KR20010022274A - device for analysing exhaust emissions from motor vehicles - Google Patents

Abstract

The present invention relates to a device for the analysis of the most important environmental substances such as CO, HC and NO in the exhaust gas from a vehicle based on the principle of IR-gas absorption. In this case the measurement signals and one reference signal are picked up in the optical measuring section (special steel tube) using an infrared source and a detector so that the measured values are detected by quotient formation. The OBM system consists of modular elements such as evaluation units, analysis units, exhaust gas processors and separation units integrated within the vehicle's structure. The vibration conditions of the vehicle are compensated through the adjustment of the signal height by electronically adjustable amplification control, the correction of the temperature drift by the first derivative and the construction of a robust design. Another correction method is to calibrate the zero line using ambient air during the switching operation in addition to forming a tolerance range around the noise signal at the detector. This measurement system will be fitted to all vehicles in the future as an addition to the existing OBD (ON Board Diagnosis) system. Retrofits can be used for older vehicles.

Description

Device for analyzing exhaust gases from vehicles {device for analysing exhaust emissions from motor vehicles}

1. Introduction

Exhaust gases from passenger cars and commercial vehicles cause a lot of environmental burden. By introducing limit value provisions for limiting emissions, vehicle manufacturers have been forced to reduce the emissions of individual vehicles, for example through the development of engines and exhaust systems, and are currently unable to reduce them.

Deterioration of the exhaust gas condition during the vehicle's service life, which is manifested mainly by the gradual increase in emissions due to aging in the drive system and the exhaust gas reduction system, but also in part through defective elements, may be the reason why the above limit value regulations are not met. It may be.

Efforts to ensure emission levels comparable to original conditions are usually made through regular exhaust investigations. Disadvantages are that the defects are not found until the next exhaust gas survey and until much emissions are produced.

If the catalyst has not yet reached its operating temperature, it is very low that harmful substances of this exhaust gas are reduced through the catalyst during the first few seconds of vehicle operation. Since the engine produces about 70% of its total emissions in the cold start phase, optimization of the reduction of the toxic substances is valuable at this stage, ie at this stage with no exhaust gas irradiation at that point.

2. Prior art

A new starting point for reducing the release of these hazardous substances is this "On-Board-Diagnose" (OBD). This means a system for controlling the exhaust gas by monitoring the faithful functioning of the individual members associated with the exhaust gas of a passenger car or a commercial vehicle via sensors. In the United States, there was already a first form of OBD for passenger cars a long time ago (OBD I-law), which has been phased out through the extensive OBD II-law since the 1995 model. While this OBD I focuses solely on controlling the faithful functioning of the devices involved in electronic engine control, the OBD II requires monitoring of all devices related to exhaust gas emissions. Emphasis is placed on monitoring the detection of catalysts, lambda-sonde, fuel systems, secondary ventilation systems, exhaust gas returns, tank vents and combustion failures. If you identify a fault or malfunction of the device, the signal lamp lights up in the instrument cluster and an error code is stored. Since the identified error function is localized and recorded as accurately as possible and the information is stored, it is read by a standardized interface for quick identification by the repair center and repair of the error.

The use of "On-Board-Measurement (OBM)" provides a broad starting point. Various systems are known for directly analyzing emissions from a vehicle. German public publication 32 32 416, 33 39 073, 36 08 122, 37 16 350, 39 32 838, 40 05 803, 41 24 116, 42 35 225, 43 07 190, DE 43 19 282 C1, US-patent publication 4 803 052 and 5 281 817 and in other applications GB 2 264 170 A, EP 0 196 993 A2 and WO 94/09266. These publications are incorporated by reference for the purpose of explanation of all details not set forth herein separately.

Patent applications / 1 / and / 2 / are related in a narrow sense to neighboring theme ranges and are discussed for this reason. Thus, the patent / 1 / describes an infrared measuring device which monitors the operating state of the catalyst, in which the measuring device can look into the catalyst from the side and determine the dominant gas in the catalyst through the opening. In / 2 / a fast clocked measuring device is shown, which allows for a time resolution of 0.1 to 0.2 s by connecting multiple infrared vessels in series. Both data do not provide any indication for continuously measuring the release of hazardous substances behind the catalyst in the exhaust gas system.

It can be seen from the above documents that no measuring system can currently detect the actual emissions in the cold start phase and during operation in order to record all deviations and signal an error.

3. Description of this patent subject

Future vehicles will have an integrated OBM system for exhaust gas analysis. At this time, a certain amount of this exhaust gas is analyzed. The stored target-characteristic curve is compared with the instantaneous concentration curve to close against errors in the combustion system. A warning is then issued if the curves stored for various vehicles and considered "good" stop for a long time and are repeated and apparently exceeded. "Long-term stop" means longer periods of time, "repeated" means that the excess does not occur once but occurs multiple times, and "obviously" means that the concentration is It means outside the tolerance range. These criteria are used to ensure the above analysis so that false reports are not provided.

1 shows by way of example how the concentration of a hazardous substance is affected by an error in the combustion system, here ignition failure (1).

The measurement of this exhaust gas becomes difficult due to vibration conditions in the vehicle. On the one hand, the measurement system must comply with the usual tolerance limits and conditions applicable to the vehicle, and on the other hand, under strong vibrations where the exhaust gas characteristics pressure, moisture, temperature and perfusion affect the concentration measurement. Lies. To solve this problem, strong and not only for exhaust gas processing but also for the measurement of exhaust gas components require microsystem technical components.

A device for the analysis of exhaust gases of vehicles is already known from DE 196 05 053 A1. However, problems arise in such applications as are necessary for the measuring devices described in further patent publications. Due to the impact present on the vehicle, this measuring system is very stable and furthermore it does not react to soot, dust and aerosol deposits. Nevertheless, high decomposition must be achieved, because the concentration of the component to be measured of the exhaust gases such as CO, HC and NO is very low in the catalyst-equipped auto-engine-vehicle.

In the OBM system of the present invention, an infrared gas absorption method is used as the exhaust gas analysis method. The basic idea from which the present invention begins is that a large optical path length is required to achieve the required resolution. The container can be mounted in the vehicle once it is integrated into the configuration of the vehicle.

4. Technical composition of this measuring system

2 shows the most important elements of the principle interior and combustion systems of the OBM system into the vehicle. An internal combustion engine, engine 2, produces exhaust gas, and in the catalyst 3, harmful substances are converted into substances of low toxicity. The separation point 4, the exhaust gas processor 5, the analysis device 6, the exhaust device 7, and the data line 8 for connecting the display unit 9 and the analysis device 6 are described above in the vehicle. Form an OBM system.

Separation of the exhaust gas from the outlet of the vehicle takes place behind the catalyst, since an assessment of the overall combustion system and the condition of the catalyst can be made.

3 shows the exhaust gas processing as a gas flow diagram. In this exhaust gas, soot and particles are cleaned by a replaceable exhaust gas filter 11. Solenoid valve 12 is used for switching between the exhaust gas and the calibration gas (see no. 7). The measuring gas pump 13 transfers the gas to be measured through the pressure attenuator 14 and the perfusion meter 15 to the analysis device 6.

Exhaust gas analysis is carried out in accordance with the principle of infrared gas absorption in the analysis device (container). It consists of an infrared source (transparent cylinder) and its beam strikes the measuring head past the measuring section (container). In this case the container consists of a straight, high refractive pipe or a plurality of pipes with a mirror head that reflects the beam. Two pyroelectric measuring sensors are installed in the measuring head, which are equipped with various optical filters and also produce a reference signal according to the measuring gas. The formation of quotes of these signals reduces the disturbing effects (temperature, pressure, dirt, aging) on the measurement signal. The use of the pyro electric principle requires a radiation source to be clocked. The electrical clock to the radiation source avoids mechanical components (choppers) that are prone to failure. The rigidity of this measuring system is improved by the vessel (measuring section) being made of special steel. If the device is dirty or its members fail, the device can be modular and the individual components can simply be replaced, for example with a filter.

5. Follow-up kits for exhaust gas analysis in conventional vehicles

In older vehicles, where the manufacturer did not embed the OBD- or OBM-system directly into the vehicle, engine fidelity and exhaust gas post-processing could not be checked outside the exhaust gas inspection. Therefore, a method for later mounting should be provided.

A disadvantage of the later installation of the OBD is a large number of measured value recorders which provide no place or connection in the electronic device. Thus, the embedding of the on-board-measuring system is better.

In FIG. 4 such a modular OBM-future mounting system is shown. This exhaust gas separation consists of a separation probe 16 fixed to the outlet end. This exhaust gas is purified in an exhaust gas processor 17, dried and further pumped into the analysis device 6. In the instrument cluster, the display unit 9 shows information on the status and operation of the OBM system.

5 shows the installation of a later mounting set in a vehicle. In this case, this separation probe 16 is fixed to the outlet end. The analyzing device 6 and the gas processor 17 can be installed in the trunk. This display unit 9 can be hooked to a ventilating grid or fixed to the instrument panel on the other side.

6. Cold start measurement and absorption trap

In the cold start stage 70% of the total exhaust emission of the engine is emitted (see FIG. 6). The emissions are measured with this on-board measurement system. These values connect the HC-absorption trap 10 (see FIG. 2) to collect the cold start emissions in the exhaust gas path. This exhaust gas measurement allows the absorption trap to be connected to the exhaust gas path or induces emissions at optimum times. When the catalyst reaches a temperature that ensures satisfactory conversion, the release of hydrocarbon particles is inhibited.

Since this cold start-measurement system requires only a little energy, it can already be operated before the cold start phase. This control is effected, for example, by a seat position sensor or a sensor in an ignition-lock, through which the HC-absorbing trap 10 is connected to the exhaust gas path.

7. Zero lines calibrating

The measuring principle of infrared gas absorption is well known. The problems with the measuring principle under varying environmental conditions have already been described in Section 3. Modification of the measurement through various methods is described below.

The most frequent problem is that the measured value detected during the zero point movement, i.e., the measurement of unburdened gas, is not zero. In order to solve this problem, the system is frequently calibrated using ambient air according to the following method. The solenoid valve 12 of the exhaust gas processor 5, 17 is automatically switched and switched after a predetermined time point or because of measured external influences, so that the outside air reaches the analyzer. Since the concentrations for CO, HC and NO in this outside air are small, it can be observed with zero gas with sufficient accuracy. The mathematical adjustment corrects the zero line. Thus, in addition to this zero line, the sensitivity generally also reaches its correct value again and therefore the system shows again reproducible values. 7 shows the corrective action of this zero line. The zero line 18 shifted through the temperature drift and the correct measurement curve 19 are again found after the calibration. The process of stopping recording of these emissions does not aim at the absolute continuity of the observations anyway, but rather at error detection in the exhaust gas system and does not have a significant reference influence on the evaluation capability of the measurement.

8. Adjusting the Sensitivity of the Measurement Signal Using CO ₂ -Concentration in Outside Air

The advantage of the method for zero line calibration described in point 7 is that the continuous sensitivity adjustment can be omitted, in which case the sensitivity point (and everything else) Because correct corrections are obtained. Nevertheless, control of this sensitivity is also possible in the following way:

Atmospheric CO ₂ -content averages 350 ppm worldwide (in clean air outside cities). This fact can be used for sensitivity control because this concentration is suitable for the measuring range of the elements to be detected in the exhaust stream. CO, HC, in particular NO, in fact has a weaker absorption range than CO ₂ , but with higher peak values in terms of concentration. Therefore, according to the Lambert-Beersch equation, the same vessel length, in fact the same vessel is used. When the outside gas is provided to the exhaust gas analyzer 6 without burden, the system shows an average CO ₂ -concentration after the aforementioned zero point adjustment is performed. Then, with sufficient safety, the sensitivity points are matched for the other measuring channels.

A disadvantage of the above method is that the local CO ₂ -concentration fluctuates strongly through external influences. In particular, the concentration of CO ₂ -at the center of concentration caused by street traffic is very high. 8 shows the carbon dioxide concentration in the outside air during measuring running. After adjusting the zero point through the synthetic air 20, a run through the small neighborhood 21 with a relatively uniform CO ₂ -concentration is achieved. The run through the larger city 22 with intersections and traffic lights shows a high CO ₂ -concentration that fluctuates strongly. Measurements in the quiet patio 23 are close to natural CO ₂ -concentrations.

9. Adjustment of sensitivity using CO ₂ -concentration in exhaust gas

Observation of the CO ₂ -concentration in the exhaust gas flow of the vehicle is recommended as a possible escape from the difficulties described in 8, resulting from the natural CO ₂ -concentration fluctuations. Since this value is relatively stable throughout the combustion process, this concentration can be used as a comparative value for the adjustment of the sensitivity of the individual measuring channels. However, through the high concentration of CO ₂ (12 vol%) in the exhaust gas, the arrangement of the CO ₂ -beam path in the measuring vessel is made differently than for other harmful gases. Basically the optical path for the CO ₂ -measurement is much shorter than for noxious gases (CO, NO and HC).

10. Correction of movements caused by temperature drift of the zero line of measurement signals via a software technical filter

It is common for detection of measured values through the formation of a quotient from a signal (measurement signal) and a reference signal for a toxic substance component.

The signal curves of the measurement signal and the reference signal have a high similarity. Thus, the quotient method can be modified to the extent that it establishes a constant tolerance range around the signal curve and sets the quotients to "1" within this range. Therefore, only if there is an area for zero-concentration and it is outside this tolerance range, a concentration that matches the values of a constant true quotient is displayed. Although it is not necessary to match the concentration "0" to the quotient "1", it is common that the best measurement result is obtained.

11. Compensation for temperature drift through the dynamic observation of signal curves

Due to experience in the vehicle, extremely dynamic conditions are dominant (compared to the fast change in time in the system, compared to the clock time of the radiator), which is caused by temperature, in which the measurement signals made from the exhaust gases oscillate more slowly. Distinguished drifts. For correction, the first derivative of the concentration curve must be formed over time. The first derivative detects only the true jump function that occurs in the vehicle, for example, upon acceleration. 9 shows a specific measured value curve. The first derivative 25 is formed from the first measurement signal of the harmful substance component HC 24. It is clear that the measurement signal drift 26 caused by the temperature influences goes from zero in the first derivative 25.

By finding the points of the jump functions from the first derivative over time, it is possible to clearly detect the points with jump characteristics. If such an intrinsic jump appears, ie the measurement is emphasized from the differential curve with an acceptable width from a predetermined tolerance range, it is approached for evaluation from the point to a true concentration curve. When the first derivative returns to zero point, the zero line is again provided as a stable line unchanged from a filter in software technology. The jump function does not appear and the drift caused by temperature is neglected, thus having absolute zero lines without drift during driving or when generating truly dynamic jump functions, i.e. during acceleration, gear change, braking, etc. The first measurement signal obtained from the concentration curve after the first derivative is observed.

12. Adjustment of the original signal values in the channels of the IR gas analyzer

Another modification is to later adjust the signal magnitude through electronically adjustable amplification control.

When the infrared gas is absorbed, the reference range is planned so that no absorption is basically made in the range, so that the measurement signal of this reference channel of the infrared detector always has the original magnitudes. However, because of temperature effects and aging, this signal is noteworthy in the vehicle.

In order to compensate for the drift caused by the temperature of these signals, there is a method of continuously observing the reference signal through the measurement-control-device of the system itself. If this reference signal deviates from the initial calibration value initially adjusted by a predetermined constant value, all signals are brought to the original signal height through electronically adjustable amplification control. 10 shows the initial curve of this reference signal 27, the curve 28 attenuated through aging or temperature drift, and the signal curve 29 corrected through electronically adjustable amplification. These measures maintain the entire area of the signal dynamics.

(Drawing symbol)

1: Toxic substance concentration curve at ignition failure

1 ignition failure

Figure 2: Principle of the OBM-system in a vehicle

2 engine

3 catalyst

4 separation points

5 exhaust processor

6 analysis device

7 exhaust system

8 data lines

9 Display Unit

10 HC-absorption trap

Figure 3: Gas Flowchart of Exhaust Gas Processing

11 exhaust gas filter

12 solenoid valve

13 measuring gas pump

14 pressure attenuator

15 perfusion meter

Figure 4: The principle structure of the later mounting set

16 separation probe

17 Exhaust Gas Processing

5: Installation of the later mounting set in the trunk

Figure 6: Cold Start Measurement

Figure 7: Zero Line Correction

18 Zero line shifted through temperature drift

19 modified measurement curve

8: Carbon dioxide concentration in outside air

20 Synthetic Air

Driving through neighborhoods smaller than 21

Driving through cities greater than 22

23 Measurements in the quiet courtyard

9: Differential as a correction function

24 First measuring signal

25 1st derivative

26 Measurement signal drift caused by temperature

Figure 10: Correction of signal size

27 First curve of reference signal

28 Curve weakened due to aging

29 Corrected Signal Curve

(literature)

US patent: system for monitoring exhaust gas components.

Patent number: 5,475,223. Patent date: December 12,995

/ 2 / Published publication DE 196 05 053 A1: On-board-diagnostics / OBD / -methods and devices in micro-units for the continuous measurement of hazardous substance emissions from vehicles

Claims (9)

In an apparatus for the analysis of environmentally important substances in the exhaust gases of vehicles, such as CO, HC and NO, with the aim of controlling the combustion processes, early detection and correction of errors in the engine and in the catalyst, Measurements are made according to the method of infrared gas absorption, in which case a container made of special steel has a relatively large optical path length, through which the exhaust gas of the vehicle flows, and light from a special infrared source made of a transparent cylinder passes, An apparatus for exhaust gas analysis of a vehicle, characterized in that one detector receives light according to the measurement channel / reference signal-principle and from which a share is formed for detection of the measured value. 2. The apparatus of claim 1, wherein the measurement system can be installed at the bottom of the vehicle, in the trunk, at the body of the vehicle, or at another suitable point in the vehicle. As an exhaust gas analysis device of a vehicle, a measurement system integrated into the structure of the vehicle consists of, for example, a separation point, an exhaust gas processor, an analysis device, a data line and a display unit, in which case the individual components are provided via a modular structure. Exhaust gas filter, solenoid valve, measuring gas pump, pressure, which can be replaced and later embedded in the vehicle, and the exhaust gas processor is configured to be strong and stable, for example replaceable and regenerated by heating And an attenuator and perfusion meter, wherein the members do not react to soot, dust and aerosol deposits caused by the predominantly rocking and rough conditions prevailing in the vehicle. The method of any one of the preceding claims, wherein the zero point adjustment of the measuring device for the HC- and CO-concentrations in clean ambient air is achieved through continuous, short-term switching off of the switch, in which case the sensitivity adjustment is performed in a clean atmosphere. A vehicle's exhaust gas analyzer, characterized in that it is made possible by the dependence on the natural CO ₂ -concentration (350 ppm normal value) or the CO ₂ content in the exhaust gas. The apparatus of any one of the preceding claims, wherein the temperature drift is corrected by forming a first derivative of the concentration graph in which jump functions of the vehicle operation can be distinguished from a slow drift effect. An apparatus according to any one of the preceding claims, wherein the signal magnitude is later adjusted via electronically adjustable amplification control that accepts an unchanged, unobstructed graph of the reference signal as a basis. As a vehicle's exhaust gas analyzer, a later set of installations, which are not mandatory, is also provided for conventional vehicles, which are provided with a separation probe fixed at the outlet end, an analyzer with an exhaust gas processor in the trunk and a display unit in the instrument cluster. And the later mounting set includes a characteristic curve licensed by the Office according to the vehicle type and year of shipment as a comparable base for on-board measurement, in which case the special old vehicle With the exception of the direct provisions in measurement technology for determining the intrinsic characteristic curve, the vehicle's exhaust gas analysis device. As a vehicle's exhaust gas analyzer, it shows an increase in emissions of hazardous substances above the regulated limits and detects errors early in combustion systems and in exhaust gas aftertreatment systems, with other failures and unnecessary Analyze the vehicle's exhaust gas, which avoids consumption and eliminates defects at the repair center in a timely manner, or enhances citizens' environmental awareness by ensuring that emissions of environmentally relevant substances are displayed and voluntary speed limits are achieved. Device. As an exhaust gas analyzer of a vehicle, this measuring device is connected with other switching members by any sensor such as a seat position sensor and an ignition-lock sensor, so that it can measure the cold start from the beginning, Since the fluid can be controlled in accordance with the operating conditions of the exhaust gas analysis device of the vehicle, characterized in that the absorption and release is made at the optimum time.