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    • 专利摘要:
    The present invention relates to a method for determining a sensor function for a PM sensor intended to predetermine a particle content in an exhaust gas resulting from combustion at a single-combustion engine (101), wherein a post-treatment system (200) is provided for post-treating said exhaust stream. The method comprises: - determining a first representation of a concentration prevailing at said PM sensor and / or fraction of a substance (S1) present in said first exhaust gas stream by utilizing means arranged at said PM sensor for determining a representation of a concentration and / or fraction of said first substance (S1), and - based on said determined representation of a concentration and / or fraction of said first substance (S1), determining whether said PM sensor emits a signal representative of said exhaust stream. The invention also relates to a system and a vehicle. Fig. 3
    公开号:SE1250963A1
    申请号:SE1250963
    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 a determination of a particle emission.
    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 provided for post-treatment of said exhaust stream. The method comprises: - determining a first representation of a concentration present at said PM sensor and / or fraction of a first substance present in said exhaust gas stream by using means arranged at said PM sensor for determining a representation of a concentration and / or fraction of said first substance, and - based on said determined representation of a concentration and / or fraction of said first substance, determining whether said PM sensor emits a signal representative of said exhaust gas stream.
    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 particulate presence 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 so 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, even in this way, the PM sensor can thus be made 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 very difficult to determine if 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 concentration and / or fraction for a substance present in the exhaust gas stream. These bodies can e.g. consists of a concentration / fraction sensor, which measures the concentration / fraction of any substance other than particles in the exhaust gas stream, and which is integrated with the PM sensor, ie. uses common components such as substrates or the like, or constitute its own but in a common housing with the PM sensor integrated concentration / fraction sensor.
    The concentration / fraction sensor can e.g. is a gas concentration sensor, and wherein said first substance is a gas, but also, according to an embodiment, of a PM sensor where the concentration of particles is determined, wherein the PM sensor can be constituted by an electrostatic or resistive PM SGHSOI.
    The concentration / fraction sensor may be an electrochemical type sensor, or a semiconductor type sensor, such as a silicon carbide based sensor.
    Thus, by determining a representation of the concentration / fraction of any substance present in the exhaust stream, this concentration / fraction can be compared with a representation of an expected concentration / fraction, and based on the comparison it can be determined whether the PM sensor can be considered to be exposed to a representative exhaust gas, 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 drawings Figs.
    FIG.
    FIG.
    FIG.
    Fig. 1a 1b schematically shows a vehicle in which the present invention can be used. shows a control unit in the control system for the vehicle shown in Fig. 1. shows the finishing system in more detail for the vehicle shown in Fig. 1. shows an exemplary method according to the present invention. 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 100 schematically shown in Fig. 1A comprises only one axle with drive wheels 113, 114, 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 internal combustion chamber 101 (e.g. cylinders) of the internal combustion engine.
    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 has several functions, and is normally used primarily to oxidize residual hydrocarbons and carbon monoxide in the exhaust stream to carbon dioxide and water during the post-treatment of the exhaust gas stream. During the oxidation of hydrocarbons, heat is also formed, which can be used to raise the temperature of the particle filter at e.g. emptying (regeneration) of the particulate filter.
    The oxidation catalyst 205 can also oxidize nitrogen monoxide (NO) to nitrogen dioxide (NO 2), which is used in e.g. NO2-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 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 reduction of the amount of nitrogen oxides NOX in the exhaust stream. According to one embodiment of the present invention, a concentration / fraction sensor is used to determine the presence of ammonia 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, the function of which is determined according to the present invention, and which in the present example is shown downstream of the exhaust gas purification unit 203. However, the PM sensor can also be arranged upstream the exhaust gas cleaning unit 203, as well as upstream of the turbocharger 220. Likewise, the vehicle's exhaust system may comprise more than one PM sensor, which may be arranged at different positions, and the function of all PM sensors present in the vehicle may be evaluated.
    The PM sensor 213 in the present invention is integrated or co-located with a concentration / fraction sensor 214, where the concentration / fraction sensor 214 is adapted to determine the concentration of any applicable substance normally present in the exhaust stream.
    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. The soot particles are captured by the particle 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 particle filter 202. By means of the particle filter 202 a very large proportion of the particles are separated from the exhaust gas stream.
    The PM sensor 213 can be used to check that the particle filter 202 works in the 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 also 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. Fig. 3 shows an exemplary method 300 according to the present invention by means of which the environment of the PM sensor, such as the exhaust gas current surrounding the PM sensor, can be evaluated and erroneous sensor signals due to non-representative exhaust current 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. 10 15 20 25 30 11 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 wholly or partly 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 relying on sensor signals from a sensor 210 for determining a concentration and / or fraction of a substance 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.
    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. further receive sensor signals as above, as well as from other control units other than the control unit 115. Such control units are furthermore usually arranged to emit control signals to various vehicle parts and components. For example. the control unit 208 can emit signals to e.g. motor control unit 115.
    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 usually forms part of a computer program product, the computer program product comprising an applicable storage medium 121 (see Fig. 1B) with the computer program 109 stored on said storage medium 121.
    Said digital storage medium 121 may 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 121, which provides the computing unit 120 e.g. the stored program code 109 and / or the stored data calculation unit 120 need 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 122 devices 125, 125 may be detected as information for processing the computing unit 120. The output signals 123, 124 are transmitted. arranged to convert calculation results from the calculation unit 120 into 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 consist of 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.
    According to the above, according to the present invention, the reliability of the PM sensor signals can be increased by evaluating the environment in which the PM sensor is located. Thus, Fig. 3 shows a first exemplary method 300 according to the present invention. The process 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 appropriate intervals, each time the vehicle is started or at other applicable times.
    In step 302, a first concentration / fraction Cj is determined for a first substance S1 present in the exhaust stream. This concentration / fraction is determined by means of said concentration / fraction sensor 214, where the concentration / fraction sensor 214 is adapted to determine the concentration / fraction of any substance normally present in the exhaust stream.
    In the following, the concentration / fraction sensor 214 is assumed to be a gas concentration sensor 214 for determining the concentration C of an applicable gas, so for the sake of simplicity this term is used instead of the concentration / fraction sensor in the following. Instead of determining a concentration, however, the sensor may be arranged to determine a fraction of any applicable substance, i.e. the mole fraction (or weight fraction) of the substance in relation to the total mole (or weight) of any applicable composition, such as the whole exhaust gas stream or in relation to any other substance present in the exhaust gas stream. Thus, in general, concentration and / or fraction can be used in accordance with the present invention, and as will be appreciated, the following description applies equally to a gas fraction sensor, as well as to a particle concentration or fraction sensor.
    The gas concentration sensor 214 can e.g. be of a type which emits signals representing, or by means of which can be calculated, the concentration of a given substance.
    The gas concentration sensor can e.g. consists of an oxygen (Og) sensor, nitric oxide (NO) sensor, nitrogen dioxide (NO2) sensor, hydrocarbon (HC) sensor, ammonia (NH3) sensor or other applicable sensor intended to determine the concentration of any applicable in the exhaust stream substance present.
    With regard to the example of ammonia, this is particularly applicable to after-treatment systems where a so-called SCR catalyst as above is used to reduce nitrogen oxides.
    Thus, in step 302, a first concentration Cj of any applicable first substance S1 is determined. Thus, when the concentration C1 for said first substance S1 has been determined in step 302, the process proceeds to step 303, in which an expected concentration Cæw for said first substance S1 is determined. 10 15 20 25 30 15 This expected concentration Cam can e.g. is determined by table look-up where expected concentrations C for the substance S1 in question can be indicated 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, supercharging, VGT mode, engine speed, internal combustion engine load, HC dosing, etc.
    To ensure that as reliable values as possible for Cj and Cæw 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 for to avoid that dynamic processes incorrectly affect the measurement results.
    After the expected concentration Cæw has been determined in step 303, the method proceeds to step 304, where the concentration C1 for said first substance determined by using the concentration sensor 214 is compared with the expected concentration Cam for said first substance Sh, whereby a deviation A between expected concentration Cam and measured concentration Cl is determined. In step 305, it is then determined whether the deviation A between the expected concentration Cæw and the measured concentration Clär is greater than any applicable limit value Alm fl. The limit value A¿m¿ 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 composition of the exhaust gas stream can be difficult to predict with the desired accuracy. As long as this is not the case, the process proceeds to step 306, where the appropriate signal can be generated to indicate that the PM sensor 213 can be assumed to give representative measurements of the particle presence in the exhaust stream because the sensor can at least be assumed to perform measurements on a representative exhaust flow and thus be at the intended position in the exhaust system. The method then returns to step 301 for re-determining the function of the PM sensor at the applicable time as above. Alternatively, the method may return directly to step 301 from step 305 because action does not really need to be taken.
    If, on the other hand, it is determined in step 305 that the deviation A is greater than the limit value A¿m¿, 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, a method is provided 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. Thus, by means of the present invention, attempts to manipulate the function of the PM sensor 213 can be detected during operation of the vehicle 100, thereby reducing the possibilities of inadvertently manipulating the finishing system.
    In the example shown in Fig. 3, a determined concentration C1 has been compared with an expected concentration Cam at one time.
    As will be appreciated, the composition of the exhaust gases of an internal combustion engine 101 may vary considerably, and although e.g. a table lookup or calculation as above is used to determine an expected concentration Cææ, a measured individual value in adverse conditions may deviate from the expected value by more than said deviation Ajmd even though the PM sensor 213 is actually correctly arranged in the exhaust stream. 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 A¿m¿, and where the weighted value is used to determine whether the PM sensor 213 can be assumed to be exposed to a representative exhaust stream.
    The deviation Alma 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 Almd can be set because the weighted accuracy increases with the number of measured values X.
    Fig. 4 shows a further exemplary method 400 according to the present invention, in which the expected concentration Cam is determined in an alternative manner.
    The method 400 shown in Fig. 4 begins in step 401 where, just as in step 301 in Fig. 3, it is determined whether the function of the PM sensor is to be determined. When so, the process proceeds to step 402, where a first concentration of said first substance S1 is determined by means of said concentration sensor 214 as above. The process then proceeds to step 403. Instead of determining an expected concentration Cam as in Fig. 3, an active influence of the exhaust gas flow is performed in step 403. This can e.g. performed by changing the work of the internal combustion engine 101.
    The work of the internal combustion engine 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 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 mode, alternating engine torque, in said internal combustion engine is performed, such as e.g. from Otto to HCCI, or from Diesel to PPC. Alternatively, the load can be increased by e.g. switch on inactive internal combustion engine units.
    By changing the way in which the internal combustion engine 101 operates, or otherwise influencing the exhaust gas flow as above, the composition of the exhaust gas stream will also change.
    If e.g. the internal combustion engine 101 is forced to operate harder, the oxygen content of the exhaust stream will usually decrease, i.e. the concentration of oxygen in the exhaust stream will decrease.
    Conversely, the presence of nitrogen oxides usually increases with increasing load. Thus, in step 403, any applicable change is made to the operation of the internal combustion engine 101 and thus the composition of the exhaust stream. Preferably, a change is made which results in a relatively large change in the composition of the exhaust gas stream. Instead of changing the operation of the internal combustion engine 101, the exhaust gas stream may, instead, or in combination, be actively actuated in step 403 by bypassing one or more components of the aftertreatment system, or by engaging an additional component to pass at least a portion of said exhaust gas stream, the composition of the exhaust gas stream being changed in this way instead.
    The exhaust gas flow can also be affected by throttling the exhaust flow by means of throttling means in the form of e.g. an exhaust brake, where said throttling means e.g. may be arranged downstream of an intended position for said PM sensor 213.
    Furthermore, the exhaust gas flow can be affected e.g. by adding hydrocarbon (fuel) or urea to the exhaust gas stream, this in itself affecting the exhaust gas stream, and where further influence can be obtained in reactions in one or more of the components of the after-treatment system. The exhaust stream can also be arranged to be actuated upstream or downstream of a turbine, e.g. according to any of the methods exemplified above.
    The process then proceeds to step 404, where a second concentration C2 of said first substance S1 is determined, i.e. a concentration C2 in the exhaust stream after the said one or more measures for changing the composition of the exhaust stream have been performed. In step 405, then, an expected change AC @ @ @ is determined for the concentration of said first substance. After the measures taken in step 403, the change ACU between said first C1 and the second value C, respectively; compared with the expected change AC @ @ for the concentration of said first substance S1. Ie. according to this embodiment of the method shown in Fig. 4, no absolute concentrations need be determined, but it is sufficient to determine an expected change AC @ m, where this expected change AC @ m can be determined by calculation or table lookup from the outside. made changes as above.
    In step 406, the actual change ACH is then compared with the expected change AC @ @ in a manner corresponding to step 304 in Fig. 3, it being determined in step 407 whether the deviation A is greater or less than any applicable deviation Ajmü. If the deviation is less than the limit AjmQ, the procedure returns to step 401 via a step 408 corresponding to step 306 as above, while if the deviation A exceeds the limit value Ajmü an error signal, such as an alarm signal, is generated in step 409 in a manner corresponding to step 307 in Fig. 3. The procedure is then completed in step 410.
    By means of the method shown in Fig. 4, it can thus be determined not only that the PM sensor 213 is placed in an exhaust composition, but also that the PM sensor 213 is arranged in an exhaust flow whose composition varies with varying operating conditions in a representative manner. Using this procedure, it can e.g. it is ensured that the PM sensor 213 has not been manipulated in such a way that it has been placed in an isolated environment such as in a test tube with exhaust gases and thus separated from the actual exhaust gas flow.
    As with the method shown in Fig. 3, the method shown in Fig. 4 may be arranged to be run through a number of times for determining a number of measured values by performing a number of changes in the composition of the exhaust gas stream.
    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 101 concentration change can be applied according to Fig. 4, but where at the same time the values before each change of the exhaust stream are compared with expected values before the respective change are determined, which can further improve the accuracy.
    In addition, the method can be performed for more than one substance present in the exhaust stream, whereby a sensor capable of performing concentration / fraction measurements for more than one substance separated from particles can be used. Alternatively, two or more sensors for the respective concentration / fraction measurements for a respective substance separated from particles can be used, wherein more than one concentration sensor is integrated / co-located with the PM sensor. According to a further embodiment, concentration / fraction measurements are performed for particles and at least one additional substance.
    The present invention also has the advantage that since a concentration of a substance present in the exhaust stream is determined, determination according to the present invention can be performed regardless of the position of the PM sensor in the exhaust system. Depending on the application, PM sensors can be arranged at different positions in an 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. Regardless of location, concentration changes in the exhaust stream will occur with changed operating parameters.
    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 one thread per revolution for two-stroke engines and one thread every other revolution for four-stroke engines. l0 l5 20 25 30 22 This means that the exhaust gas flow will be “pulsed” out via the exhaust valves, and there will be pulsating differences in the flow of the exhaust gas over time. This also means that the pulsation will give rise to concentration variations with the same frequency for the substances present 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 concentration 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 concentration / fraction 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. motors where the rate factor can be controlled controllably). 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 concentration 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 either in the time domain 10 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.
    Depending on which substance (s) present in the exhaust gas stream are analyzed, frequency analysis can also be arranged to be performed on dosing of additives such as urea or fuel to the exhaust gas stream.
    As explained above, after-treatment systems may be of a type where additives are added to the exhaust stream to facilitate reduction of one or more substances present in the exhaust stream.
    For example, SCR catalysts usually use ammonia (NH3), or a composition from which ammonia can be generated / formed, such as e.g. urea, as an additive to reduce the amount of nitrogen oxides NOX in the exhaust gas stream. This additive is injected into the exhaust gas stream resulting from the internal combustion engine upstream of the SCR catalyst, the additive supplied to the catalyst being adsorbed (stored) in the catalyst, and the nitrogen oxides in the exhaust gases reacting with the additive stored in the catalyst. This dosing of additives and fuel such as diesel in the exhaust stream is often performed as injection pulses, typically with frequencies between e.g. O.l and 10 Hz. Thus, variations in these concentrations or in concentrations of substances dependent thereon (such as, for example, the concentration of NOX after an SCR catalyst) will often vary with this frequency, so that a corresponding frequency analysis can also be performed with respect to this.
    It also happens that e.g. fuel is supplied to the exhaust gas stream as injection pulses, whereby a corresponding frequency analysis can be performed against the applicable substance in the pulsation caused by the fuel injection.
    In general, for the frequency analysis, the closer to the pulsation source the analysis is performed, the more reliable the analysis results will be obtained.
    Thus, according to this embodiment, said frequency analysis constitutes a representation of a concentration and / or fraction of the substance in question prevailing at said PM sensor 213.
    Furthermore, there are different types of PM sensors, and the present invention is applicable to all types of PM sensors.
    There are e.g. s.k. IDE sensors where ceramic plates coated with conductive materials are used to determine a particle content of a passing exhaust stream. As an exhaust stream containing particles passes through the coated ceramic plates, particles will become stuck, which in turn means that the conductivity between two adjacent non-contacting plates will change. As particles (soot) stick to these plates, the conductivity will increase, which means that e.g. a resistance, current, voltage, conductivity or inductance or the like can be detected, and where changes in relevant magnitude indicate particle occurrence. By determining a gradient for a change over time, particle occurrence can be estimated by determining how fast e.g. a resistance, current or voltage etc. changes. This type of particle sensor thus involves a relatively slow detection of particle occurrence, whereby it can take a long time before malfunction is detected. According to the present invention, however, manipulation of this type of sensors can be detected at an early stage.
    There are also other types of particle sensors, such as e.g. electrostatic particle sensors, where particles pass a first electrode to pick up a charge and then pass a second electrode arranged in the particle sensor where the charge is emitted. Depending on the particle presence, the number of electrons per unit time transferred between the electrodes will thus vary, whereby both the particle presence and also the number of particles can be determined with immediate and very high accuracy.
    According to one embodiment, this type of particle sensor is used to determine the concentration and / or fraction of particles in the exhaust gas stream. Thanks to the speed of the sensor, present value measurements can be performed, ie. values representing instantaneous particle contents are obtained. Thus, according to one embodiment, said first substance may consist of particles, wherein concentration determinations and concentration change determinations, respectively, as above, consist of particle content determinations and particle content change determinations, respectively.
    However, it has been realized that PM sensors can exhibit cross-sensitivity to substances that are added to the exhaust gas stream when adding additives as above. For example. this cruelty may refer to water, urea, ammonia or other added substance. This means that for at least some PM sensors the output signal, ie. the signal which normally constitutes a representation of the presence of particles in the exhaust stream to be affected by this cross-sensitivity. This cross-sensitivity means that the PM sensor reacts to the presence of additives in the exhaust stream and thus generates a signal that indicates a different presence of particles than is actually the case.
    This cross-sensitivity can thus lead to reduced accuracy in diagnosing PM sensors in systems where the PM sensor is located downstream of the position where the supply of additives takes place, and where the PM sensor signals are used in the diagnosis as may be the case as above.
    This insight into cross-sensitivity can therefore be used in the diagnosis of PM sensors, whereby dosing (supply) of additives according to one embodiment can be switched off during the diagnosis of the PM sensor, whereby safer measured values compared to not taking this shut-off measure can be obtained.
    Furthermore, the method according to the invention can be combined with that in the parallel Swedish application no. 1250961-8 with the title "PROCEDURE AND SYSTEM FOR EXHAUST CLEANING" and the same inventor and filing date as the present application, described to determine a sensor function for a PM sensor. According to the said application "PROCEDURE AND SYSTEM FOR EXHAUST CLEANING" a method according to the present invention is provided, but where the sensor function of the PM sensor is determined based on a representation of a pressure prevailing at the PM sensor, where the pressure is determined using a pressure sensor arranged at the PM sensor. . 10 15 20 25 27 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 filing 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.
    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 independent the scope of protection of the 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 first representation of a concentration and / or fraction ML) prevailing at said PM sensor (213) of a first substance (S1) present in said exhaust gas stream by using means arranged at said PM sensor (213) for determining a representation of a concentration and / or fraction of said first substance (S1), and - based on said determined representation of a concentration and / or fraction (C1) of said first substance (S1), determining whether said PM sensor (213) emits a signal representative of said exhaust current. A method according to claim 1, wherein said means for determining said representation of a concentration and / or fraction of said first substance (S1) is constituted by a concentration sensor for determining a representation of a concentration and / or fraction of said first substance (SU. A method according to claim 2, wherein said concentration sensor is a gas concentration sensor (214), and wherein said first substance (S1) is a gas A method according to claim 3, wherein said concentration sensor (214) is a gas concentration sensor (214). An electrochemical type sensor, or a semiconductor type sensor A method according to claim 1, wherein said first substance (S1) is constituted by particles in said exhaust gas flow, and wherein said representation of a concentration and / or fraction of said particles is determined by using said semiconductor device. The PM sensor (213), said PM sensor (213) being an electrostatic or resistive PM sensor, The method of claim 1, further comprising determining whether said PM sensor (213) emits a signal representative of said exhaust gas by determining based on said representation of a concentration and / or fraction of said first substance (S1) whether said PM sensor (213) can be assumed to be located in said exhaust stream. A method according to any one of the preceding claims, further comprising determining, based on said determined representation of a concentration and / or fraction of said first substance (S1), whether said finishing system (200) and / or PM sensor (213) can be assumed to have been manipulated. A method according to any one of the preceding claims, wherein said means (214) for determining a representation of a concentration and / or fraction of said first substance (S1) is constituted by means integrated with said PM sensor (213). A method according to any one of claims 1-8, wherein said means (214) for determining a representation of a 10. ll. The concentration and / or fraction of said first substance (S1) consists of means fixedly connected to said PM sensor (213) and / or means arranged in a common housing with said PM sensor (213). A method according to any one of the preceding claims, further comprising: - comparing said first concentration and / or fraction UL) of said first substance (S1) with an expected concentration and / or fraction (Cæw) of said first substance (S1), and - based on said comparison, determining whether said PM sensor emits a signal representative of said exhaust current. The method of claim 10, further comprising: - determining a deviation (A) between said first concentration and / or fraction (C1) of said first substance (S1) and said expected concentration and / or fraction (Cam) of said first substance ( SU, and - wherein said PM sensor (213) is considered to emit a signal not representative of said exhaust current if said deviation (A) exceeds a first limit value (Ahm fl. A method according to any one of the preceding claims, further comprising: - By using said first means (214) for determining a concentration and / or fraction of said first substance (S1), determining a first change (ACÜ) of a concentration and / or fraction of said first substance (SQ, - comparing said first change (SQ); ACU) of the concentration and / or fraction of said first substance (S1) with an expected change (AC @ @) of the concentration and / or fraction of said first substance (S1), and - based on said comparison, determining whether said PM sensor emits a signal representative of said exhaust current. The method of claim 12, further comprising: - determining a deviation (A) between said first change (ACU) of the concentration and / or the fraction of said first substance (S1) and said expected change (AC @ @) of the concentration and / or the fraction of said first substance (S1), and - wherein said PM sensor (213) is considered to emit a signal not representative of said exhaust gas if said deviation (A) exceeds a second limit value (Note fi. Method according to claim ll or 13, wherein said deviation (A) is determined as an absolute amount of a difference between said first concentration and / or fraction (Cj) and said expected concentration and / or fraction (Cam), or as an absolute amount of a difference between said first change (ACQ) and said expected change (ACHW) of the concentration and / or fraction of said first substance (SU. A method according to any one of claims 10-14, further comprising: - determining a deviation between said first a concentration and / or fraction (C1) of, or change (ACQ) of the concentration and / or fraction of, said first substance (S1) and said expected concentration and / or fraction (Cam) of, or said expected change (AC @ @) of the concentration and / or fraction of, said first substance (S1) at a plurality of times, and - said PM sensor (213) being considered to emit a signal not representative of said exhaust current of said deviation (A) exceeds said limit value (A1mü; Note) for at least a subset of said times. A method according to any one of claims 10-15, further 17. comprising: - determining a deviation between said first concentration and / or fraction (C1) of, or change (ACU) of the concentration and / or fraction of, said first substance (S1) and said expected concentration and / or fraction (Cam) of, or said expected change (AC @ m) of the concentration and / or fraction of, said first substance (S1) at a plurality of times, and - wherein said PM sensor (213) is considered to emit a signal not representative of said exhaust current if a weighted value of said deviations (A) for said plurality of times exceeds said limit value (A1m¿; Note). A method according to any one of the preceding claims, further comprising: - determining said first representation of a concentration and / or fraction (C1) of a first substance present in said PM sensor (213) rescuing a substance (S1) present in said exhaust gas stream by means of frequency analysis by a signal emitted by said means for determining a representation of a concentration and / or fraction of said first substance (S1). A method according to any one of claims 10-17, comprising generating a signal indicating a malfunction of said PM sensor (213) when said first concentration and / or fraction (C fl of; or change (ACU) of the concentration and / or fraction of, said first substance (S1) does not correspond to an expected (Cam) concentration and / or fraction of, or expected change (ACHW) of the concentration and / or fraction of, said first substance (SU. 19. according to any one of claims 10-18, further 20. 21. 22. comprising actively influencing said change in the concentration and / or fraction of said first substance (S1) by actively influencing said exhaust stream. influencing said exhaust flow by controlling said internal combustion engine, 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, supercharging, VGT mode, engine speed, combustion mode change at said internal combustion engine, such as from Otto to HCCI or from Diesel to PPC. A method according to claim 19 or 20, wherein said method further comprises actively influencing said exhaust gas flow by controlling throttling means arranged for controllable throttling of said exhaust gas flow. A method according to claim 21, wherein said method further comprises actively actuating said exhaust gas stream 10 25 25 24 24. 25. 26 27 28. 34 by controlling throttling means arranged downstream of an intended position for said PM sensor. A method according to claim 21 or 22, further comprising actively actuating said exhaust stream by controllable throttling of said exhaust stream with throttling means in the form of an exhaust brake. A method according to any one of claims 19-23, further comprising actively influencing said exhaust gas stream by supplying hydrocarbon to the exhaust gas stream. A method according to any one of claims 19-24, further comprising actively actuating said exhaust stream upstream or downstream of a turbine. A method according to any one of claims 19-25, further comprising actively actuating said exhaust stream by bypassing one or more components in said aftertreatment system (200), or by engaging 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 particulate filter (202), and wherein the intended PM sensor position is upstream or downstream of said particulate filter (202) in said exhaust gas stream. A method according to any one of the preceding claims, wherein said finishing system (200) comprises at least one particle filter (202), and wherein the intended PM sensor position is upstream or downstream of a component with which a concentration and / or fraction of said first substance can be changed, such as a turbine, DOC or SCR catalyst. A method according to any one of the preceding claims, wherein said 30. 3l. An internal combustion engine consists of an engine in a vehicle, and extractable power from said internal combustion engine is limited by using a control system arranged in said vehicle if said PM sensor does not emit a signal representative of said exhaust current. A method according to any one of the preceding claims, further comprising using said means for determining concentration and / or fraction of a first substance present in said exhaust gas stream (SU determining the concentration and / or fraction of at least one further substance present in said exhaust gas stream, and determining whether said PM sensor emits a signal representative of said exhaust gas based on concentrations and / or fractions of said first (SQ and at least one additional substance, respectively). The method of claim 30, further comprising determining a particle concentration and / or fraction by means of said PM sensor (213), said particle concentration and / or fraction constituting the concentration and / or fraction of said at least one further substance present in said exhaust gas stream A method according to any one of the preceding claims, wherein the method further comprises: - determining a representation of a first at n said pressure prevailing by utilizing a pressure sensor arranged at said PM sensor, and - determining whether said PM sensor emits a signal representative of said exhaust current also based on said PM sensor. established first print. 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 means arranged at said PM sensor to emit a representation of a prevailing at said PM sensor (213). temperature, and - determining whether said PM sensor emits a signal representative of said exhaust current also based on said determined first temperature. A method according to any one of the preceding claims, wherein said vehicle comprises means for supplying additives to said exhaust gas stream, and wherein supplying of additives is interrupted when the sensor function of said PM sensor (213) is to be determined. A process according to any one of the preceding claims, wherein said first substance consists of one of the group: hydrocarbons, ammonia, oxygen, particles, nitrogen oxide, nitrogen dioxide, carbon monoxide, carbon dioxide. 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 1-35. A computer program product comprising a computer readable medium and a computer program according to claim 36, wherein said computer program is included in said computer readable medium. 38. 38. A system for determining a sensor function for a PM sensor intended for determining a particle content of an exhaust gas from an internal 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 concentration prevailing at said PM sensor and / or fraction of a first substance (S1) present in said exhaust gas stream by using means arranged at said PM sensor for determining a representation of a concentration and / or fraction of said first substance (S1), and - means for determining, based on said determined representation of a concentration of said first substance (S1), whether said PM sensor emits a signal representative of said exhaust gas stream. . System according to claim 38, 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 38 or 39.
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    同族专利:
    公开号 | 公开日
    SE536845C2|2014-09-30|
    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
    SE1250963A|SE536845C2|2012-08-30|2012-08-30|Method and system for determining a sensor function for a PM sensor by means of concentration and / or fraction comparisons|SE1250963A| SE536845C2|2012-08-30|2012-08-30|Method and system for determining a sensor function for a PM sensor by means of concentration and / or fraction comparisons|
    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|
    PCT/SE2013/051004| WO2014035322A1|2012-08-30|2013-08-28|Method and system to establish a sensor function for a pm sensor|
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