EXHAUST STREAM

Technical field

The present invention pertains to a method for the regulation of a concentration/fraction of one or several substances comprised in an exhaust stream by way of control of a motor vehicle's driveline. Further, the invention pertains to a computer program, a computer program product, a system and a motor vehicle comprising such a system. Background of the invention

Laws and regulations for exhaust emission from motor vehicles have been drafted in many jurisdictions because of pollution and air quality, primarily in urban areas. These laws and regulations often consist of sets of requirements which define acceptable limits for exhaust emissions (emission standards) for motor vehicles equipped with combustion engines. For example, emission levels of nitrogen oxides (NO _x ), hydrocarbons (HC). carbon monoxide (CO) and particles are often regulated for most types of vehicles.

In order to meet such emission standards, the exhausts caused by the combustion in combustion engines are aftertreated (purified). By way of example, a so-called catalytic purification process may be used, which is why aftertreatment systems usually comprise a catalyst. Further, aftertreatment systems may alternatively or in combination with one or several catalysts comprise other components, such as one or several particulate filters.

Figure 1 shows the combustion engine 101 of a motor vehicle 100, where the exhaust stream generated by the combustion is led via a turbocharger 220. The exhaust stream is subsequently led via a pipe 204 (indicated with arrows) to a particulate filter (Diesel Particulate Filter. DPF) 202 via a diesel oxidation catalyst (DOC) 205. Further, the aftertreatment system comprises an SCR catalyst 201 (Selective Catalytic Reduction, SRC), arranged downstream of the particulate filter 202, which uses ammonia (NH3), or a composition from which ammonia may be generated/formed, as an additive for the reduction of the quantity of nitrogen oxides NO _x . The particulate filter 202 may alternatively be arranged downstream of the SCR catalyst 201. The diesel oxidation catalyst DOC 205 has several functions and uses the surplus of air which the engine process generally creates in the exhaust stream as a chemical reactor jointly with a precious metal coating in the diesel oxidation catalyst. The said diesel oxidation catalyst is normally primarily used to oxidise remaining hydrocarbons and carbon monoxide in the exhaust stream into carbon dioxide, water and heat, and conversion of nitrogen monoxide into nitrogen dioxide.

In connection with combustion of fuel in the combustion engine's combustion chamber (cylinders), soot particles are formed. For this reason the particulate filter is used to catch soot particles and thus functions so that the exhaust stream is led through a filter structure where soot particles are caught from the passing exhaust stream and stored in the particulate filter. The particulate filter is filled with soot as the vehicle is driven, and sooner or later the filter must be emptied of soot, which is usually achieved with the help of so-called regeneration. The said regeneration entails that the soot particles (mainly carbon particles) are converted into carbon dioxide and/or carbon monoxide in one or several chemical processes. Regeneration may occur in various ways and may, for example, occur with the help of so- called NC>2-based regeneration, often also called passive regeneration, or through so-called oxygen (02)-based regeneration, also called active regeneration.

In connection with passive regeneration, nitrogen oxide and carbon oxide are formed in a reaction between carbon and nitrogen dioxide according to e.g. equation 1 :

N0 ₂ + C = NO + CO (1)

The passive regeneration, however, is heavily dependent on the availability of nitrogen dioxide. If the supply of nitrogen dioxide is reduced, the regeneration speed is also reduced. The supply of nitrogen dioxide may e.g. be reduced if the formation of nitrogen dioxide is hampered, which may e.g. occur if one or several components in the aftertreatment system are contaminated by sulphur, which normally occurs in at least some types of fuel, e.g. diesel. Competing chemical reactions also hamper the nitrogen dioxide transformation.

The advantage of passive regeneration is that desired reaction speeds, and thus the speed at which the filter is emptied, are achieved at a lower temperature. Typically, regeneration of the particulate filter during passive regeneration occurs at temperatures in the range of 200°C to 500°C. although temperatures in the higher part of this interval are normally preferable. Notw ithstanding this, compared to the significantly lower temperature interval in active regeneration, this thus constitutes a great advantage if e.g. an SCR catalyst is present, since there is no risk that such a high temperature level is achieved that there is a risk of damage to the SCR catalyst. Nevertheless, it is important that a relatively high temperature is achieved in order for an effective passive regeneration to take place.

In the event of active regeneration, so-called oxygen (0:)-based regeneration, a chemical process occurs mainly according to equation 2:

C + 0 ₂ = C0 ₂ + heat (2)

Thus, carbon plus oxygen are converted in active regeneration into carbon dioxide plus heat. This chemical reaction, however, is heavily temperature-dependent and requires relatively high filter temperatures in order for a significant reaction speed to arise at all. Typically, a minimum particulate filter temperature of 500°C is required, but preferably the filter temperature should be even higher in order for regeneration to occur at the desired speed. The reaction speed for chemical reactions, e.g. the reactions according to equation 1 and 2 above, are also dependent on the concentration of the reactants. If, for example, the concentration of any reactant is low, the reaction speed will be low, and if a reactant is missing, no reaction at all will occur.

Often the maximum temperature which may be used in active regeneration is limited by tolerances for some of the components comprised in the aftertreatment system/exhaust system. For example, often the particulate filter 202 and/or (where applicable) a subsequent SCR catalyst have constructional limitations with regard to the maximum temperature they may be subjected to. This entails that the active regeneration may have a maximum component temperature which is often undesirably low. Simultaneously, a very high minimum temperature is required in order for any usable reaction speed to arise at all. In active regeneration, the soot load is normally essentially totally burned in the particulate filter 202. This means that a total regeneration of the particulate filter is obtained, following which the soot level in the particulate filter is essentially 0%. Today it is increasingly common for vehicles to be equipped, in addition to a particulate filter 202, with an SCR catalyst 201, which is why active regeneration may entail problems in the form of overheating for the subsequent SCR catalyst treatment process.

It is therefore of utmost importance to be able to stop a rapid increase in temperature in the exhausts before the SCR catalyst. Such a rapidly rising temperature may e.g. be the result of a runaway oxidation in the particulate filer (DFP), which may be inhibited or stopped if the concentration of oxygen into the particulate filter is reduced to a low or zero level. As mentioned above it is also important, however, that the temperature be regulated in other components in the exhaust system, for example in order to prevent or inhibit local or global excess temperature in the particulate filter (DPF). etc.

Depending on how a vehicle is driven, the concentration/fraction for the exhaust stream resulting from the combustion will vary. If the combustion engine is working hard, the exhaust stream will have a higher concentration/fraction of combustion products and lower concentrations/fractions of combustion reactants, and if the load on the combustion engine is relatively low the exhaust stream's concentration/fraction will be essentially the reverse. If the vehicle is driven for a longer period of time in such a manner that the exhaust stream contains relatively high concentrations/fractions of undesired combustion products, such as sulphur oxides, a degradation of the function of the diesel oxidation catalyst 205 will occur because the reaction of the sulphur which is usually present in the fuel in various forms with the diesel oxidation catalyst 205's active coating, usually comprising one or several precious metals or other applicable metals, e.g. aluminium. These problems usually arise at low (150°C) to medium (300°C) temperatures. At temperatures below 150°C to 250°C, for example, an SCR catalyst will not function well. On the other hand, if the vehicle is driven for a longer period of time in such a manner that the exhaust stream's temperature maintains relatively high temperatures, this means that active regeneration may take place at the desired speed. However, the temperature in the exhaust stream may not exceed a maximum permitted temperature so that heat sensitive components in the aftertreatment system are damaged as previously mentioned. It is then particularly important to ensure that the concentration of NO is maintained at low levels and that the balance N02/NO _x is optimal.

The concentration C of a substance in a gas may be expressed according to the equation: C = N /V, where N is the number of molecules of a given substance and V is the volume, i.e. the number of molecules of a given substance in a given volume. The total concentration C _Tot , which increases in an ideal gas if the pressure has increased and the temperature is falling, is expressed by the general gas law as C _Tot = N _Tot /V, where N _Tot is the total number of molecules. The fraction X of a substance is expressed as the relationship between the concentration C and the fraction X as: : C = X · C _Tot . If no chemical reactions take place, the fraction which specifies the proportion of molecules in a volume which belongs to a certain substance is not changed unless additional molecules are mixed with the original volume. This may e.g. occur through diffusion and/or through remixing of gas elements through so- called turbulence. The new molecules which are mixed in may e.g. come from urea and/or diesel injected into the exhaust pipe, which may be evaporated or reacted. They may also come from previously stored substances which are released, e.g. condensed water which is dragged along with the exhaust stream and/or evaporated. Examples of substances in the exhaust system which may be regulated are: carbon monoxide (CO) and nitrogen oxide (NO). which react e.g. with oxygen into carbon dioxide (C02) and nitrogen dioxide (N02) respectively.

Brief description of the invention

One objective of the present invention is to provide a solution which wholly or partly resolves problems and/or disadvantages with solutions for the regulation of a concentration/fraction of one or several substances comprised in an exhaust stream according to prior art.

According to a first aspect of the invention, the above mentioned objective is achieved with a method for the regulation of a concentration/fraction of one or several substances comprised in an exhaust stream in a motor vehicle through control of its driveline, the motor vehicle of which comprises: a driveline comprising a combustion engine which may be connected to a continuously variable gearbox (CVT/IVT) via a clutch device, and an exhaust system arranged for the removal of an exhaust stream from the said combustion engine; where the said method comprises the step:

- control of the said continuously variable gearbox (CVT/IVT), and thus an operating point in the said combustion engine, based on the said one or several first parameters P _x for the regulation of a concentration/fraction C _Ex /X _Ex of one or several substances comprised in the said exhaust stream, where at least one of the said one or several first parameters P ₁ are a first concentration/fraction difference between the said first concentration/fraction C _X IX in the said exhaust stream and a reference concentration/fraction C _Re flX _Re f . Different embodiments of the above method are defined in the non-independent patent claims enclosed to the method. One method according to the invention may also be implemented in a computer program, which when executed in a computer achieves that the computer carries out the method according to the invention.

According to a second aspect of the invention, the above said objective is achieved with a system arranged for the control of one or several functions in a motor vehicle, the motor vehicle of which comprises: a driveline comprising a combustion engine which may be connected to a continuously variable gearbox (CVT/1VT) via a clutch device, and an exhaust system arranged for the removal of an exhaust stream from the said combustion engine; where the said system comprises a control device arranged to control the said continuously variable gearbox (CVT/IVT), and thus an operating point in the said combustion engine, based on the said one or several first parameters P _x for the regulation of a concentration/fraction C _Ex IX _Ex of one or several substances comprised in the said exhaust stream, where at least one of the said one or several first parameters P _l is a first concentration/fraction difference between the said first concentration/fraction C ₁ /X ₁ in the said exhaust stream and a reference concentration/fraction _Re ^IX _Re ^.

The above mentioned system is preferably arranged in a motor vehicle, such as a bus, a truck or another similar motor vehicle.

With a method or a system according to the present invention, an improved solution for the regulation/control of a concentration/fraction of one or several substances comprised in an exhaust stream in a motor vehicle is obtained. For example, the invention enables the regulation of the concentration/fraction of one or several substances comprised in such operating conditions where regulation of the concentration/fraction has not been possible or sufficient with solutions according to prior art.

One method or a system for the regulation of the concentration/fraction of comprised substances according to the present invention facilitates that components in the exhaust system, such as particulate filters and catalysts, may work efficiently since the concentration/fraction of substances comprised in the exhaust system may efficiently and accurately be adjusted to the said components' optimal working concentration/fraction. The risk that components in the exhaust system are damaged due to e.g. overheating and contamination is thus also reduced. Further, the invention provides a more fuel effective method for achieving a desired concentration/fraction of substances comprised, or for maintaining a current concentration/fraction of substances comprised in the exhaust stream compared to prior art. By regulating the concentration/fraction of substances comprised through control of the driveline with one or several first parameters P according to the invention, measures resulting in high fuel consumption may be avoided, such as activation of an external heater or engine control prioritising the concentration/fraction over the engine's efficiency.

Another advantage of the invention is that it is not necessary to equip the vehicle with further parts/components in order to achieve the advantages of the invention since already existing parts/components in the vehicle may be used, which entails a great cost saving.

Further advantages and embodiments of the invention are set out in the following detailed description. Brief description of figures

The present invention is described with reference to the enclosed figures where:

Figure 1 is a schematic diagram of a system comprising a combustion engine and an exhaust system;

Figure 2 is a schematic diagram of an example vehicle;

- Figure 3 is a schematic diagram of a gas flow in an engine system;

Figure 4 is a schematic diagram of a control device; and

Figure 5 shows a flow diagram of one embodiment of the invention.

Detailed description of the invention

Fig. 2 is a schematic diagram of a motor vehicle 100, such as a truck, bus or other similar motor vehicle. The vehicle 100 schematically shown in Fig. 2 comprises a pair of front wheels 1 1 1 , 1 12 and a pair of rear wheels with driving wheels 1 13, 1 14. The vehicle also comprises a driveline with a combustion engine 101 (e.g. a diesel engine), which via an output shaft 102 on the combustion engine is connected to a gearbox 103, for example via a clutch device 106. The clutch device may consist of an automatically controlled clutch and be controlled by the vehicle's control system via a control device 1 15, 208, which may also control the gearbox 103. An output shaft 107 from the gearbox 103 drives the driving wheels 1 13, 1 14 via a final drive 108. such as a differential, and drive shafts 104, 105 connected to the said final drive 108.

The vehicle 100 also has an exhaust system arranged to remove an exhaust stream generated by the combustion engine 101 on a combustion in the same. As showed in Fig. 1 , the exhaust system may comprise an aftertreatment system (exhaust purification system) for the treatment (purification) of exhaust emissions from the combustion engine 101. However, it is not necessary for the exhaust system to comprise such an aftertreatment system, and in addition the exhaust system may comprise other parts/components, for example a turbo, a silencer system, and gas flow systems for EGR.

The gearbox 103 is usually a manual gearbox; an automatic gearbox, such as an automatic gearbox, automatic manual gearbox (Automatic Manual Transmission, AMT) or double clutch gearbox (Double Clutch Transmission, DCT); or a continuous variable gearbox (Continuous Variable Transmission/Infinitely Variable Transmission, CVT/IVT).

A manual gearbox 103 is a gearbox with a number of discrete gears and is arranged to be manoeuvred by the driver for engagement or disengagement of gears (e.g. forward and reverse gears). An automatic gearbox also has a number of gears, i.e. it comprises several discrete gears. However, it differs from a manual gearbox in that it is controlled/manoeuvred by a control system comprising one or several control devices, also called ECUs (Electronic Control Unit). The control device or ECU is arranged to control the gearbox 103, for example on a shift from gear selection at a certain speed with a certain running resistance. Also, the ECU may measure the speed and torque of the engine 101 and the condition of the gearbox. Information from the engine or the gearbox may be sent to the ECU in the form of electric communications signals via e.g. a so-called CAN (Controller Area Network) bus installed in the motor vehicle 100. The gearbox 103 has been illustrated schematically as one device. However, it should be noted that the gearbox may also physically consist of several cooperating gearboxes, for example a so-called range gearbox, a main gearbox and a split gearbox, which are arranged along the vehicle's driveline. Gearboxes according to the above may comprise any number of suitable discrete gears. Today's gearboxes for heavy goods vehicles usually have twelve forward gears, two reverse gears and one neutral gear.

A continuously variable gearbox, also called a CVT gearbox or IVT gearbox, is another type of well known gearbox which differs from the previous gearbox types since it does not have a number of discrete gears corresponding to different gearings but instead has a continuously variable gearing. In this type of gearbox, gearing may thus within certain limits be controlled to the exact gearing desired. In relation to upshifts and downshifts, an upshift means that a higher possible gear in the gearbox is selected while a downshift means that a lower possible gear in the gearbox is selected. This applies to gearboxes with several discrete gears. For continuously variable gearboxes, "fictitious" gear steps may be defined and shifting gears may occur in the same manner as for a gearbox with discrete gear steps. However, the usual way of controlling such a continuously variable gearbox is to let the gearing vary depending on other parameters which is described in more detail below. The control of such a gearbox is usually integrated with the control of the combustion engine's speed and torque, i.e. its operating point. A common method is to let control of the continuously variable gearbox be based on a current driving power requirement, e.g. calculated based on a gas pedal position and a speed for the vehicle, and which operating point that gives the best effect in order to achieve the said driving power requirement. Gearing in the continuously variable gearbox thus becomes a result of which engine speed leads to the optimal operating point for the current driving power requirement. Aspects other than efficiency are also often taken into account in the choice of operating point for the engine. These may e.g. be driveability related aspects, such as torque response times, i.e. how long it would take to achieve a higher driving wheel torque, or how much more torque may be obtained during a certain time period. Further, a so-called activation of coasting entails that the vehicle's engine 1 0 1 is mechanically disconnected from the vehicle's driving wheels 1 10, 1 1 1 , i.e. that the driveline is opened, while deactivation of coasting entai ls that the driveline is closed. Disconnection of the driving wheels from the engine may, for example, be achieved by putting the gearbox 103 in a neutral gear, or by opening the clutch device 106. In other words, essentially no power is transmitted through the gearbox from the engine to the driving wheels during coasting.

In the present invention it is assumed that the driveline of the motor vehicle 100 comprises a continuously variable gearbox (CVT/IVT) of the type described above. Further, it is assumed that the motor vehicle comprises a combustion engine 101 and an exhaust system connected to the combustion engine for removal of an exhaust stream from the combustion engine.

One method according to the present invention for the regulation of a concentration/fraction of one or several substances comprised in the exhaust stream comprises the step: control of a continuously variable gearbox (CVT/IVT). and thus an operating point in a combustion engine, based on one or several first parameters P for the regulation of a concentration/fraction C _Ex IX _Ex of one or several substances comprised in the exhaust stream, where at least one of the said one or several first parameters P _x is a first concentration/fraction difference between the said first concentration/fraction C Xi in the said exhaust stream and a reference concentration/fraction C _Re f/X _Re f. The reference concentration/fraction C _Re flX _Re f is a desired concentration/fraction in the exhaust stream.

The one or several first parameters P _x are preferably used as in-parameters for a control algorithm arranged to control the concentration/fraction in the exhaust stream at a desired value through control of the driveline (e.g. gearbox and clutch). The control algorithm may be of many different types and may be an algorithm which only looks at the first parameter and uses one or several threshold values (e.g. one higher and one lower threshold value) to determine which control measure should be taken. A more advanced control algorithm also takes into account other variables as explained in the description below .

With the use of one or several parameters P _x for the regulation of a concentration/fraction of one or several substances comprised in the exhaust stream through control of the driveline, the possibility of maintaining the concentration/fraction into or out of e.g. a catalyst at the desired level is obtained, which thus guarantees that certain emission levels from the vehicle are below statutory limits. This is also a fuel effective manner of controlling the concentration/fraction of substances compared to other measures such as deteriorating the combustion efficiency in the engine.

The exhaust stream is the gas stream which leaves a combustion engine and is led out via the exhaust system's different components to the surrounding atmosphere. The exhaust stream may to some extent be recirculated (so-called EGR), expanded over a turbine in order to generate a mechanical energy (to e.g. a turbo compressor or for the propulsion of the vehicle), expanded over an exhaust brake damper (in order to increase losses in the engine and brake the vehicle or in order to generate warmer exhausts to optimise the exhaust treatment), cooled over an WHR plant and/or purified in a more or less advanced exhaust treatment plant. The components in the exhaust system in which the concentration/fraction and temperature in/on the exhaust stream (or the bulk flow of the exhaust stream) may need to be regulated are according to one embodiment of the invention: the high pressure part of the exhaust and EGR system (upstream of the turbo turbine) and pipe elements in the low pressure part before and after restrictions, such as an exhaust brake, catalyst or catalyst bypass and after urea and HC dosage systems. The concentration/fraction in the gas in catalysts (e.g. DOC, ASC and SCR), traps (e.g. NOx trap) and filters, both bulk and those inside the boundary layer against the component surface, may need to be regulated.

Further, according to one embodiment of the invention, the said first concentration/fraction and/or the said second concentration/fraction C ₂ /X ₂ is a concentration/fraction of one or several substances from the group comprising: oxygen 02, carbon dioxide C02, carbon oxide CO, sulphur oxides SOx, nitrogen oxides NOx, nitrogen oxide NO, nitrogen dioxide N02, nitrous oxide N20, ammonia NH3; and particles such as soot, HC drops and ash. Preferred concentrations/fractions in the exhaust pipe after the final exhaust treatment step (the step immediately after before the exhausts leave the exhaust pipe, i.e. the step following which the exhaust emissions must meet the statutory requirements) are those which, with a minimal total fuel and urea consumption, meet the statutory emission requirements. The preferred values for a N02 NO _x ratio entering the SCR catalyst are around 50%, for example between 40-60% for the best conversion grade of NO _x to be achieved. The preferred N02 content upstream of the particulate filter (DPF), however, is heavily dependent on the temperature and the NO _x /PM relationship. Further, certain components in the exhaust system are sensitive to certain substances in certain phases. For example, NO _x sensors are sensitive to water in liquid form. If the sensors come into contact with liquid water, there is a risk they may be damaged, which is why the preferred concentration of liquid water drops in this case is zero. In order to achieve this preferred concentration of liquid water drops, the preferred concentration margin, i.e. the difference between the concentration of water in gaseous form in the exhausts and the concentration of evaporated water on the liquid surface, is maximised during an integrated period of time.

Other ways of regulating the concentration/fraction with a method according to the present invention is, for example, to reduce the oxygen concentration in the exhaust system, so that a local or global excess temperature is prevented in components such as the particulate filter, the diesel oxidation catalyst, the SCR dosage device and the SCR catalyst.

According to one embodiment of the invention, the one or several first parameters P _x are selected from a group comprising:

• a first concentration/fraction C ₁ /X _i which may be a concentration/fraction in an area of the exhaust stream or a concentration/fraction in the exhaust stream on/nearest a surface or substrate in any part or component of the exhaust system, such as a particulate filter, catalyst, silencer, sensor, etc.; and

• a second current concentration/fraction difference between the first concentration/fraction C^X^ and a concentration/fraction C ₂ / ₂ ^{m me} exhaust system. The second concentration/fraction C _z /X2 is a different concentration/fraction in the exhaust stream from the first concentration/fraction ΟχΙΧ . However, the second concentration/fraction C ₂ / ₂ may be a concentration/fraction in an area of the exhaust stream; According to another embodiment of the invention, one or several of the first parameters P _x is a time derivative and/or time integral of the first concentration/fraction ΟχΙΧ, or the first concentration/fraction difference, or the second concentration/fraction difference. The use of a time derivative is advantageous if the control system is to react quickly to a concentration/fraction change, while the use of a time integral instead entails that the control system takes into consideration long term trends in the concentration/fraction change, which is advantageous for long term control of the concentration/fraction in the exhaust system.

The above mentioned current concentrations/fractions and concentration/fraction differences and functions thereof may be based on sensor values obtained from one or several sensors arranged at, in connection with, or inside the exhaust system. Signals from sensors may be sent over, for example, a communications bus or a wireless link to one or several control devices for signal processing. Also, the concentrations/fractions and concentration/fraction differences as well as functions thereof may be based on so-called virtual sensors, i.e. (current) sensor values which are calculated with other real sensor signals with the use of one or several sensor models. The advantage of using current concentrations/fractions and concentration/fraction differences and functions thereof is that these may be used directly for the determination of the first parameter P _x without complex or resource-demanding calculations with the use of various simulation models. Thus, these current values may also be obtained quickly. According to another embodiment of the invention, one of the one or several first parameters P ₁ are calculated (predicted) values selected from a group comprising:

• one calculated first concentration/fraction C IX which may be a concentration/fraction in an area of the exhaust stream or a concentration/fraction in the exhaust stream on/nearest a surface or substrate in any part or component of the exhaust system, such as a particulate filter, catalyst, silencer, sensor, etc.;

• a first calculated concentration/fraction difference between the first concentration/fraction C ₁ /X ₁ and a second reference concentration/fraction C _Re f ₂ IXRe 2 in the exhaust stream. The second reference concentration/fraction C _Re f ₂ IXRef2 is ^a desired concentration/fraction in e.g. a component, such as a particulate filter or a catalyst, in the exhaust system in order for it to function as well as possible or not to be damaged; • a second calculated concentration/fraction difference between the first concentration/fraction C ₁ /X ₁ and a concentration/fraction C ₂ /X ₂ ' ⁿ the exhaust stream. The second concentration/fraction C ₂ /X ₂ is another concentration/fraction in the exhaust system than the first concentration/fraction C^X _j^ . However, the second concentration/fraction C ₂ /X ₂ may also be a concentration/fraction in an area of the exhaust stream or a concentration/fraction in the exhaust stream on/nearest a surface or substrate in any part or component of the exhaust stream, such as a particulate filter, catalyst, silencer, sensor, etc.;

• a third calculated concentration/fraction difference between the second predicted concentration/fraction difference and a reference concentration/fraction C _Re f/X _Re f in the exhaust system; and

• a time derivative and/or a time integral of the calculated first concentration/fraction C X-y , or the first calculated concentration/fraction difference, or the second calculated concentration/fraction difference, or the third calculated concentration/fraction difference. The use of a time derivative is advantageous if the control system is to react quickly to a concentration/fraction change, while the use of a time integral instead entails that the control system takes into consideration long term trends in the concentration/fraction change, which is advantageous for long term control of the concentration/fraction in the exhaust stream.

By using one or several first calculated parameters P ₁ , information is obtained about how the relevant parameters will vary over time, which means that the system for the regulation of the concentration/fraction of substances comprised in the exhaust stream may be controlled so that the desired concentration/fraction may be achieved in the best possible manner in the future. This applies in particular to slow systems in which a change of a concentration/fraction takes a long time to change, e.g. via storage in catalysts or other components, which require early measures for the avoidance of overshoots in the regulation of a concentration/fraction.

Calculated parameters means that they are calculated or simulated in advance based on (mathematical) models of the vehicle and/or the components comprised in the vehicle. Based on one or several calculated first parameters P _{l f} a control strategy for the control of the continuously variable gearbox may be selected among several different possible control strategies. By calculating/simulating how the one or several first parameter P ₁ will vary over the road sections lying ahead for the vehicle according to one or several different control strategies, the control strategy w hich meets certain requirements, e.g. that the concentration/fraction remains within a predefined limit value while being optimal from another perspective, such as fuel and/or urea consumption, may be selected. The above therefore entails that the one or several first parameters P _x may also be calculated based on one or several different future control strategies for the gearbox. This embodiment thus pertains to a feedback method where one or several first parameters P ₁ are used for the calculation of one or several control strategies based on one or several possible operating points, i.e. operating points which may possibly be used having regard to other requirements such as driveability or fuel consumption. The said one or several control strategies are subsequently used in order to calculate new one or several first parameters P _x , or in order to update the existing parameters. Further, it should be noted that even if only one control strategy is calculated, information derived from this single control strategy may be used by the control system in order to determine whether it may reasonably be used or whether it is better to let the vehicle be driven with the current operating point for the control of the gearbox.

The inventors have also realised that the one or several calculated first parameters P _x may be calculated over a road section ahead of the vehicle, for example by simulation over the road section ahead. According to this embodiment, the calculated first parameters P _x may be determined based on one or several vehicle-specific and/or road-specific data for the vehicle. These may preferably be selected from the group comprising: inclination of the road ahead of the vehicle, curve radii of the road section ahead, speed limits of the road section ahead; motor vehicle weight; rolling resistance of the motor vehicle; air resistance of the motor vehicle; engine-specific data such as maximum output, minimum output, maximum torque, minimum torque, exhaust flow, exhaust gas recirculation content and lambda values (i.e. air/fuel mixture); and installation-specific data such as the possible accumulation of substances and/or release of substances and/or conversion of substances in the exhaust system and a surface in the exhaust system in contact with the exhaust stream. Further, driver- interactive data which is related to the driver's driving style may be used in connection with the calculation of the one or several first parameters P _x , so that the vehicle's future behaviour is taken into account when the calculation is made. Examples of driver-interactive data include the use of blinkers, gas pedal position, and use of brakes.

One advantage with the use of vehicle-specific and/or road-specific data for control is that the system may determine in advance whether any control strategy for one or several functions (e.g. gearing, external load, external heater, regulations of flow, etc.) needs to be used for the concentration/fraction not to end up outside a preferred interval. Thus, the use of unnecessary control strategies is avoided and also the system may act proactively in the event any measure should be required, i.e. the system may act in advance.

According to one specific embodiment, the first concentration/fraction C ₁ IX _l is a concentration/fraction in the gas stream, or a concentration/fraction over a liquid or a particle in the exhaust stream, and the second concentration/fraction C ₂ /^ ₂ ^{iS a} concentration/fraction in the exhaust stream on/nearest a surface or substrate in the exhaust system. The surface concentration/fraction is a concentration/fraction in the gas on/nearest a surface of the exhaust system or on a part thereof, which impacts the transport of the substance to and from the surface and the chemical reactions on the surface. The concentration/fraction over a liquid refers to the concentration/fraction on a surface in the exhaust system. This concentration/fraction over a liquid will impact the transport of substance amounts to or from the liquid, e.g. condensation or evaporation. The liquid may in this case consist of e.g. urea, water or fuel. The concentration/fraction immediately over a particle in the gas will on the other hand determine the reaction speed, such as growth, decomposition or oxidation for the particle which in this case may be e.g. a soot or urea particle in the exhaust system According to another embodiment, the first concentration/fraction Ο ΙΧ^ is a concentration/fraction in the exhaust stream upstream of an area in the exhaust system at which a concentration/fraction is desired to be obtained. This is especially advantageous where the conversion level of a component comprised in the exhaust system (e.g. a particulate filter or catalyst) is unambiguous, so that the output concentration/fraction will be determined by the input concentration/fraction and/or the fraction entering the component. This is the case e.g. in an equilibrium-controlled conversion of NO into N02 in a diesel oxidation catalyst (DOC) or conversion of NO _x in an SCR catalyst at high temperatures. It is also particularly advantageous if a particulate filter (DPF) is about to overheat and the overheating process may be stopped by removing oxygen in the particulate filter.

Further, it should be understood that the one or first parameters P used in the control of the gearbox may consist of only current values, or consist of only calculated values, or be a combination of current and calculated values depending on the application.

The control of the gearbox may according to another preferred embodiment take place by calculating an operating point for the combustion engine based on the one or several first parameters P ₁ . Subsequently, the calculated operating point is used to control a gearing in the gearbox and thus to regulate the concentration/fraction in the exhaust stream. Generally, a desired/optimal operating point is selected among several possible operating points, and subsequently the driveline is controlled, e.g. by control of the gearbox in this case, so that the engine achieves or approximates the optimal operating point. A desired/optimal operating point means an operating point which is the best among all possible operating points for the purpose which the system wishes to achieve. In this case, the best operating point is the operating point which causes the concentration/fraction in the exhaust stream to approximate its corresponding reference concentration/fraction as much as possible. In other cases, it may relate to e.g. an operating point which leads to the lowest consumption of e.g. fuel or urea, having regard to the statutory emission requirements and driveability, etc.

Usually, a gearbox is controlled with an operating point to achieve the best total efficiency in the driveline, but driveability aspects are usually also taken into consideration. For example, the engine speed may be set higher than optimal in order for a torque reserve to be available if the driver accelerates before an uphill slope, for example. According to the embodiment above, the concentration/fraction in the exhaust system is used as a parameter in the calculation of an operating point for the engine, and thus the emission targets are also weighed into the choice of an operating point for the engine. Thus, the emission target may be achieved without requiring any additional fuel demanding measures. Alternatively, it is not necessary to equip the vehicle with additional parts/components in order to maintain a determined conversion level, or determined emissions, in the flow emitted from the catalyst, for example. The following principles for control of the continuously variable gearbox are applicable in order for the engine to achieve a desired calculated operating point: if the gearing is increased, the engine speed is increased and thus the engine load is reduced, which leads to an increase of the total concentration C _Tot in the exhaust stream and an increase of the exhaust flow; if on the other hand the gearing is reduced, the engine speed is reduced and thus the engine's load increases as well as the exhaust flow, which leads to a decrease of the total concentration C _Tot in the exhaust system. All concentrations/fractions of different substances do not behave in the same manner on a load increase or a load decrease. Based on knowledge regarding fundamental combustion relationships, emission chemistry, the exhaust treatment system and the engine's control strategy with respect to e.g. the air/fuel relationship, load pressure, EGR content, injection time(s), and dosage of substances in the exhaust system, a person skilled in the art knows how engine load and engine speed should be varied in order to achieve a change of a given concentration or fraction. With respect to a change in a concentration/fraction over catalysts in the exhaust system, their efficiency generally deteriorates with an increased flow and falling temperature. With a given drive power requirement, the efficiency will generally thus decrease when the engine speed increases. However, there are exceptions and therefore, in practice, virtual sensors are also used here in order to decide in which direction the engine speed should be changed. In practice, this is realised with the use of one or several virtual sensors arranged to calculate a quantity such as a concentration or fraction of substances. With the use of sensor values from the said sensors, the engine load and the engine speed may be controlled for the regulation of a concentration/fraction.

The calculation of the operating point may be based on additional parameters. Such an additional parameter is related to a requested drive power requirement, which is usually used for the vehicle to be driveable, i.e. for it to have characteristics so that it may be driven in a comfortable manner and in a manner where the vehicle to the greatest extent possible behaves as requested by the driver, e.g. maintains a certain speed, delivers the torque requested by the driver with the gas pedal, etc. This requested drive power requirement value may also be taken having regard to an offset value V ₀ ffset _< which means that the offset value is added to or subtracted from the drive power requirement value in the calculation of the operating point. With this embodiment, the freedom in choosing an operating point increases as do the possibilities of achieving a desired concentration/fraction in the exhaust system since the control system allows for the control to diverge from the vehicle's current drive power requirement, i.e. the control system may intentionally allow the vehicle to accelerate or decelerate in order to achieve a desired concentration/fraction in the exhaust system. However, since there is a danger in letting the vehicle accelerate if the offset value is added to the drive power requirement value, it is preferred if the offset value V ₀ ffset > ^s subtracted from the drive power requirement value, which means that the vehicle decelerates or at least that it does not accelerate since if a driver requests a drive power equivalent to an acceleration, a reduction of the drive power by ^ off set ^m ay lead to a reduced acceleration and not necessarily to a deceleration of the vehicle.

Other additional parameters which may be used in the calculation of the operating point are parameters related to:

• an efficiency level for the driveline, which must be taken into consideration in order to achieve as fuel efficient driving of the vehicle as possible;

· an efficiency for an exhaust treatment system (also called an aftertreatment system) installed in the exhaust system in order to achieve as high conversion levels in catalysts, and thus as low emission levels as possible;

• exhaust emissions for the combustion engine before they have been purified by an exhaust treatment system;

· speed limits in the engine and the driveline in order not to end up at higher or lower engine speeds than what the driveline is dimensioned for;

• the engine's torque/power curve as a function of the engine speed in order to determine the torque that is available;

• a torque response, i.e. how quickly a requested increased drive wheel torque impacts on the vehicle's actual drive wheel torque. This aspect is relevant in the calculation of the operating point since the driver's control of the gas pedal must also be taken into consideration. Otherwise there is a risk that the driver perceives that the vehicle does not respond to the driver's control of the gas pedal; and

• other driveability aspects, such as noise, vibrations and turning of the vehicle so that the vehicle may be driven comfortably. Parameters related to external loads are also very useful in the calculation and control of the operating point. Examples of external loads are a system arranged for the conversion of exhaust heat into energy (WHR); auxiliaries such as a water pump, fan or compressor; generator; hybrid generator or sim i lar energy recycling system; retarder, exhaust brake or other auxiliary brake. The external load's power requirement may be controllable, so that the freedom in selecting an operating point for the engine is increased, which in turn means that also operating points which lie outside the vehicle's driving power requirement may be used for the regulation of the concentration in the exhaust system. In some cases the external load is of the "on" or "off type, i.e. it is either activated or not, and in these cases the control and calculation of the operating point is limited to determining whether or not the external load should be activated.

Further, i f no exhaust brake is instal led in the exhaust system, or if the exhaust brake is arranged to regulate the exhaust stream downstream of the same, the external load must be increased if a total concentration C _ExTot in the exhaust stream is to be reduced; and if the total concentration C _ExTot is to be increased, the external load must be reduced. On the other hand, if an exhaust brake is installed in the exhaust system and arranged to regulate an exhaust stream upstream of the same, the external load must instead be increased if the total concentration C _ExTot in an area upstream of the exhaust brake is to be increased in the event that a quota for the pressure above the temperature increases. In the reverse, the external load must be reduced if the total concentration C _ExTot in the area is to be reduced in case the quota for the pressure above the temperature decreases. The total concentration's dependency on the external load is given by the general gas law. With an increased load, the temperature of the exhausts normally increases and thus the total concentration falls, given that the pressure is kept constant.

The inventors have also realised that the one or several first parameters P _x are suitable for the control of other functions in the vehicle for regulation of the concentration/fraction. These functions must have a direct or indirect impact on the concentration/fraction. Thus, the regulation of the concentration/fraction may be more efficient and faster. Suitable functions are related to the conversion of external heat into energy; injection of fuel into the engine; injection of fuel, urea or other suitable l iquids to the exhaust system; and regulation of the exhaust flow. It should be realised that the one or several first parameters P _l may be used to control such a function or a combination of two or several such functions.

According to one embodiment, the one or several first parameters P _x may be used for the control of at least one external heater for the exhaust system. The external heater's task is to increase or decrease the concentration/fraction of substances comprised in the exhaust flow or any part/component in the exhaust system. Preferably, the external heater is:

• a burner installed in the exhaust system after the combustion engine's cylinders;

• a system arranged for the post injection of hydrocarbons for oxidation or combustion on a catalyst placed in the exhaust system;

• an electric heater installed in the exhaust system after the combustion engine's cylinders; or

• any other suitable external heater installed in, or in close connection with, the exhaust system.

The external heater is preferably controlled so that a maximum concentration decrease is obtained in relation to the input energy or total energy. However, the external heater may instead be controlled so that the speed at which the concentration/fraction changes is prioritised. The control of the external heater may be configured as a P1D or MPC regulator.

As mentioned above, the one or several first parameters Ρχ may also be used to control a fuel injection system arranged for the injection of fuel to the combustion engine. This may occur through control of the number of post injections, the time (CAD) for post-injections, and the fuel amount per post- injection. The control of the fuel injection system may be implemented as pre-controlled or feedback control with e.g. MAP (matrix-based regulation structure), PID or MPC (Model Predictive Control). As a setpoint for this control, a concentration/fraction downstream of the engine as well as a particulate filter (DOC) or a concentration/fraction difference over the said particulate filter may be used. In one embodiment, the regulation compensates for the efficiency of reactions in a component comprised in the exhaust system, for example the efficiency for NO into N02-conversion in a diesel oxidation catalyst. Further, the one or several first parameters Ρ may be used for the control of an injection system arranged for the injection of fuel, urea or another suitable liquid to the exhaust system for regulation of the concentration/fraction C _Ex IX _Ex of one or several substances comprised in the exhaust stream.

Another factor impacting the concentration/fraction in the exhaust system C _Ex /X _Ex are the characteristics for the exhaust flow in the exhaust stream. For this reason, the one or several first parameters P _x may also be used for the control of the exhaust flow, or one of the exhaust flows depending on the parameter, for example mass transfer coefficients.

Control of the exhaust flow may occur through control of a gas flow system for exhaust gas recirculation (EGR) and/or through control of an intake system for the engine. Fig. 3 shows schematically a general gas flow in an engine system, where the engine system in this example comprises a diesel engine with a turbo and a number of pipes connected to the engine. Air is sucked in from the left in Fig. 3 with an intake system for the engine. The air which is sucked in passes through an intake pipe and is compressed in a turbocharger in order to be cooled subsequently by an intercooler before it passes a throttle butterfly that regulates the amount of air into the diesel engine. After the throttle butterfly, the air is mixed with recirculated exhausts with a gas flow system for exhaust gas recirculation (EGR), and this mixture is then sucked into the engine's cylinders in order to be mixed with diesel or another fuel before combustion occurs in the engine.

The exhausts from the combustion process then pass through a turbo turbine which sets the turbocharger into motion. Parts of the exhausts, however, enter into an EGR pipe and are led back to the intake pipe via an EGR damper and one or several EGR coolers. The EGR damper's function is to regulate the amount of recirculated exhausts back to the combustion process. When the EGR gases are cooled, the use of EGR will move heat energy from the exhausts to the engine's cooling system. Before the exhausts disappear entirely from the engine system, in some engines they pass through an exhaust damper (if installed) which controls the pressure in an exhaust collector (not shown in the figure). Subsequently, the exhausts pass through an aftertreatment system which may contain a diesel particulate filter and/or an SCR catalyst as mentioned previously. If the engine 101 is not heavily loaded, the exhausts will have a lower temperature than desired and thus cool the catalyst. One way of limiting the amount of cooling exhausts is to use a damper arranged in an intake pipe for air to the engine. Thus, the amount of air entering the engine may be limited, which in turn means the exhausts exiting the engine are also limited, which, with a given load, results in warmer exhausts with a usually higher fraction of combustion products. This damper is usually called a throttle butterfly, as mentioned above. The amount of air which the engine consumes is determined to a large extent by the speed of the engine, which in this case means that: the higher the engine speed, the more air flow is required to the engine.

According to the present invention, the one or several parameters P _x may be used to control the gas flow system for exhaust gas recirculation (EGR) and/or the air intake system arranged for the regulation of an air flow to the engine. In addition, the control of the gas flow system for exhaust gas recirculation (EGR) may be controlled with an additional parameter related to emissions produced by the said combustion engine. Emissions in this context mean, for example, exhausts and noise. Further, a reduction of the exhaust flow may be combined with an increase of the engine load to change the fraction of a component comprised in the exhaust system. This embodiment may be realised with, for example, pre-controlled or feedback control of an exhaust brake with the use of a setpoint for the fraction or a value which is a function of the said setpoint for the fraction.

Further, Fig. 5 shows a flow diagram of an exemplified embodiment of the method according to the invention:

A. At A, the first parameter P _x from other sensor signals (virtual sensor) is measured or calculated. The first parameter P _x may also be calculated over the road section ahead for the vehicle at A.

B. Based on the value of the first parameter P _t . at B it is decided whether a measure regulating the concentration/fraction of substances comprised in the exhaust stream needs to be taken. This may, for example, take place by a comparison of the first parameter P ₁ with a threshold value, or by comparing several calculations of the first parameter P _x with related control strategies and based on these selecting which regulations measure(s) that need(s) to be taken.

C. If a regulating measure is to be taken, then the operating point for the engine which best (e.g. in the fastest or most fuel efficient manner) leads to a desired concentration/fraction is calculated at C. D. The operating point calculated at C is weighed together with other operating points at D, which have been calculated having regard to other aspects, for example driveability. This may e.g. entail that the resulting engine speed becomes an average value for several input operating points. At D it is also decided how the operating point will be achieved, i.e. how an external load, engine and gearbox will be controlled.

E. At E the external load is controlled to the desired position (desired torque).

F. At F the gearbox and the engine are controlled so that the desired operating point (speed/torque) is achieved.

G. If the adjustment of the operating point is not sufficient to achieve the desired concentration/fraction, it is decided at G whether an external heater should be activated. However, the external heater could have been activated already at B.

H. At H the external heater is controlled following the decision at G.

I. If the adjustment of the operating point is insufficient to achieve a desired concentration/fraction in the exhaust system, it is decided at 1 whether the exhaust flow needs to be controlled with e.g. the help of an EGR and/or a throttle butterfly. J. At J the exhaust flow is controlled after the decision at I.

The present invention may also be implemented in a control system arranged to control all or parts of a driveline in a motor vehicle 100. Further, the system may comprise additional control devices arranged to control other functions such as external load, external heater, etc. Control devices of the type displayed are normally arranged to receive sensor signals from different parts of the vehicle as well as from other control devices. These control devices are also usually arranged to emit control signals to different vehicle parts and vehicle components. The control devices may also comprise, or be connected to, a calculation device arranged for the calculation/simulation of predicted parameter values.

Generally, control systems in modern vehicles consist of a communications bus system consisting of one or several communications buses for the connection of a number of electronic control devices (ECUs) or controllers 1 15, 208 and different components arranged on the vehicle. Such a control system may comprise a large number of control devices, and the responsibility for a specific function in the vehicle may be distributed among one or more control devices. The control usually takes place with 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 control, such as methods 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 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, whereby the computer program is executed by the control device.

An example control device (control device 208) is displayed in the diagram in Fig. 4, and the control device in turn may comprise a calculation device 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 predetermined specific function (Application Specific Integrated Circuit, ASIC). The calculation device 120 is connected to a memory device 121, which provides the calculation device with e.g. the stored program code 109 and/or the stored data which the calculation device needs in order to be able to carry out calculations. The calculation device is also arranged to store interim or final results of calculations in the memory device 121.

Further, the control device is equipped with elements/devices 122, 123, 124, 125 for receipt and sending of input and output signals, respectively. These input and output signals may contain waveforms, pulses or other attributes, which may be detected by the devices for the receipt of input signals as information for processing by the calculation device 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 of a cable; a data bus, such as a CAN (Controller Area Network) bus, a MOST (Media Oriented Systems Transport), or any other suitable bus configuration; or of a wireless communications connection.

More specifically, a system according to the present invention comprises: a control device arranged to control a continuously variable gearbox (CVT/IVT), and thus an operating point in a combustion engine, based on one or several first parameters P ₁ for the regulation of a concentration/fraction C _Ex IX _Ex of one or several substances comprised in an exhaust stream, where at least one of the said one or several first parameters P _x is a first concentration/fraction difference between the said first concentration/fraction C ₁ /X ₁ in the said exhaust stream and a reference concentration/fraction C _Re flX _Re f . Further the present invention also pertains to a motor vehicle 100, such as a bus, a truck or a similar motor vehicle, comprising at least one system according to the above.

Finally, it should be realised that the present invention is not limited to the embodiments of the invention described above, but pertains to and comprises all embodiments within the protected scope of the enclosed independent claims.