DE112013003883T5 - Method and system for determining a sensor function for a PM sensor in an exhaust stream - Google Patents

Abstract

The present invention relates to a method for determining a sensor function for a PM sensor (213), which is provided for determining a particle content in an exhaust gas stream, which results from the combustion in an internal combustion engine (101), wherein an aftertreatment system (200) for the post-treatment of the exhaust gas flow is installed, the vehicle comprising an element for the supply of additives into the exhaust gas flow. The method comprises: detecting a change in a signal emitted by the PM sensor (213) in response to a change in the supply of additives and, based on the change in the signal emitted by the PM sensor, determining whether the PM sensor (213) emits a signal representative of the exhaust gas flow. The invention also relates to a system and a vehicle.

Description

Field of the invention

The present invention relates to a system for treating exhaust gas streams resulting from a combustion process, and more particularly to a method for detecting a sensor function for a PM sensor according to the preamble of claim 1. The invention also relates to a system and a vehicle as well as a computer program and a computer program product in which the method according to the invention is implemented.

Background of the invention

In the context of heightened governmental concerns about pollution and air quality, particularly in metropolitan areas, emissions standards and regulations have been drafted in many jurisdictions.

Such emission regulations often consist of requirements which define permissible exhaust emission limits for vehicles with internal combustion engines. For example, the values of nitrogen oxides (NOx), hydrocarbons (HC) and carbon monoxide (CO) are often regulated. These emissions regulations also generally involve, at least with respect to certain types of vehicles, the presence of particulate matter in exhaust emissions.

In an effort to comply with these emissions regulations, the exhaust gases caused by the combustion of the internal combustion engine are treated (purified). By way of example, a so-called catalytic purification process can be used, so that after-treatment systems, for example in vehicles and other means of transport, generally comprise one or more catalysts.

Further, such aftertreatment systems often include additional components as an alternative to or in combination with a single or multiple catalysts. For example, aftertreatment systems on diesel engine vehicles often include particulate filters.

By combustion of fuel in the combustion chamber of the engine (for example, cylinder) form soot particles. According to the above, there are emission regulations and standards which also pertain to these soot particles, and in order to meet the requirements, particulate filters can be used to trap soot particles. In such cases, the exhaust gas flow is passed, for example, through a filter structure, where soot particles are collected from the passed-through exhaust gas stream for storage in the particle filter.

As a result, there are numerous methods for reducing emissions from an internal combustion engine. In addition to regulations concerning emission levels, legislative requirements for so-called on-board diagnostic (OBD) systems are becoming increasingly common to ensure that vehicles actually meet the regulatory requirements for emissions during daily operations, and not, for example only when visiting a workshop.

With respect to particulate emissions, this may be achieved, for example, by means of a particulate sensor installed in the exhaust system or aftertreatment system, hereinafter referred to as PM sensor (PM = particulate matter, particulate matter (particulate matter)), which is the particulate concentration in the exhaust stream measures. For example, the particle concentration may be determined as a particle mass per volume or weight unit, or as a particular number of particles of particular size per unit volume, and multiple determinations of the amount of particles of different sizes may be used to determine particle emission.

Aftertreatment systems with particulate filters can be very efficient, and the resulting particulate concentration after passing the exhaust stream through the vehicle aftertreatment system is often low in a fully functional aftertreatment system. This also means that the signals that the sensor emits will indicate little or no particulate emissions.

Brief description of the invention

An object of the present invention is to provide a method for determining a sensor function for a PM sensor, which is to determine a particle concentration in an exhaust gas stream resulting from combustion in an internal combustion engine. This object is achieved by a method according to claim 1.

• – Erreichen einer Änderung bei einem Signal, das vom PM-Sensor als Reaktion auf eine Änderung bei der Zufuhr von Zusatzstoffen ausgegeben wird, und
• – basierend auf der Änderung bei dem vom PM-Sensor ausgegebenen Signal, Feststellen, ob der PM-Sensor ein Signal aussendet, das für den Abgasstrom repräsentativ ist.

The present invention relates to a method for determining a sensor function for a PM sensor, which is to determine a particle concentration in an exhaust gas stream resulting from combustion in an internal combustion engine, wherein an aftertreatment system is installed for post-treatment of the exhaust gas flow and wherein the vehicle elements for feeding additives into the exhaust stream. The method comprises:

• Achieving a change in a signal output by the PM sensor in response to a change in the supply of additives, and
• Based on the change in the signal output from the PM sensor, determining if the PM sensor is emitting a signal representative of the exhaust gas flow.

As mentioned above, PM sensors may be used to ensure that particulate levels in the exhaust stream resulting from the engine do not exceed specified levels.

However, to ensure that the presence of particles in the exhaust stream is below the specified levels, the PM sensor must emit a correct signal. A PM sensor may be set up at various locations in the exhaust flow and, depending on its position, a PM sensor may be set up so that the presence of particles at the location of the PM sensor is very low. This is true, for example, for a PM sensor installed downstream of a particulate filter, where a properly functioning particulate filter is often capable of separating a very significant portion of the particulates expelled from the combustion chamber of the combustion engine.

This, in turn, means that it may be difficult to have a situation where the particulate filter is functioning properly, but the concentration of particulate matter downstream of the particulate filter is very low, from a situation where the PM sensor is low in concentration due to an actual particulate matter Malfunction of the PM sensor or lack of a representative signal for another reason indicates to distinguish.

There may be several reasons why a PM sensor does not send a representative signal, i. H. Not only a disturbance of the PM sensor causes a lower concentration than the actual one. As such, however, the PM sensor may emit a signal representative of the environment in which the PM sensor is located, with the PM sensor and / or the aftertreatment system manipulated so that the sensor no longer controls the particle concentration in the sensor measures a representative exhaust stream.

For example, the sensor may have been moved from the intended position in the exhaust flow, for example, to a position where it measures the concentration of particles in the environment of the vehicle. In such cases, the PM sensor will always emit a signal that represents a very low or no particle concentration, regardless of the actual particulate concentration of the exhaust stream.

Another way of manipulating the signal emitted by the PM sensor to reduce the detected particulate concentration is to bypass all or part of the exhaust flow past the PM sensor so that the latter is no longer exposed to the representative exhaust gas flow. In this way, the PM sensor can also be made to emit signals representing a lower particle concentration than the actual one. Another way of manipulating the sensor signal is to block the sensor so that the exhaust stream is not passed through the sensor.

Thus, there are many possibilities of manipulating a PM sensor, and since the PM sensor according to the above can be arranged in such a manner that only a very small particle concentration is detected, the determination of whether the sensor has been manipulated or not can be difficult be.

According to the invention, a method is provided for determining whether the PM sensor can be assumed to send out a representative signal and to determine whether the sensor is faulty or has been manipulated.

This has been achieved according to the invention, thanks to a finding that different types of PM sensors can be cross-sensitive to additives supplied in the exhaust gas stream. For example, the Selective Catalyst Reduction (SCR) catalyst is at least prevalent in certain aftertreatment systems, and perhaps primarily in heavy vehicles.

SCR catalysts typically use ammonia (NH ₃ ) or a composition from which ammonia can be generated / formed, such as urea, as an additive for the reduction of nitrogen oxides NO _x in the exhaust stream. This additive is injected into the exhaust stream from the internal combustion engine upstream of the SCR catalyst, and the additive added to the catalyst is adsorbed (stored) in the catalyst so that nitrogen oxides in the exhaust gas react with the additive stored in the catalyst.

It has also been seen that the signal emitted by at least some PM sensors, ie the signal which normally represents a representation of the particle concentration in the exhaust stream, is cross-sensitive to such additives. This cross-sensitivity brings with it the PM sensor on the Presence of an additive in the exhaust stream reacts and thus generates a signal indicating a higher particle concentration than the actual values.

This finding is used in the present invention in such a manner that a change in a signal sent out from one of the PM sensors in response to a change in the supply of additives is detected, and based on the change in that from the PM sensor emitted signal is determined whether the PM sensor emits a signal that is representative of the exhaust gas flow.

If the signal sent by the PM sensor shows no expected change, it can be assumed that the PM sensor is not performing measurements of a representative exhaust stream, i. H. an exhaust gas flow, which correctly reproduces the composition in the exhaust gas flow leaving the combustion chamber of the internal combustion engine, and is thus disturbed or manipulated. Further features of the present invention and its advantages will be described in the detailed description of exemplary embodiments and the accompanying drawings set forth below.

Brief description of the drawings

1a shows a diagram of a vehicle, in which the present invention can be used.

1b shows a control device in the control system for the vehicle in 1 ,

2 shows the aftertreatment system for the vehicle in 1 a little more detailed.

3 shows an exemplary embodiment of the invention.

4 shows an alternative exemplary embodiment according to the invention.

Detailed description of the embodiments

The expressed particle concentration in the following description and the following claim comprises a concentration in terms of mass per unit and a concentration as the number of particles per unit. Further, the unit may consist of any applicable unit and the concentration may be expressed, for example, as mass or number of particles per unit volume, per unit mass, per unit time, per completed work or per distance traveled by the vehicle.

1A shows a diagram of a drive train in a vehicle 100 according to an embodiment of the present invention. The graph of the vehicle 100 in 1a includes only one shaft with wheels 113 . 114 but the invention is also applicable to vehicles in which more than one shaft is equipped with wheels and vehicles having one or more shafts such as one or more support shafts. The powertrain includes an internal combustion engine 101 in a standard way via an output shaft on the combustion engine 101 , usually a flywheel 102 , via a clutch 106 with a gear 103 connected is.

The internal combustion engine 101 is controlled by the engine control system via a control device 115 controlled. That's exactly how the clutch works 106 , which may consist of an automatically controlled clutch, for example, as well as the transmission 103 controlled by the control system of the vehicle by means of one or more applicable control devices (not shown). Of course, the powertrain of the vehicle may also be of a different type, such as a type with a conventional automatic transmission, etc.

An output shaft 107 from the gearbox 103 drives the wheels 113 . 114 via a final drive 108 such as a conventional differential and the drive shafts 104 . 105 that with the final drive 108 connected to.

The vehicle 100 also includes an exhaust system with an aftertreatment system 200 for treating (for cleaning) exhaust emissions resulting from combustion in the combustion chamber (eg cylinders) of the internal combustion engine 101 arise.

An example of an aftertreatment system 200 is more detailed in 2 shown. The figure shows the internal combustion engine 101 of the vehicle 100 in which the exhaust gas generated by the combustion (the exhaust gas flow) over the turbocharger 220 to be led. In turbocharged engines, the exhaust flow produced by combustion often drives a turbocharger, which in turn compresses the incoming air for combustion in the cylinder.

Alternatively, the turbocharger may be, for example, of the composite type. The function of the various types of turbochargers is well known and will therefore not be described in detail here. The exhaust stream is then passed through a pipe 204 (indicated by arrows) over a Diesel Oxidation Catalyst (DOC) 205 to a diesel particulate filter (DPF) 202 guided.

The DOC 205 has several functions and is normally used primarily in post-treatment to residual Hydrocarbons and residual carbon monoxide in the exhaust stream to oxidize in carbon dioxide. During the oxidation of hydrocarbons, heat is also formed, which can be used to increase the temperature of the particulate filter, for example, when the particulate filter is emptied (regenerated).

The oxidation catalyst 205 can also oxidize nitric oxide (NO) into nitrogen dioxide (NO ₂ ), which is used for NO ₂ -based regeneration, for example. In an oxidation catalyst, further reactions can take place.

In addition, the aftertreatment system may include more components than indicated in the above examples, or fewer components. For example, the aftertreatment system as in the present example, an SCR catalyst (catalyst with selective catalytic reduction) 201 downstream of the particulate filter 202 include. As mentioned above, SCR catalysts typically use ammonia (NH ₃ ) or a composition from which ammonia can be generated / formed, such as urea, as an additive for the reduction of nitrogen oxides NO _x in the exhaust gas stream. This additive can be used according to the invention to determine whether the PM sensor emits a representative signal.

In the embodiment shown, the components are DOC 205 , DPF 202 and the SCR catalyst 201 in one and the same exhaust gas cleaning unit 203 integrated. It should be understood, however, that these components need not be integrated into one and the same exhaust gas purification unit, but the components may be otherwise arranged as appropriate, and one or more of the components may be, for example, separate units. 2 also shows the temperature sensors 210 to 212 and a differential pressure sensor 209 , The figure also shows a PM sensor 213 , whose function is determined according to the invention and the downstream of the exhaust gas purification unit in the present example 203 is shown. However, the PM sensor may also be upstream of the exhaust gas purification unit 203 as well as upstream of the turbocharger 220 be furnished. In addition, the exhaust system of the vehicle may include more than one PM sensor, which may be located at different locations, and therefore the functionality of all PM sensors in the vehicle may be assessed. The PM sensor 213 in the present invention is a concentration / fraction sensor 214 integrated or arranged with this same location, wherein the concentration / fraction sensor 214 suitable for determining the concentration of an applicable substance normally found in the exhaust stream.

As mentioned above, during combustion in the internal combustion engine 101 Soot particles are formed, and these soot particles may not be ejected into the environment surrounding the vehicle in many cases. The soot particles are from the particulate filter 202 which works by passing the exhaust stream through a filter structure where soot particles are trapped by the passed exhaust stream and then in the particulate filter 202 be deposited. With the help of the particle filter 202 a very large part of the particles can be separated from the exhaust gas flow.

The PM sensor 213 can be used to control that of the particulate filter 202 works in the desired way, but also to monitor, for example, the functionality of the internal combustion engine 101 for example, in the case of a position of the PM sensor upstream of the particulate filter. The PM sensor 213 can also be used for other purposes.

However, in order to be representative of the presence of particulate matter determined by the PM sensor signals, the PM sensor must 213 Send signals that are representative of the environment in which the PM sensor is to be installed.

The present invention improves the reliability of the PM sensor signals by assessing the environment around the PM sensor. 3 shows an exemplary embodiment of the invention 300 with which the PM sensor can be assessed and incorrect sensor signals, which are caused by non-representative exhaust gas flows, can be detected. The method according to the present example for a control device 208 performed in 1A to B and 2 is shown.

In general, control systems in modern vehicles consist of a communication bus system consisting of one or more communication buses for connecting a number of electronic control devices (ECUs), such as the control devices or control units, 115 . 208 , and various components disposed on the vehicle. Such a control system may include a large number of control devices, and responsibility for a particular function may be distributed to more than one control device.

For simplicity's sake 1A to B only the control devices 115 . 208 ,

Thus, in the illustrated embodiment, the present invention is in the control device 208 that may be responsible for other functions in the illustrated embodiment, as well as in the aftertreatment system 200 implemented, such as regeneration (emptying) of the particulate filter 202 However, the invention can thus also in a control device dedicated to the present invention, or in whole or in part in one or more already existing in the vehicle control devices such as the engine control device 115 to be implemented.

The inventive function of the control device 208 (or the control device (s) in which the present invention is implemented) is in addition to the dependence of the sensor signals from a sensor 210 For example, to determine a concentration and / or fraction of a substance is likely to depend, for example, on information received from a PM sensor, for example, and the control device (s) controlling the engine function, ie, the control device in the present example 115 , Control devices of the type illustrated are normally arranged to receive sensor signals from various parts of the vehicle. For example, the control device 208 Sensor signals as above and from other control devices than the control device 115 receive. Such control devices are also usually adapted to send control signals to various parts and components of the vehicle. For example, the control device 208 Signals to the engine control device, for example 115 send out.

The controller is often controlled by programmed instructions. These programmed instructions typically consist of a computer program which, when executed in a computer or control device, causes the computer / controller to perform the desired control as a process step in the process in accordance with the invention.

The computer program usually consists of a computer program product, the computer program product being an applicable storage medium 121 includes (see 1B ), where the computer program product 109 on the storage medium 121 is stored. The digital storage medium 121 For example, it may consist of one of the following groups: a ROM (Read-Only Memory), a Programmable Read-Only Memory (PROM), an Erasable PROM (Erasable Programmable Nur Read-only memory), a flash memory, EEPROM (Electrically Erasable PROM), a hard disk unit, etc., and may be arranged in or in combination with the control device, the computer program being executed by the control device , By changing the instructions of the computer program, the behavior of the vehicle can thus be adapted to a particular situation.

An exemplary control device (control device 208 ) is in 1B shown, and the control device may in turn a computing unit 120 may for example consist of a suitable type of processor or microcomputer, such as a digital signal processing circuit (digital signal processor, DSP) or a circuit with a specific function (application-specific integrated circuit, ASIC). The arithmetic unit 120 is with a storage unit 121 connected, for example, for the arithmetic unit 120 the stored program code 109 and / or the stored data provides the computing unit 120 needed to be able to perform arithmetic operations. The arithmetic unit 120 is also set up for intermediate or final results of the arithmetic operations in the memory unit 121 save.

Furthermore, the control device is for receiving and transmitting input and output signals with the devices 122 . 123 . 124 . 125 fitted. These input and output signals may include waveforms, pulses or other attributes provided by the devices 122 . 125 for receiving input signals referred to as information for processing by the computing unit 120 be recognized, be recognized. The devices 123 . 124 for transmitting output signals are arranged for the calculation result from the arithmetic 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 to be output. Each of the connections to devices for receiving and transmitting input and output signals may be from one or more cables or data buses, such as a Controller Area Network (CAN) bus, a Media Oriented Systems Transport (MOST) bus, or other bus configuration a wireless connection.

According to the above, the reliability for signals of the PM sensor can be increased according to the present invention by evaluating the signal output from the PM sensor. 3 shows a first exemplary embodiment according to the invention 300 , The procedure begins with step 301 , which determines if the PM sensor 213 to be evaluated. If the PM sensor 213 is to be evaluated, the process continues with step 302 continued. The transition from step 301 to step 302 For example, it can be set up so that it passes through the Time is controlled since a previous evaluation of the PM sensor 213 has passed. The PM sensor 213 may also be arranged to be continually evaluated, at applicable intervals, at each vehicle start-up or other appropriate time, for example, if, for some reason, for example, based on emitted PM sensor signals or signals from other sensors / units, that the PM sensor does not send any representative signals.

In step 302 will be a change of the PM sensor 213 emitted signal S ₁ detected, wherein the emitted signal S ₁ generally represents particulate matter in the exhaust stream. This change can for example be represented by a frequency for an amplitude fluctuation, ie the emitted signal S ₁ can have amplitude peaks with a certain frequency. This determination can be determined, for example, by the applicable signal processing. The in step 302 The change detected may also be due to some other applicable determination, such as the determination of an amplitude change that has occurred, for subsequent comparison with an expected change according to the following statements.

If the change is that of the PM sensor 213 emitted signal S ₁ in step 302 has been determined, the method continues with step 303 continued. In step 303 a corresponding change in the supply of additives in the exhaust gas flow is detected. This change may for example consist of a determination of the frequency in which the additives are supplied to the exhaust gas stream. The metering of the additive is normally achieved by use of an injector mounted, for example, in the exhaust system, and the injection is carried out with an applicable injection duration of an applicable frequency, for example a frequency of the interval 0.1 to 10 Hz. This information can be obtained, for example, from the part of the control system which is responsible for the metering of additives into the exhaust gas flow, which according to one embodiment can consist of the same control device in which the present invention is implemented. The change in the supply of additives may for example also consist of a change in the injection frequency or a change in the injected amount of additive or any applicable combination of these changes. The change in the additive supplied may be controlled by factors separate from the present invention, such change being only observed, but the change may also be arranged to be carried out in accordance with the invention by a separate step, step 303 in 3 is preceded, is regulated.

The procedure then sets in step 304 , wherein the change in the signal emitted by the PM sensor is compared with the change in the supply of additives. For example, the frequency of the amplitude peaks of the signal emitted by the PM sensor can be compared with the metering frequency. When these frequencies coincide with each other to an applicable extent, it can be assumed that the PM sensor is making measurements in the exhaust gas stream to which the additives are supplied and therefore it is most likely exposed to a representative exhaust gas flow. Also, a change in amplitude during an applicable period of time in the signal emitted by the PM sensor may be compared to an expected amplitude change caused by the change in the amount of additive added. In step 305 it is determined if the comparison indicates that the PM sensor 2013 sends a representative signal, and if so, the process goes to step 301 continued. If, on the other hand, the comparison indicates that the PM sensor 213 sends no representative signal, the method continues with step 306 in which an error signal, for example an alarm signal and / or error code, is generated, thus the control system of the vehicle 100 indicating that it can not be assumed that the PM sensor 213 emits a representative signal because it is not assumed to be exposed to a representative exhaust gas flow.

The generated signal may be, for example, from the control system of the vehicle 100 be used to check the status of the vehicle 100 to put in a status in which the vehicle 100 has an immediate need for maintenance, so the PM sensor 213 works. The control system can also be set up for the functionality of the vehicle 100 to restrict, for example, by limiting the maximum power of the engine 101 of the vehicle 100 until the error is resolved. The procedure is then in step 307 completed.

According to the in 3 In the embodiment shown, an active measure, which is specially provided to change the supply of additives, can be carried out, but does not have to be carried out, and the determination according to the invention can be carried out if the vehicle is driven in such a way that it is already in use detectable change in the supply of additives, for example, achieved by the pulsation, which normally occurs in the supply of Additives or when changing the amount of additives is applied.

In 4 is an exemplary embodiment of the invention 400 shown in which a change in the supply of additives is actively implemented.

The procedure begins in step 401 and the transition to step 402 can be controlled as described above. In step 402 For example, an initial representation P _{1 of} the particulate matter in the exhaust stream is determined using the PM sensor 213 detected.

When the particulate matter P ₁ in step 402 has been determined, the method continues with step 403 continued. In step 403 a change in the supply of additives is made. This change can be made in various ways and, according to one embodiment, involves completely shutting off the supply of additives into the exhaust stream or changing the amount of additives supplied to the exhaust stream. According to one embodiment, the supply of additives may instead be switched off or in one step, the step 403 precedes, be shut off, and the feed can be in step 403 be reactivated. According to the above, for example, the injection frequency or the amount of the supplied additives may also be changed.

According to one embodiment, however, no action is taken which is specifically intended to change the supply according to the invention, instead, in step 403 expects that the applicable change in the feed additives will be for another reason controlled by the vehicle control system, such change being one of the examples herein or another applicable change.

In one embodiment, the method continues with a step where the method waits for an initial period t ₁ to compensate for potential delays in the system such that the effects of the previously added additives are reduced or at least reduced. The initial period may be controlled, for example, by the position of the additive injector in the exhaust system with respect to the PM sensor and the number / type of components installed therebetween.

The time period t ₁ may be short, and according to the embodiment, this waiting step is not applied.

The procedure then sets itself apart 403 with step 405 in which a second representation of the particulate matter in the exhaust stream using the PM sensor 213 is determined, ie, a particle concentration P ₂ is the PM sensor 213 after the measure to change the intake of additives has been completed.

In step 405 Then, an expected change ΔP _{exp of} the PM sensor signal is detected (at the position of the PM sensor 213 after the change in step 403 was performed on the supply of additives, and the change ΔP ₁₂ in step 406 between the initial P ₁ and the second particle concentration indicated by the PM sensor P ₂ is compared with the expected change in the particle concentration (change in the sensor signal) ΔP _exp . Even if certain particle concentrations P ₁ , P ₂ can be detected, this is not a requirement; in principle, it suffices to establish applicable representations of the particle concentrations P ₁ , P ₂ on the basis of which the particle concentration change ΔP ₁₂ can be determined (obviously the particle concentrations as such are not necessarily correct, since at least one of the detected particle concentrations is due to cross-sensitivity to the additive) can be influenced and thus emit a higher or significantly higher specified particle concentration than is actually the case.)

It is thus sufficient to detect a signal difference between the various determinations, wherein this signal difference can be converted into a particle concentration difference or compared with an expected signal difference. The same applies to the expected particle concentration change ΔP _exp , ie it is sufficient to determine an expected difference without particularly determining between which actual values / particle concentrations an occurrence of the difference is expected.

The expected particle concentration change Δ _Pexp may be determined, for example, by looking up a table, where the signal emitted by the PM sensor, which is expected for different dosages, may be indicated, and this expected particular signal may represent the signal difference that the additive as such due to cross-sensitivity caused as expected, and thus forms the difference signal caused by the additive.

In step 406 the actual particle concentration change (sensor signal change) ΔP _{12 is} then compared with the expected particle concentration change ΔP _exp , wherein a discrepancy A between the expected Particle concentration change ΔP _exp and the measured particle concentration change ΔP _{12 is} detected.

In step 407 it is determined whether the discrepancy A between the expected particle concentration change ΔP _exp and the measured particle concentration change ΔP _{12 is} greater than an applicable limit A _lim . For example, the threshold A _lim may be set in such a manner that a large discrepancy that may be applicable may be allowed to unnecessarily avoid alarming the function of the PM sensor 213 because the particle concentration change that the PM sensor will report due to the additive is difficult to predict with the desired accuracy.

As long as this is not the case, ie as long as the discrepancy A is below the limit A _lim , it can be assumed that the PM sensor 213 representative measured values with respect to the fine dust in the exhaust gas flow, since it can be assumed that the PM sensor 213 is located at a position where the PM signal fluctuates in an expected manner and is thus likely to be in the intended position in the exhaust gas flow, thus performing measurements of a representative exhaust gas flow. The procedure goes with step 401 Continue to redetermine the function of the PM sensor 213 in the applicable time as above.

If, on the other hand, in step 408 it is determined that the discrepancy A is greater than the limit A _lim , the method continues with step 408 continued. In step 408 an error signal is generated as in the above description, and the method is entered in step 409 completed.

Thus, according to the invention, a method is provided that can be used to determine if the PM sensor 2013 emits a representative signal by determining whether it is exposed to a representative exhaust gas flow, as determined by determining whether the emitted signal from the PM sensor 213 changes with a change in the intake of additives in the expected manner.

Thus, with the aid of the present invention, an attempt may be made to manipulate the function of the PM sensor 213 be set, for example, by moving the PM sensor to a position outside of the exhaust stream, alternatively, for example, by guiding the exhaust stream at the PM sensor 213 passing during the operation of the vehicle 200 is detected because the PM sensor will show no change in the emitted signal in such a manipulation compared to a correctly positioned PM sensor, where there is a change in the additives supplied. The invention thus reduces the possibilities of unnoticed manipulation of the aftertreatment system.

With respect to the methods described above, a comparison was made on one occasion. Obviously, the fine dust in the exhaust stream 200 also vary significantly depending on other factors such as the current operating parameters of the internal combustion engine, wherein a measured single particle concentration change under unfavorable conditions of the expected particle concentration change by more than the discrepancy can change arm, even if the PM sensor 213 installed correctly in the exhaust stream and exposed to a representative exhaust stream.

For this reason, a series of values can be determined as above. For example, each method may be arranged to iterate through an applicable number of times x, for example, a relatively large number of times x, where x measurements and thus x discrepancies A are determined, with an integrated total discrepancy determined for these x discrepancies can be compared with the discrepancy threshold A _lim and the total integrated value is used to determine if the PM sensor can be assumed 213 is exposed to a representative exhaust gas flow.

The discrepancy A _lim can also be set up to fluctuate according to the number of measured values x. The greater the number of measured values x used, the lower the permissible discrepancy A _{lim may be} set, since the integrated overall accuracy increases with the number of measured values x.

In one embodiment, a series of determinations are made instead, for example, at regular or appropriate intervals, comparing the change in the PM sensor signal over time with an expected change in the PM sensor signal. In this case, discrepancies for each measured value can also be determined and compared with the expected value. Discrepancies can also be compared, and as long as the discrepancies are significantly similar, it can still be assumed that the PM sensor has been positioned correctly.

It can thus not only be determined that the PM sensor 213 is positioned in an exhaust gas composition, but also that the PM sensor 213 is disposed within an exhaust stream whose composition with the fluctuating operating conditions in a representative manner.

The present invention also has the advantage that a determination according to the invention is carried out regardless of the position of the PM sensor in the exhaust system, as long as the change in the supplied additives is carried out upstream of the PM sensor.

According to one embodiment, a frequency analysis is used to determine if the PM sensor 213 sends a representative signal. This frequency analysis can be done by means of an applicable transformation such as a Fourier transform or FFT (fast Fourier transform). As mentioned above, injection of additives is usually carried out at a certain frequency, such as a frequency in the interval 0.1 to 10 Hz. This means that the additive is "pulsed" into the exhaust stream, and over time, pulse-like differences in the additive content of the exhaust stream occur. This also means that the pulsation causes fluctuations in the concentration at the same frequency as for the additive, which is also used above, but which can be used in a way that ensures reliable detection.

Instead, if the PM sensor signal is evaluated in the frequency domain, injection pulsing may be clarified and used in the present invention.

The pulses of the additives, in accordance with the above, become visible as amplitude fluctuations at a frequency equal to the injection frequency. Thus, in the frequency domain, a spike / peak may occur at the frequency (as the frequency is repeated, weaker shadow pulses may also occur).

This frequency analysis can thus be used, at least in certain cases, to improve the reliability of the diagnosis of the PM sensor, because if this pulsation can be detected, it can also be assumed that the PM sensor is exposed to a representative exhaust gas flow , The frequency analysis can be used alone or in combination with a comparison with a threshold as above, this threshold can be set in the time domain or in the frequency domain. By performing the determination in the frequency domain, the detection is possible with less fluctuation, that is, a smaller limit A _lim can be used.

Since the injection frequency can vary according to the method of the invention, fluctuations in the frequency domain can also be actively used to give a more reliable diagnosis. For example, if A _lim , for an injection frequency is exceeded, a pending error may be adjusted so that one or more further diagnostics may be performed for further injection frequencies before the disturbance is finally determined.

In frequency analysis, the closer the pulse source is to the analysis, the more reliable the result obtained from the analysis.

According to this embodiment, the frequency analysis constitutes a representation of a change in the signal received from the PM sensor 213 is sent out.

In addition, there are various types of PM sensors, and the present invention is applicable to all types of PM sensors having cross-sensitivity to additives. For example, there are so-called IDE sensors in which conductive materials coated ceramic plates are used to detect a particulate content for a passed exhaust stream. As a particulate exhaust flow passes through the coated ceramic plates, particles stick together, which in turn causes the conductivity to change between the two adjacent non-contacting plates. When particles (soot) stick to these plates, the conductivity increases, resulting in that, for example, a resistance, a current, a voltage, a conductivity or inductance or the like can be detected, and changes in the relevant magnitude indicate the content of the particles. By determining a gradient for the change over time, the particle content can be estimated by determining how rapidly, for example, the resistance, current, or voltage changes. This type of particle sensor thus results in a relatively slow detection of particulate matter, and it may take a long time before the disturbance is detected. According to the invention, however, a manipulation of this type of sensor can be detected at an early stage.

There are also other types of particle sensors, such as electrostatic particle sensors, in which particles pass through a first electrode to pick up a charge and then pass through a second electrode set up in the particle sensor where the charge is delivered. Thus, depending on the particle content, the number of electrons per unit time transferred between electrodes varies, and therefore both the particle content and the number of particles can be determined with immediate and very high accuracy.

In one embodiment, this type of particulate sensor is used to determine the concentration and / or fraction of particulates in the exhaust stream. Thanks to the speed of the sensor very good measurements of the current values can be made, i. H. Very good values can be obtained that represent the instantaneous particle content.

In addition, the method according to the invention can be combined with the method described in US Pat Swedish Application No. 1250961-8 entitled " METHOD AND SYSTEM PERTAINING TO EXHAUST AFTER TREATMENT " by the same inventor and filing date to set a sensor function for a PM sensor. According to the application "METHOD AND SYSTEM PERTAINING TO EXHAUST AFTER TREATMENT", a method is provided for determining if a PM sensor is emitting a representative signal, wherein the sensor function for the PM sensor is determined based on a representation of a pressure present in the PM sensor is, wherein the pressure is determined by a pressure sensor arranged in the PM sensor.

In addition, the method according to the invention can be combined with the method described in US Pat Swedish Application No. 1250963-4 entitled "METHOD AND SYSTEM PERTAINING TO EXHAUST AFTERTREATMENT II" by the same inventor and filing date, to establish a sensor function for a PM sensor. According to the application "METHOD AND SYSTEM PERTAINING TO EXHAUST AFTERTREATMENT II", a method is provided for determining whether a PM sensor is emitting a representative signal in which a representation of a concentration by the PM sensor and / or a fraction of a substance, which occurs in the exhaust stream is detected. Based on the detected representation of a concentration and / or a fraction of the first substance, it is determined whether the PM sensor is emitting a representative signal.

Also, the method according to the invention can alternatively or additionally be combined with the method described in US Pat Swedish Application No. 1250964-2 entitled "METHOD AND SYSTEM PERTAINING TO EXHAUST AFTERTREATMENT III" by the same inventor and date of filing as the present application, for detecting a sensor function for a PM sensor. According to the application "METHOD AND SYSTEM PERTAINING TO EXHAUST AFTERTREATMENT III", a method is provided for determining whether a PM sensor is emitting a representative signal, wherein the sensor function for the PM sensor is detected using elements to obtain a representation of a PM sensor To determine the temperature at the PM sensor.

By combining the method of the invention with one or more of the methods described above, a more reliable evaluation of the function of the PM sensor can be performed.

The present invention has been described above with respect to certain additives. However, PM sensors may also be cross-sensitive to other types of additives, and the present invention is also applicable to such additives.

In addition, the present invention has been described above by way of example with reference to vehicles. However, the invention is applicable to all transportation means / processes in which particulate filter systems such as the above are applicable, such as water and air vehicles with combustion process as above.

In addition, the internal combustion engine may for example consist of at least one of the group: motor vehicle engine, marine engine, industrial engine, diesel engine, gasoline engine, gasoline engine with direct injection, gas engine.

Other embodiments of the method and system of the invention are available in the claims contained herein.

It should also be understood that the system may be varied according to various embodiments of the method of the invention (and vice versa) and that the present invention is by no means limited to the embodiments of the inventive method described above, but to all embodiments within the scope of the appended claims Claims and this includes.

Claims (28)

Method for determining a sensor function for a PM sensor ( 213 ) for determining a particulate content in an exhaust stream resulting from combustion in an internal combustion engine ( 101 ) is provided, wherein an aftertreatment system ( 202 ) is installed for post-treatment of the exhaust stream and the vehicle comprises elements for the supply of additives into the exhaust stream and the method is characterized by the step: - detecting a change in a signal coming from the PM sensor ( 213 ) is emitted in response to a change in the supply of additives, and Based on the change in the signal emitted by the PM sensor, determining whether the PM sensor ( 213 ) emits a signal that is representative of the exhaust gas flow. The method of claim 1, further comprising performing a series of sequential changes in the delivery of the additive to the exhaust stream and, based on similarly detected changes in the signal emitted by the PM sensor, determining whether the PM sensor (FIG. 213 ) emits a signal that is representative of the exhaust gas flow. The method of claim 1 or 2, wherein the change in the supply of additives to the exhaust gas stream comprises an increase or decrease in the amount of added additives. The method of any one of claims 1 to 3, wherein the change in the supply of additive to the exhaust stream comprises a change in a frequency for the supply of additives to the exhaust stream. The method of any preceding claim, wherein the change in the supply of additives to the exhaust stream comprises shutting off the supply of additives or resuming supply after shutting off the supply of additives. Method according to one of claims 1 to 5, wherein the PM sensor ( 213 ) consists of an electrostatic or resistive PM sensor. Method according to one of claims 1 to 6, further comprising determining a representation of a change (ΔP ₁₂ ) in the signal transmitted by the PM sensor ( 213 ) is emitted in response to the change in the supply of additive, - comparing the representation of the change (ΔP ₁₂ ) in the signal received from the PM sensor ( 213 ) with a representation of an expected change (ΔP _exp ) of the PM sensor ( 213 ) emitted signal, and - based on the comparison of the representation of the change (ΔP ₁₂ ) in the signal of the PM sensor ( 213 ) with the representation of the expected change (ΔP _exp ) of the PM sensor ( 213 ) signal, determining whether the PM sensor ( 213 ) emits a signal representative of the exhaust gas flow. Method according to claim 7, also comprising, when the representation of the first change (ΔP ₁₂ ) in the PM sensor ( 213 ) signal is detected, - detecting a first of the PM sensor ( 213 ) Emitted representation of a particle content (P ₁₎ at an initial time point, - at a second time which is separated from the first time, determining a second (from the PM sensor 213 ) representation of a particle content (P ₂ ), wherein the change (ΔP ₁₂ ) at the PM sensor ( 213 ) emitted signal from a difference between that of the PM sensor ( 213 ) emitted first (P ₁ ) and second representation (P ₂ ) of a particle content. Method according to one of claims 1 to 8, also comprising determining a change (ΔP ₁₂ ) in the case of the PM sensor ( 213 ) emitted signal at a number of times. Comparing the respective detected change (ΔP ₁₂ ) with that of the PM sensor ( 213 ) signal with a similar expected change (ΔP _exp ) at the PM sensor ( 213 ) signal and, based on the number of comparisons, determining whether the PM sensor ( 213 ) emits a signal that is representative of the exhaust gas flow. Method according to one of claims 1 to 9, also comprising determining, based on the detected change in the PM sensor ( 213 ) emitted signal in response to the change in the supply of the additive, whether it can be assumed that the aftertreatment system ( 200 ) and / or the PM sensor ( 213 ) were manipulated. Method according to one of claims 1 to 10, also comprising determining whether the PM sensor ( 213 ) emits a signal representative of the exhaust flow by determining, based on the change in the signal emitted by the PM sensor in response to the change in the supply of additives, whether the PM sensor ( 213 ) is located in the exhaust stream. Method according to one of the preceding claims, also comprising: - detecting the change in the signal emitted by the PM sensor by means of a frequency analysis of the signal emitted by the PM sensor, wherein the frequency analysis of the frequency-analyzed PM signal is compared with an injection frequency for the supply of additives. The method of claim 12, further comprising performing the frequency analysis for a number of injection frequencies for the supply of additives to the exhaust stream. The method of claim 12 or 13, wherein during the frequency analysis, a frequency for an amplitude peak in the frequency domain with the Injection frequency for the supply of additives to the exhaust stream is compared. Method according to one of the preceding claims, comprising generating a signal indicative of a disturbance in the PM sensor ( 213 ) if the change in the signal sent by the PM sensor shows no expected change. Method according to one of the preceding claims, wherein the aftertreatment system ( 200 ) at least one particle filter ( 202 ) and wherein the intended position of the PM sensor upstream or downstream of the particulate filter ( 202 ) is in the exhaust stream. The method of claim 1, wherein the internal combustion engine comprises an engine in a vehicle, and wherein the output from the internal combustion engine is limited by the use of an in-vehicle control system when the PM sensor does not emit a signal representative of the exhaust flow , Method according to one of the preceding claims, in the event of a change in the supply of the additive also comprising: - waiting for an initial period (t1) before the change in the time of the PM sensor ( 213 ) emitted signal is detected. Method according to one of the preceding claims, also comprising determining a representation of an initial concentration in the PM sensor and / or a fraction of a starting material (S ₁ ) in the exhaust gas stream using the elements provided in the PM sensor for determining a representation of a concentration and / or Fraction of the starting material (S ₁ ), and element, also based on the change in the detected representation of a concentration of the first substance (S ₁ ), for determining whether the PM sensor is emitting a signal representative of the exhaust gas flow. Method according to one of the preceding claims, wherein the method also comprises: - Establishing a representation of the first pressure in the PM sensor by means of a pressure sensor arranged in the PM sensor, and - Determine if the PM sensor is emitting a signal representative of the exhaust flow, also based on the detected first pressure. Method according to one of the preceding claims, wherein the method also comprises: - detecting a first temperature at the PM sensor by means of elements installed in the PM sensor in order to obtain a representation of a PM sensor ( 213 ) to determine whether the PM sensor is emitting a signal representative of the exhaust gas flow, also based on the detected first temperature. Method according to one of the preceding claims, wherein the additive consists of urea or ammonia. A computer program comprising program code which, when executing the program code in a computer, causes the computer to carry out the method according to one of the claims 1 to 22. A computer program product comprising a computer readable medium and a computer program according to claim 23, wherein the computer program is contained in the computer readable medium. System for detecting a sensor function for a PM sensor ( 213 ) for determining a particulate content in an exhaust gas stream resulting from combustion in an internal combustion engine ( 101 ), whereby an aftertreatment system ( 202 ) is installed for post-treatment of the exhaust gas stream and the vehicle comprises an element for the supply of additives into the exhaust stream, characterized in that the system comprises: an element which is arranged so that it is at one of the PM sensors ( 213 ) detected a change in response to a change in the supply of additives, and - an element which is adapted to determine based on the change in the signal emitted by the PM sensor, whether the PM sensor ( 213 ) emits a signal that is representative of the exhaust gas flow. System according to claim 25, characterized by the internal combustion engine, which consists of at least one of the group: motor vehicle engine, marine engine, industrial engine, diesel engine, gasoline engine, gasoline engine with direct injection, gas engine. The system of claim 25 or 26, wherein the additive delivery elements are installed upstream of the PM sensor. Vehicle ( 100 ), characterized in that it comprises a system according to any one of claims 25 to 27.

Images