WO2014035323A1

WO2014035323A1 - Method and system to establish a sensor function for a pm sensor

Info

Publication number: WO2014035323A1
Application number: PCT/SE2013/051005
Authority: WO
Inventors: Ola Stenlåås
Original assignee: Scania Cv Ab
Priority date: 2012-08-30
Filing date: 2013-08-28
Publication date: 2014-03-06
Also published as: DE112013003885T5; DE112013003885B4

Abstract

The present invention pertains to a method to establish a sensor function for a PM sensor (213) intended for the determination of a particle concentration in an exhaust stream resulting from combustion in a combustion engine (101), where the said PM sensor (213) comprises elements to produce a representation of the temperature prevailing in the said PM sensor (213), and where an aftertreatment system (200) is installed for aftertreatment of the said exhaust stream. The method comprises, when the temperature for the said PM sensor (213) is essentially not affected by sensor-internal heating elements : - establishing a representation of a first temperature change ( ΔΤ₁₂ ) at the said PM sensor (213), - comparing the said representation of the said first temperature change (ΔΤ12) with a representation of an expected temperature change (ΛΤ_exp) in the said PM sensor (213), and - based on the said comparison of the said representation of the said first ( ΔΤ₁₂ ) temperature change with the said representation of the said expected temperature change (ΔΤ_exp), establishing whether the said PM sensor (213) emits a signal which is representative of the said exhaust stream. The invention also relates to a system and a vehicle.

Description

Method and system to establish a sensor function for a PM sensor

Field of the invention

The present invention pertains to a system for the treatment of exhaust streams resulting from a combustion process, and i] particular to a method by which a sensor function for a PM sensor is confirmed according to the preamble of patent claim 1. The invention also relates to a system and a vehicle, as well as a computer program and a computer program product, which implement the method according to the invention.

Background of the invention

In connection with increased government interests concerning pollution and air quality, primarily in metropolitan areas, emission standards and regulations have been drafted in many j urisdictions .

Such emission regulations often consist of requirements which define acceptable limits for exhaust emissions in vehicles equipped with combustion engines. For example, levels of nitrogen oxides (NO_::) , hydrocarbons (HC) and carbon monoxide (CO) are often regulated. These emission regulations usually also pertain to, at least in relation to certain types of vehicles, the presence of particles in exhaust emissions.

In an effort to fulfil these emission regulations, the exhausts caused by the combustion of the combustion engine ar treated (purified) . By way of example, a so-called catalytic purification process may be used, so that aftertreatment systems in e.g. vehicles and other vessels usually comprise one or more catalysts.

Further, such aftertreatment systems often comprise, as an alternative to or in combination with a single or several catalysts, other components. Aftertreatment systems in vehicles with diesel engines, for example, often comprise particulate filters.

The combustion of fuel in the engine combustion chamber (e.g. cylinders) forms soot particles. According to the above, there are emission regulations and standards also pertaining to these soot particles, and in order to comply with the

regulations, particulate filters may be used to catch soot particles. In such cases, the exhaust stream is led e.g.

through a filter structure where soot particles are caught from the exhaust stream passing through for storage in the particulate filter.

Thus, there are numerous methods to reduce emissions from a combustion engine. In addition to regulations pertaining to emission levels, legislative requirements regarding so-called OBD systems (On-Board Diagnostics) are increasingly common, ensuring that vehicles actually comply with regulatory requirements regarding emissions in their daily operation, and not just during e.g. visits to a garage.

In relation to particle emissions, this may be achieved e.g. with the help of a particle sensor installed in the exhaust system or the aftertreatment system, referred to below in the description and patent claim as a PM sensor (PM = Particulate Matter, Particulate Mass), which measures the particle concentration in the exhaust stream. Particle concentration may be determined e.g. as a particle mass per volume or weight unit, or as a certain number of particles of a certain size per volume unit, and several determinations of the amount of particles of varying sizes may be used to determine particle emission . Aftertreatment systems with particulate filters may be very efficient, and the resulting particle concentration after the passage of the exhaust stream through the aftertreatment system of the vehicle is often low with a fully functional aftertreatment system. This also means that the signals which the sensor emits will indicate a low or no particle emission.

Summary of the invention

One objective of the present invention is to provide a method to establish a sensor function for a PM sensor intended to determine a particle concentration in an exhaust stream resulting from combustion in a combustion engine. This objective is achieved with a method according to patent claim 1.

The present invention pertains to a method to establish a sensor function for a PM sensor intended for the determination of a particle concentration in an exhaust stream resulting from combustion in a combustion engine, where the said PM sensor comprises elements to produce a representation of the temperature prevailing in the said PM sensor, and where an aftertreatment system is installed for aftertreatment of the said exhaust stream. The method comprises, when the

temperature for the said PM sensor is essentially not affected by sensor-internal heating elements:

- establishing a representation of a first temperature change in the said PM sensor,

- comparing the said first representation of the said

temperature change with a representation of an expected temperature change in the said PM sensor, and

- based on the said comparison of the said representation of the said first temperature change with the said representation of the said expected temperature change, establishing whether the said PM sensor emits a signal which is representative of the said exhaust stream. As mentioned above, PM sensors may be used to ensure that the level of particles in the exhaust stream resulting from the combustion engine does not exceed stipulated levels.

In order to ensure that the presence of particles in the exhaust stream is below the stipulated level, the PM sensor must, however, emit a correct signal. A PM sensor may be set up at various points in the exhaust stream, 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 small. This applies e.g. to a PM sensor which is set up downstream from a particulate filter, where a correctly functioning particulate filter is often capable of separating a very significant part of the particles emitted from the combustion engine's combustion chamber. This in turn means that it may be difficult to differentiate a situation where the particulate filter is functioning

correctly, but where the presence of particles downstream from the particulate filter is very small, from a situation where the PM sensor indicates a low concentration because of actual malfunction of the PM sensor or lack of a representative signal for another reason.

There may be several reasons why a PM sensor does not emit a representative signal, i.e. not only a malfunction of the PM sensor causing a lower concentration than what is actually the case. However, the PM sensor may, as such, emit a signal representative of the environment in which the PM sensor is located, where the PM sensor and/or the aftertreatment system have been manipulated so that the sensor no longer measures particle concentration 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 particle concentration in the vehicle's surroundings. In such cases, the PM sensor will always emit a signal representing a very low or no particle concentration

regardless of the actual particle concentration of the exhaust stream.

Another way of manipulating the signal emitted by the PM sensor in order to reduce the detected particle concentration is to divert all or part of the exhaust stream past the PM sensor so that the latter is no longer exposed to a

representative exhaust stream. In this manner, the PM sensor may also be induced to emit signals representing a lower particle concentration than what is actually the case. Another way of manipulating the sensor signal is by blocking the sensor so that the exhaust stream is not led through the sensor .

Thus, there are numerous ways of manipulating a PM sensor, and since the PM sensor as per the above may be placed in such a way that only a very small particle concentration is detected, it may be difficult to determine whether or not the sensor has been manipulated.

According to the present invention, a method is provided in order to determine whether the PM sensor may be assumed to emit a representative signal and to determine whether the sensor is faulty or if it has been manipulated.

This is achieved according to the present invention by using elements installed in the PM sensor to determine a

representation of the temperature prevailing in the PM sensor. These elements for the determination of a temperature may be integrated with the PM sensor, i.e. may use joint components such as substrate or similar, or e.g. consist of a separate temperature sensor incorporated into a joint housing with the PM sensor.

PM sensors may also comprise elements to heat the PM sensor, e.g. in order to regenerate (clean) the PM sensor of gathered soot particles, where needed. According to one embodiment, these elements are used to heat the PM sensor when the temperature is determined according to the present invention.

By determining a temperature change at the PM sensor, this temperature change may be compared with an expected

temperature change, and based on the comparison, it may be determined whether the PM sensor may be deemed to be subject to a representative exhaust stream, i.e. an exhaust stream which correctly reflects the composition in the exhaust stream which leaves the combustion chamber of the combustion engine. If e.g. a temperature increase is expected, e.g. due to an increased combustion engine load, while the PM sensor fails to show a similar temperature increase or even a temperature decrease, it may be assumed that the PM sensor was not exposed to a representative exhaust stream.

Further characteristics of the present invention and

advantages thereof will be described in the detailed

description of example embodiments set out below and the enclosed drawings.

Brief description of drawings

Fig. la shows a diagram of a vehicle in which the present invention may be used.

Fig. lb shows a control device in the control system for the vehicle in Fig. 1.

Fig. 2 shows the aftertreatment system in more detail for the vehicle in Fig. 1. Fig. 3 shows an example embodiment according to the present invention .

Fig. 4 shows a diagram of a PM sensor in which the present invention may be applied.

Detailed description of embodiments

The expression particle concentration comprises, in the description below and the subsequent patent claim,

concentration in the form of mass per unit and concentration as number of particles per unit. Further, the unit may be comprised of any applicable unit and the concentration may be expressed as, for example, mass or number of particles per volume unit, per mass unit, per time unit, per work completed or per distance travelled by the vehicle.

Fig. 1A shows a diagram of a driveline in a vehicle 100, according to an embodiment of the present invention. The diagram of the vehicle 100 in Fig. 1A comprises only one shaft with wheels 113, 114, but the invention is applicable also to vehicles where more than one shaft is equipped with wheels, and vehicles with one or more shafts, such as one or more support shafts. The driveline comprises one combustion engine 101, which in a customary manner, via an output shaft on the combustion engine 101, usually via a flywheel 102, is

connected to a gearbox 103 via a clutch 106.

The combustion engine 101 is controlled by the engine's control system via a control device 115. Likewise, the clutch 106, which may consist of e.g. an automatically controlled clutch, as well as the gearbox 103 are controlled by the vehicle's control system with the help of one or more

applicable control devices (not shown) . Naturally, the vehicle's driveline may also be of another type such as a type with a conventional automatic gearbox, etc. An output shaft 107 from the gearbox 103 drives the wheels 113, 114 via a final drive 108, such as a customary

differential, and driveshafts 104, 105 connected to the said final drive 108.

The vehicle 100 also comprises an exhaust system with an aftertreatment system 200 for treatment (purification) of exhaust emissions resulting from combustion in the combustion chamber (e.g. cylinders) of the combustion engine 101.

One example of an aftertreatment system 200 is displayed in more detail in Fig. 2. The figure shows the combustion engine 101 of the vehicle 100, where the exhaust generated by the combustion (the exhaust stream) is led via a turbocharger 220. In turbo engines, the exhaust stream resulting from the combustion often drives a turbocharger which in turn

compresses the incoming air to the cylinders' combustion.

Alternatively, the turbocharger may e.g. be of compound type. The function of various types of turbochargers is well-known, and is therefore not described in any detail herein. The exhaust stream is subsequently led via a pipe 204 (indicated with arrows) to a diesel particulate filter (DPF) 202 via a diesel oxidation catalyst (DOC) 205.

The DOC 205 may have several functions, and is normally used primarily in the aftertreatment to oxidise remaining

hydrocarbons and carbon monoxide in the exhaust stream into carbon dioxide and water. The oxidation catalyst 205 may also oxidise e.g. nitric oxide (NO) into nitrogen dioxide (NO^) , which is used for e.g. NO-based regeneration. Further

reactions may occur in an oxidation catalyst.

Also, the aftertreatment system may comprise more components than as exemplified above, as well as fewer, alternatively, other types of components. For example, the aftertreatment system may, as in the present example, comprise a SCR (Selective Catalytic Reduction) catalyst 201 downstream of the particulate filter 202. SCR catalysts use ammoniac (NH₃) , or a composition from which ammoniac may be generated/formed, as an additive to reduce the amount of nitrogen oxides NO_;; in the exhaust stream.

In the embodiment shown, the components DOC 205, DPF 202 and the SCR catalyst 201 are integrated into one and the same exhaust purification unit 203. However, it should be

understood that these components need not be integrated into one and the same exhaust purification unit, but the components may be arranged in another manner, where suitable, and one or several of the said components may e.g. consist of separate units. Fig. 2 also shows temperature sensors 210-212 and a differential pressure sensor 209. The figure also shows a PM sensor 213, which in the present example is shown upstream of the exhaust purification unit 203 and also upstream of an exhaust brake 215. The PM sensor may also be set up downstream of the exhaust purification unit 203, as well as upstream of the turbocharger 220. According to the present invention, it is established whether the PM sensor 213 functions in the desired manner.

Additionally, the vehicle's exhaust system may comprise more than one PM sensor, which may be set up at various positions, and by virtue of which the functionality of all the PM sensors in the vehicle may be assessed. The PM sensor 213 is,

according to one embodiment of the present invention,

integrated or collocated with a temperature sensor 214, where the temperature sensor 214 is a temperature sensor fixedly connected with the said PM sensor 213 and/or incorporated in a joint housing with the said PM sensor 213, and where the temperature sensor 214 is adapted to establish a

representation of a temperature prevailing at the position of the PM sensor 213. According to one embodiment of the present invention, a heating element installed in the PM sensor 213 is used instead or in addition, which, when applicable, and according to the explanation below, is normally used to purify (regenerate) the PM sensor of accumulated particles (soot) .

As mentioned above, soot particles are formed during the combustion of the combustion engine 101, and these soot particles may in many cases not be emitted into the

environment surrounding the vehicle 100. The soot particles are caught by the particulate filter 202, which functions so that the exhaust stream is led through a filter structure where soot particles are caught from the passing exhaust stream and subsequently stored in the particulate filter 202. With the help of the particulate filter 202, a very large part of the particles may be separated from the exhaust stream.

The PM sensor 213 may be used to control that the particulate filter 202 functions in the desired manner, but also to monitor e.g. the functionality of the combustion engine 101 at e.g. a PM sensor position upstream from the particulate filter. The PM sensor 213 may also be used for other purposes.

However, in order for the particle occurrence determined with the help of PM sensor signals to be representative, the PM sensor 213 must emit signals which are representative of the environment in which the PM sensor is intended to be

installed .

The present invention increases the reliability of PM sensor signals by evaluating the environment of the PM sensor 213, which is achieved with the help of the temperature sensor and/or the heating element. Fig. 3 shows an example embodiment 300, according to the present invention, with the help of which the environment of the PM sensor 213, such as the exhaust stream surrounding the PM sensor 213, may be evaluated and incorrect sensor signals contingent on non-representative exhaust streams may be detected. The method is carried out according to the present example of the control device 208 shown in Fig. 1A-B and Fig. 2.

In general, control systems in modern vehicles consist of a communication bus system consisting of one or more

communications buses to connect a number of electronic control devices (ECUs) , such as the control devices, or controllers, 115, 208, and various components arranged on the vehicle. Such a control system may comprise a large number of control devices, and the responsibility for a specific function may be distributed among more than one control device.

For the sake of simplicity, Fig. 1A-B shows only the control devices 115, 208.

The present invention is thus in the embodiment displayed implemented in the control device 208, which in the embodiment displayed may be in charge of other functions as well in the aftertreatment system 200, such as regeneration (emptying) of the particulate filter 202, but the invention may thus also be implemented in a control device dedicated to the present invention, or wholly or partly in one or more other control devices already existing in the vehicle, such as the engine control device 115.

The function according to the present invention of control device 208 (or the control device (s) in which the present invention is implemented) will, in addition to depending on sensor signals from the temperature sensor and/or heating element for determination of a representation of a

temperature, likely depend on e.g. information which e.g. is received from a PM sensor and e.g. the control device (s) which control the engine's function, i.e. in the present example the control device 115. Control devices of the type displayed are normally arranged to receive sensor signals from different parts of the vehicle. The control device 208 may e.g. receive sensor signals as per the above, and from other control devices than the control device 115. Such control devices are usually also set up to emit control signals to different parts and components of the vehicle. For example, the control device 208 may emit signals to e.g. the engine control device 115.

Control is often controlled by programmed instructions. These programmed instructions typically consist of a computer program, which, when it is executed in a computer or control device, causes the computer/control device to carry out the desired steering, as a method step in the process according to the present invention.

The computer program usually consists of a computer program product, where the computer program product comprises an applicable storage medium 121 (see Fig. IB) with the computer program 109 stored on the said storage medium 121. The said digital storage medium 121 may e.g. consist of any from the following group: ROM (Read-Only Memory), PROM (Programmable Read-Only Memory) , EPROM (Erasable PROM) , Flash, EEPROM

(Electrically Erasable PROM), a hard disk unit, etc., and may be set up in or in combination with the control device, where the computer program is executed by the control device. By changing the computer program's instructions, the vehicle's behaviour may thus be adjusted in a specific situation.

An example control device (control device 208) is displayed in the diagram in Fig. IB, and the control device in turn may comprise a calculation unit 120, which may consist of e.g. a suitable type of processor or microcomputer, e.g. a circuit for digital signal processing (Digital Signal Processor, DSP) , or a circuit with a specific function (Application Specific Integrated Circuit, ASIC) . The calculation unit 120 is connected to a memory unit 121, which provides the calculation unit 120 with e.g. the stored program code 109 and/or the stored data which the calculation unit 120 needs in order to be able to carry out calculations. The calculation unit 120 is also set up to store interim or final results of calculations in the memory unit 121.

Further, the control device is equipped with devices 122, 123, 124, 125 for receipt and sending of input and output signals. These input and output signals may contain waveforms, pulses, or other attributes, which may be detected by the devices 122, 125 for the receipt of input signals that may be detected as information for processing of the calculation unit 120. The devices 123, 124 for sending output signals are arranged to convert the calculation result from the calculation unit 120 to output signals for transfer to other parts of the vehicle's control system and/or the component (s) for which the signals are intended. Each one of the connections to the devices for receipt and sending of input and output signals may consist of one or several cables; or bata buses, such as a CAN

(Controller Area Network) bus, a MOST (Media Oriented Systems Transport) bus, or any other bus configuration; or of a wireless connection.

According to the above, the reliability of emitted PM sensor signals may, according to the present invention, be increased by assessing the environment in which the PM sensor is located, and Fig. 3 shows an example embodiment 300 according to the present invention. The method 300, according to the invention, utilises the fact that the circumstances at various positions in the aftertreatment system, such as temperature, pressure and flow, may often be modelled/estimated with relatively good accuracy based on prevailing and/or historical operational parameters and applicable model descriptions of the aftertreatment system, where e.g. the expected temperature change at any given position in the aftertreatment system may be estimated based on the prevailing operational parameters. The method begins at step 301, where it is established 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 continues to step 302. The transition from step 301 to step 302 may e.g. be arranged to be controlled by the time elapsed since a previous evaluation of the environment of the PM sensor 213. The environment of the PM sensor 213 may also be arranged to be evaluated continuously, at applicable intervals, each time the vehicle starts or at other suitable times, e.g. if for any reason, e.g. based on PM sensor signals emitted or signals from other sensors/units, it may be

suspected that the PM sensor does not emit representative signals .

At step 302, a first prevailing temperature T_: at the PM sensor 213 is established, where the temperature T-_. is confirmed with the help of the said temperature sensor integrated with the PM sensor 213 or installed in the PM sensor 213, alternatively with the heating element installed in the said PM sensor.

Fig. 4 shows an example of the function of a PM sensor 213. The PM sensor 213 comprises a first 401 and second 402

electrode, which are produced with an electricity conducting material and which are installed on an insulating substrate 403 of applicable type. The electrodes 401 and 402,

respectively, generally exhibit a comb shape where the comb teeth overlap, as shown. When the exhaust stream passes the electrodes 401, 402 of the PM sensor 213, particles will get caught on the electrodes 401, 402, and as more and more particles attach to the electrodes, the electrical properties of the electrodes' connection with each other via the teeth will change because of the particles' higher conductivity compared to the insulating substrate. In e.g. the event the PM sensor is of resistive type, the resistance between the electrodes 401, 402 will decrease, because of the particles' conductivity, as more and more particles attach to the

electrodes 401, 402, where the change in conductivity may be confirmed in an applicable customary manner. By observing the change in conductivity over time, the particle presence in the exhaust stream may be estimated. In addition to the

determination of resistance, e.g. changes in tension,

conductivity, inductance, etc. may instead be used to confirm a particle content in the aftertreatment system.

By determining the change in conductivity over time, the particle content in the exhaust stream may thus be estimated. Over time, however, the electrodes 401, 402 of the PM sensor 213 will be saturated by particles, so that variations in resistance, etc. may no longer be detected, or at least not to the same extent. For this reason, PM sensors of the type shown in Fig. 4 must be regenerated, i.e. the electrodes 401, 402 must be "cleaned" (released) from accumulated particles. This is usually achieved by heating the electrodes 401, 402 to a relatively high temperature, so that the soot particles are burnt and the electrodes are "cleaned" for new determination of particle content. This heating of the electrodes 401, 402 may e.g. be achieved with the help of a heating element 404, which e.g. may be installed on the opposite side of the insulating substrate 403 (indicated with an arrow in the diagram) . The heating element 404, and therefore the

electrodes 401, 402 via the substrate 403, may be heated to a desired temperature by e.g. applying a desired voltage or current to the heating element 404 for an applicable duration. The PM sensor 213 may also comprise a separate temperature sensor 405, which according to the above may be used according to the present invention, and which, according to known technology, may be used to confirm that the heating element 404 is functioning in the desired manner so that the desired heating is also achieved. When the present invention is used, the heating element 404 is used in the reverse manner, where the passive heating of the heating element 404, caused primarily by the passing exhaust stream, may be read by e.g. reading a resistance change over the heating element 404, e.g. if the heating element is of type PTC or NTC. Obviously, similar temperature-dependent changes may be read also with other types of heating elements. Thus, according to the invention, no active heating of the heating element 404 is carried out.

When the temperature T, has thus been established at step 302, the method continues to step 303. At step 303, the exhaust stream is actively impacted. This may be achieved e.g. by changing the operation of the combustion engine 101. The operation of the combustion engine 101 may e.g. be altered by changing the load or operating point for a given load. For example, the operating point of the combustion engine 101 may be changed by changing one or several of the fuel injection times, fuel injection durations, fuel injection amounts, fuel pressure, number of injections, EGR and air supply,

ventilation times, compression conditions, overload, VGT position, engine speed, combustion engine load, etc.

Alternatively, or additionally, the combustion mode at the said combustion engine may be switched, e.g. from Otto to HCCI or from Diesel to PPC. Alternatively, the load may be

increased/reduced by e.g. connecting inactive combustion engine-dri en aggregates or disconnecting active combustion engine-driven aggregates.

By changing the manner in which the combustion engine 101 operates, or by otherwise impacting the exhaust stream, e.g. by throttling the exhaust stream upstream of the position of the PM sensor 213, e.g. with the help of the exhaust brake 215, the flow of the exhaust stream will also change. If e.g. the combustion engine 101 is induced to work harder or with a reduced efficiency, usually the exhaust stream's temperature will be increased, and consequently the temperature in/at the aftertreatment system's components increases, so that the temperature of the PM sensor 213 will also vary with the exhaust stream's temperature variations. In the reverse, the exhaust stream's temperature, and thus the temperature of components in the aftertreatment system will drop at a reduced combustion engine load or operation with higher efficiency. At step 303, an applicable change of the operation of the combustion engine 101 may thus be made, alternatively, another exhaust stream temperature impacting measure as described below, in such a manner that the temperature for the exhaust stream passing by the PM sensor is also affected, so that the temperature at the position of the PM sensor 213 is also affected. Preferably, a change resulting in a relatively large expected change of the exhaust stream's temperature when it passes by the PM sensor 213 is carried out.

Instead of changing the operation of the combustion engine 101, the exhaust stream may, as mentioned, be actively impacted in another manner in step 303. For example, one or several components upstream of the PM sensor 213 may be bypassed, alternatively, more components may be connected upstream of the PM sensor 213, so that the temperature prevailing at the PM sensor 213 will be affected, even if the exhaust stream remains unchanged, through the changed

temperature change which the exhaust stream will go through when it passes through the aftertreatment system's components on the way to the PM sensor 213.

The exhaust stream's temperature may also be impacted by throttling the exhaust flow with a restrictor, such as an exhaust brake, where the said restrictor may be installed upstream or downstream of an intended position for the said PM sensor 213.

Another example of how the exhaust stream's temperature may be impacted, with the help of e.g. an injector in the

aftertreatment system or via the combustion engine's

cylinders, is to supply unburned fuel to the aftertreatment system, so that this fuel may be oxidised in e.g. a DOC catalyst, as per the above, with associated temperature increases as a consequence.

According to one embodiment, however, no measure is taken which is specifically intended to change the temperature of the exhaust stream, instead the determination according to the present invention is carried out when the vehicle is driven in such a manner that a temperature change is expected anyway, e.g. in case of acceleration or uphill operation of the vehicle .

The method then continues to step 304, where a second

temperature Tj is confirmed, i.e. a temperature T₂ is confirmed at the PM sensor 213 after the said one or several measures to change the temperature of the exhaust stream have been carried out, or operation of the vehicle has been changed in another manner with the expected temperature increase in the exhaust stream as s consequence. At step 305 an expected temperature change is then confirmed Δ at the position of the PM sensor 213 after the measures taken at step 303 (alternatively, the time elapsed) , so that the change A _JJ at step 306 between the said first T, and second temperatures T₂ is compared to the expected temperature change Δ3ν_:;:,. Even if specific temperatures T_ir T₂ may be confirmed as per the above, this is no requirement, and in principle it is sufficient to confirm applicable

representations of the temperatures T_ir Tr, based on which the temperature change ΔΤ;_. may be confirmed. Thus, it is

sufficient to confirm a signal difference, where this signal difference may be converted to a temperature difference or compared to an expected signal difference. The same applies to the expected temperature change Δ2ν_{; /} i.e. it is sufficient to confirm an expected difference without specifically confirming between which actual levels/temperatures the difference is expected to arise.

This expected temperature change 3V_;;, may e.g. be established by table lookup, where the expected temperature T at the PM sensor's position may be specified for a number of different operational cases, such as different combinations of fuel injection times, fuel injection durations, fuel injection amounts, fuel pressure, number of injections, EGR and air supply, ventilation times, compression ratio, overcharging, VGT position, engine speed, combustion load, etc.

Alternatively, the expected temperature change may be

specified for various operational cases, where the expected change may also be specified e.g. as a temperature change per time unit. The expected temperature change Δ ΐ may also e.g. be confirmed by applicable calculation, e.g. based on models of combustion engine and/or aftertreatment system. At step 306, the actual temperature change ΔΤ^ is then compared to the expected temperature change ΔΤ._:::ρ, where the temperature difference confirmed through the use of the temperature sensor/heating element at the PM sensor 213 is compared with the temperature difference expected under prevailing conditions, where any discrepancy A between the expected temperature change ΔΓ^_:Γ, and the measured temperature change ΔΓ_/:-> is confirmed.

At step 307, it is then confirmed whether the discrepancy A between the expected temperature change ΔΤ_::ρ and the measured temperature change ΔΤ- is greater than any applicable limit m. The limit An,,, may e.g. be fixed in such a way that an applicably large discrepancy may be permitted in order to avoid giving rise unnecessarily to an alarm relating to the function of the PM sensor 213, since the composition of the exhaust stream may be difficult to predict with the desired accuracy .

Provided this is not the case, i.e. as long as the discrepancy A is below the limit An,,,, the method continues to step 308, where the applicable signal may be generated to indicate that the PM sensor 213 may be assumed to emit representative values regarding the particle content in the exhaust stream, since the PM sensor 213 may be assumed to be at a position where the temperature varies in the expected manner, and is thus likely also at the intended position in the exhaust system and therefore carries out measurements in a representative exhaust stream. The method resumes to step 301 in order to carry out a new determination of the function of the PM sensor 213 at the applicable time as per the above. Alternatively, the method may revert directly to step 301 from step 307, since the signal to indicate that the PM sensor 213 may be assumed to emit representative values regarding the particle content does not actually need to be generated, since this information may be assumed to be implicit as long as no signal indicating an erroneous sensor function has been obtained as per the below.

If, on the other hand, it is confirmed at step 307 that the discrepancy A is greater than the limit An,-,,, the method continues to step 309. At step 309, an error signal is generated, e.g. an alarm signal, in order for the control system of the vehicle 100 to indicate that the PM sensor 213 may not be deemed to emit a representative signal, since it is not deemed to be subjected to a representative exhaust stream. The signal generated at step 309 may e.g. be used by the control system of the vehicle 100 in order to place the status of the vehicle 100 to a status where the vehicle 100 is in immediate need of service for action by the PM sensor 213. The control system may also be arranged to limit the functionality of the vehicle 100, e.g. by limiting the maximum output of the combustion engine 101 of the vehicle 100 until the fault is remedied. The method is then completed at step 310.

According to the present invention, a method is thus provided which may be used to confirm whether the PM sensor 213 emits a representative signal by confirming whether it is subjected to a representative exhaust stream, which is confirmed by confirming whether the temperature of the PM sensor 213 changes in the expected manner at an expected temperature change .

With the help of the present invention, an attempt at

manipulating the function of the PM sensor 213 may thus be made by e.g. moving the PM sensor to a position outside the exhaust stream, alternatively, by e.g. leading the exhaust stream past the PM sensor 213 discovered during the operation of the vehicle 100, since the PM sensor will not, in the event of such manipulation, show any or a different temperature change compared to a correctly positioned PM sensor. The invention thus reduces the possibilities of manipulating the aftertreatment system unnoticed.

In the example in Fig. 3, a confirmed temperature change Τ₁₂ is compared with an expected temperature change Δ¾, on one occasion. Obviously, the temperature may vary significantly in the aftertreatment system 200 depending on e.g. the flow of the exhaust stream, oxidation of unburned fuel, etc., so that even if e.g. a table lookup or calculation as per the above is used to determine an expected temperature change AT_;: , a measured single temperature change in unfavourable conditions may differ from the expected temperature change by more than the said discrepancy Ann even though the PM sensor 213 is correctly installed in the exhaust stream and exposed to a representative exhaust stream.

For this reason, the method shown in Fig. 3 may be arranged to be completed a number of times in order to determine a number of measured values by carrying out a number of changes affecting the temperature. For example, each method may be set up to be completed an applicable number of times x, e.g. a relatively big number of times x, where x measured values are confirmed, and thus x discrepancies A, where an overall integrated discrepancy for these x discrepancies may be determined and compared with the discrepancy limit Ai_ira, and where the overall integrated value is used to confirm whether the PM sensor 213 may be assumed to be subjected to a

representative exhaust stream.

The discrepancy Ai_im may also be set up to vary according to the number of measured values x. The greater the number of measured values x used, the lower the permitted discrepancy A ,,, may be set, since the overall integrated accuracy

increases with the number of measured values x.

Also, the method may be arranged to comprise waiting for a certain period of time between the determinations of the said first Ti and second temperature Ί₂, in order to take into account the system's inertia. For example, a particulate filter has a thermal inertia, and it may take a number of seconds as of a load increase in the combustion engine, with e.g. a warmer exhaust stream and higher flow as a result, resulting in an increased temperature in the PM sensor 213 if this is placed e.g. downstream of a particulate filter.

According to one alternative embodiment, instead a number of temperature determinations in the PM sensor 213 are carried out, e.g. at equal or applicable intervals, so that the temperature change over time is compared to an expected temperature change. Also in this case, discrepancies for each measured value may be confirmed and compared with the expected value. Discrepancies may also be compared with each other, and as long as the discrepancies are significantly similar, the PM sensor may still be deemed to have been correctly placed.

The expected temperature change may also be confirmed with the help of one or other temperature sensors in the aftertreatment system, such as one or several of the temperature sensors shown in Fig. 2. With the help of temperature data from these sensors, a good estimate of the expected temperature change in the PM sensor's temperature sensor/heating element may be made .

Also, it should be noted that the determination according to the present invention is made by way of passive temperature determination, i.e. there is no active heating of the PM sensor 213 with the help of the heating element, instead the PM sensor temperature is controlled entirely by environmental factors and in particular by the temperature of the exhaust stream. In the event the heating element is used to confirm a temperature variation according to the present invention, the confirmed temperature variations generally become slower compared to the temperature determination with a temperature sensor, so that this should be taken into account in cases where the heating element is used as a temperature source.

Also, it may be that the PM sensor in operation to any extent is kept heated by internal electronics, e.g. by the internal electronics controlling the heating element, where such internal heating may be difficult to estimate. According to one embodiment, the determination is therefore carried out according to the present invention with the particle sensor shut off, so that it may be confirmed that the heating/cooling of the sensor is entirely contingent on the environment. It may also be the case that the sensor-internal electronics as such may result in heating, but such heating is generally viewed as constant and thus constitutes a lesser problem.

However, this type of heating may also be eliminated by shutting off the sensor on determination according to the present invention.

As opposed to a solution where the PM sensor 213 is actively heated to a high temperature with the help of a heating element before a temperature change is confirmed, the solution according to the present invention entails that temperature changes in the PM sensor caused by relatively small changes of the exhaust stream may also be detected, which markedly increases the potential for actually confirming whether the PM sensor is correctly positioned. This also means that the temperature change may occur both upwards and downwards in temperature, and not only in the form of a cooling down of the PM sensor. According to one embodiment, a determination for a temperature increase and a determination for a temperature decrease are carried out, so that an overall appraisal of these determinations may be used to confirm whether the PM sensor may be deemed to emit a representative signal.

Depending on the application, the PM sensors may be arranged at different positions in the exhaust system. For example, the PM sensor 213 may be installed upstream or downstream of an exhaust brake, as well as upstream or downstream of a

particulate filter, or upstream of a turbocharger . Regardless of the placement, there will be temperature changes in the PM sensor when the temperature of the exhaust stream is affected. The invention is thus applicable essentially regardless of where in the exhaust and/or aftertreatment system the PM sensor 213 is placed.

There are various types of PM sensors, and the present invention is applicable to all types of PM sensors.

In addition, the method according to the invention may be combined with that in the parallel Swedish application No. 1250963-4 entitled "ME THOD AND SYSTEM PERTAINING TO EXHAUST AFTERTREATMENT I I " , by the same inventor and with the same submission date as the present application, described in order to establish a sensor function for a PM sensor. According to the said application "ME THOD AND SYSTEM PERTAINING TO EXHAUST AFTERTREATMENT I I " , a method similar to the present method is provided, with the difference that a representation of a concentration by the PM sensor and/or fraction of a substance occurring in the exhaust stream is established. Based on the confirmed representation of a concentration and/or fraction of the said first substance, it is determined whether the PM sensor emits a representative signal. This is achieved with the use of elements installed by the PM sensor for the determination of a representation of a concentration and/or fraction of a substance occurring in the exhaust stream. These elements may e.g. consist of a concentration/ fraction sensor, which measures the concentration/ fraction for some substance other than particles in the exhaust stream, and which is integrated with the PM sensor, i.e. it uses joint components as substrate or similar, or constitute a separate

concentration/ fraction sensor, incorporated into a joint housing with the PM sensor.

The concentration/ fraction sensor may e.g. consist of a gas concentration sensor, and the said first substance of a gas, but may also consist of a PM sensor where the concentration of particles is established, and where the PM sensor may consist of an electrostatic or resistive PM sensor.

The concentration/ fraction sensor may consist of a sensor of electrochemical type, or of a sensor of semiconductor type, such as a silicone carbide-based sensor.

By thus establishing a representation of the

concentration/ fraction for a substance occurring in the exhaust stream, such concentration/fraction may be compared to a representation of an expected concentration/fraction .

Also, the method according to the invention may, alternatively or additionally, be combined with that in the parallel Swedish application No. 1250961-8 entitled "METHOD AND SYSTEM

PERTAINING TO EXHAUST AFTERTREATMENT " , by the same inventor and with the same date of submission as the present

application, described in order to establish a sensor function for a PM sensor. According to the said application "METHOD AND SYSTEM PERTAINING TO EXHAUST AFTERTREATMENT " , a method similar to the present method is provided, with the difference that the sensor function for the PM sensor is confirmed with the use of elements to confirm a representation of a pressure in the PM sensor. This is achieved by using elements installed in the PM sensor to determine a representation of a pressure prevailing at the PM sensor. These elements may e.g. consist of a pressure sensor integrated with the PM sensor, i.e. the pressure sensor uses joint components such as substratum or similar. Alternatively, the pressure sensor may constitute a separate pressure sensor, but be installed in a common housing with the PM sensor.

By thus determining a prevailing pressure at the PM sensor, this pressure may be compared with an expected pressure, and based on the comparison, it may be determined whether the PM sensor may be deemed to be subject to a representative exhaust stream, i.e. an exhaust stream which correctly reflects the composition in the exhaust stream which leaves the combustion chamber of the combustion engine.

By combining the method according to the present invention with one or more of the above described methods, a more reliable evaluation of the PM sensor's function may be carried out .

Additionally, the present invention has been exemplified above in relation to vehicles. The invention is, however, applicable to any vessels/processes where particulate filter systems as per the above are applicable, such as watercrafts and

aircrafts with combustion processes as per the above.

Additionally, the combustion engine may e.g. consist of at least one of the group: automotive engine, marine engine, industrial engine, diesel engine, spark ignition engine, GDI engine, gas engine.

Other embodiments of the method and the system according to the invention are available in the patent claims enclosed hereto . It should also be noted that the system may be modified according to various embodiments of the method according to the invention (and vice versa) and that the present invention is in no way limited to the above described embodiments of the method according to the invention, but pertain to and comprise all embodiments in the scope of the enclosed independent claims .

Claims

Method to establish a sensor function for a PM sensor (213) intended for the determination of a particle concentration in an exhaust stream resulting from combustion in a combustion engine (101), comprising elements to emit a representation of a temperature prevailing at the said PM sensor (213) , and where an aftertreatment system (200) is installed for the

aftertreatment of the said exhaust stream, characterised by the fact that the method comprises, when the

temperature for the said PM sensor (213) is essentially unaffected by sensor-internal heating elements:

- establishing a representation of a first temperature change (ΔΤ₁₂) at the said PM sensor (213) ,

- comparing the said representation of the said first temperature change (ΔΤ_: ) with a representation of an expected temperature change (ΔΓ._:,·:·.) in the said PM sensor (213), and

- based on the said comparison of the said representation of the said first (Δϊγ,.) temperature change with the said representation of the said expected temperature change (.L_:.) , confirming whether the said PM sensor (213) emits a signal representative of the said exhaust stream.

Method according to claim 1, further comprising, when the said representation of the said first temperature change (ΔΊν·) at the said PM sensor (213) is confirmed,

- at a first point in time, confirming a first

representation of a temperature prevailing at the said PM sensor (213) ( T_- ) ,

- at a second point in time, separate from the said first point in time, confirming a second representation of a temperature prevailing at the said PM sensor (213) (T₂) , where the said first temperature change (Δ2 ~ consists of a difference between the said first ( T_- ) and second, (T₂) representation of a temperature prevailing at the said PM sensor (213) .

3. Method according to any of claims 1-2, further comprising establishing a temperature change

at the said PM sensor (213) at several points in time,

- comparing the respective confirmed temperature changes (AT, ) with a corresponding expected temperature change, and

- based on the said numerous comparisons, establishing whether the said PM sensor (213) emits a signal

representative of the said exhaust stream.

4. Method according to any of the claims 1-3, where the said PM sensor comprises elements for heating of the said PM sensor, also comprising establishing the said temperature change (A3V) with the use of the said elements for heating of the said PM sensor without active heating of the said PM sensor with the use of the said elements for heating of the said PM sensor.

5. Method according to any of the claims 1-4, also

comprising carrying out the said establishing of the said temperature change with the use of a temperature sensor installed in the said PM sensor.

6. Method according to claim 5, where the said first

temperature sensor (214) consists of a temperature sensor (214) integrated with the said PM sensor (213) .

7. Method according to claim 5, where the said temperature sensor (214) consists of a temperature sensor (214) fixedly connected with the said PM sensor (213) and/or incorporated in a joint housing with the said PM sensor (213) .

8. Method according to any of the claims 1-7, also

comprising establishing whether the said PM sensor (213) emits a signal representative of the said exhaust stream by, based on the said representation of the said first temperature change (ΔΓ^;) , confirming whether the said PM sensor (213) may be deemed to be present in the said exhaust stream.

9. Method according to any of claims 1-8, further

comprising :

- based on the said established temperature change (ΔΤ₁₂) , establishing whether the said aftertreatment system (200) and/or PM sensor (213) may be deemed to have been

manipulated.

10. Method according to any of the previous claims, further comprising, at the said comparison:

- establishing a discrepancy (A) between the said first temperature change (ΔΤ₁₂) and the said expected

temperature change (AT_exp) , and

- where the said PM sensor (213) is not deemed to emit a signal representative of the said exhaust stream if the said discrepancy exceeds a limit (An_m) .

11. Method according to any of the previous claims, further comprising:

- establishing a discrepancy {A) between the said

established temperature change (ΔΤ₁ ) and the said expected temperature change (ΔΓ_^._.-._..) , at several points in time, and

- where the said PM sensor (213) is not deemed to emit a signal representative of the said exhaust stream if the said discrepancy (A) exceeds a limit (A_{li i}) for at least some of the said points in time.

12. Method according to any of the previous claims, further comprising :

- establishing a discrepancy (A) between the said first temperature change (Δϊν.) , and the said expected

temperature change (ΔΤ_θ:: ) , at several points in time, and

- where the said PM sensor (213) is not deemed to emit a signal which is representative for the said exhaust stream if an overall value of the said discrepancies (A) for the said several points in time exceeds a limit

13. Method according to any of the previous claims, further comprising generating a signal, indicating a malfunction for the said PM sensor (213) when the said first

temperature change ( Δ ΐν ) is not consistent with the expected temperature change ( Δ Τ₆,-_: ,) .

14. Method according to any of the previous claims, further comprising impacting the said expected temperature change (Δΐ ,ρ) by impacting the said exhaust stream upstream of the said PM sensor.

15. Method according to claim 14, further comprising

impacting the said exhaust stream by controlling the said combustion engine (101), e.g. by way of controlling at least one of the fuel injection times, the fuel injection durations, fuel injection amount, fuel pressure, number of fuel injections, EGR and air supply, vent times, compression conditions, overload, VGT position, engine speed, change of combustion mode of the said combustion engine, e.g. from Otto to HCCI or from Diesel to PPC.

16. Method according to claim 14 or 15, where the said method further comprises impacting the said exhaust stream through control of throttles (215) installed for

controllable throttling of the said exhaust stream.

17. Method according to claim 16, further comprising

impacting the said exhaust stream through controllable throttling of the said exhaust stream with throttling elements in the form of an exhaust brake (215) .

18. Method according to any of the claims 14-17, further

comprising impacting the said exhaust stream by supplying unburned fuel to the said aftertreatment system.

19. Method according to any of the claims 14-18, further

comprising impacting the said exhaust stream through bypassing of one or several components in the said aftertreatment system (200) , or by connecting another component for the passage of, and thus bypassing of the said particle sensor (213) , of at least a part of the said exhaust stream.

20. Method according to any of the previous claims, where the said aftertreatment system (200) comprises at least one particulate filter (202), and where the intended PM sensor position is upstream or downstream of the said particulate filter (202) in the said exhaust stream.

21. Method according to any of the previous claims, where the said combustion engine (101) consists of an engine in a vehicle, and where the output power from the said

combustion engine is limited by the use of a control system set up in the said vehicle if the said PM sensor (213) does not emit a signal representative of the said exhaust stream.

22. Method according to any of the previous claims, where the method also comprises:

- establishing a representation of a prevailing

concentration and/or fraction (d) in the said PM sensor (213) of an initial substance (Si) in the said exhaust stream with the use of the elements set up in the said PM sensor (213) for the determination of a representation of a concentration and/or fraction of the said first

substance (Si) , and

- establishing whether the said PM sensor emits a signal representative of the said exhaust stream even based on the said confirmed representation of a concentration and/or fraction (d) of the said first substance (Si) .

23. Method according to any of the previous claims, where the method also comprises:

- establishing a first pressure prevailing at the said PM sensor with the use of elements set up in the said PM sensor in order to emit a representation of a pressure prevailing at the said PM sensor (213) , and

- establishing whether the said PM sensor emits a signal representative of the said exhaust stream also based on the said confirmed first pressure.

24. Computer program comprising a program code which, when the said program code is executed in a computer, achieves that the said computer carries out the method according to any of the patent claims 1-23.

25. Computer program product including a computer readable medium and a computer program according to patent claim 24, where the said computer program is included in the said computer readable medium.

26. System to establish a sensor function for a PM sensor (213) intended for the determination of a particle concentration in an exhaust stream resulting from

combustion in a combustion engine (101), where the said PM sensor (213) comprises elements to emit a

representation of a temperature prevailing at the said PM sensor (213) , and where an aftertreatment system (200) is installed for the aftertreatment of the said exhaust stream, characterised by the fact that the system comprises, when the temperature for the said PM sensor (213) is essentially unaffected by sensor-internal heating elements:

- establishing a representation of a first temperature change (ΔΪΥ-.) at the said PM sensor (213) ,

- comparing the said representation of the said first temperature change (ΔΤ^) with a representation of an expected temperature change (AT_;, ) in the said PM sensor (213), and

- based on the said comparison of the said representation of the said first (ΔΤ^) temperature change with the said representation of the said expected temperature change (ΔΓ_÷;:. ) , confirming whether the said PM sensor (213) emits a signal representative of the said exhaust stream.

27. System according to claim 26, characterised by the said combustion engine consisting of at least one out of the group: automotive engine, marine engine, industrial engine, diesel engine, spark ignition engine, GDI engine, gas engine.

28. Vehicle (100), characterised by the fact that it

comprises a system according to one of the claims 26 or 27.