AU4574302A - Device for analysing exhaust emissions from motor vehicles - Google Patents

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: Device for analysing exhaust emissions from motor vehicles The following statement is a full description of this invention, including the best method of performing it known to us: Freehills Carter Smith Beadle Melbourne\004072351 Printed 31 May 2002 (15:13) page Freehills Carter Smith Beadle Melbourne\004072351 Printed 31 May 2002 (15:13) page 2 Device for the analysis of motor vehicle exhaust emissions 1 Introduction The exhaust emissions of passenger and commercial vehicles are the cause of various types of harm to the environment. The introduction of emission-limiting legislation has forced, and is forcing, vehicle manufacturers to reduce the emissions of individual vehicles by for example developing advanced engines and exhaust systems.

One reason for a vehicle failing to conform to emission regulation is worsening performance, in terms of a gradual increase in exhaust emissions, as the vehicle ages. This is caused by wear and also, in part, by the incorrect functioning of components in the drive and emission-reduction systems.

The normal inspection procedure involves regular tests to attempt to keep emissions at or near their original level. The disadvantage of this method is that faults remain undetected until the next inspection, and excessive emissions meanwhile continue to be produced.

In the first few seconds after the engine is started, the catalytic converter which has not yet reached its running temperature barely affects the level of harmful exhaust emissions. An engine produces about 70% of its total emissions just after starting from cold, so an ideal system for reducing harmful emissions would cover this phase, which is precisely the phase that remains untouched by current systems of emission control detection.

2 The state. of the art ,,On board diagnosis" (OBD) is one new system for reducing harmful emissions. The term refers to an emission control system which uses sensors to monitor the performance of those individual.

components, of a passenger or commercial vehicle that have a bearing on exhaust emissions. An early version of OBD for passenger cars the OBD I Law has already been in use for a considerable time in the USA and is gradually being superseded b,_ the more stringent OBD II Law for models from 1995 onwards. .Wie OBD I only affected the performance monitoring of componentS&i forming part of an electronic engine control system, OBD II requires the control of all components relevant to emissions. The law expressly stipulates the monitoring of catalytic converters, lambda probes, fuel systems, air injection systems, exhaust gas recirculation, tank ventilation and the detection of misfiring. In the event of a component breaking down or malfunctioning, a warning lamp lights up on the dashboard and an error code is memorised.

The fault detected should be located as precisely as possible and described. The information is then stored in order to permit swift identification of the fault at the workshop (using a standard interface) and to allow repair of the defective part.

A further step in this field is the use of ,,On Board Measurement" (OBM). Systems for the direct analysis of vehicle emissions are widely familiar. Some examples, among many others, are the German public patents 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, the DE specification 43 19 282 Cl and US patent specifications 4 803 052 and 5 281 817, along with further patent applications GB 2 264 170 A, EP 0 196 993 A2 and WO 94/09266. These documents should be referred to for explanations in greater detail of items mentioned here.

Applications/1/ and are concerned, in a narrow sense, with subjects related to this field and are dealt with in greater detail for this reason. Thus patent describes an infrared measuring system that monitors the operating condition of the catalytic converter via a lateral access opening in the unit and measures the gases present inside. In the system in question is a rapid detector that uses several infrared cells connected in series to permit a chronological resolution of 0.1 0.2 sec. Neither source gives an indication of continuous measurement of harmful exhaust system emissions upstream of the catalytic converter.

Written sources reveal that no current measuring system is capable of providing a continuous record of actual emissions, either in the cold-start phase or during operation. Neither is it possible to detect fluctuations or indicate faults.

3 Description of the object of the patent Vehicles will, in the future, be fitted with an integrated OBM system for the purposes of emission analysis. This system will analyse certain elements of the exhaust gases, and a comparison of current concentrations with a set of stored target values will permit the detection of faults in the ignition system. A warning system will then be activated whenever the ,,satisfactory" level specified for the individual model of vehicle is exceeded, clearly and repeatedly, over a period. ,,Over a period" means an extended length of time, ,,repeatedly" signifies an excessive reading on not one, but various occasions and ,clearly" refers to a concentration that is outside the margin of tolerance specified.

Fig. 1 shows an example of how the concentration of harmful substances is affected by faults in the ignition system (caused by misfiring in this case).

The measurement of emissions is hindered by the fluctuating conditions present in the vehicle. A measuring system must on one hand keep to the general margins of tolerance and specifications valid for the vehicle while, on the other hand, it is precisely the exhaust-related elements of pressure, moisture, temperature and flow rate that are subject to sharp fluctuations. In order to solve this problem, especially robust micro system components are required both for exhaust gas processing and for the detection of the elements of which the gas consists.

One device for the analysis of vehicle exhaust gases is already familiar in the shape of DE 196 05 053 Al. Problems related to specified operation have however been encountered with this device, as they have with measuring devices described in other documents. The presence of vibrations in the vehicle requires that measuring systems be of highly stable construction and also resistant to soot, dust and aerosol precipitation. They must furthermore attain a high level of resolution, as the constituent components of the exhaust gas being analysed e.g. carbon monoxide hydrocarbons and oxides of nitrogen (NO) are present in extremely low concentrations, precisely in those petrol-driven vehicles that are fitted with a catalytic converter.

The emission analysis method used in the new OBM system, submitted here is an infrared gas absorption process. This irlventiG..is based the assumption that, in order to obtain the required resolution, optical path length must be increased. The optical cell can thus be fitted to a vehicle if it is incorporated at the construction stage.

4 Technical design of the measuring system The main assembly of the OBM system in a vehicle is shown in Fig.

2, along with the main components of the ignition system. The engine produces exhaust fumes as it burns fuel. In the catalytic converter harmful elements are transformed into less toxic substances. The vehicle OBM system consists of the sampling point exhaust gas processing unit analysing device exhaust system and data cable that provides the link between the display unit and analysing device Gas is extracted from the exhaust system upstream of the catalytic converter, as this is the only way in which an evaluation of the condition of the ignition system as a whole can be made.

Exhaust gas processing is illustrated in the gas flow diagram (Fig.

Soot and particles are removed from the exhaust gas using a disposable filter A solenoid valve (12) is used to change over between exhaust gas and calibration gas (see chapter The measuring gas pump (13) sends the gas to be measured to the analysing device via the pressure reducer (14) and flow meter Exhaust gas analysis is carried out in the analysis device (optical cell) following the principle of infrared gas absorption. This device consists of an infrared source (transparent tube), the radiation from which is directed to the measuring head via a measured length (optical cell). The optical cell can consist of one straight, highly reflective tube or of several tubes with reflective heads. The two pyroelectric measuring sensors fitted to the measuring head are equipped with various optical filters and produce one signal that depends on measurements and another which acts as a reference signal. The ratio formation of these signals reduces the disturbing influences (temperature, pressure, contamination) acting on the measuring signal. The use of the pyroelectric principle requires a synchronised radiation source. Electrical timing of the radiation" source avoids delicate mechanical components (chopper). TTe measuring system is thus rendered more robust, with an optiCal .eIJ, (measured length) made of stainless steel. In the event of the device being contaminated or suffering component faults, the advantage of the modular construction of the unit becomes clear. Single components such as filters can simply be replaced.

Modification kit for emission analysis on older vehicles In the case of older vehicles, which have not been fitted by the manufacturer with an OBD or OBM system, engine and exhaust gas processing performance cannot be measured other than by analysis of the exhaust gas itself. For this reason, a modification option should be available.

The disadvantage of carrying out modifications with an OBD system is the large number of transducers, for which there is neither sufficient room nor electronic connections. It is therefore more convenient to install an- on board measuring system.

Fig. 4 shows a modular OBM modification system of this type.

Exhaust gas sampling is carried out using a sampling sensor (16) fitted to the end of the exhaust pipe. The gas is cleaned and dried in the exhaust gas processing unit (17) and then pumped onwards to the analysing device The display unit on the dashboard then indicates information about the status and operation of the OBM system.

The fitting of the modification kit to the vehicle is illustrated in Fig. This involves attaching the sampling sensor (16) to the end of the exhaust pipe, while the analysing device and gas processing unit (17) can be installed in the car boot. The display unit can be hung from a ventilator grille or fitted elsewhere on the dashboard.

6 Cold-start measurement and adsorption trap The cold-start phase (see Fig. 6) is when 70% of total engine emissions are produced, and an on board measurement system calibrates these gases. These readings can be used to activate an HC adsorption trap (10, see Fig..2) used for collecting cold-start emissions in the exhaust flow path. Emission measuring makes it possible to synchronise the adsorption trap in the exhaust flow path to activate at exactly the right moment, or to start desorption..

Desorption of the small amount of retained hydrocarbons until-the catalytic converter reaches a temperature at which satisfactory conversion is guaranteed.

The energy consumption of the cold-start measuring system is extremely low, so it can enter operation before the cold-start phase has actually commenced. Control can be carried out, for example, by means of either a seat occupation sensor or a sensor on the ignition lock, which can also be used to activate the HC adsorption trap in the exhaust flow path.

7 Reference line calibration The measuring principle of infrared gas absorption is sufficiently well known. The problems with this measuring principle with regard to fluctuating ambient conditions have already been described in section 3. We will now examine the various measurement correction methods used.

The most common problem is the shifting of the zero point i.e. the reading for uncontaminated gas is not zero. This problem can be solved by calibrating the system with ambient air, proceeding as follows: The solenoid valve (12) in the exhaust gas processing unit (5,17) is automatically switched' over either after a pre-set period or as a result of detected external factors, allowing ambient air to enter the analysis device The concentrations of CO, HC and NO present in the ambient air are so low that they can safely be regarded as zero. The use of mathematical compensation allows the zero line to be calibrated. After this has been carried out, the sensitivity of the device usually recovers its original levels and the system begins once again to display reproducible readings. Fig. 7 shows the effect of a zero line correction. The graph illustrates how the zero line (18) has been displaced by temperature drift and also shows the recorrected measuring curve (19) produced after calibration. This procedure, with an interruption in emission recording, has no influence in terms of nominal values on the meaningfulness of measurements, whose purpose is in any case the detection of faults in the exhaust system rather than the providing of continuous monitoring.

8 Adjusting the sensitivity of the measuring signals using the C02 concentration of the ambient air The zero-calibration procedure described in section 7 has the advantage of avoiding the need for constant sensitivity adjustment, as this procedure also produces the right correction for the sensitivity level (and thus all others). A sensitivity check can nevertheless be carried out as follows: The atmosphere in all parts of the world (with clean non-city air) has an average C02 concentration of 350ppm. This fact can be used to check sensitivity, as this concentration matches the measuring ranges of the components normally detected in the stream of exhaust gas. CO, HC and above all NO in fact have weaker absorption bands than C02, but with correspondingly higher peak concentrations. According to the Lambert-Beerschen equation, the same optical cell length or in practical terms the same optical cell, can thus be used. If uncontaminated ambient air is now fed into the exhaust gas analysing device the system should show the average C02 concentration once the zero point reset procedure described above has been carried out. One can now be sufficiently sure that the sensitivity level of the other measurement factors is also correct.

The disadvantage of the above procedure is that local C02 concentrations fluctuate sharply due to external influences. This is especially true in densely populated areas, where road traffic can produce extremely high concentrations of C02. Fig 8 shows the carbon dioxide concentration of the ambient air during a test drive. After adjustment of the zero point using synthetic air the vehicle was driven through a small municipality (21) where the C02 concentration was relatively constant. A test drive through a larger town (22) with crossings and traffic lights reveals high, sharply-fluctuating C02 concentrations. Finally, a measurement carried out in a quiet interior courtyard (23) is closer to a natural CO2 concentration.

9 Sensitivity adjustment via the C02 concentration in the exhaust gas One possible way of avoiding the problems resulting from the fluctuations from natural 002 concentrations described in section .8.

is the monitoring of the C02 concentration in the vehicle exhaust:;.

The ignition process makes this value relatively stable, so that'thiS.

concentration can be used as a reference value for adjusting the sensitivity of the individual meter flumes. However, the high concentration (12% by volume) of CO2 in the exhaust gas means that the CO2 beam path in the optical measuring cell must be arranged differently to that used for other harmful gases. The optical path for CO2 measurement basically has to be shorter than that used for the contaminants CO, NO and HC.

Correction using a software-controlled filter of zero line of measuring signal displaced due to temperature fluctuations A measurement value is normally determined by the production of a ratio from the signal for the contaminant present (measuring signal) and the reference signal.

The signal progressions for measuring signals and reference signals reveal a great similarity. A ratio procedure can thus be modified if a certain margin of tolerance is determined around the signal progression and the ratio is set to,,one" within this margin. This allows a range for zero concentration to be obtained, and only in the event of this margin of tolerance being exceeded will a concentration corresponding to the values of the then determined real ratio be displayed. Note: the concentration ,,zero" need not necessarily correspond to the ratio but it does obtain the best measuring result.

11 Compensation of temperature drift by examination of the dynamics of the signal progressions Experience shows that extreme dynamic conditions are present in motor vehicles (brusque momentary system alterations, compared to the cycle period of the radiation emitter). This means that it is easy to differentiate between genuine measuring signals those produced by the exhaust gas) and the slower-fluctuating variations that depend on temperature. To carry out correction, the first derivation of the concentration process must be produced according to time. The first derivation records only genuine step functions that occur, for example, when the vehicle accelerates. Fig. 9 shows an actual measuring value progression. The first derivation (25) was produced from the original measuring signal of contaminant HC (24).

It can be clearly seen that measurement signal fluctuations (26) provoked by the influence of temperature approach zero in the...

derivation

IV

Once the step function places from the first derivation have been found according to time, the points can be recognised with clear step characteristics. If such a genuine step function appears, i.e. if a measurement value exceeds the previously defined margin of tolerance by a permitted amount relative to the differential curve, this point must be used as a reference relative to the actual concentration curve used for evaluation. When the first derivation returns to zero, the software-controlled filter once again emits the zero line as an unaltered, stable line. Thus you have at your disposal during the test drive one of two things. The first possibility is an absolute zero line without fluctuations, as no step functions have appeared and the fluctuations caused by temperature are ignored. The other possibility is that whenever real, dynamic step functions occur, such as when accelerating, changing gear, braking, etc., the original measuring signals (obtained from the concentration curve) are observed according to the first derivative.

12 Setting the original signal strengths in the channels of the IR gas analyser A further correction.method involves resetting the signal strength by means of an electronically regulated amplification controller.

Since the margin of reference for infrared gas absorption is set in such a way that virtually no absorption takes place at this limit, the infrared detector reference channel measuring signal should always maintain its original strength. The effects of temperature and vehicle wear do however cause noticeable fluctuations in this signal.

In order to compensate for the signal fluctuations caused by temperature conditions, the possibility exists to monitor continuously the reference signal by means of a measurement, control and regulating device built into the system. Whenever the reference signal deviates by a pre-defined margin from the value originally adjusted at initial calibration, all signals are realigned using an electronically regulated amplification controller with the original signal strength. Fig. 10 shows the original curve for the reference signal the weakened curve resulting from wear or temperature drift (28) and the curve that has been corrected by electronically controlled amplification This method retains the full range of signal dynamics.

Summary This description refers to a device for analysing the most important environmentally relevant substances, such as CO, HC and NO, that are present in vehicle exhaust emissions. It is based on the principle of IR gas absorption. This involves producing measuring signals and a reference signal in a measured optical length (stainless steel tube), with the aid of an infrared source and detector. The production of a ratio then gives a reading and a warning signal is produced whenever a certain limit value is exceeded.

The OBM system is made up of modular components, such as a sampling device, exhaust gas processing unit, analysing device and evaluation unit, which are built into the vehicle (see Fig. 2).

The fluctuating conditions present in the vehicle are compensated for by robust construction and correction of temperature drift by means of production of the first derivation and readjustment of signal strength using an electronically regulated amplification control.

Further correction possibilities are: calibration of the zero line using ambient air via a switchover system, and the establishment of a tolerance limit around the noise signals in the detector.

The measuring system should in future be installed in all motor vehicles as an extension to existing OBD (on board diagnosis) systems. Modification kits are available for older vehicles.

s. ,1 4.3 EDITORIAL NOTE No. 45743/02 Pages 12 to 14 are claims pages, they come after the illustration key, which is pages 15 to 17 Key to illustrations Fig. 1: Contaminant concentrations caused by misfiring 1 Misfiring Fig. 2: Main installation of the OBM system inside the motor vehicle 2 Engine 3 Catalytic converter 4 Sampling point Exhaust processing unit 6 Analysing device 7 Exhaust system 8 Data link 9 Display unit HC adsorption trap Fig. 3: Exhaust processing unit gas flow diagram 11 Exhaust gas filter 12 Solenoid valve 13 Measuring gas pump 14 Pressure reducer 15 Flow meter Fig. 4: Main layout of modification kit- 16 Sampling sensor 17 Exhaust gas processing unit including water separator KMC:EK 40423774.RS1 14 June 2001 Fig. 5: Fitting the modification kit in the car boot Fig. 6: Cold-start measurement Fig. 7: Zero-line correction 18 Zero line displaced by temperature drift 19 Corrected measuring curve Fig. 8: Carbon dioxide concentration in ambient air Adjustment using synthetic air 21 Test drive through a small municipality 22 Test drive through a larger town 23 Measurement carried out in quiet interior courtyard Fig. 9: Derivation in correction function 24 Original measuring signal First derivative 26 Measuring signal fluctuation due to temperature Fig. 10: Correcting signal strength 27 Original progression of reference signal 28 Curve affected by wear 29 Corrected signal curve KMC:EK 40423774.RS1 14 June 2001 Bibliography United States Patent: System for monitoring gas composition. Patent number 5,475,223. Date of Patent: Dec. 12 1995 Public patent DE 196 05 053 Al: On board diagnosis (OBD) procedure and device on micro-scale for the constant monitoring of motor vehicle contaminant emissions.

KMC:EK 40423774.RS1 14 June 2001

Claims (7)

1. This is a device for the analysis of the most important environmentally relevant substances present in the exhaust gas of motor vehicles, such as carbon monoxide hydrocarbons (HC) and nitrogen monoxide Its object is the control of the ignition process within the engine and catalytic converter and the prompt detection and rectification of any faults. It is hereby stated that the device indicates increases in contaminant emissions that exceed the pre-set limit values and thus helps to recognise promptly any faults that occur in the ignition and exhaust processing systems. It also helps to avoid consequent damage and unnecessarily excessive fuel consumption, and allows faults to be rectified promptly in the workshop. Finally, it helps increase the public sense of environmental awareness in the sense that the emission of environmentally harmful substances is indicated and can thus bring about a voluntary limitation of driving speeds. It is hereby stated that measurement is carried out using the principle of infrared gas ab-sorption, with an optical cell made of stainless steel and with a relatively high optical path length. Vehicle exhaust gas is allowed to flow through this device and is subjected to the light from a special infrared source, consisting of a transparent tube. A detector picks up this light according to the measuring channel/reference channel principle and extracts a ratio, which is used to determine the reading. It is hereby claimed that the zero point adjustment of the measuring device for HC and CO concentrations is carried out with clean ambient air using constant, brief switchover pauses. This permits sensitivity adjustment dependant either on the natural CO2 concentration in ambient air (normal value: 350ppm) or the CO2 component of the exhaust gas.

2. This is a device for the analysis of the most important environmentally relevant substances present in the exhaust gas of motor vehicles, such as carbon monoxide hydrocarbons.(HC) and nitrogen monoxide Its object is the control of the ignition process within the engine and catalytic converter and the prompt detection and rectification of any faults. Melbourne\003865846 Printed 28 July 2001 (12:52) It is hereby stated that the increase in harmful emission exceeding the set limit value is displayed and thus provides an aid for an early detection of defects in the ignition and in the exhaust preparation system, and for avoiding additional subsequent damage and unnecessary surplus consumption as well as for having defects remedied by the garage in time and/or to heighten the awareness of the citizen to act in an environmentally-friendly fashion by displaying the exhaust of environmentally important harmful substances and resulting in a limiting of speed. It is hereby stated that measurement is carried out using the principle of infrared gas ab-sorption, with an optical cell made of stainless steel and with a relatively high optical path length. Vehicle exhaust gas is allowed to flow through this device and is subjected to the light from a special infrared source, consisting of a transparent tube. A detector picks up this light according to the measuring channel/reference channel principle and extracts a ratio, which is used to determine the reading. It is hereby claimed that temperature drift is corrected by the production of the first derivation of the concentration curve, in which the step functions of the motor vehicle drive system can be differentiated from the slow drift effects.

3. Device in accordance with claim 1 or 2 in which the measuring system can be accommodated in the underside of the vehicle, in the boot, in the car body or in another suitable location of the vehicle.

4. A device in accordance with claims 1 -3 in which the measuring system built into the vehicle can consist, for example, of a sampling point, exhaust processing unit, analysing device, data link and display unit. Individual components can be replaced due to the modular design of the unit and can also be built into the vehicle as later modifications. The exhaust processing unit consists of replaceable parts (which can also be regenerated by heating) such as exhaust filters, solenoid valves, measuring gas pumps, pressure reducers and flow meters, It is sufficiently stable and robust for these coimponents to withstand the sharply fluctuating and tough conditions present in the vehicle, such as soot, dust and aerosol deposits.

Device in accordance with claims 1 4 in which the signal strength is Melboume\003865846 Printed 28 July 2001 (12:52) readjusted by means of an electronically regulated control system, based on the constant, undisturbed reference signal curve.

6. Device in accordance with one of the claims 1 5 in which a modification kit, which does not require official approval, is available for older vehicles. This consists of a sampling sensor attached to the end of the exhaust pipe, an exhaust gas processing unit installed in the car boot and a display unit fitted to the dashboard. This modification kit possesses officially authorised performance characteristics, according to the model and year of construction of each vehicle, as the base of comparison for on board measurement. This means that, with the exception of vehicles recognised as vintage cars, no immediate measurements need be made to determine the specific performance characteristics.

7. Device in accordance with one of the claims 1 6 in which the measuring device is activated, with the help of any type of sensor seat occupation sensors, ignition lock sensors), along with other activated elements. This means that measurement can begin at the moment of cold-starting and that flexible control of the adsorption trap according to current operating conditions is possible allowing adsorption and desorption to take place at exactly the right moment. Wissenschaftliche Werstatt fur UnI-weltmesstechnik CrbH By Freehills Carter Smith Beadle Registered Patent Attorneys for the Applicant 31 May 2002 Melboume\003865846 Printed 28 July 2001 (12:52)