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    • 专利摘要:

    公开号:SE1250961A1
    申请号:SE1250961
    申请日:2012-08-30
    公开日:2014-03-01
    发明作者:Ola Stenlaaaas
    申请人:Scania Cv Ab；
    IPC主号:
    专利说明:

    10 l5 20 25 30 aftertreatment systems in vehicles with diesel engines often particulate filters.
    When combustion of fuel in the combustion chamber (eg cylinders) of the internal combustion engine, soot particles are formed.
    According to the above, emission regulations and standards also apply to these soot particles, and to comply with the regulations, particulate filters can be used to capture the soot particles. In this case, the exhaust gas flow is led e.g. through a filter structure where soot particles are captured from the passing exhaust stream for storage in the particulate filter.
    Thus, there are several methods for reducing emissions from an internal combustion engine. In addition to regulations regarding emission levels, it is also becoming more common with statutory requirements for in-vehicle diagnostic systems, so-called On-Board Diagnostics (OBD) system to ensure that the vehicle is also in daily operation, and not only in e.g. workshop visits, in fact comply with established regulations regarding emissions.
    Regarding particulate emissions, this can e.g. is achieved by means of a particle sensor arranged in the exhaust system or the after-treatment system, in the following description and claims called PM sensor (PM = Particulate Matter, Particulate Mass), which measures the particle content in the exhaust stream. The particle content can e.g. be arranged to be determined as a particle mass per unit volume or weight, or a certain number of particles of a certain size per unit volume, where several determinations of the number of particles of different sizes can be used in evaluating particle emissions.
    Particulate filter after-treatment systems can be very effective, and the resulting particle content after the exhaust stream passes through the vehicle's after-treatment system is often low with a fully functioning after-treatment system. This also means that the signals emitted by the sensor will indicate a low or no particle emission.
    SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for determining a sensor function for a PM sensor intended for determining a particle content in an exhaust stream resulting from combustion at an internal combustion engine. This object is achieved with a method according to claim 1.
    The present invention relates to a method for determining a sensor function for a PM sensor intended for determining a particle content in an exhaust stream resulting from combustion at an internal combustion engine, wherein a post-treatment system is arranged for post-treatment of said exhaust stream, and wherein the method is characterized by determining: - determining a representation of a first pressure prevailing at said PM sensor by using a pressure sensor arranged at said PM sensor, and - based on said representation of said determined first pressure, determining whether said PM sensor emits a pressure for said PM sensor. exhaust current representative signal.
    As mentioned above, PM sensors can be used to ensure that the presence of particles in the exhaust gas stream resulting from the internal combustion engine does not exceed the prescribed levels.
    However, in order to ensure that the presence of particles in the exhaust stream falls below the prescribed levels, the PM sensor is required to emit a correct signal. A PM sensor can be arranged at different positions in the exhaust stream, and depending on the position, the PM sensor can be arranged such that the particle presence at the location of the PM sensor is very small.
    This applies to e.g. a PM sensor arranged downstream of a particulate filter, where a properly functioning particulate filter is often capable of separating a very large part of the particles emitted from the combustion chamber of the internal combustion engine.
    This in turn means that it can be difficult to distinguish a situation where the particle filter works correctly, but where the particle occurrence downstream of the particle filter is very small, from a situation where the PM sensor indicates a small occurrence that the PM sensor actually works incorrectly or off otherwise does not emit a representative signal.
    The reason why a PM sensor does not emit a representative signal may be several, and not only that the sensor is malfunctioning and thus indicates a lower incidence than is actually the case. However, the PM sensor itself can emit a representative signal for the environment in which the PM sensor is located, but instead the PM sensor and / or the after-treatment system have been manipulated in such a way that the sensor no longer measures the presence of particles in a representative exhaust stream.
    For example. the sensor may have been moved from the intended position in the exhaust stream to e.g. a position where it measures the presence of particles in the vicinity of the vehicle. In this case, the PM sensor will always emit a signal representing a very low or no particle occurrence regardless of the actual particle content of the exhaust stream.
    Another way of manipulating the signal emitted by the PM sensor in order to reduce detected particle occurrence is to divert all or part of the exhaust current past the PM sensor so that it is no longer exposed to a representative exhaust current. Thus, also in this way, the PM sensor can be caused to emit signals representing a lower particle occurrence than is actually the case. Another way to manipulate the sensor signal is to block the sensor so that the exhaust current is not conducted through the sensor.
    Thus, there are several ways to manipulate a PM sensor, and since the PM sensor as above can be positioned in such a way that only a very small particle occurrence is detected, it can be difficult to determine whether the sensor is manipulated or not.
    According to the present invention, there is provided a method for determining whether the PM sensor can be assumed to emit a representative signal so as to also be able to determine whether the sensor is malfunctioning or has been tampered with.
    This is achieved according to the present invention by using means arranged at the PM sensor for determining a representation of a pressure prevailing at the PM sensor.
    These bodies can e.g. consists of a pressure sensor integrated with the PM sensor, ie. the pressure sensor utilizes common components such as substrates or the like. Alternatively, the pressure sensor can be a separate pressure sensor arranged in a common house with the PM sensor.
    Thus, by determining a prevailing pressure at the PM sensor, this pressure can be compared with an expected pressure, and based on the comparison, it can be determined whether the PM sensor can be considered to be exposed to a representative exhaust current, ie. an exhaust stream that accurately reflects the composition of the exhaust stream leaving the combustion chamber of the internal combustion engine.
    Additional features of the present invention and advantages thereof will become apparent from the following detailed description of exemplary embodiments and the accompanying drawings.
    Brief Description of the Drawings Fig. 1a schematically shows a vehicle in which the present invention can be used.
    Fig. 1b shows a control unit in the control system for the vehicle shown in Fig. 1.
    Fig. 2 shows the finishing system in more detail for the vehicle shown in Fig. 1.
    Fig. 3 shows an exemplary method according to the present invention.
    Fig. 4 shows an alternative exemplary method according to the present invention.
    Detailed description of embodiments In the following description and the following claims, the term particulate content includes both content in the form of mass per unit and content / concentration, ie. number of particles per unit.
    Furthermore, the unit can consist of any applicable unit and the content is expressed as e.g. mass or number of particles per unit of volume, per unit of mass, per unit of time, per work performed, or per distance traveled by the vehicle.
    Fig. 1A schematically shows a driveline in a vehicle 100 according to an embodiment of the present invention. The vehicle 1000 schematically shown in Fig. 1A comprises only one axle with drive wheels 133, 144, but the invention is also applicable to vehicles where more than one axle is provided with drive wheels, as well as to vehicles with one or more additional axles, such as one or more several support axles. The driveline comprises an internal combustion engine 101, which is connected in a conventional manner, via a shaft outgoing on the internal combustion engine 101, usually via a flywheel 102, to a gearbox 103 via a clutch 106.
    The internal combustion engine 101 is controlled by the control system of the vehicle via a control unit 115. Likewise, the clutch 106, which e.g. may be an automatically controlled clutch, and the gearbox 103 of the vehicle control system by means of one or more applicable control units (not shown). Of course, the driveline of the vehicle can also be of another type such as of a type with conventional automatic transmission etc.
    A shaft 107 emanating from the gearbox 103 drives the drive wheels 113, 114 via an end gear 108, such as e.g. a conventional differential, and drive shafts 104, 105 connected to said final gear 108.
    The vehicle 100 further includes an exhaust system with an after-treatment system 200 for treating (purifying) exhaust emissions resulting from combustion in the combustion engine 101 combustion chamber (eg, cylinders).
    An example of a post-treatment system 200 is shown in more detail in Fig. 2. The figure shows the internal combustion engine 101 of the vehicle 100, where the exhaust gases generated during combustion are led via a turbocharger 220. In turbocharged engines, the combustion exhaust gas often drives a turbocharger. in turn compresses the incoming air to the combustion of the cylinders. Alternatively, the turbocharger can e.g. be of compound type. The function for different types of turbochargers is well known, and is therefore not described in more detail here. The exhaust stream is then passed via a pipe 204 (indicated by arrows) to a Diesel Particulate Filter (DPF) 202 via an Oxidation Catalyst (DOC) 205.
    The oxidation catalyst DOC 205 can have several functions, and is normally used primarily to oxidize residual hydrocarbons and carbon monoxide in the exhaust stream to carbon dioxide and water during post-treatment of the exhaust gas stream.
    The oxidation catalyst 205 can also e.g. oxidize nitrogen monoxide (NO) to nitrogen dioxide (NO2), which is used in e.g. N02-based regeneration. Additional reactions may also occur in the oxidation catalyst.
    Furthermore, the finishing system may comprise more components than those exemplified above, as well as fewer or other types of components. For example. The after-treatment system as in the present example may comprise a SCR (Selective Catalytic Reduction) catalyst 201 arranged downstream of the particulate filter 202. SCR catalysts use ammonia (NH3), or a composition from which ammonia can be generated / formed, as an additive for reducing the amount of nitrogen oxides. NOX in the exhaust stream.
    In the embodiment shown, the components DOC 205, DPF 202 and SCR catalyst 201 are integrated in one and the same exhaust gas cleaning unit 203. However, it should be understood that these components do not have to be integrated in one and the same exhaust gas cleaning unit, but the components can be arranged in other ways where as deemed appropriate, and one or more of said components may e.g. consist of separate units. Fig. 2 also shows temperature sensors 210-212 and a differential pressure sensor 209, respectively. The figure also shows a PM sensor 213, which in the present example is shown upstream of the exhaust gas purification unit 203, and also upstream of an exhaust brake 215.
    However, the PM sensor can also be arranged downstream of the exhaust gas purification unit 203, as well as upstream of the turbocharger 220.
    According to the present invention, it is determined whether the PM sensor 213 functions in the desired manner. Furthermore, the vehicle's exhaust system can comprise more than one PM sensor, which can be arranged at different positions, whereby the function of all PM sensors present in the vehicle can be evaluated. In the present invention, the PM sensor 213 is integrated or co-located with a pressure sensor 214, the pressure sensor 214 constituting a pressure sensor arranged with said PM sensor 213 and / or a pressure sensor arranged with said PM sensor 213 in a common housing, where the pressure sensor 214 is adapted to determine a representation of the prevailing pressure at the location of the PM sensor 213.
    As has been mentioned, soot particles are formed during the combustion of the internal combustion engine 101, and in many cases these soot particles must not be released into the environment of the vehicle 100. The soot particles are captured by the particulate filter 202, which works in such a way that the exhaust stream is passed through a filter structure where soot particles are captured from the passing exhaust stream and then stored in the particulate filter 202. By means of the particulate filter 202 a very large proportion of the particles can be separated from the exhaust stream.
    The PM sensor 213 can be used to check that the particle filter 202 functions in a desired manner, but also to monitor e.g. the function of the internal combustion engine 101 at e.g. a PM sensor position upstream of the particulate filter. The PM sensor 213 can also be used for other purposes.
    However, in order for the particle occurrences determined by means of PM sensor signals to be representative, it is required that the PM sensor 213 itself actually emits signals which are representative of the environment in which the PM sensor is intended to be installed.
    The present invention increases the reliability of the PM sensor signals by evaluating the environment of the PM sensor 213 which is accomplished by the pressure sensor 214. Fig. 3 shows an exemplary method 300 according to the present invention by which the environment of the PM sensor 213, such as the PM 10 The sensor 213 surrounding the exhaust gas flow, can be evaluated and erroneous sensor signals due to non-representative exhaust flow can be detected. The method is carried out according to the present example of the control unit 208 shown in Figs. 1A-B and Fig. 2, respectively.
    In general, control systems in modern vehicles consist of a communication bus system consisting of one or more communication buses for interconnecting a number of electronic control units (ECUs) such as the control units, or controllers, 115, 208, and various components arranged on the vehicle. Such a control system can comprise a large number of control units, and the responsibility for a specific function can be divided into more than one control unit.
    For the sake of simplicity, in Figs. 1A-B only the control units 115, 208 are shown.
    The present invention is thus in the illustrated embodiment implemented in the control unit 208, which in the illustrated embodiment may also be responsible for other functions in the finishing system 200, such as e.g. regeneration (emptying) of the particle filter 202, but the invention can thus also be implemented in a control unit dedicated to the present invention, or in whole or in part in one or more other control units already present in the vehicle, such as e.g. motor control unit 115.
    The function of the control unit 208 (or the control unit (s) to which the present invention is implemented) according to the present invention will, in addition to being dependent on sensor signals from the pressure sensor 214 for determining a pressure, be likely to e.g. depend on information such as received from a PM sensor and e.g. the control unit (s) that control motor functions, ie. in the present example the control unit 115. 10 ll 20 25 30 ll Control units of the type shown are normally arranged to receive sensor signals from different parts of the vehicle. The control unit 208 can e.g. receive sensor signals as above, as well as from controllers other than controller 115. Furthermore, such control units are usually arranged to output control signals to various vehicle parts and components. For example. the control unit 208 can emit signals to e.g. engine control unit ll5.
    The control is often controlled by programmed instructions. These programmed instructions typically consist of a computer program, which when executed in a computer or controller causes the computer / controller to perform the desired control, such as method steps of the present invention.
    The computer program is usually part of a computer program product, the computer program product comprising an applicable storage medium 112 (see Fig. 1B) with the computer program 109 stored on said storage medium 112.
    Said digital storage medium l2l can e.g. consists of someone from the group: ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically Erasable PROM), a hard disk drive, etc., and be arranged in or in connection with the control unit, the computer program being executed by the control unit. By changing the instructions of the computer program, the behavior of the vehicle in a specific situation can thus be adapted.
    An exemplary control unit (control unit 208) is shown schematically in Fig. 1B, wherein the control unit may in turn comprise a calculation unit 120, which may consist of e.g. any suitable type of processor or microcomputer, e.g. a Digital Signal Processor (DSP), or an Application Specific Integrated Circuit (ASIC). The computing unit 120 is connected to a memory unit 112, which provides the computing unit 120 e.g. the stored program code 109 and / or the stored data computing unit 120 are needed to be able to perform calculations. The calculation unit 120 is also arranged to store partial or final results of calculations in the memory unit 121.
    Furthermore, the control unit is provided with devices 122, 123, 124, 125 for receiving and transmitting input and output signals, respectively. These input and output signals may contain waveforms, pulses, or other attributes, which of the input signals receiving devices 122, 125 may be detected as information for processing the calculation unit 120. The output signals 123, 124 for transmitting output signals are arranged to convert calculation results from the calculation unit. 120 to output signals for transmission to other parts of the vehicle control system and / or the component (s) for which the signals are intended. Each of the connections to the devices for receiving and transmitting input and output signals, respectively, may be one or more of a cable; a data bus, such as a CAN bus (Controller Area Network bus), a MOST bus (Media Oriented Systems Transport), or any other bus configuration; or by a wireless connection.
    As above, according to the present invention, the reliability of emitted PM sensor signals can be improved by evaluating the environment in which the PM sensor is located, and thus Fig. 3 shows an exemplary method 300 according to the present invention.
    The method 300 according to the invention utilizes that the conditions at different positions in the finishing system, such as temperature, pressure and flow, can often be modeled / estimated with relatively good accuracy based on prevailing and / or historical operating parameters and the applicable model description of the finishing system. .ex. expected pressure change at any given position in the finishing system can be estimated based on prevailing operating parameters.
    The procedure begins in step 301, where it is determined whether the environment of the PM sensor 213 should be evaluated. If the environment of the PM sensor 213 is to be evaluated, the method proceeds to step 302. Transition from step 301 to step 302 can e.g. be arranged to be controlled by a past time since a previous evaluation of the environment of the PM sensor 213. The environment of the PM sensor 213 may also be arranged to be evaluated continuously, at applicable intervals, each time the vehicle is started or at other applicable times, such as e.g. if for any reason, e.g. based on emitted PM sensor signals, or signals from other sensors / devices, it may be suspected that the PM sensor does not emit representative signals.
    In step 302, a first pressure P1 prevailing at the PM sensor 213 is determined, where the pressure P1 is determined by means of the pressure sensor 214 integrated with the PM sensor 213, or arranged at the PM sensor 213, when the pressure Plhar is determined in step 302, the procedure proceeds. to step 303, in which an expected pressure Pmm at the PM sensor 213 is determined.
    This expected pressure Pmm can e.g. is determined by table look-up, where the expected pressure P at the PM sensor position can be specified for a number of different operating cases, such as e.g. different combinations of fuel injection times, fuel injection times, fuel injection amount, fuel pressure, number of injections, EGR and air supply, valve times, compression ratio, overcharging, VGT mode, engine speed, internal combustion engine load etc. The expected pressure Pmm can e.g. also determined 10 15 20 25 30 14 based on e.g. prevailing operating parameters and applicable model description of the finishing system and its components, whereby e.g. expected pressure at any given position in the finishing system can be estimated.
    To ensure that as reliable values as possible for P1 and Pam, respectively, are obtained, the transition between step 301 and step 302 can also be controlled to be performed only in cases where the vehicle 100 has been driven under substantially continuous conditions for a certain time, such as a certain number of seconds. to avoid that dynamic processes incorrectly affect the measurement results.
    After the expected pressure Pam has been determined in step 303, the method proceeds to step 304, where the pressure Plvid PM sensor 213 determined by using the pressure sensor 214 is compared with the pressure Pam at the PM sensor 213 expected under the prevailing conditions, whereby a deviation A between expected pressure Pam and measured pressure Plfastställs. In step 305, it is then determined whether the deviation A between the expected pressure Pam and the measured pressure Plär is greater than any applicable limit value Alma. The limit value Almü can e.g. be set in such a way that a relatively large deviation can be allowed so as not to unnecessarily give rise to alarms regarding the function of the PM sensor 213, since the pressure prevailing at the PM sensor 213 can be difficult to predict with the desired accuracy.
    As long as this is not the case, ie. as long as the deviation is below the limit value Almü, the procedure proceeds to step 306, where the applicable signal can be generated to indicate that the PM sensor 213 can be assumed to give representative measured values regarding the particle presence in the exhaust stream, since the PM sensor 213 can be assumed to be in a position with expected pressure, and thus probably also be at the intended position in the exhaust system and thus perform measurements on a representative exhaust flow. The method then returns to step 301 for re-determining the function of the PM sensor 213 at the applicable time as above. Alternatively, the method may return directly to step 301 from step 305 because signal to indicate that PM sensor 213 can be assumed to give representative measurements of particle occurrence need not actually be generated, as this information can be assumed implicitly as long as no signal indicating faulty sensor function is obtained below. .
    If, on the other hand, it is determined in step 305 that the deviation A is greater than the limit value Almü, the procedure proceeds to step 307. In step 307, an error signal is generated, such as e.g. an alarm signal, to indicate to the control system of the vehicle 100 that the PM sensor 213 cannot be considered to emit a representative signal as this is not considered to be exposed to a representative exhaust flow. The signal generated in step 307 may e.g. be used by the control system of the vehicle 100 to set the status of the vehicle 100 to a state where the vehicle 100 is in immediate need of service for action by the PM sensor 213. The control system may further be arranged to limit the functionality of the vehicle 100, such as e.g. by limiting the maximum removable power from the internal combustion engine 101 of the vehicle 100 until the fault has been rectified. The process is then terminated in step 308.
    Thus, according to the present invention, there is provided a method which can be used to determine whether the PM sensor 213 emits a representative signal by determining whether it is exposed to a representative exhaust flow, which is determined by determining whether the pressure at the PM sensor 213 is an expected pressure. . Thus, by means of the present invention, attempts to manipulate the function of the PM sensor 213 by e.g. move the PM sensor to a position outside the exhaust flow, alternatively that e.g. directing the exhaust flow past the PM sensor 213 is detected during operation of the vehicle 100, thereby reducing the possibilities of inadvertently manipulating the after-treatment system.
    In the example shown in Fig. 3, a fixed pressure P1 has been compared with an expected pressure Pam at one time. As will be appreciated, the pressure in the finishing system 200 may vary significantly depending on e.g. the flow of the exhaust gas and e.g. degree of filling in a particle filter arranged downstream of the particle sensor, wherein even if e.g. a table lookup or calculation as above is used to determine an expected pressure Pæw, a measured individual value in adverse conditions may deviate from the expected value by more than the said deviation A¿m¿ even though the PM sensor 213 is actually correctly arranged in the exhaust flow. For this reason, the method shown in Fig. 3 can be arranged to be traversed some applicable number of times X, such as e.g. a relatively large number of times X, whereby X measured values are determined, and thus X deviations A, whereby a weighted deviation for these X deviations can be determined and compared with the deviation limit value Alm fl, and where the weighted value is used to determine whether the PM sensor 213 can be assumed be exposed to a representative exhaust gas flow.
    The deviation A¿md can furthermore be arranged to vary depending on the number of measured values X. The larger the number of measured values X used, the lower the permissible deviation Aim fl can be set because the weighted accuracy increases with the number of measured values X. 10 15 20 25 30 17 I Fig. 4 shows a further exemplary method 400 according to the present invention, in which the pressure Pam expected at the PM sensor is determined in an alternative manner.
    The method 400 shown in Fig. 4 begins in step 401 where, as in step 301 in Fig. 3, it is determined whether the function of the PM sensor is to be determined. In that case, the process proceeds to step 402, where a first pressure prevailing at the PM sensor 213 is determined by means of said pressure sensor 214 as above. The process then proceeds to step 403.
    Instead of directly determining an expected pressure Eë @> as in Fig. 3 by means of e.g. table look-up is performed in step 403 an active influence of the exhaust gas flow. This can e.g. performed by changing the work of the internal combustion engine 101.
    The work of the internal combustion engine 101 can e.g. changes by changing the load or operating point of a given load.
    For example. the operating point of the internal combustion engine 101 can be changed by changing one or more of the fuel injection times, fuel injection times, fuel injection amount, fuel pressure, number of injections, EGR and air supply, valve times, compression ratio, supercharging, VGT position, engine speed, engine speed, etc.
    Alternatively, or in addition, change of combustion mode at said internal combustion engine may be performed, such as e.g. from Otto to HCCI, or from Diesel to PPC. Alternatively, the load can be increased / decreased by e.g. switch on or disconnect internal combustion engine units.
    By changing the way in which the internal combustion engine 101 operates, or by otherwise influencing the exhaust gas flow, such as e.g. by restricting the exhaust gas flow upstream of the position of the PM sensor 213, e.g. by means of the exhaust brake 215, the flow of the exhaust stream will also change. If e.g. If the internal combustion engine 101 is forced to operate harder, the flow of the exhaust gas stream will usually increase, with the result that the differential pressure (ie the pressure difference between the input and output side of the component) over the aftertreatment system components will increase, the pressure at the PM sensor will vary with variations in differential pressure changes across components downstream of the PM sensor 213. Conversely, the differential pressure across a component decreases with reduced flow. In step 403, an applicable change of the work of the internal combustion engine 101 is thus performed, alternatively another exhaust current influencing measure is performed as below, in such a way that the flow of the exhaust stream past the PM sensor is affected, whereby the absolute pressure, ie. prevailing pressure based on absolute vacuum at the position of the PM sensor 213 is also affected. Preferably, a change is made which results in a relatively large change of the pressure P prevailing at the PM sensor 213. Instead of measuring absolute pressure at the PM sensor 213, the pressure sensor 214 may be arranged to determine any applicable differential pressure, such as e.g. a pressure difference in relation to the ambient pressure of the vehicle.
    Instead of changing the work of the internal combustion engine 101, as mentioned, the exhaust gas can instead be actively affected in whole or in part also in another way in step 403. Eg. one or more components downstream of the PM sensor 213 can be bypassed, the pressure prevailing at the PM sensor 213 even at unchanged exhaust flow will be reduced due to the differential pressure over the bypassed component (s) no longer affecting that of the PM sensor 213 prevailing pressure. According to another example, one or more additional components are switched on downstream of the PM sensor 213, whereby the absolute pressure at the position of the PM 213 sensor 213 will rise correspondingly due to the differential pressure which will arise over the connected components.
    The pressure at the PM sensor 213 can also be influenced by throttling the exhaust gas flow by means of throttling means in the form of e.g. an exhaust brake, wherein said throttling means may be arranged upstream or downstream of an intended position of said PM sensor 213.
    According to one embodiment, however, no action is specifically intended to change the pressure at the PM sensor 213, but the determination according to the present invention is performed when the vehicle is driven in such a way that pressure change is still expected to occur, as in e.g. a hard acceleration or transition of driving of the vehicle from downhill or flat road to uphill.
    The process then proceeds to step 404, where a second pressure is determined, i.e. a pressure Pg at the PM sensor 213 is determined after the said one or more measures for changing the pressure at the intended position of the PM sensor 213 have been performed, or the driving of the vehicle has otherwise changed with the expected pressure change at the PM sensor 213 as a result.
    In step 405, an expected pressure change AP @@ is then determined at the position of the PM sensor 213 after the measures taken in step 403 (alternatively the elapsed time), whereby in step 406 the change APu7 between said first few and second presses P2 is compared with the expected pressure change AP @@.
    According to this embodiment of the method shown in Fig. 4, no absolute pressures need be determined, it is sufficient to determine an expected pressure change AP @ m, without specifically determining between which actual levels / pressures the difference is expected to occur. where this expected pressure change APWW can be determined by applicable calculation using models of after-treatment system / internal combustion engine, or applicable table lookup as described above and based on changes made.
    Likewise, although specific pressures P1, P2 can be determined as above, this is not a requirement, but in principle it is sufficient to determine applicable representations of the pressures P1, P2, from which the pressure change APU can be determined. Thus, it is sufficient to determine a signal difference, where this signal difference can be converted into a pressure difference or compared with an expected signal difference.
    In step 406, the actual pressure change APu is then compared with the expected pressure change AP @ @ in a manner corresponding to step 304 in Fig. 3, it being determined in step 407 whether the deviation A between the actual AP fl and the expected pressure change APWW is greater or less than any applicable limit value ALÜQ. If the deviation is less than the limit value Alma, the procedure returns to step 401 via step 408, which corresponds to step 306 as above, while if the deviation A exceeds the limit value @m @ an error signal, such as an alarm signal, is generated in step 409 in a manner corresponding to step 307 in fig. 3, e.g. to set the status of the vehicle l00 to a status where the vehicle l00 is in immediate need of service for the operation of the PM sensor 213.
    As above, the control system can be arranged to limit the functionality of the vehicle 100, e.g. by limiting maximum removable power. The process is then terminated in step 4110.
    By means of the method shown in Fig. 4, it can thus be determined that the PM sensor 213 is arranged at a position where the prevailing pressure varies with varying operating conditions in a representative manner. As above, with the aid of this procedure e.g. ensure that the PM sensor 213 has not been manipulated in such a way that it has been moved from the intended position, or that the exhaust stream has not been passed past the PM sensor 213, since the PM sensor will not show any or a different pressure change compared to with a correctly positioned PM sensor, thus reducing the possibilities of unnoticed manipulation of the finishing system.
    As with the method shown in Fig. 3, the method shown in Fig. 4 can be arranged to be run through a number of times for determining a number of measured values by performing a number of pressure-acting changes, whereby a number of deviations can be determined, whereby a weighted deviation for these deviations can be determined and compared with the limit value Ajmg, and where the weighted value is used to determine whether the PM sensor 213 can be assumed to be exposed to a representative exhaust current. As above, the limit value A¿m @ can be arranged to vary depending on the number of measured pressure changes.
    According to one embodiment, a number of pressure determinations are performed at the PM sensor 213, e.g. at regular or applicable intervals, the pressure change over time being compared with an expected pressure change. Even in this case, deviations for each measured value can be determined and compared with the expected value.
    The deviations can also be compared with each other, and as long as the deviations are substantially similar, the PM sensor can still be considered to be correctly positioned.
    The expected pressure change can also be determined by means of one or other pressure sensors arranged in the finishing system, if any, whereby the expected pressure change of the PM sensor 213 can be estimated based on pressure changes at other positions in the system.
    The method can also be arranged, which also applies to the method shown in Fig. 3, to go through a certain time in order to see that expected changes with time also actually occur.
    Furthermore, a combination of the methods shown in Fig. 3 and Fig. 4, respectively, can be applied, i.e. a pressure change can be applied according to Fig. 4, but where simultaneously prevailing pressure before and after pressure-acting measures is compared with expected values before and after taking pressure-influencing measures, which can further improve the accuracy.
    Depending on the application, PM sensors can be arranged at different positions in the exhaust system. For example. For example, the PM sensor may be located upstream or downstream of an exhaust brake, as well as upstream or downstream of a particulate filter, or upstream of a turbocharger.
    The present invention also has the advantage that it can be applied regardless of where the PM sensor 213 is arranged in the exhaust system. Regardless of location, pressure changes will occur in measures as above as long as some form of throttling occurs downstream of the PM sensor, so that a pressure change across the part of the exhaust system located downstream of the PM sensor 213 can occur.
    There are different types of PM sensors, and the present invention is applicable to all types of PM sensors.
    Furthermore, at least in some cases, a frequency analysis can be applied in determining whether the PM sensor 213 emits a representative signal. In general, the exhaust valves of the internal combustion engine are opened with a certain regularity. For example. exhaust valves are usually opened once per revolution for two-stroke engines and once every other revolution for four-stroke engines.
    This means that the exhaust flow will be "pulsed" out via the exhaust valves, and there will be pulsating differences in the flow of the exhaust flow over time. This also means that the pulsation will give rise to pressure variations in the exhaust stream.
    Normally, however, the balance between e.g. air supply, EGR return and supplied fuel are not exactly the same for each cylinder, or for successive combustions, e.g. pga. tolerances, etc. In the schedule, therefore, these pulse / concentration variations in the exhaust stream will appear to be rather irregular.
    If, on the other hand, the sensor signal from the pressure sensor is instead evaluated in the frequency domain, this pulsation can be clarified and used according to the present invention.
    The exhaust pulses from the different cylinders will be seen as pressure variations with a frequency equal to the speed of the internal combustion engine multiplied by the number of cylinders and divided by the rate factor (ie divided by one for a two-stroke engine and divided by two for a four-stroke engine. controllable can be varied). In the frequency plane, a clear spike / peak will thus appear at said frequency (weaker shadow pulses at multiples of the frequency can also occur).
    This frequency analysis can be used to improve the certainty in the diagnosis of the PM sensor, because if this pulsation can be identified, it can also be assumed that the pressure sensor, and thus the PM sensor, is exposed to a representative exhaust current.
    The frequency analysis can be used alone, or combined with a comparison with a limit value as above, where this limit value can be set in either the time domain or the frequency domain. By performing the determination in the frequency domain, detection with smaller variations is possible, ie. a lower limit value Note can be used.
    The variation in the frequency domain can also be used actively since the speed according to the method according to the invention can be varied to give a more reliable diagnosis. If e.g. If a frequency (motor speed) is exceeded, a waiting fault can be set, whereby one or more additional diagnoses for additional frequencies can be performed before a malfunction is finally found.
    In general, it applies to the frequency analysis that the closer to the pulsation source the analysis is performed, ie. the closer the PM sensor is to the internal combustion engine, the more reliable the analysis results will be obtained.
    Thus, according to this embodiment, said frequency analysis constitutes a representation of a type P1 prevailing at said PM sensor 213.
    Furthermore, the method according to the invention can be combined with that in the parallel Swedish application entitled "PROCEDURE AND SYSTEM FOR EXHAUST CLEANING II" and the same inventor and submission date as the present application, described to determine a sensor function for a PM sensor. According to the said application "EXHAUST CLEANING PROCEDURE AND SYSTEM II", a method corresponding to the present invention is provided, but in which a representation of a concentration prevailing at the PM sensor and / or fraction of a substance present in the exhaust stream is determined. Based on the determined representation of a concentration and / or fraction of said first substance, it is determined whether the PM sensor emits a representative signal.
    Likewise, the method according to the invention can alternatively, or in addition, be combined with that in the parallel Swedish application entitled "PROCEDURE AND SYSTEM FOR EXHAUST CLEANING III" and the same inventor and submission date as the present application, described to determine a sensor function for a PM sensor. According to the said application "PROCESS AND SYSTEM FOR EXHAUST CLEANING III", a method corresponding to the present invention is provided, but in which the sensor function of the PM sensor is determined by means of means for determining a representation of a temperature at the PM sensor.
    By combining the method according to the present invention with either or both of the methods described above, an even more reliable assessment of the function of the PM sensor can be performed.
    Furthermore, the present invention has been exemplified above in connection with vehicles. However, the invention is also applicable to arbitrary vessels / processes where particulate filter systems as above are applicable, such as e.g. water or aircraft with combustion processes as above. Furthermore, the internal combustion engine can e.g. consists of someone from the group: vehicle engine, marine engine, industrial engine, diesel engine, otto engine, GDI engine, gas engine.
    Further embodiments of the method and system according to the invention are found in the appended claims.
    It should also be noted that the system may be modified according to various embodiments of the method of the invention (and vice versa) and that the present invention is in no way limited to the above-described embodiments of the method of the invention, but relates to and includes all embodiments within the appended claims. the scope of protection of the independent requirements.
    权利要求:
    Claims (1)
    [1]
    A method for determining a sensor function for a PM sensor (213) intended for determining a particle content in an exhaust stream resulting from combustion at an internal combustion engine (101), wherein a post-treatment system (200) is arranged for post-treatment of said exhaust gas stream, and wherein the method is characterized by: - determining a representation of a first pressure (P1) prevailing at said PM sensor (213) by using a pressure sensor arranged at said PM sensor (213) (214), and - based on said determined representation of said first pressure (P1), determining whether said PM sensor (213) emits a signal representative of said exhaust current. The method of claim 1, further comprising determining whether said PM sensor (213) emits a signal representative of said exhaust stream by determining based on said representation of said first pressure (PU) whether said PM sensor (213) can be assumed to be in A method according to any one of claims 1-2, further comprising: - based on said determined representation of said first pressure (P1), determining whether said after-treatment system (200) and / or PM sensor (213) can be assumed to have A method according to any one of claims 1-3, wherein said first pressure sensor (214) is a pressure sensor (214) integrated with said PM sensor (213) A method according to any one of claims 1-4, wherein said first pressure sensor (214). 214) constitutes a pressure sensor (214) fixedly connected to said PM sensor (153) and / or a pressure sensor (214) arranged with said PM sensor (213) in a common housing. , further comprising: - comparing said first pressure (P1) with an expected pressure (Pam) prevailing at said PM sensor (213), and - based on said comparison, determining whether said PM sensor (213) emits a representative of said exhaust gas signal. A method according to any one of the preceding claims, further comprising: - by using said first pressure sensor (214) determining a first pressure change (APU) at said PM sensor (213), comparing said first pressure change (APU) with an expected pressure change ( APWW) at said PM sensor (213), and - based on said comparison of said first (APU) pressure change with said expected pressure change (AP @ m), determine whether said PM sensor (213) emits a signal representative of said exhaust current . A method according to claim 7, comprising, in said comparison: - determining a deviation (A) between said first pressure change (APU) and said expected pressure change (AP @ m), and - wherein said PM sensor (213) is not considered to emit a for said exhaust gas representative signal if said deviation exceeds a second limit value (Aum fi. A method according to any one of claims 6-8, further comprising: determining a deviation (A) between said first pressure (P fl, or first pressure change (APU), and said expected pressure (Pam), or said expected pressure change (APam), at a plurality of times, and - said PM sensor (213) not being considered to emit a representative of said exhaust current signal if said deviation (A) exceeds a first (ALM1), or a second (A¿m2), limit value for at least a subset of said times A method according to any one of claims 6-9, further comprising: - determining a deviation ( A) between said first try ck (P fl, or first pressure change (APU), and said expected pressure (Pam) or said expected pressure change (APam), at a plurality of times, and - said PM sensor (213) not being considered to emit a signal representative of said exhaust current if a weighted value of said deviations (A) for said plurality of times exceeds a first (Alm fl), or a second (ALMZ), limit value. A method according to any one of claims 6-11, comprising generating a signal indicating a malfunction of said PM sensor (213) when said first pressure (P1) or pressure change (APU) does not correspond to expected pressure (Pam) or expected pressure change (APam) . A method according to any one of claims 6-11, further comprising actively influencing said expected pressure (P1) or pressure change (APU) by actively influencing said exhaust gas flow. The method of claim 12, further comprising actively actuating said exhaust stream by controlling said internal combustion engine (101), such as by controlling at least one of the fuel injection times, fuel injection times, fuel injection amount. , fuel pressure, number of fuel injections, EGR and air supply, valve timing, compression ratio, overcharging, VGT mode, engine speed, change of combustion mode at said combustion engine, such as from Otto to HCCI or from Diesel to PPC. A method according to claim 12 or 13, wherein said method further comprises actively actuating said exhaust stream by controlling throttling means (215) arranged for controllable throttling of said exhaust stream. The method of claim 14, wherein said method further comprises actively actuating said exhaust stream by controlling throttling means (215) disposed downstream of an intended position for said PM sensor (213). A method according to claim 14 or 15, further comprising actively actuating said exhaust stream by controllably throttling said exhaust stream with throttling means in the form of an exhaust brake (215). A method according to any one of claims 12-16, further comprising actively actuating said exhaust stream upstream or downstream of a turbine. A method according to any one of claims 12-17, further comprising actively actuating said exhaust stream by bypassing one or more components in said finishing system (200), or by connecting an additional component for passage of, and thereby bypassing, said particle sensor (213). of, at least a portion of said exhaust stream. A method according to any one of the preceding claims, wherein said after-treatment system (200) comprises at least one particle filter (202), and wherein the intended PM sensor position is upstream or downstream of said particle filter (202). 202) in said exhaust stream. A method according to any one of the preceding claims, wherein said intended PM sensor position consists of a position upstream of a component in an exhaust system over which, at a varying flow for said exhaust stream, a differential pressure varying with said varying flow arises. A method according to any one of the preceding claims, wherein said internal combustion engine (101) is an engine in a vehicle, and wherein removable power from said internal combustion engine by utilizing a control system arranged in said vehicle is limited if said PM sensor (213) does not emit a signal representative of said exhaust current. A method according to any one of the preceding claims, further comprising: - determining a variation over time of the pressure prevailing at said PM sensor, and - comparing said variation over time with an expected variation over time of the pressure prevailing at said PM sensor. Method according to any one of the preceding claims, wherein the prevailing pressure expected at said PM sensor is determined by means of table look-up and / or a mathematical representation of the finishing system. A method according to any one of the preceding claims, further comprising: - determining said representation of said first pressure (P1) prevailing at said PM sensor (213) by means of frequency analysis of a signal emitted by said pressure sensor . A method according to any one of the preceding claims, wherein the method further comprises: - determining a representation of a concentration and / or fraction (Cg) prevailing at said PM sensor (213) of a first substance present in said exhaust gas stream (SU by using at said PM sensor (213) arranged means for determining a representation of a concentration and / or fraction of said first substance (S1), and - determining whether said PM sensor emits a signal representative of said exhaust gas also based on said determined representation A concentration and / or fraction (Cj) of said first substance (SU. 26). A method according to any one of the preceding claims, wherein the method further comprises: - determining a first temperature prevailing at said PM sensor by using at said PM- means arranged to emit a representation of a temperature prevailing at said PM sensor (213), and - determining whether said PM sensor emits a for said exhaust gas representative signal also based on said determined first temperature. A computer program comprising program code, which when said program code is executed in a computer causes said computer to perform the method according to any one of claims 1-26. A computer program product comprising a computer readable medium and a computer program according to claim 27, wherein said computer program is included in said computer readable medium. 29.System for determining a sensor function for a PM-30. 3l. sensor (213) intended for determining a particle content in an exhaust stream resulting from combustion at an internal combustion engine (101), a post-treatment system (200) being provided for post-treatment of said exhaust stream, characterized in that the system comprises: means for determining a representation of a first pressure (P1) prevailing at said PM sensor (213) by utilizing a pressure sensor (214) arranged at said PM sensor (213), and - means for, based on said determined representation of said first pressure ( P1), determining whether said PM sensor (213) emits a signal representative of said exhaust current. System according to claim 29, characterized in that said internal combustion engine consists of one of the group: vehicle engine, marine engine, industrial engine, diesel engine, otto engine, GDI engine, gas engine. Vehicle (100), characterized in that it comprises a system according to claim 29 or 30.
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    同族专利:
    公开号 | 公开日
    SE536774C2|2014-07-29|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    DE112013003883B4|2012-08-30|2018-09-20|Scania Cv Ab|Method and system for determining a sensor function for a PM sensor in an exhaust stream|
    DE112013003885B4|2012-08-30|2018-12-06|Scania Cv Ab|Method and system for determining a sensor function for a PM sensor|
    法律状态:
    2021-03-30| NUG| Patent has lapsed|
    优先权:
    申请号 | 申请日 | 专利标题
    SE1250961A|SE536774C2|2012-08-30|2012-08-30|Method and system for determining a sensor function for a PM sensor by means of pressure comparisons|SE1250961A| SE536774C2|2012-08-30|2012-08-30|Method and system for determining a sensor function for a PM sensor by means of pressure comparisons|
    PCT/SE2013/051004| WO2014035322A1|2012-08-30|2013-08-28|Method and system to establish a sensor function for a pm sensor|
    PCT/SE2013/051005| WO2014035323A1|2012-08-30|2013-08-28|Method and system to establish a sensor function for a pm sensor|
    DE112013003885.4T| DE112013003885B4|2012-08-30|2013-08-28|Method and system for determining a sensor function for a PM sensor|
    DE112013003836.6T| DE112013003836B4|2012-08-30|2013-08-28|Method and system for determining a sensor function for a PM sensor|
    PCT/SE2013/051003| WO2014035321A1|2012-08-30|2013-08-28|Method and system to establish a sensor function for a pm sensor|
    DE112013003871.4T| DE112013003871T5|2012-08-30|2013-08-28|Method and system for determining a sensor function for a PM sensor|
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