The present, invention pertains to combustion engines, and. in particular to a method for the control of a combustion engine according to the preamble of claim 1. The invention also relates to a system and a vehicle, as well as a computer program and. a computer program product, which implement the method according to the invention.

Background of the invention

The background description below constitutes a background description for the invention, and thus need not necessarily constitute prior art techno1ogy .

In connection with increased government interests concerning pollution and air quality, emission standards and regulations regarding emissions from combustion engines have been, drafted in many jurisdict ions .

Such emission regulations often consist of requirements defining acceptable limits for exhaust emissions in vehicles equipped with combustion engines. For example, levels of nitrogen oxides (N0 _X ) , hydrocarbons (HC) and carbon monoxide (CO) are often regulated. These emission regulations may also handle the occurrence of particles in exhaust emissions.

In an effort to comply with these emission regulations, exhausts caused by the combustion of the combustion engine are treated (purified) , By way of example, a so-called catalytic purification process may be used, so that exhaust treatment systems in e.g. vehicles and other vessels usually comprise one or more catalysts and/or other components . For example, the exhaust treatment systems in vehicles with diesel engines often comprise particu1ate filters. Catalysts at combustion engines may be of several different types, where different types may be required for different fuels and/or conversion of different unwanted contaminants occurring in the exhaust stream. The expression "contaminant" here also compr ses substances and chemical compounds. In relation to at least nitrous gases (nitrogen monoxide, nitrogen dioxide) , referred to below as nitrogen oxides ^' O _x , heavy goods vehicles often comprise a catalyst where an additive is supplied to the exhaust stream resulting from the combustion in the combustion engine, in order to reduce nitrogen oxides NO _K , primarily to nitrogen gas and aqueous vapour .

This reduction of emissions of nitrogen oxides from diesel engines is usually carried out through a method called SCR (Selective Catalytic Reduction). This method entails that an additive, usually an aqueous solution comprising the substance urea, is supplied in a suitable dose to the exhaust stream upstream of an SCR catalyst.

The SCR catalyst's function usually requires access to ammonia (NH3) , and e.g. at evaporation of urea ammonia is also formed, so that ammonia subsequently reacts with nitrogen oxides in the exhaust stream, in the SCR catalyst, with a conversion into nitrogen gas and aqueous vapour as a result. "

One objective of the present invention is to provide a method to control a combustion engine. This objective is achieved with a method according to claim. 1 ,

The present invention pertains to a method for the control of a. combustion engine, where said combustion engine comprises at least one combustion chamber and elements for the supply of fuel to said combustion chamber, wherein the combustion in said combustion chamber occurs in combustion cycles. The method is characterised in:

- determining, during a first combustion cycle and with the use of a first sensor element, a first parameter value

representing a quantity relating to the combustion in said combustion chamber,

- estimating, with the use of said first parameter value, during a first part, of said first combustion cycle, a first, measure of a first compound resulting during the combustion during said first combustion cycle,

- determining, based on said first measure, a first amount of additive for supply to said combustion chamber, and

- adding said first, amount of additive to said combustion chamber during a subsequent part of said first combustion cycle .

Said additive may e.g. consist of an additive for the

reduction of at least a first compound, such as e.g. nitrogen oxides resulting during combustion in said combustion chamber. During combustion, in combustion engines, in particular diesel engines, unwanted nitrogen oxides NO _x are generated, at least partly because of the excess oxygen, which is generally applied during combustion in diesel engines. Alternatively, the additive may consists of an additive intended for

reduction, of one or several contaminants resulting during the combust ion .

As mentioned, due to for example government regulations, some type of treatment of the exhaust stream is often required, with the objective to reduce the amount of nitrogen, oxides in the exhaust stream., before the exhaust stream is released, into the vehicle's environment, wherein such reduction of emissions may be carried out by injecting additives n a suitable dose into the exhaust stream upstream of an SCR catalyst.

The additive then evaporates on contact with the hot exhausts, whereby ammonia is created/released, in order to subsequently reduce nitrogen oxides in the exhausts to nitrogen gas and aqueous vapour in the SCR catalyst.

The additive may be supplied with the help of an injection system, comprising one or several nozzles for injection of the additive into the exhaust stream. With the correct dosage of additive, the emission of nitrogen oxides may be reduced to a great extent .

However, the desired function at injection of additive is dependent on the exhausts keeping a sufficiently high

temperature, in order for the additive to evaporate . During large parts of a diesel engine's operating mode, the exhausts usually do maintain a sufficiently high temperature for the desired evaporation to occur.

However, there are situations where this may not be

guaranteed, and it may be difficult, at least during some operating modes, to avoid that some of the injected additive, e.g. a urea/aqueous solution, comes into contact with wall surfaces of e.g. one or several of exhaust pipes, catalysts, silencers while in a non-evaporated condition. In such

situations, urea/urea-based compounds may attach to wall surfaces in the exhaust system.

If the formation of solid formations is greater than the evaporation of the coating formed, a successive build-up of deposits will occur. In unfavourable conditions, the result may be a significant build-up of solid, material. Such build- up may grow so large that the combustion engine's performance is impacted, since the exhaust stream in the exhaust system is impacted (throttled) , and in case of a large build-up of the deposit, the continued operation of t e engine may in extreme cases be completely prevented. The deposit may also damage components in the after treatment system, if the formations created, e.g. in the form of lumps, are released from the location where they were formed and then carried along the exhaust stream to e.g. a subsequent SCR catalyst or other components. The formation of the deposit may also entail a reduced exhaust purification function.

According to the present invention, such problems with deposit formation may be reduced. Similarly, the need for SCR

catalysts may be reduced or completely eliminated.

Additionally, the use of additive may be adapted to the prevailing requirements, so that an exaggerated supply of additive, with the associated costs, may be reduced. According to the invention, additive is injected directly into the combustion engine's combustion chamber. The temperature in the combustion chamber is, at least during the combustion of fuel, substantially higher than in e.g. the SCR catalyst, where the exhaust stream is successively cooled down when passing through the exhaust pipe, among others as the exhaust, pipe usually is cooled by the surrounding air. The SCR

catalyst is, among other things, required because of this cooling down, since otherwise the reaction rate during the reduction of NO _x with the use of the additive would be too low for the desired reduction to be carried out before the exhaust stream is released into the vehicle's environment.

In the combustion engine's combustion chamber, on the other hand, the temperature is usually so high that the wanted reaction rate may be achieved without a catalyst, and by injecting additive directly into the combustion chamber a very high reaction rate may be obtained at the reduction of the resulting nitrogen oxides, as the exhaust temperature is still high.

According to one preferred embodimen of the present

invention., the nitrogen oxides resulting during combustion are estimated, so that a suitable amount of additive may be injected as a function of the estimated amount of resulting nitrogen oxides .

When the applicable amount of additive for injection is determined, e.g. the known chemical ratios during the reaction between the additive and nitrogen oxides may be applied, to determine the applicable amount of additive for supply to the combustion chamber. At this determination, the combustion chamber's temperature may also be estimated, e.g. with the use of said first parameter value, wherein the amount of additives may e.g. depend on the expected reaction rate.

According to one embodiment, a part of the required additive may be arranged to be injected into the combustion chamber, while another part may be injected conventionally downstream of the combustion engine, wherein one part of the reduction may be carried out in the combustion chamber and one part may be carried out in e.g. an SCR catalyst.

Further, the estimation of the amount of nitrogen oxides resulting during combustion may e.g. be arranged to be carried out at applicable points in time, such as every time a

significant change of the combustion occurs, e.g. a change in the injected amount of fuel. For example, the estimation may be carried out during one or a suitable number of combustion cycles, so that the injection of additive may subsequently be carried out based on said estimation, e.g. as long as the conditions remain the same or substantially the same.

According to one embodiment, the amount of resulting nitrogen oxides are estimated for each combustion cycle and during the ongoing combustion cycle, whereby the supply of additives during each combustion cycle may be adapted to the ongoing combustion cycle's combustion during this ongoing combustion cycle, and may also be injected during the ongoing combustion cycle .

According to one embodiment , signals from an NO _x sensor arranged downstream of the combustion engine are applied in the determination of the applicable amount of additives for supply to the combustion chamber. In this case, e.g. an undesirably high NO _x level indicated by the NOx sensor may entail an increase in the amount of reductant supplied.

According to one embodiment , the temperature prevailing in the combustion chamber is also estimated/used, so that the

injection of additive may e.g. be arranged to be carried out only if the combustion chamber ' s temperature exceeds some applicable temperature . This has the advantage that unwanted deposit formations in/downstream of the combustion chamber, and caused by additive, may to a great extent be avoided.

According to one embodiment of the invention, an extra fuel injection is carried out before or at the same time as the injection of additive, so that the temperature in the

combustion chamber may be increased through the use of the extra fuel injection, in order thus to facilitate desired chemical reactions.

According to one embodiment of the invention, the invention is combined with regulation of the combustion engine ' s combustion during an ongoing combustion cycle, wherein the combustion may be regulated towards one applicable criterion out of several, such as one or several of : resulting nitrogen oxides,

combustion temperature, pressure amplitude and/or pressure change rate, heat losses, work generated at combustion. The injection of additive may also be arranged to be carried out individually for each cylinder, i.e. resulting nitrogen oxides may be determined individually for each combustion chamber, so that the injection of additive may be adapted indi.vidua.lly for each combustion chamber.

The invention thus enables a regulation, where e.g.

differences between, different cylinders may be detected, and. nitrogen oxide variations may be compensated by using

individual adaptation of the injected amount of additive for each combustion chamber. It may also be the case that

injection of different amounts of additive in. different combustion chambers may be desirable, e.g. in order to control certain cylinders towards the fulfilment of some criterion, and other cylinders towards some other applicable criterion, which may also be achieved according to the invention.

Further, only one or some of the cylinders may be arranged to be controlled according to the invention, while combustion in the remaining cylinders may be carried out in a customary or other applicable manner.

The method according to the present invention may e.g. be implemented with the use of one or several FPGA (Field- Programmable Gate Array} circuits, and/or one or several ASICs (Application-Specific Integrated Circuit) , or other types of circuits that may handle the desired calculation speed.

Further characteristics of the present invention and

advantages thereof will be described in. the detailed

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

Brief description of drawings

Fig. 1A schematically shows a vehicle, in which the present invention may be used. q

Fig. IB shows a control device in the control system for the vehicle shown in Fig. 1A.

Fig. 2 shows the after-treatment system for the vehicle

displayed in Fig. 1 in more detail.

Fig. 3 snows an example of a dosage system for the supply of additives to the exhaust stream.

Fig. 4 shows the combustion engine in the vehicle shown in

Fig. 1A in more detail.

Fig. 5 shows an example method according to the present

invention .

Fig, 6 shows an example of a temperature track, nitrogen oxide change and heat release for a combustion.

Detailed description of embodiments

Fig, 1A schematically shows a driveline in a vehicle 100, according to an embodiment of the present invention. 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 several 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, or a type with a manual gearbox, etc.

An output shaft 107 from the gearbox 103 operates the driving wheels 113, 114 in a customary manner via the end gear and driving shafts 104, 105. Fig, 1A shows only one shaft with driving wheels 113, 114, but in a customary manner the vehicle may comprise more than one shaft equipped with driving wheels, or one or more extra shafts, such as one or more support shafts. The vehicle 100 also comprises an exhaust system with an after-treatment system 200 for customary treatment

(purification) of exhaust emissions resulting from combustion in the combustion chamber (e.g. cylinders) of the combustion engine 101. The after-treatment system is displayed in more detail in Fig. 2, The figure shows the combustion engine 101 of the vehicle 100, which consists of an engine with turbo, which is why the exhaust, generated, by the combustion (the exhaust stream) is led via a turbocharger 220. 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 detai 1 herein .

The exhaust stream is subsequently led via a pipe 204

(indicated, by arrows) to a diesel particulate filter (DPF) 202, via a diesel oxidation catalyst (DOC) 205. During the combustion in the combustion engine, soot particles are formed, and the particulate filter 202 is used to catch these soot particles. The exhaust stream is led through a filter structure where soot, particles are caught from, the exha st stream passing through, and are stored in the particulate filter.

The oxidation catalyst DOC 205 has several functions, and. is normally primarily used in the after treatment to oxidise remaining hydrocarbons and carbon monoxide in the exhaust stream into carbon dioxide and water. The oxidation catalyst 205 may also oxidise a large fraction of the nitrogen

monoxides (NO) occurring in the exhaust, stream, into nitrogen dioxide (NO ₂ ) - Oxidation of nitrogen monoxide NO into nitrogen dioxide NO ₂ is advantageous at the reduction of nitrogen oxides NO _x · As mentioned above, an SCR (Selective Catalytic Reduction} catalyst 201 is usually used for this purpose, using ammonia (NH ₃ ) , or a composition from which ammonia may be

generated/formed, e.g. urea, as an additive for the reduction of nitrogen oxides NO _x in the exhaust stream. The efficiency of this reduction is impacted, however, by the ratio between NO and. NO ₂ in the exhaust stream, so that the reduction reaction is impacted in a positive direction by the previous oxidation of NO into N0 ₂ .

Regarding the present invention, the after-treatment system may generally be of different types, and does not need to comprise e.g. a particulate filter 202 or an oxidation

catalyst 205. According to a preferred embodiment, no SCR catalyst is required, since the reduction, of nitrogen, oxides may be carried out. entirely in the combustion engine ' s

combustion chamber. The after-treatment system may also comprise additional non-displayed components .

The SCR catalyst thus requires an additive to reduce the concentration of nitrogen oxides in the exhausts. This

additive is often urea-based and may consist of the product AdBlue, which basically consists of urea diluted with water.

One example of a conventional system for the supply of

additive is displayed, more in. detail, in Fig-. 3, where of the above components only the particulate filter 202 and the SCR catalyst 201 are displayed, and where the system, apart from said catalyst 201, comprises a urea tank 302 connected to a urea dosage system (UDS ) 303. The urea dosage system 303 comprises or is controlled by, an LIDS control device 304, generating control signals for the control of the supply of additive, so that the desired amount of additive is injected from the urea tank 302 into the exhaust stream resulting from the combustion in the cylinders of the combustion engine 101, with the help of an injection noz z 1e 305 upstream of the SCR catalyst 201. Fig-, 3 also shows an NO _x sensor 308 arranged downstream of the SCR catalyst 201.

The more specific functions of urea dosage systems are well described in prior art technology, and the exact method for the injection of additives is therefore not described in any further detail herein. Generally, however, the temperature at the injection point/SCR catalyst 201 should be at least 200- 250 °C, preferably over 300 °C, for the desired reaction rates to be obtained and thus the desired reduction of said first compound, such as one or several types of nitrogen oxides.

According to the above, however, such systems are associated with certain disadvantages. If e.g. the temperature at the position in the after-treatment system where the supply of additive occurs is too low, there is a risk that urea injected with the injection nozzle 305, instead of directly evaporating as a result of the passing exhaust stream, encounters

relatively low temperature pipe walls, which causes the additive to attach and begin to build, up crystals. As long as the vehicle is driven with varying and periodically higher load with associated increases of temperature in the after- treatment system, this build-up of crystals will not be able to grow undesirably large before the crystals are burned away by the passing exhaust stream. If, on the other hand, the vehicle during a period of time is driven under relatively static conditions with a relatively low load, with low

temperatures in the exhaust system, as a consequence, such crystal build-up may continue until the vehicle ' s performance to an undesirable extent is adversely impacted by the increased flow resistance. The crystal build-up may also entail that the SCR system's ability to convert NO _x is

impacted, if the supply of urea (e.g. spray image, amount) is disrupted because a deposit in the form of caking- arises.

According to be above, this is resolved with the present invention by injecting the additive directly into the

combustion chamber.

Combustion engines in vehicles of the type shown in Fig. 1A are often equipped with controllable injectors in order to supply the desired amount of fuel at the desired point in time in the combustion cycle to the combustion engine's combustion chamber, such as at a specific piston position (crank angle degree) in the case of a piston engine.

Fig. 4 schematically shows an example of a fuel injection system for the combustion engine 101, exemplified in Fig. 1A. The fuel injection system consists of a so-called Common Rail system, but the invention is equally applicable in other types of injection systems. Fig. 4 shows only one

cylinder/combustion chamber 401 with a piston 403 active in the cylinder, but the combustion engine 101 consists, in the present example, of a six-cylinder combustion engine and may generally consist of an engine with any number of

cylinders/combustion chambers, e.g. any number of

cylinders/combustion chambers in the range 1-20 or even more. The combustion engine also comprises at least one respective injector 402 for each combustion chamber (cylinder) 401. Each respective injector is thus used for injection/supply of fuel into a respective combustion chamber 401. Alternatively, two or more injectors per combustion chamber may be used. The injectors 402 are individually controlled, by respective actuators (not shown) arranged at. the respective injectors, which., based on received control signals e.g. from the control device 115, control the opening/closing of the injectors 402.

The control signals for the control of the actuators '

opening/closing of the injectors 402 may be generated by some applicable control device, such as by the engine control device 115 in this example. The engine control device 115 thus determines the amount, of fuel which actually is to be injected at any given time, e.g. based on prevailing operating

conditions in the vehicle 100. The injection system shown in Fig. 4 thus consists of a so- called Common Rail system, which means that all injectors (and therefore all combustion chambers) are supplied with fuel from a common fuel conduit 404 (Common Rail), which, with the use of a fuel pump 405, is filled, with fuel from a fuel tank, (not shown) at the same time as the fuel in the conduit 404 is pressurised to a certain pressure, also with the help of the fuel Pump 405. When the respective injector 402 is opened, the highly pressurised fuel in the common conduit 404 is then injected into the combustion chamber 401 of the combustion engine 101. Several openings/closings of a specific injector may be carried out during- one and the same combustion cycle, whereby several injections may thus be carried out during the combustion of one combustion cycle. Further, each combustion chamber is equipped with a respective pressure sensor 406 for sending of signals regarding a prevailing pressure in the combustion chamber to e.g. the control device 115. The

pressure sensor may e.g. be piezo-based, and should be fast enough to be able to send crank angle resolved pressure signals, for instance at every 10th, every 5th or every crank angle degree, or at. another suitable interval, e.g. more frequently . With the help of a system of the type shown in Fig, 4, the combustion during a combustion cycle in a combustion chamber may to a large extent be controlled, e.g. by using multiple injections, where the times and/or duration of the injections may be controlled., and where data from. e.g. the pressure sensors 406 may be taken into consideration in connection with this control. By using data from e.g. the pressure sensor the nitrogen oxides resulting from the combustion, may also be estimated, so that, additive may be supplied, to the combustion, for instance depending on the estimated amount of resulting nitrogen oxides. Regarding the supply of additive, each combustion chamber, or only a part of the combustion engine's combustion chambers, each, comprises an injector 410 through the use of which the additive may be supplied to the

combustion chamber 401 from a tank 411.

Fig. 5 shows an example method 500 for the supply of additive to the combustion chamber according to the present invention, where the method according to the present example is arranged to be carried out by the engine control device 115 shown in Figs. 1A-B.

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 device or controller 115, and various components arranged on the vehicle. According to prior art, 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. Figs. 1A-B show only the control device 115, in which the present invention is implemented in the embodiment displayed. The invention may, however, also be implemented, in a control device dedicated to the present invention, or wholly or partly in one or several other control devices already existing in the vehicle. Considering the speed at which calculations according to the present invention are carried out.., the invention may be arranged to be implemented in a control device which is especially adapted for real time calculations of the type described below. The implementation of the present invention has shown that e.g. ASIC and. FPGA. solutions a.re suitable for and cope well with calculations according to the present invention.

The function of the control device 115 (or the control

device (s) at which the present invention is implemented.) according to the present invention, may, apart from depending on sensor signals from the pressure sensor 202, e.g. depend on signals from other control devices or sensors. Generally, control devices of the type shown are normally arranged to receive sensor signals from different parts of the vehicle, as well as from different control devices arranged on the

vehicle .

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

The computer program usually is a part of a computer program product, where the computer program product, comprises an applicable storage medium 121 (see Fig. IB), with the computer program stored on said storage medium 121. 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 115) is shown schematically 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) , one or several FPGA (Field-Programmable Gate Array) circuits or one or several circuits with, a predetermined 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 and/or the stored data that 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 receiving 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 as

information for processing by the calculation unit 120. The devices 123, 124 for sending output signals are arranged to convert the calculation result from the calculation unit 120 into 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 receiving and sending of input and output signals may consist of one or several of the following: a. cable, a data bus, 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.

Reverting to the method. 500 shown in Fig, 5, the method, begins with step 501, where it is determined whether the supply, according to the invention, of additive to the combustion chamber for nitrogen oxide reduction should, be carried out . The control according to the invention may e.g. be arranged to be carried out continuously, as soon as the combustion engine 101 is started. According to one embodiment, the injection of additive into a combustion chamber is carried, out only if the injection is preceded by a combustion during the same

combustion cycle .

The method, according to the present invention thus consists of a method for the supply of additives to the combustion chamber of the combustion engine 101, while the combustion takes place in said combustion chamber 201 in combustion cycles. As is previously known, the term combustion cycle is defined as the steps comprised in a combustion in a combustion engine, e.g. a two-stroke engine's two strokes and a four-stroke engine's four strokes. The term also includes cycles where no fuel is actually injected, but where the combustion engine is still operated with a certain engine speed, such as by the vehicle's driving wheels via the driveline, in e.g. dragging. That is to say, even if no injection of fuel is carried out, a combustion cycle is still completed for e.g. every two revolutions (for four-stroke engines ) , or e.g. every revo1ution (two-stroke engines) by the combustion engine's output shaft. The same applies to other types of combustion engines.

In step 502, it is determined whether a combustion cycle has or will be started, and when this is the case, the method continues to step 503, where an amount of nitrogen oxides resulting during combustion is estimated.

Generally, the supply of fuel to the combustion chamber, both with respect to quantity and manner of supply, i.e. the one or several fuel injections that are to be carried out during the combustion cycle, is normally defined in advance, e.g.

depending on the work (torque) that the combustion engine must carry out during the combustion cycle.

Fuel injection is thus normally carried out. according to an injection schedule, where several injections may be arranged to be carried out during one and the same combustion cycle. Combustion in connection with these fuel injections will give rise to resulting- nitrogen oxides.

According to the present invention, during the combustion cycle the prevailing pressure in the combustion chamber is determined substantially continuously with the use of the pressure sensor 406, for instance at applicable intervals, e.g. every 0.1-10 crank angle degrees.

The combustion process in a combustion chamber may generally be described with the pressure change that the combustion gives rise to in the combustion chamber. The pressure change during a combustion cycle may be represented by a pressure track, i.e. a representation of how the pressure in the combustion chamber varies during the combustion.

In step 503 thus the pressure p _f is determined substantially continuously in said combustion chamber 401, by using said pressure sensor 206 during the course of the combustion in the combustion chamber. By using the pressure change, nitrogen oxides NO, generated may during the combustion cycle be estimated with the use of applicable calculations, and one way of carrying out the calculation is exemplified below.

Alternatively, other models with similar functions may be applied .

Generally, nitrogen oxides N0 _X are mainly formed for three different reasons during a combustion process. The fuel may comprise nitrogen, and nitrogen will be released during combustion and at. least generate nitrogen gas N2 and nitrogen oxides NO, . This type of NO _x formation may in some types of combustion, and depending on the type of fuel, account for a large part of the total amount of nitrogen oxides NO _x generated at combustion. As explained below, this type of NO _x formation may, however, be disregarded during normal combustion

according to e.g. the diesel cycle. Another source of KO _x formation consists of so-called prompt NO _x formation, but this source may generally be disregarded since the impact is small in relation to other sources, A third, source, which during normal combustion also constitutes the primary cause of KO _x formation during combustion at high combustion temperatures, consists of thermal formation, of NO _x , which may account for in the range of 90-95% or even more of the NO _x formation during the combustion cycle.

The ΝΟχ formation is thus heavily dependent on the combustion temperature, and the formation of thermal NO _x may in itself be described in a well-known manner, e.g. according to three main reactions (the expanded Zeldovich mechanism} :

, 'where thus the reaction, speed is heavily dependent on temperature, and where also the temperature dependency as such is known, so that the amount, of nitrogen oxid.es N0 _X formed may be estimated through knowledge about the (substance) amount of the substances comprised and the temperature.

According to the present invention, NO _x formation is estimated by using the above chemical reaction formula, equation (1), and by using an estimation of additional combustion data. The calculation thus also requires knowledge about the available amount of nitrogen and oxygen 0 ₂ , as well as knowledge about access to hydrogen H. These may be obtained from the

combustion's combustion chemistry, which is known to a person skilled in the art, and for which the supplied amount of fuel and combustion air as well as any exhaust recirculation is known, whereby, in combination with the fact that the fuel composition is normally known, the amounts of the substances comprised in equation (1) may be calculated. Also, an estimation of the combustion's temperature is

required for estimating the amount of nitrogen oxides KO _x generated, since the reaction speed is dependent on

temperature . Likewise, pressure and./or mean temperature in the combustion chamber is required in order to, through the combustion chemistry, be able to estimate released nitrogen and oxygen during- the combustion.

At the estimation of the amount of nitrogen oxides NO _x formed, knowledge about the combustion temperature itself is therefore required. The temperature is higher in the part of the

combustion chamber where the combustion is ongoing, and the combustion chamber may be considered to consist of two zones, where combustion takes place in one zone, with a nigh

temperature in this zone as a consequence, while no

combustion, with a lower resulting temperature, takes place in the other zone. In total, at each moment a mean temperature in the combustion chamber is thus obtained, falling below the ^c ombustion ' s tem.perat.ure where combustion is ongoing. In order to be able to carry out a desirable determination of the combustion's temperature, knowledge about the heat release during combustion is also required.

This may be determined in different ways. For example, as described below, the heat release may be predicted through the use of a combustion model . This is exemplified in the

international patent applications described below. In these applications, future parts of a combustion are estimated, while, according to one embodiment of the present invention, pressure signals from the pressure sensor 406 may be used, to calculate heat release during combustion.

Heat release during combustion may then, be expressed as:

Where dQ is released heat, p constitutes the pressure in the combustion chamber,

V constitutes the volume of the combustion chamber, while dV constitutes the volume change of the combustion chamber. ν(φ) i.e. the combustion chamber's volume as a function of crank angle may advantageously be tabulated in the control system's memory, or be calculated in an applicable manner, dV

whereby also may be determined .

where C _p and./ or C _v are preoared and tabulated.

for different molecules, and since the combustion chemistry is known, these tabulated values may be used together with the combustion chemistry in order to thus calculate each

molecule's {e.g. water, nitrogen, oxygen, etc.) impact on e.g. the total C ₀ value, so that this may be determined for the calculations above with a good accuracy. Alternatively, C _p and/or C _v may be approximated in a suitable manner. dp constitutes the pressure change in the combustion chamber, determined with the pressure sensor 406. dQ _HT represents the heat released during combustion, which may be determined in a manner that is well described in the prior art technology by e.g. Woschni, Here, regard may also be had to blackbody radiation in the combustion chamber in a known manner. The international patent application PCT/SE2014/050493 entitled "METHOD AND SYSTEM FOR CONTROL OF AN INTERNAL

COMBUSTION ENGINE" describes a method for estimating released heat during an ongoing combustion. The method described in this application may be applied according to the present invention. Further, the method shown in said application may be simplified, as no estimation of the pressure is required according to the present embodiment, and pressure signals from the pressure sensor 406 may be used, during an ongoing

combustion cycle up to the point in time when the maximum amount of nitrogen oxides is deemed to nave been generated, according to the below. Said application also shows how the neat release may be estimated before a combustion.

According to the present example, the heat release may, however, be estimated according to equation (2) through the use of signals from the pressure sensor 406. Fig, 6 shows, as a rough approximation, how the heat release 603 may change during a combustion cycle. Instead of expressing the combustion process as a function of time, it is expressed as a function of crank angle degree <p. Fig. 6 also shows how the modelled ISIOx amount 601 resulting during combustion changes during the combustion cycle, as well as how the mean

temperature 602 in the combustion chamber changes during the combustion cycle.

The pressure change pas a function of crank angle degree φ in a cylinder (combustion chamber) for a combustion cycle may, according to the above, be obtained through the use of sensor signals from the pressure sensor 406. Further, by using a determined pressure, the temperature for the part of the combustion chamber where no combustion occurs may be estimated with the help of an estimated pressure and by using equation (3), where the temperature for the part of the combustion chamber where no combustion takes place is expressed as:

, where T _ir^0 may constitute corresponding combustion air temperature for e.g. the point in time/crank angle position where the valves are closed after the supply of combustion air ,

Further, n, n+1, etc. constitute consecutive points in time or crank angle positions.

K ----- Y where thus also K may be determined according to what is specit red for γ above.

By using equation (3) the temperature for the part of the combustion chamber where no combustion takes place may be determined, this temperature, however, being impacted by ongoing combustion through the effect of the neat release on the pressure, which is reflected in the signals emitted by the pressure sensor, which in turn impacts the temperature

according to equation (3). When a combustion then takes place, the heat release will give rise to a temperature increase in the part (s) of the combustion chamber where combustion is taking place. This temperature increase, which is added to the temperature determined according to equation (3) in order to obtain the combustion, temperature, may be calculated based on. t.he corre 1a.tion :

, where dO constitutes heat release, which may be determined as above . m consists of burned mass (i.e. fuel + air + EGR comprised in the combustion) , which is also determined as set out above,

C , i.e. specific neat capacity, which may also be calculated as set out above. dT constitutes the temperature increase obtained from the combustion, with a given burned mass and with a given C value .

By using equation (4), d'T and therefore ΔΤ may thus be determined, so that the increase generated by the combustion at each point, in time/crank angle position may be added, to the temperature of the part of the combustion chamber where no combustion occurs, and as provided by equation (3), to obtain the combustion temperature.

When the combustion temperature has been estimated, the concentrations and/or absolute amounts of primarily ]¾ and 0 ₂ may thus be calculated by using the combustion chemistry, so that later, by using equation (1) and its combustion

temperature dependency, generated nitrogen oxides NO _x may successively be estimated and accumulated for the combustion cycle. The modelled nitrogen oxides basically are generated up to the maximum combustion temperature having been reached., or during a certain time thereafter, indicated with the crank angle position φ ₁ in Fig. 6.

Thus, in parallel with the estimation of the resulting

nitrogen oxides, it may be determined whether T _i;iax for the combustion cycle has been reached - step 504 - so that, when this is the case, the method continues to step 505 for the determination of an applicable amount of additive for

injection into the combustion chamber 201 by using the

injector 410, where the applicable amount of additive for injection may e.g. be determined through the use of known chemical correlations in the reaction between additives and nitrogen oxides. For example, the amount of additive may be determined as a stoichiometric amount of additive, i.e. the amount of additive required in order to entirely convert the amount of nitrogen oxides . The amount of additive supplied to the combustion chamber may also e.g. consist of some

applicable fraction of a stoichiometric amount, such as more or less than this amount . For example, it may be desirable only to reduce the nitrogen oxides NO _x to a certain extent, meaning that a smaller amount may be supplied. For example, an amount may be supplied which is expected to entail that the vehic1e ' s emiss ions meet the prevai 1ing regu1atory

requirements where the vehicle is driven.

Alternatively, the amount may be arranged to exceed the stoichiometric amount, e.g. in order to obtain a high reaction rate . According to one embodiment , the combustion chamber ' s

temperature is also used, i.e. the temperature track 602 in Fig. 6, for the determination of the applicable amount of additive, where the reaction rate is heavily temperature- dependent, so that the amount of additive may thus e.g. be determined as a function of one or several of the amount of resulting nitrogen oxides, pressure in the combustion chamber, temperature in the combustion chamber .

According to one embodiment, the amount of resulting NO _x is estimated successively, so that when it is determined that this has reached the maximum and/or begins to decrease, such as at or after the position (pi in Fig. 6, which normally also occurs via other chemical reactions than via a reaction with an additive, although with a significantly lower reaction rate, the applicable amount of additive for supply may be determined .

The additive is then injected in step 506, wherein the method may revert to step 501 for a new determination for a

subsequent combustion cycle. According to the present

invention, the amount of resulting nitrogen oxides during a combustion cycle thus may be estimated, so that an amount of additive adapted to the amount of generated nitrogen oxides may be injected into the combustion chamber in order to already achieve reduction of the nitrogen oxides in the combustion engine where a high temperature prevails, and therefore without any need for an SCR catalyst . The present invention thus has the advantage that the need for an SCR catalyst may be eliminated completely, or at least reduced . According to one embodiment, additives may also be injected upstream of an SCR catalyst where needed, wherein e.g. a smaller SCR catalyst than would otherwise be possible may be used, but in many cases the need for an SCR catalyst disappears entirely when the present invention is used.

Further, problems with crystal formation, etc. , due to low temperatures according to the above, may also be completely or to a great extent avoided according to the present invention.

According to one embodiment, the injection of additives is not carried out unless the combustion chamber's mean temperature exceeds some applicable temperature Tii _m , e.g. 700---750 °C . This embodiment thus requires knowledge about not only the

combustion's temperature, according to the above, but also about the mean temperature for the combustion chamber, i.e. the curve 602 in Fig, 6. This mean tem.perat.ure 602 may e.g. be estimated according to the description in the international patent application PCT/SE2014/050491, which describes in detail how the mean temperature in a combustion chamber may be estimated through the use of e.g. the pressure in the

combustion chamber, which may be obtained with the pressure sensor 406.

According to the method, shown in said application, an

estimation for future time is carried out, and such estimation may also be applied in the present invention in order to thus, through estimation, predict the applicable amount for

injection already before the generated nitrogen oxides have reached the maximum level. In this case, the model shown in said application or another applicable model of the combustion may also be used.

One embodiment, however, uses the fact that pressure signals from the pressure sensor 206, representing the actually prevailing pressure in the combustion chamber, may be used up to the point when the amount of nitrogen oxides has reached the maximum amount of nitrogen oxides, e.g. the position <p _x in Fig. 6, so that no estimation is required, and where the heat release may e.g. be estimated according to the above, and where the mean temperature may be determined e.g. according to the general gas law. Thus, according to one embodiment , it may be determined that the temperature is sufficiently high for the desired reactions to arise, such as a prevailing mean temperature in the combustion chamber exceeding 700-750 °C, where such mean temperature may thus be determined using the general gas law in known manner and as also shown, in said application, so that the unwanted crystal formation may be avoided .

Thus, according to one embodiment , injection is carried out only if the temperature exceeds the temperature Tlim., shown in Fig. 6, so that thus the interval φ ι - <p ₂ constitutes a "window" in which the injection of additive should occur. This "window" may also e.g. be limited with respect to maximum temperature, i.e. injection may be arranged to occur only if the

temperature in the combustion chamber is below some applicable temperature, where thus cpi may be shifted to the right in Fig. 6, Further, it should, be noted that the injection, of an additive need not. be carried out precisely where a combustion is actually ongoing in the combustion chamber, but the

injection may occur in any location inside the combustion chamber, e.g. with the additional condition, that said mean temperature does not. drop below Tlim,

According to one embodiment, the method shown, in said, patent application. PCT/SE2014/050491 may e.g. also be applied in order to, e.g. before the position <pj , estimate whether the mean temperature will be sufficiently high for injection to possible, and if it is concluded that this is not the case, an extra, fuel injection may e.g. be carried out. based on such estimation, in order to increase the tem.perat.ure in the combustion chamber to enable injection of additive. If this injection is carried out sufficiently late during the combustion cycle, the injection will not contribute to NO _x formation, but will increase the temperature. At the

application of such an extra injection, this may be arranged to be of a size determined in advance, but it may also be arranged to be determined using estimation according to the method shown in said international patent application

PCT/SE2014/05049, for example to determine the applicable amount of fuel for injection, separately or jointly with the injection of additive, in order to obtain the desired

temperature .

According to the hitherto described embodiment, the estimation of the resulting amount of nitrogen oxides has been carried out during the ongoing combustion cycle, so that likewise the amount of additive based on the estimated resulting amount of nitrogen oxides is supplied.

According to one embodiment, nitrogen oxides are estimated and injected during a combustion cycle, where, based on this estimation, the injection of additive is also carried out during one or several subsequent combustion cycles. This has the advantage that the estimation may be carried out more infrequently .

According to a simplest form of the invention, no estimation of nitrogen oxides is carried out, but additive is injected, into the combustion chamber at the applicable point in time, where e.g. the injected amount may instead be arranged to depend on the amount of fuel that is supplied to the

combustion, or a standard, amount may always be applied, e.g. as long as at least one minimal amount of fuel is injected. According to a preferred embodiment, however, an estimation of the resulting nitrogen oxides is carried out. According to one embodiment , the invention may be combined with a method that adapts the combustion as the combustion progresses, wherein the combustion is controlled based on some applicable criterion. In e.g. the international patent application PCT/SE2014/050495, a method is described where the combustion is controlled during the combustion cycle based on an expected and, during an ongoing combustion cycle, estimated amount of resulting- nitrogen oxides. According to one

embodiment, the method according to the invention may be combined with the method shown in said application, so that the amount of resulting nitrogen oxides KO _x before the supply of additive may be arranged to be controlled through control of the combustion. Further, the amount of additive for supply to the combustion chamber may be arranged to be determined based on an estimation of the resulting nitrogen oxides, according to the description in said international patent application PCT/SE2G14/G50495.

Further, the method may be arranged to be interrupted when the temperature in the combustion chamber has reached the maximum temperature during the combustion, as substantially all nitrogen oxide generation likely will have taken place before this point in time, so that subsequent control may instead e.g. be carried out entirely according to the selected

injection schedule, or may be carried, out based on some other applicable criterion.

The invention has often been exemplified in a manner where a pressure sensor 406 is used to determine a pressure in the combustion chamber, and with the help of which the temperature and nitrogen oxide generation, as set out above, may be estimated. One alternative to using pressure sensors may instead consist of the use of one (or several) other sensors, e.g. high-resolution ion current sensors, knock sensors or strain gauges, where the pressure in the combustion chamber may be modelled using sensor signals from such sensors. It is also possible to combine different types of sensors, e.g. in order to obtain a more reliable estimation of the pressure in the combustion chamber, and/or to use other applicable

sensors, where the sensor signals are converted into

corresponding pressures for use in control, as set out above.

The method according to the invention for the control of the combustion engine may also be combined with sensor signals from other sensor systems, where the resolution of the crank angle level is not available, such as another pressure

transmitter, NOx sensors, NH3 sensors, PM sensors, oxygen sensors and/or temperature transmitters, etc., the input signals of which may e.g. be used as input parameters in the estimation of e.g. expected pressure/temperature by wholly or partly using computer-driven models instead of models of the type described above. For example, signals from a NO _x sensor arranged downstream of the combustion engine may be used for the determination of the applicable amount of additive for supply to the combustion chamber. In this case, e.g. an undesirably high NO _x level indicated by the NO _x sensor may entail an increase of the amount of reductant supplied.

Additionally, the present invention has been exemplified above in relation to vehicles. The invention is, however, also applicable to any vessels/processes where nitrogen oxide control as set out above is applicable, e.g. watercrafts or aircrafts with combustion processes as per the above.

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 pertains to and comprises all embodiments in the protection scope of the enclosed independent claims. For example, the invention is applicable to injection of any additive in the combustion engine's combustion chamber, where such additive may be intended to reduce nitrogen oxides, or one or several other contaminant s .