according to claim 6, characterized in that, a pressure reducer and a flow meter have been provided. The device according to one of claims 5 to 7 or according to the idea of claim 1, characterized in that the signal courses diverge from one another by the action of temperature, from the two detector cells sensitive to infrared rays. (reference channel and measurement channel) are moved to the measurement phases that remain between the null phases. The device according to one of claims 5 to 8, characterized in that the height of the signals is subsequently adjusted by an amplification control which can be adjusted electronically to the course without disturbing the reference signal, correspondingly. The device according to one of claims 1 to 9 or according to the main idea of claim 1, characterized in that, the push of the signals caused by the course of the temperature from the concentration variation in the form of jumps in the normal operation of motor vehicles, is differentiated by the formation of the first derivative with respect to the time of each concentration course. The device according to one of claims 1 to 10, characterized in that the sensitivity adjustment is made by reference to the natural concentration of C02 in clean room air, 340 ppm normal value or the C02 fraction in the exhaust gas, 14% of the volume. Device according to one of claims 1 to 11, characterized in that the device is placed on the lower floor of the motor vehicle, in the space of the hood in the bodywork or in other suitable places of the motor vehicle. Device according to one of claims 1 to 12, characterized in that the device is integrated in the construction of the vehicle and consists of a removal position, preparation of the exhaust gas, analysis device, data line and indicating unit , where the individual components, by the modular structure, are changeable and can also be subsequently placed on the motor vehicle. The device according to one of claims 1 to 13, characterized in that, the device is connected with the aid of a seat measurement sensor or a sensor of the ignition connection so that it measures the cold start-up, at the beginning. The device according to one of claims 1 to 14, characterized in that the measurement signal serves for the control of the combustion process in the engine and in the catalytic converter, as well as for the time recognition and correction of the faults. ABSTRACT A device is described for the analysis of environmental pollutants such as CO, HC and NO in the exhaust or waste gas of motor vehicles based on the principle of absorption by infrared gas. Here, an optical measurement section (stainless steel tube) is obtained with the aid of an infrared source and a detector, measurement and reference signals and by the formation of a quotient, a measurement value, when a limit value is exceeded. Make a warning. The OBM system consists of modular constructive elements, such as withdrawal device, waste gas preparation, analysis device and evaluation unit, which are integrated in the construction of the motor vehicle. The changing conditions in the motor vehicle are matched by a robust structure and the correction of the temperature action by the formation of the first derivative and the subsequent adjustment of the signal height by means of an electronically adjustable amplification regulation. Other possibilities of correction are the calibration of the null line by switching measurements as well as the creation of a tolerance band and the important signals in the detector. The measurement system must in the future be integrated into all vehicles also as an addition to the existing OBD (On-Boards-Diagnostic) system. For older motor vehicles are applicable equipment that will be placed later.