SE1151141A1 - Method and system for adapting at least one injector to an internal combustion engine - Google Patents

Abstract

The present invention relates to a method pertaining to adaptation of at least one injector (301-306) for a combustion engine (101), such that said engine (101) comprises at least one combustion chamber, fuel is injected into said at least combustion chamber by use of said at least one injector (301- 306) and a post-treatment system (200) is provided to treat an exhaust flow arising from combustion in said engine (101). Adaptation comprises a plurality of injections by means of said at least one injector (301-306) whereby unburnt fuel is supplied to said post-treatment system (200) via said combustion chamber. The method comprises, after a first injection (i) from said plurality of injections, the steps of estimating an amount (Mest) of unburnt fuel which has become stored in said post-treatment system(200), and conducting a second injection (i+1) following upon said first injection (i) if said estimated fuel stored (Mest) is less than a first amount (ML). The invention relates also to a system and a vehicle.

Description

l0 l5 20 25 30 manufacturing tolerances. For the above reasons, for example, during the manufacture or assembly of the internal combustion engine, a mapping is created, such as a look-up table, where the actual amount of fuel supplied is specified for specific opening times and for the pressure to which the fuel supplied when the injector is opened is pressurized.

The amount of fuel that is actually supplied to a combustion chamber when an injector is opened is thus directly affected by the opening time the injector is open, as well as the pressure to which the fuel is pressurized. The injection pressure can be arranged to always be the same, but can also be arranged to vary, whereby different amounts of fuel can thus be specified for one and the same opening time, but for different injection pressures.

The amount of fuel that is actually to be supplied to a combustion chamber at any given time is usually determined by a control unit in the vehicle's internal control system, which determines a fuel quantity for injection, e.g. based on the prevailing operating conditions of the vehicle, and which then, with the aid of said mapping, determines opening times for the respective injector.

When operating an internal combustion engine, it is important that the actual amount of fuel supplied to the combustion chamber of the internal combustion engine also corresponds to the intended amount of fuel for injection as above. This is achieved by means of the aforementioned mapping, where the injectors are individually calibrated during manufacture of the injector and/or internal combustion engine, so that the mapping can be adapted for each individual injector.

However, the properties of an injector can change over time, e.g. due to wear of the hole(s) through which fuel injection takes place, with the result that a certain opening time no longer necessarily results in the desired amount of fuel being supplied at a specific opening time. For this reason, an adaptation of the injectors is usually carried out, regularly or when necessary, whereby the opening time of the injectors is corrected if necessary.

Summary of the invention It is an object of the present invention to provide a method for adapting at least one injector to an internal combustion engine in a vehicle. This object is achieved by a method according to claim 1.

The present invention relates to a method for adapting at least one injector to an internal combustion engine, said internal combustion engine comprising at least one combustion chamber, and wherein fuel is injected into said at least one combustion chamber by utilizing said at least one injector, wherein an aftertreatment system is arranged for treating an exhaust gas stream resulting from combustion at said internal combustion engine. The adaptation comprises a plurality of injections by means of said at least one injector, wherein unburned fuel is supplied to said aftertreatment system via said combustion chamber.

The method comprises the steps of, after a first injection of said plurality of injections: - estimating an amount of unburned fuel stored in said aftertreatment system, and - if said estimated stored fuel amount is less than a first fuel amount, performing a second injection following said first injection.

By estimating, according to the present invention, an amount of unburned fuel stored in an aftertreatment system 10 l5 20 25 during adaptation and only performing a subsequent injection in a sequence of injections in an adaptation schedule when the estimated stored fuel amount is less than a first fuel amount, it can be ensured that a larger amount of fuel is not stored than can be allowed to oxidize or evaporate in the aftertreatment system during a subsequent possible temperature increase.

Thus, a method is provided that can reduce or completely eliminate problems when adapting injectors to an internal combustion engine. For example, the risk of irreversible so-called poisoning can be reduced, i.e. the risk of situations where hydrocarbons become trapped in the active sites present in catalysts where the catalyst reaction takes place and cause permanent damage can be reduced. In addition, the risk of harmful overheating caused by rapid oxidation of larger amounts of stored fuel in the aftertreatment system is reduced, where the fuel storage has been caused by injector injection when low temperatures in the aftertreatment system prevail.

Further features of the present invention and advantages thereof will become apparent from the following detailed description of exemplary embodiments and the accompanying drawings.

Brief description of the drawings Fig. 1a shows a driveline in a vehicle in which the present invention can be advantageously used.

Fig. 1b shows a control unit in a vehicle control system.

Fig. 2 shows an example of an aftertreatment system in a vehicle in which the present invention can be advantageously used. 10 15 20 25 30 Fig. 3 shows schematically an injection system in the vehicle shown in Fig. 1.

Fig. 4 schematically shows a method according to an exemplary embodiment of the present invention.

Detailed description of preferred embodiments Fig. 1a schematically shows a drive train in a vehicle 100 according to an embodiment of the present invention. The vehicle 100 schematically shown in Fig. 1 comprises only one axle with drive wheels 113, 114, but the invention is also applicable to vehicles where more than one axle is provided with drive wheels, as well as to vehicles with one or more additional axles, such as one or more support axles. The drive train comprises an internal combustion engine 101, which in a conventional manner, via a shaft output from the internal combustion engine 101, usually via a flywheel 102, is connected to a gearbox 103 via a clutch 106.

The internal combustion engine 101 is controlled by the vehicle control system via a control unit 115. Likewise, the clutch 106, which may for example be an automatically controlled clutch, and the gearbox 103 are controlled by the vehicle control system by means of one or more applicable control units (not shown). Of course, the vehicle driveline may also be of another type, such as a type with a conventional automatic gearbox, etc.

A shaft 107 coming out of the gearbox 103 then drives the drive wheels 113, 114 via a final gear 108, such as a conventional differential, and drive shafts 104, 105 connected to said final gear 108.

Internal combustion engines in vehicles of the type shown in Fig. 1a are often provided with controllable injectors to supply a desired amount of fuel at a desired time, and furthermore at a desired time in the combustion cycle, such as at a specific piston position in the case of a piston engine, to the combustion chamber of the internal combustion engine.

Fig. 3 schematically shows the fuel injection system for the internal combustion engine 101 exemplified in Fig. 1a. According to the following, the fuel injection system consists of a so-called common rail system, but the invention is equally applicable to other types of injection systems. The internal combustion engine 101 consists of a six-cylinder internal combustion engine with a respective injector for each combustion chamber (cylinder), schematically indicated as 301-306. Each respective injector is thus responsible for injecting (supplying) fuel into a respective combustion chamber. As can be seen, the internal combustion engine can consist of an engine with any number of cylinders (combustion chambers). Likewise, two or more injectors per combustion chamber can be used. The injectors 301-306 are individually controlled by respective actuators (not shown) arranged at each injector, which, based on received control signals, control the opening/closing of the injectors 301-306.

The control signals for controlling the actuators opening/closing the injectors can be generated by any applicable control unit, such as in this example the engine control unit 115. The control unit 115 thus determines the amount of fuel that is actually to be injected at any given time, e.g. based on the prevailing operating conditions of the vehicle. Specifically how the required amount of fuel is determined is well described in the prior art, which is why this is not described in more detail. The control unit 115 uses a mapping such as e.g. a table as described above to translate a desired amount of fuel into a corresponding opening time for the injectors.

The injection system shown in Fig. 3 further consists of a so-called Common Rail system, which means that all 10 15 20 25 30 injectors (and thus combustion chambers) are served by a common fuel pipe 307 (Common Rail), which is filled with fuel by means of a fuel pump 308 at the same time as the fuel in the pipe 307, also by means of the fuel pump 308, is pressurized to a certain pressure. The highly pressurized fuel in the common pipe 307 is then injected into the combustion chamber 101 of the internal combustion engine when the respective injector 301-306 is opened. Several openings/closings of a specific injector can be carried out during one and the same combustion cycle.

Regardless of how injection occurs during a combustion cycle in a combustion chamber, such as whether it occurs by means of one or more consecutive injections, etc., it is very important that the actual amount of fuel injected into the combustion chamber of the internal combustion engine truly corresponds to the intended amount of fuel for injection. If the actual amount of fuel injected is too small in relation to the desired amount of fuel injected, the internal combustion engine will exhibit lower performance than intended, and compared to what has been promised, with poorer driveability as a result. Conversely, if the amount of fuel injected is too high in relation to the intended amount of fuel, the internal combustion engine may exhibit improved performance, such as higher torque/power than intended. This may in turn cause damage to the internal combustion engine and/or other components present in the vehicle that are not dimensioned for the higher power.

It is therefore very important that the injected fuel quantity actually corresponds to the intended fuel quantity. For this reason, as mentioned above, a mapping, such as a look-up table, is also generated during the manufacture/assembly of the combustion engine 101 and/or the injectors 301-306, where the desired fuel quantity for supply to a combustion chamber 10 15 20 25 30 is translated into a certain opening time for the respective injector, in order to take into account individual differences from injector to injector. That is, the injectors are calibrated at the injector level so that the mapping can be adapted for each individual injector. Although it can thus be ensured during the manufacture of a vehicle that the combustion engine functions in the intended manner, the properties of an injector can change over time, whereby a certain opening time no longer reliably results in the injection of the intended amount of fuel. For example. the characteristics of the injectors can be changed in such a way that a higher amount of fuel than desired is injected for a given opening time/injection pressure ratio, with the disadvantages as above as a result. For this reason, an adaptation of the injectors is usually carried out, regularly or when necessary, where the opening time of the injectors is corrected so that the amount of fuel actually supplied to the combustion also corresponds to the intended amount of fuel supplied.

Adaptation to a system according to Fig. 3 can be carried out as follows. First, the pipe (rail) 307 is pressurized with pressurized fuel by means of the fuel pump 308, whereby continued fuel supply by means of the fuel pump 308 is then shut off.

This means that the tube 307 will contain a certain amount of fuel at a certain pressure. By then opening and closing an injector, such as the injector 301, so that the injector is open for a first opening time to achieve an injection of an expected amount of fuel, the actual amount of fuel injected can be determined by means of the opening time and a determination of the pressure difference (pressure drop) that occurs in the tube 307 when part of the fuel stored in the tube 307 upon opening the injector 301 is supplied to the combustion chamber of the internal combustion engine. The pressure difference can be determined, for example, by means of an appropriate pressure sensor. The actual amount of fuel injected can then be compared with the expected amount of fuel injected, whereby the opening time stored in the vehicle control system for a certain desired amount of fuel can be shortened or extended if necessary so that the actual amount of fuel injected will continue to correspond to the expected amount of fuel. This determination is carried out individually for each respective injector 301-306, and possibly also for different injection pressures if different injection pressures are used in operation of the combustion engine.

When adapting the injectors of the combustion engine, a number of injections are thus carried out, where the number of injections depends on the number of injectors and the number of different opening times to be tested. Each injector/opening time combination can also be arranged to be tested several times during an adaptation. When completely adapting the injectors of the combustion engine 101, a large number of injections can thus be carried out. Since the pressure difference in the fuel pipe 307 is to be determined for each respective injection, however, no other injection can be in progress at the same time. However, the adaptation is still usually carried out while the vehicle is being driven, which means that adaptation is usually carried out during so-called "towing", i.e. in situations where the vehicle is driven with a closed driveline, i.e. with the combustion engine 101 connected to the vehicle's drive wheels 113, 114, at the same time as the fuel supply to the combustion engine 101 is shut off. This is usually done when there is a reduced driving force requirement, such as when driving downhill. Furthermore, the fuel is injected so late during the combustion phase of the combustion cycle that none or only parts of the fuel are burned in the combustion chambers, whereby fuel will follow the exhaust gas stream to the aftertreatment system. For example, the injection can take place 30-40 10 15 20 25 30 10 crankshaft degrees, or even later, after top dead center. Such injection angles mean that the fuel is in principle not ignited at all, but instead follows the exhaust gas stream in unburned form. The adaptation thus means that unburned fuel will be supplied to the vehicle's usually existing aftertreatment system.

Due to increased government concerns regarding pollution and air quality, especially in metropolitan areas, emission standards and regulations have been developed in many jurisdictions, and in an effort to meet these emission regulations, systems have been developed for aftertreatment (purification) of the exhaust gases formed during combustion in the internal combustion engine.

These aftertreatment systems often include some form of catalytic cleaning process, where one or more catalysts are used to clean the exhaust gases. Vehicles with diesel engines often include a particulate filter to capture the soot particles formed during the combustion of fuel in the combustion chamber of the internal combustion engine.

In Fig. 2, the aftertreatment system 200 for the vehicle shown in Fig. 1 is shown in more detail, and the system shown is only one example of an aftertreatment system. The figure shows the internal combustion engine 101 of the vehicle 100, and the exhaust gases generated during combustion (the exhaust gas stream) are led to the aftertreatment system via a turbocharger 220.

The turbocharger can be of different types and the function of different types of turbochargers is well known and is therefore not described in more detail here. The exhaust gas stream is then led via a pipe 204 (indicated by arrows) to a diesel particulate filter (DPF) 202 via an oxidation catalyst (Diesel Oxidation Catalyst, DOC) 205. lO l5 20 25 30 ll The oxidation catalyst DOC 205 is normally used primarily to oxidize residual hydrocarbons and carbon monoxide in the exhaust gas stream to carbon dioxide and water. During the oxidation of hydrocarbons (i.e. oxidation of unburned fuel), heat is also generated, which can e.g. be used to raise the temperature of the particulate filter when emptying, so-called regeneration, of the particulate filter.

Aftertreatment systems of the type shown may also include other components such as, for example, an SCR (Selective Catalytic Reduction) catalyst 201 arranged (in the present example) downstream of the particulate filter 202. SCR catalysts are generally used for reducing the amount of nitrogen oxides NOX.

The aftertreatment system 200 may also include more components than what has been exemplified above, or fewer.

For example, the aftertreatment system may, in addition to, or instead of, the DOC 205, include an ASC (ammonia slip) catalyst (not shown).

The adaptation will thus entail a supply of unburned fuel to the aftertreatment system. Although the supply of unburned fuel is desirable in certain situations, such as in certain types of regeneration of the particulate filter, the supply during adaptation can have undesirable consequences. If the prevailing heat in the aftertreatment system is high during the adaptation, the unburned fuel can be oxidized (ignited) and thereby further increase the temperature of all or parts of the aftertreatment system. If this temperature increase becomes too high, there is a risk of damage to components in the aftertreatment system. If, on the other hand, the prevailing temperature in the aftertreatment system is low and the unburned fuel is thus not oxidized, hydrocarbons will be trapped in e.g. the active sites present in catalysts where the catalyst reaction takes place, and thereby prevent the substances that are actually wanted to react in the catalyst from reaching the catalytic site. The catalyst is thus "poisoned" by the unburned fuel. Heating the catalyst to such a temperature that the stored fuel is oxidized or vaporized can reverse this negative poisoning, but if excessive amounts of fuel are stored in the catalyst, irreversible, i.e. permanent, poisoning can occur, whereby the catalyst function can thus deteriorate slightly each time an adaptation is carried out.

In the event that large amounts of fuel have been stored in the catalyst, when it is heated at a later time and a large amount of fuel "releases" and is simultaneously oxidized, the catalyst temperature can, at least locally, rise to very high levels, with the result that the so-called "wash coat", which constitutes a carrier for catalytic materials and which is used to increase the effective area of the catalyst, overheats, whereby surfaces can sinter together and permanently reduce the active area of the catalyst. In general, hydrocarbons (i.e. unburned fuel) can easily stick to the various parts present in the aftertreatment system, with the risk of poisoning and/or overheating damage as a result.

Supply of unburned fuel to the aftertreatment system can thus result in unwanted and potentially harmful storage of unburned fuel. According to the present invention, a method and a system are provided for reducing the risk of negative effects in the aftertreatment system when adapting the injectors of the internal combustion engine. An exemplary method 400 according to the present invention is shown in Fig. 4. The invention can be implemented in any applicable control unit, such as e.g. the shown engine control unit 115 but also in a control unit dedicated to the present invention, or in whole or in part in one or more other control units already present in the vehicle. Generally, control systems in 10 15 20 25 30 13 modern vehicles consist of a communication bus system consisting of one or more communication buses for interconnecting a number of electronic control units (ECUs) such as the control units, or controllers, 115 and various components located on the vehicle. Such a control system may include a large number of control units, and the responsibility for a specific function may be divided among more than one control unit. For the sake of simplicity, only the control unit 115 is shown in Fig. 1a.

Control units of the type shown are normally arranged to receive sensor signals from various parts of the vehicle. The function of the control unit 115 (or the control unit(s) in which the present invention is implemented) will likely depend, for example, on information such as received sensor signals from various sensors arranged at the combustion engine, as well as from other control units such as the control unit responsible for temperature determinations in the aftertreatment system and/or signals from temperature sensors in the aftertreatment system.

Such control units are further usually arranged to emit control signals to various vehicle parts and components. For example, the control unit 115 will emit signals to, for example, the actuators of the injectors. 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 unit causes the computer/control unit to perform the desired control, such as method steps according to the present invention. The computer program usually forms part of a computer program product, where the computer program product comprises a digital storage medium 121 (see Fig. lb) with the computer program 109 stored on said storage medium 121.

Said digital storage medium 121 may, for example, consist of one of the following: ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically Erasable PROM), a hard disk drive, etc., and be arranged in or in connection with the control unit, whereby the computer program is executed by the control unit. By changing the instructions of the computer program, the behavior of the vehicle in a specific situation can thus be adapted.

An example control unit (control unit 115) is shown schematically in Fig. lb, wherein the control unit in turn may comprise a computing unit 120, which may consist of, for example, any suitable type of processor or microcomputer, for example, a digital signal processing circuit (Digital Signal Processor, DSP), or a circuit with a predetermined specific function (Application Specific Integrated Circuit, ASIC). The computing unit 120 is connected to a memory unit 121, which provides the computing unit 120 with, for example, the stored program code 109 and/or the stored data the computing unit 120 needs to be able to perform calculations. The computing unit 120 is also arranged to store partial or final results of calculations in the memory unit 121.

Furthermore, the control unit is provided with devices 122, 123, 124, 125 for receiving and transmitting input and output signals, respectively. These input and output signals may contain waveforms, pulses, or other attributes, which can be detected by the devices 122, 125 for receiving input signals as information for processing by the computing unit 120. The devices 123, 124 for transmitting output signals are arranged to convert calculation results from the computing unit 120 into output signals for transmission to other parts of the vehicle's control system and/or the component(s) for which the signals are intended. Each of the connections to the devices for receiving and transmitting input and output signals may consist of one or more of a cable; a data bus, such as a CAN bus (Controller Area Network bus), a MOST bus (Media Oriented Systems 10 15 20 25 30 15 Transport), or some other bus configuration; or by a wireless connection. Returning to Fig. 4, it is determined in step 401 whether adaptation of injectors is to be started. If so, the method continues to step 402 at the same time as a counter i is set = 1. The transition from step 401 to 402 may be dependent on various conditions. For example, it may be decided that adaptation should be performed because a certain time has elapsed since the previous adaptation and/or for some other reason. In general, reference is made to the prior art regarding applicable conditions for starting the adaptation. Furthermore, according to the above, it may be required that the vehicle is driven with the fuel supply turned off, such as when towing, which is why it may also be required that this criterion must be met when transitioning from steps 401-402. The invention itself is, however, applicable in all cases where unburned fuel is supplied during adaptation, i.e. also in cases where adaptation is carried out with ongoing fuel supply for generating a propulsive force.

However, the invention is exemplified below for the case where adaptation is performed during towing.

As mentioned above, the number of injections during a complete adaptation procedure can consist of a fairly large number of injections, which is why it is not certain that a complete adaptation will be carried out during the time the vehicle is being driven while towing. A total adaptation of all injectors for all injection times can therefore be divided into a plurality or a large number of consecutive occasions where the vehicle is being driven while towing. In addition to the criterion that towing must be fulfilled, there are also criteria, as described below, which must be fulfilled according to the present invention for the adaptation to be carried out. The counter i represents injection no. i, where i can for example represent l0 l5 20 25 30 l6 adaptation of a certain injector and a certain opening time.

The adaptation can be arranged to be carried out according to a scheme with a number of injector/injection time combinations as above, where the injectors are adapted one after the other and for different opening times and possibly different injection pressures.

In step 402, injection number i in the adaptation scheme is carried out, in this case injection number l. In the case where the adaptation has previously been interrupted, e.g. because the driving of the vehicle has changed from dragging to an operating condition where torque is requested and fuel is thus injected for propulsion of the vehicle, i can instead be set to the next non-performed injection when transitioning from step 401 to step 402, i.e. the adaptation can be resumed where it was previously interrupted. The injection carried out in step 402 is carried out as above with fuel supply to the fuel pipe 307 turned off. The pressure in the fuel pipe 307 in such systems can e.g. amount to any applicable pressure in the interval 1000-2000 bar.

When the injection i has then been carried out in step 402, the method continues to step 403 where an amount Mi of injected fuel is determined for the injection i. This determination can be carried out as above using the injector opening time and the pressure/pressure change that the fuel pipe 307 undergoes during the injection i. The amount of fuel can be determined in any suitable form such as e.g. volume and/or mass. Depending on a prevailing temperature T in the aftertreatment system, the method then continues to step 404 or 405. If the temperature T in the aftertreatment system is below a temperature TO, the method continues to step 404, where an estimated stored amount of fuel Mæta in the aftertreatment system is accumulated as a previously estimated amount Mgfi plus the amount Mi determined in step 403. If, however, the temperature T in the aftertreatment system exceeds the temperature T=T0, the method instead continues to step 405, where the injected and estimated stored amount of fuel M is determined as a function of time since the previous injection and the prevailing temperature T.

The temperature T can be arranged to be measured at an appropriate location in the aftertreatment system, such as e.g. at a particulate filter and/or the oxidation catalyst. The temperature TO means that the temperature T in the aftertreatment system is so high that the injected fuel that is supplied to the aftertreatment system in unburned form begins to oxidize and thus does not give rise to unwanted storage in the aftertreatment system to the same extent. TO can e.g. be in the range 200-250°, but also higher or lower. The temperature specifications are examples, and actual values may deviate from these. For example, the way in which the temperatures are determined/calculated can have an impact on the temperature limits. Regarding the example of an aftertreatment system shown in Fig. 2, the temperature T can e.g. be determined upstream and/or downstream of the oxidation catalyst 205 and/or upstream and/or downstream of the particulate filter 202. Furthermore, the temperature TO can e.g. determined as a weighted value based on a plurality of temperature sensors. Likewise, any other suitable temperature sensor can be used, e.g. together with a model of the aftertreatment system and/or e.g. current exhaust gas flow, to calculate a temperature T for the aftertreatment system.

At lower temperatures where T oxidation, whereby the supplied fuel is essentially stored. As long as the temperature T in the aftertreatment system is below TO, the injected fuel amounts Mi are thus accumulated in step 404. When the temperature T in the aftertreatment system exceeds TO, the injected fuel will be oxidized in whole or in part, which is why the estimated accumulated stored fuel amount Mt in step 405 takes this into account by subtracting an estimated oxidized amount of fuel from the estimated accumulated stored fuel amount Mt using the time between the injections and the prevailing temperature T in the aftertreatment system. The accumulated stored fuel amount Mt can thus be increased by a smaller amount than that determined in step 403, or, depending on the prevailing temperature T, even. decrease despite injection having been performed.

The method then continues to step 406 where it is determined whether the estimated stored fuel quantity Mät is greater than or equal to a set quantity limitation ML.

The quantity limitation ML may be set to any applicable quantity of fuel such as, but is certainly not limited to, an arbitrary number of grams of fuel in the range of 1-50 grams, such as, for example, in the order of 10 grams. The quantity limitation ML may be set based on the current configuration of the aftertreatment system in question and may also be arranged to vary with the current operating parameters of the vehicle. As long as it is determined in step 406 that the injected quantity of fuel is less than the quantity limitation ML, the injection counter i is incremented by 1 and the method continues to step 413 to determine whether the adaptation is complete, in which case the method ends in step 412. Otherwise, the method returns to step 402 to perform the next injection i. It should be noted that the method shown may be subordinate to an overall method, where the adaptation is interrupted if the vehicle changes from towing to another operating mode as above. The total amount of fuel supplied/injected at a single injection may, for example, be an arbitrary applicable number 10 15 20 25 30 19 milligrams in the interval 1-500 mg fuel, which is why the quantity limitation ML may thus constitute an amount corresponding to a plurality of injections.

If it is determined in step 406 that the estimated accumulated stored amount of fuel Mæt exceeds the set amount limitation ML, the method continues to step 407, where it is determined whether a temperature T prevailing in the vehicle's aftertreatment system is in an interval T0 TO defined there as above. The upper temperature limit T1 can be set to an upper limit above which continued injection of unburned fuel should not/may not occur as further temperature increase may entail a risk of damage to components included in the aftertreatment system. As long as the temperature T in step 407 is found to be in the said interval, the method returns to step 402, via step 413 to determine whether the adaptation is complete, at the same time as the injection counter i is incremented by l.

If, however, it is determined in step 407 that the temperature T is higher than the upper temperature limit T1, the method continues to step 408, at the same time as a time counter t1 is set equal to 0. In step 408, it is determined whether the temperature T is still higher than the temperature T1, and as long as this is the case, the method remains in step 408 so that no further injections are carried out with the risk of an unwanted/harmful temperature increase. When the temperature T in the aftertreatment system has then dropped to a temperature T, the method returns to step 402 at the same time as the injection counter i is set equal to i +1, but first via step 409 to determine whether the adaptation is complete. If the adaptation is complete, the method ends in step 412. Since the high temperature will have caused any accumulated unburned fuel Mæt in the aftertreatment system to have been at least partially oxidized, the accumulated estimated amount of injected fuel Mæt upon transition to step 402 can be reduced in some appropriate manner, e.g. as a function of the time t the method has been in step 408 and/or the prevailing temperature T of the aftertreatment system while the method has remained in step 408.

Depending on the time the process has remained in step 408, the accumulated amount of fuel Mt may thus have been reduced to a greater or lesser extent, and if the process has been in step 408 long enough, the accumulated amount of fuel will have been reduced to zero, but may thus, depending on time/temperature, assume any value between 0 and the accumulated amount Mt.

Instead of determining in step 408 whether the temperature T is higher than the temperature T1, this step can instead compare whether the temperature T is higher than some lower temperature compared to the temperature T1. That is, a hysteresis function can be applied because in e.g. step 408 it may be inappropriate to continue the adaptation if the temperature T is only below T1 by a single degree or part thereof, since there is then a risk that the temperature T1 will be quickly exceeded again with the risk that the temperature T will fluctuate around T1 with a slow adaptation process as a result. In general, a similar hysteresis function can be applied to other temperature limits applied with reference to Fig. 4.

Furthermore, if in step 407 it is instead determined that the temperature T is less than the temperature TO, the method continues to step 410. The method remains in step 410 as long as the temperature T in the aftertreatment system is below the temperature TO. The reason for this is that as long as the temperature T in the aftertreatment system is below the temperature TO, no or substantially no fuel will be oxidized in the aftertreatment system, which in turn means that supplied unburned fuel will be stored in the aftertreatment system completely or at least to a large extent, with potential damage as above as a result. When the method has thus reached step 410 because the estimated accumulated stored fuel amount Mät is equal to or exceeds the fuel amount limit ML, the accumulated amount of unburned fuel would continue to rise to even higher levels exceeding ML if adaptation were continued.

Thus, when the estimated accumulated fuel quantity Mæt has reached the quantity ML, the accumulated fuel quantity Mæt has also reached the limit for accumulated amount of unburned fuel in the aftertreatment system that is permitted without significant risk of damage to components in the aftertreatment system in the event of a subsequent temperature increase. By proceeding in this way, it can be ensured during injector adaptation that no greater amount of unburned fuel is ever stored in the aftertreatment system than can be allowed to oxidize, with the associated further increase in heat, without risk of damage in the event of a subsequent temperature increase in the aftertreatment system.

The method thus remains in step 410 as long as the temperature T in the aftertreatment system is below the temperature TO since in this case essentially no oxidation of stored fuel will occur, whereby the amount of stored fuel will not decrease either. When the temperature then increases, the method continues, provided that T 10 15 20 25 30 22 is still less than T1, to step 411 at the same time as a timer tg is started. If it is determined in step 410 that T>T1, the method continues instead to step 408 as above.

The temperature increase may, for example, be due to the fact that, when the adaptation has been interrupted, the vehicle has been driven under conditions where the combustion engine has been working actively and generating an exhaust gas stream with a higher temperature, with an associated temperature increase in the aftertreatment system as a result.

In step 411, it is first determined whether the adaptation is complete, i.e. whether all injections i performed in the adaptation have been performed. If so, the adaptation is terminated in step 412. If the adaptation is not complete, the procedure in step 411 remains until the timer tg has reached a set time tT2. This value constitutes a period of time during which, due to the temperature T in the aftertreatment system exceeding TO, stored fuel in the aftertreatment system will be oxidized and the stored amount Mæt will thus be reduced. The timer tg can, for example, be set to a value that results in a reduction of the estimated stored fuel amount Mæt by a fuel amount corresponding to one or more upcoming injections i. Alternatively, the time can be set to a time that corresponds to an expected oxidation of x% of stored fuel, such as 10%, 50% or another applicable percentage in the interval 0-100%. The timer value can, for example, be arranged to depend on the current temperature in the aftertreatment system. The higher the temperature exceeding the temperature TO, the faster oxidation of stored fuel, and thus reduction of stored fuel, will occur.

Depending on how long the tT2 timer tg has been set to, it may also be advantageous in step 411 to monitor the temperature T. If, for example, tg has been set to a relatively long time, the temperature T may change during the time 10 15 20 25 30 23 in such a way that it, for example due to changed driving conditions, will, for example, exceed T1, in which case the method may proceed to step 408. Conversely, if T will fall below T0, the method may be arranged to return to step 410.

According to one embodiment, no timer is set at all when transitioning to step 411, as the temperature TO may, for example, be set to such a level that injected fuel will certainly be oxidized, whereby no increase in stored fuel will occur as long as the temperature in the aftertreatment system exceeds TO.

Thus, according to the present invention, a method is provided that can reduce or completely eliminate problems such as poisoning and/or overheating caused by fuel storage in aftertreatment systems by monitoring the amount of unburned fuel in the aftertreatment system. As will be appreciated, the method shown in Fig. 4 is only one example of how the present invention can be implemented.

Furthermore, the present invention has been exemplified above in connection with vehicles. However, the invention is also applicable to any vehicles/processes where aftertreatment systems as described above are applicable, such as, for example, watercraft or aircraft with combustion processes as described above.

Further embodiments of the method and system according to the invention are set out in the appended claims. It should also be noted that the system can be modified according to different embodiments of the method according to the invention (and vice versa) and that the present invention is thus not in any way limited to the above-described embodiments of the method according to the invention, but relates to and includes all embodiments within the scope of the appended independent claims.

Claims (1)

A method of adapting at least one injector (301-306) to an internal combustion engine, said internal combustion engine (101) comprising at least one combustion chamber, and wherein fuel is injected into said at least one combustion chamber by utilizing said at least one injector (301-306), wherein a post-treatment system (200) is provided for treating an exhaust stream resulting from combustion at said internal combustion engine (101), and wherein said adaptation comprises a plurality of injections by means of said at least one injector (301-306). ) where unburned fuel is supplied to said after-treatment system (200) via said combustion chamber, characterized by the steps of, after a first injection (i) of said plurality of injections: - estimating an amount (Mñm) of unburned fuel stored in said after-treatment system (200), and - if said estimated stored fuel quantity (Mæt) is less than a first fuel quantity (ML), perform a after said first injection (i) the following second injection (i + 1). A method according to claim 1, wherein, in said injections, fuel is injected at a time in the combustion cycle where no or only a part of said fuel is combusted in said combustion chamber. A method according to claim 1 or 2, wherein said estimated stored amount of fuel (Mäï) is an accumulation of estimated amounts (Mi) of injected fuel for a plurality of said injections. A method according to any one of the preceding claims, further comprising: - determining a temperature (T) for said after-treatment system (200), and - estimating said amount (Measure) of unburned fuel stored in said after-treatment system (200) if said temperature (T) is less than a first value (TM). the preceding claim, further comprising, in said estimating (Measuring) the amount of unburned fuel stored in said finishing system (200): estimating a conversion, such as oxidation, of stored fuel in said finishing system (200), said estimating (Measuring) of said amount of unburned fuel stored in said after-treatment system (200) consists of a difference between a supplied amount of unburned fuel and a subsequent e-processing system converted amount of fuel. A method according to claim 5, wherein said conversion of stored unburned fuel in said after-treatment system is determined as a function of a temperature (T) for said after-treatment system and / or a first elapsed time (t; t fl. A method according to any one of the preceding claims, further comprising: : - when said estimated stored fuel quantity (Mæt) exceeds said first fuel quantity (ML), determining a temperature (T) for said after-treatment system (200), and - when said temperature (T) exceeds a first temperature (TO) but falls below a second , compared to said first temperature, higher temperature (T1), performing a subsequent injection (j), said first l0 l5 20 25 30 l0. ll. 27 temperature (T0) being constituted by a temperature (T) at which fuel is oxidized in A method according to any one of the preceding claims, further comprising: - determining a temperature (T) for said finishing system (200), and - when said temperature (T) exceeds tiger a second temperature (T1), interrupt said adaptation. A method according to claim 8, further comprising resuming said adaptation when said temperature (T) has dropped to a temperature below said second temperature (TU. A method according to any one of the preceding claims, further comprising: - when said estimated stored amount of fuel (Measure) exceeds one first amount of fuel (ML), determining a temperature (T) for said after-treatment system (200), and - when said temperature (T) is below a first temperature (TO), said first temperature (TM being a temperature below which substantially no fuel oxidized in said finishing system (200), interrupting said adaptation, and, - when said temperature (T) of said finishing system (200) has risen to a higher temperature compared to said first temperature (TO), resume said adaptation. further comprising resuming said adaptation when a second time (tT2) has elapsed since said temperature (T) of said finishing system (200) s to a higher temperature compared to said first temperature (TO). A method according to any one of the preceding claims, further comprising, in an injection (i) at said adaptation, - estimating an amount of fuel (Mi) injected with said injector (301-306) , - comparing said estimated amount of fuel (Mi) with an expected amount of fuel, and - correcting an opening time for said injector (301-306) based on said comparison. A method according to any one of the preceding claims, wherein in said adaptation said at least one injector (301-306) is adapted for a plurality of opening hours. A method according to any one of the preceding claims, wherein said internal combustion engine (101) is arranged to propel a vehicle (100), and wherein, upon propulsion of said vehicle (100), fuel is injected into said combustion chamber, said adaptation being performed when said vehicle (100) driven with said fuel injection for propulsion turned off. Computer program comprising program code, which when said program code is executed in a computer causes said computer to perform the method according to any one of claims 1-14. A computer program product comprising a computer readable medium 17 and a computer program according to claim 15, wherein said computer program is included in said computer readable medium. A system for adapting at least one injector (301-306) to an internal combustion engine (101), said internal combustion engine (101) comprising at least one combustion chamber, and wherein fuel is arranged to be injected into said at least one combustion chamber by utilizing said at least one combustion chamber. (301-306), wherein a post-treatment system (200) is provided for treating an exhaust gas from said combustion at said internal combustion engine (101), and said adaptation comprises a plurality of injections (i) by means of said at least one injector. (301-306), where unburned fuel is supplied to said after-treatment system (200) via said combustion chamber, characterized by the system comprising: - means for, after a first injection (i) of said plurality of injections, estimating an amount of unburned fuel (Measure) as stored in said finishing system (200), and - means for performing a second injection after said first injection (i) injection (i + 1) if said estimated stored fuel quantity (Mæt) is less than a first fuel quantity (ML). Vehicle (100), characterized in that it comprises a system according to claim 17.