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Title:
METHOD AND SYSTEM FOR ANALYSIS OF A FUEL INJECTION DEVICE IN A COMBUSTION ENGINE
Document Type and Number:
WIPO Patent Application WO/2015/002593
Kind Code:
A1
Abstract:
A method and a system for analysis of a function for at least one injection device 131...13N in a combustion engine is described. Spin-down times T1...TN related to injection devices in an engine are first determined. Subsequently, an adjustment device 144 performs an adjustment of the original amount Mpredet of fuel which is supplied to the respective cylinder, if at least one spin-down time of the determined spin-down times T1...TN differs from a spin-down time interval Tpreciet_1...Tpredet_N for the corresponding injection device. The adjustment, which is performed by the adjustment device for each one of the injection devices with a diverging spin-down time, is performed in accordance with an iterative algorithm, until an adjusted diverging spin-down time Tacijust_1....Tadjust_N for the injection device reaches the spin-down time interval TPreciet_1-Tpredet_N. Subsequently, an adjusted amount MadjUSt_1...Madjust_N of fuel, which is related to the adjusted spin-down time Tadjust_1-Tadjust_N, which is obtained with the use of the iterative algorithm, is determined.

Inventors:
JOHANSSON BJÖRN (SE)
Application Number:
PCT/SE2014/050759
Publication Date:
January 08, 2015
Filing Date:
June 19, 2014
Export Citation:
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Assignee:
SCANIA CV AB (SE)
International Classes:
F02M65/00; F02D41/22; G01M15/04
Domestic Patent References:
WO2004003503A12004-01-08
Foreign References:
US20090192696A12009-07-30
EP1983326A12008-10-22
DE19813495C11999-07-08
US5709192A1998-01-20
DE19540826A11997-05-07
Attorney, Agent or Firm:
GARDEMARK, Niklas (Södertälje, SE)
Download PDF:
Claims:
Claims

1. Method for analysis of a function for at least one injection device (131...13N) for a combustion engine (101), wherein said combustion engine (101) comprises a number of cylinders (1...N) which are supplied with fuel by injection through a number of injection devices (131...13N); comprising:

- determination of a spin-down time ΊΊ related to a special injection device (131), where said spin-down time ΊΊ represents the time it takes for said combustion engine (101) to reduce the engine speed ω of the combustion engine from a first engine speed coi to a second lower engine speed ( 2 by

interrupting said injection of fuel for all additional

injection devices (132...13N), wherein said additional injection devices (132...13N) comprise said number of injection devices, except said special injection device (131);

- determination of at least one additional spin-down time T2...TN by repeating said determination of said spin-down time with each one of said additional injection devices (132...13N) as said special injection device;

characterised in that, if at least one spin-down time of the determined spin-down times Ti...TN differs from a spin-down time interval Tpredet i-Tpredet N for the corresponding injection device, wherein said spin-down time interval Tpreciet i-T redet N is related to an original amount Mpredet of fuel supplied to the respective cylinder by said respective injection device (131...13N), the following steps are performed for each one of the injection devices with a diverging spin-down time:

- adjustment in accordance with an iterative algorithm of said original amount Mpredet of fuel, until an adjusted diverging spin-down time ad ust ι-Tad ust N for the injection device reaches said spin-down time interval Tpredet i-T redet N;

Tadjust_l---Tadjust_N=Tpredet_l-"Tpredet_N; and - determination of an adjusted amount Macijust i-Madjust N of fuel, which is related to said adjusted spin-down time

Tadjust_l---Tadjust_N · 2. Method according to claim 1, wherein said analysis is used to diagnose at least one of said number of injection devices (131...13N) .

3. Method according to claim 2, wherein said special injection device (131) is deemed defective if said adjusted amount Mad ust i-Madjust N of fuel differs from said original amount Mpredet by more or the same as said original amount Mpredet multiplied by a factor k; I adjust_i... adjust_N - Mpredet | > k*Mpredet, where k>0.

4. Method according to claim 1, wherein said analysis is used to correct at least one of said number of injection devices (131...13N) .

5. Method according to claim 1, wherein said analysis is used to diagnose and/or correct at least one of said number of injection devices (131...13N). 6. Method according to claim 5, wherein said special injection device (131) : - is corrected if said adjusted amount MadjUSt i...MadjUSt of fuel differs from said original amount Mpredet of fuel by less than or the same as said original amount Mpredet of fuel multiplied by a first factor ki; | Madjust_i...Madjust_N - Mpredet I ≤ ki*Mpredet;

where ki>0; and

- is deemed defective if said adjusted amount MadjUSt i...MadjUSt of fuel differs from said original amount Mpredet of fuel by more than or the same as said original amount Mpredet of fuel

multiplied by a second factor k2; I MadjUSt_i...Madjust_N - Mpredet I ≥ k2*Mpredet; where k2>ki>0.

7. Method according to any one of claims 1-6, wherein said iterative algorithm comprises a bisection method.

8. Method according to claim 7, wherein said bisection method in a first step makes a first change of said original amount Mpredet of fuel, and analyses the impact of such first change on said adjusted spin-down time Tacijust ι · · · Tad ust N, and in at least one second subsequent step halves previous changes of said original amount Mpredet of fuel, until said adjusted spin- down time ad ust l-Tadjust reaches said spin-down time interval Tpredet_l"-T'predet_ ; Tacjjust_l"-Tadjust_N Tpredet_l"-T'predet_N .

9. Method according to any one of claims 1-6, wherein said iterative algorithm comprises a secant method.

10. Method according to claim 9, wherein said secant method comprises the use of one or several secant lines to change said original amount Mpredet of fuel, until said adjusted spin-down time ad ust i-Tadjust N reaches said spin-down time interval Tprecjet_l—Tpredet_IS Tadjust_l-"Tadjust_N=T'Predet_l-"'l'Predet_N ·

11. Method according to any one of claims 1-10, wherein said spin-down time interval Tpredet ι · · · Tpredet N constitutes one from the group of:

- an interval Tmean interval around a mean spin-down time Tmean for said number of spin-down times Ti...TN; and

- for each injection device (131...13N) a nominal spin-down interval Tn0minal_l-" Tn0minal_N.

12. Method according to any one of claims 1-11, wherein said method for analysis of a function for at least one injection device (131. . .13N) is repeated for different values in one or several ambient parameters, which may impact said function .

13. Method according to claim 12, wherein said one or several ambient parameters comprise at least one from the group of: - a pressure P of said fuel which is supplied to said number of injection devices (131...13N);

- a number of fuel injections performed by said number of injection devices for each cylinder during one compression stroke and one combustion stroke;

- a crank angle for start of fuel injections performed by said number of injection devices (131...13N);

- a crank angle interval between the starts of two

consecutive fuel injections performed by said number of injection devices; and

- a fuel temperature Tfuel of said fuel which is supplied to said number of injection devices (131...13N); and

- a chemical composition Kmix of said fuel.

14. Method according to any one of claims 1-13, wherein said method for analysis of a function for at least one injection device (131...13N) is repeated for different values of said original fuel amount M.

15. Method according to any one of claims 1-14, wherein said analysis of said function for said at least one injection device (131...13N) is comprised in a garage test.

16. Method according to any one of claims 1-15, wherein said combustion engine (101) is comprised in a vehicle (100) and wherein said analysis of said function for said at least one injection device (131...13N) is performed when said vehicle (100) is at a standstill, and said combustion engine (101) is disconnected from a driveline in said vehicle (100) . 17. Computer program comprising a program code which, when said program code is executed in a computer, achieves that said computer carries out the method according to any one of claims 1-16.

18. Computer program product comprising a computer- readable medium and a computer program according to claim 17, said computer program being comprised in said computer- readable medium.

19. System arranged for analysis of a function for at least one injection device (131...13N) for a combustion engine (101), wherein said combustion engine (101) comprises a number of cylinders ( 1... ) , supplied with fuel by injection through a number of injection devices (131...13N); comprising:

- a first

determination device (141), arranged for the determination of a spin-down time ΊΊ related to a special injection device (131), wherein said spin-down time ΊΊ represents the time it takes for said combustion engine (101) to reduce the engine speed ω of the combustion engine from a first engine speed coi to a second lower engine speed ( 2 by interrupting said

injection of fuel for all additional injection devices

(132...13N), wherein said additional injection devices

(132...13N) comprise said number of injection devices except said special injection device (131);

- a second determination device (142), arranged for the determination of at least one additional spin-down time T2...TN, by repeating said

determination of said spin-down time with each one of said additional injection devices (132...13N) as said special injection device;

characterised in that

- an adjustment device (144), arranged to perform an

adjustment of an original amount Mpredet of fuel if at least one spin-down time of the determined spin-down times ΊΊ ... N differs from a spin-down time interval Tpredet 1 · · · Tpredet N for the corresponding injection device, wherein said spin-down time interval Tpredet 1 · · · Tpredet N is related to said original amount Mpredet of fuel, supplied to the respective cylinder by said respective injection device (131...13N), wherein said

adjustment device (144) is arranged to perform said adjustment for each one of the injection devices with a diverging spin- down time, wherein sais adjustment of said original amount Mpredet of fuel is performed in accordance with an iterative algorithm, until an adjusted diverging spin-down time

Tadjust 1-Tadjust for the injection device reaches said spin-down time interval Tpredet_1...Tpredet_N; Tadjust^i...Tadjust_N=Tpredet_1...Tpredet_N; and - a third determination device (143), arranged for the determination of an adjusted amount MadjUSt i...MadjUSt N of fuel, which is related to said

adjusted spin-down time TadjUSt_1...Tadjust_N.

Description:
METHOD AND SYSTEM FOR ANALYSIS OF A FUEL INJECTION DEVICE IN A COMBUSTION ENGINE

Technical field

The present invention pertains to a method for analysis of a function for at least one injection devicedevice in a

combustion engine according to the preamble of claim 1. The present invention also pertains to a system arranged for analysis of a function for at least one injection devicedevice in a combustion engine according to the preamble of claim 19, and a computer program and a computer program product, which implement the method according to the invention.

Background

The following background description constitutes a description of the background to the present invention, and thus need not necessarily constitute prior art. Combustion engines, e.g. combustion engines comprised in vehicles or ships, are operated by fuel such as diesel, petrol, ethanol or mixtures of such fuels with each other and/or with different types of additives. The fuel is supplied to the combustion engine by a fuel system, comprising among others one or several fuel tanks and devices, which transport the fuel from the fuel tanks to the combustion engine. The devices that transport the fuel to the engine may comprise e.g. conduits for transport of the fuel within the vehicle, one or several pumps, which may be divided into low and high pressure circuits, filters, couplings and other devices for fuel transport. The fuel is injected into the engine's cylinders by a fuel injection system comprising one injection devicedevice, also called an injector, per cylinder. The injection devicedevice may e.g. be supplied with fuel by a common rail device, which supplies pressurised fuel to all the injection devicedevices, or by separate devices with

pressurised fuel to the respective injection device.

Brief description of the invention

It is desirable for equal amounts of fuel to be injected into each of the engine's cylinders when the engine is in

operation, in order to obtain an even torque from the engine.

However, the injection devicedevices often inject different amounts of fuel into the cylinders because of individual variations in the injection devicedevices. Such individual variations may be due to small differences arising at the manufacture of the respective injection devicedevices.

The injection devicedevices are also subjected to mechanical wear over time, for which a mean wear for the entire

population of injection devicedevices may be determined. In some cases, the injection system may also correct for such mean wear, in order to limit its impact on the driving of the vehicle .

However, there may be individual differences between the wear of individual injection devicedevices, because the injection devicedevices have individual features, which may be due to manufacturing differences among injection devicedevices and/or to the wear of the injection devicedevices. The different wearing-in behaviours of the injection devicedevices, which result in an individually different wear of the injection devicedevices, are particularly difficult to determine and to correct with prior art solutions.

Since injection devicedevices are subjected to a mechanical wear over time, problems may also arise if one or several injection devicedevices are replaced in the vehicle. The new injection devicedevice ( s ) mounted in the vehicle will then not be worn-in, and will behave differently from the injection devicedevices which have not been replaced.

The different features which may arise in the injection devicedevices mean that the torque provided by the engine is uneven. This is schematically illustrated in Figures la and lb, in which the engine speed ω, which is related to the torque M of the engine, is displayed as a function of the crank angle for the engine shaft, for an eight-cylinder four stroke engine. In Figure la, a schematic example of an engine with injection devicedevices having substantially similar features is displayed, i.e. eight injection devicedevices, which inject substantially the same amount of fuel into the respective cylinders, so that the engine speed increases and reduces in a substantially equal way, when the fuel is

injected into each one of the cylinders. If, for example, the injection devicedevices are manufactured with substantially similar features and subsequently worn substantially in the same manner, the engine speed according to Figure la may thus be obtained. If one or several injection devicedevices inject a different amount of fuel into the respective cylinder, an uneven torque is obtained instead, as illustrated in Figure lb. In the schematic example in Figure lb, the injection device injects too much fuel into the first cylinder, i.e. more fuel than the other injection devices, which means that the engine speed increases too much at the injection for this cylinder, and also that the engine speed for at least the second cylinder is impacted, so that its engine speed also becomes too high.

Subsequently, the engine speed falls again during the

injections into the subsequent cylinders, until the injections of the next cycle start. The example displayed in Figure lb would result in an uneven torque provided by the engine, which impacts negatively on the performance of the vehicle.

Additionally, the uneven torque may cooperate with resonances in e.g. a vehicle, such as resonances in the driveline, which means that the resonances and the uneven torque amplify each other and result in relatively large oscillations in the driveline and/or fluctuations in the engine torque.

Oscillations in the driveline and/or fluctuations in the torque may thus be relatively large, and will then be

experienced by the driver of a vehicle as irritating and/or unpleasant .

Prior art solutions have tried to counteract the uneven torque by setting the injection devices to compensate for, and reduce, their individual differences. However, such

compensation requires an analysis of the engine speed during idling and operation. It is difficult to make such an analysis robust, because it is difficult to differentiate between the different injection devices during the analysis, since there are resonances in the driveline and since the engine speed signal is constantly impacted by several cylinders and at the same time by its injection device, because the combustions in the cylinders are close to each other in time and crank angle for the different cylinders. The distance in crank angle between the combustions/injections depends on the number of cylinders in the engine. For an eight-cylinder engine, for example, there may be 90° between combustions/injections, while there may be 144° between combustions in a five-cylinder engine .

The resonance oscillations in the driveline may also give rise to oscillations, which are similar to and may easily be confused with engine speed fluctuations, due to defective injection devices. Thus, several factors contribute to prior art solutions not being robust and not providing reliable and/or exact results.

It is therefore one objective of the present invention to provide a method and a system for analysis of a function for at least one injection device, which at least partly resolve the problem mentioned above.

This objective is achieved through the above-mentioned method in accordance with the characterising portion of claim 1. The objective is also achieved through the above-mentioned system according to the characterising portion of claim 19, and the above-mentioned computer program and computer program product.

The analysis according to the present invention facilitates a fast and reliable indication of whether any, and if so which, injection device has a substandard function. Thus, identified injection devices may be corrected and/or replaced to achieve an even engine torque.

Through the analysis the present invention provides a

comprehensive indication for all injection devices in the fuel system, which means that defective injection devices may be identified easily and with high precision. The present

invention may thus reduce the costs of operation and/or maintenance for the vehicle considerably, since decisions based on facts regarding costly replacements of injection devices may be made, based on the analysis according to the present invention.

Driver comfort may also be increased with the use of the present invention, since torque variations and/or associated driveline oscillations may be avoided, or at least

considerably reduced. According to different embodiments of the present invention, the method according to the present invention may be repeated for different values of the original fuel amount M predet and/or for different values of the environment parameters that may impact the injection, so that the reliability and exactitude are further increased for the analysis according to the present invention.

Brief list of figures

The invention will be illustrated in more detail below, along with the enclosed drawings, where similar references are used for similar parts, and where:

Figures la-b schematically show examples of torque/engine speeds in an engine for injection devices with equal and different features, respectively, Figure 2 shows an example vehicle in which the present invention may be implemented,

Figure 3 shows a flow chart for the method according to the invention,

Figure 4 shows a control device according to the present invention.

Description of preferred embodiments

In this document, the present invention is both exemplified and described mainly for a vehicle. However, a person skilled in the art will realise that the invention may be implemented and used in essentially all devices with an engine system, e.g. a ship or airborne vessels.

Figure 2 shows schematically an example vehicle 100 which may comprise the present invention. The vehicle 100, which may be a passenger car, a truck, a bus or another vehicle, comprises a driveline which conveys power to driving wheels 110, 111 in the vehicle 100. The driveline comprises one combustion engine 101 which, in a customary manner, via an output shaft 102 on the combustion engine 101, is connected to a gearbox 103 via a clutch 106. Naturally, the vehicle's driveline may also be of another type, such as a type with a conventional automatic gearbox, of a type with a hybrid driveline, etc.

The combustion engine 101 is operated with diesel, which is provided by a fuel system 120 comprising, among others, one or several fuel tanks and devices 121 which transport the fuel from the fuel tanks to the engine 101, and a fuel injection system 130, arranged to inject fuel into the engine's

cylinders with a number N of injection devices 131...13N, where N may e.g. be the number 5, 8, 12 or another suitable number for the number of cylinders in the engine 101. The devices for fuel transport 121 are here displayed very

schematically, but may comprise e.g. one or several conduits for transport of the fuel within the vehicle, one or several pumps, which may be divided into low and high pressure

circuits, filters, couplings and other devices for fuel transport. The combustion engine 101 is controlled by the vehicle's control system via a control device 140, which is illustrated schematically in Figure 2. The fuel system 120 is controlled by the vehicle's control system via a control device 140, which in Figure 2 is schematically illustrated as the same control device that controls the combustion engine 101, but which may also be arranged separately from such control device 140. The control device 140 according to the present invention also comprises a first 141, a second 142 and a third 143

determination device and an adaptation device 144, and is 1onnected at least to the engine 101 and to the fuel system 120. The first 141, second 142 and third 143 determination devices and the adaptation device 144 are described in further detail below. The first 141, second 142 and third 143

determination devices are illustrated in Figure 2 as

individual devices. However, the functions for these devices may also be implemented in fewer devices, e.g. one and the same device, as a person skilled in the art will realise. The control device 140 may be comprised in, or cooperate with, an EMS (Engine Management System) circuit in the vehicle.

An output shaft 107 from the gearbox 103 drives the wheels 110, 111 via a final drive 108, e.g. a customary differential, and the drive shafts 104, 105 connected to said final drive 108. Exhausts created by the engine 101 during its combustion of the fuel are purified by an exhaust treatment system 150, before they are released from the vehicle.

Figure 3 shows a flow chart for a method according to the present invention, where an analysis of a function for at least one injection device 131...13N for a combustion engine 101 is carried out. The combustion engine 101 comprises a number of cylinders 1...N, which are equipped with fuel through injection with a number of injection devices

131...13N. The number N of cylinders and injection devices 131...13N may here consist of any number, suitable for a combustion engine.

In a first step 301 of the method according to the present invention, a spin-down time 1 related to a special injection device 131 is determined. This first step 301 may e.g. be carried out by a first determination device 141. The spin-down t ime 1 here repre sent s the t ime i t take s for the combus t i on engine 101 to reduce its engine speed ω from a first engine speed ω 1 to a second lower engine speed ω 2 by interrupting the injection of fuel for all injection devices 132...13N, except the special injection device 131, i.e. for all additional injection devices 132...13N. Thus, the injection from all additional injection devices 132...13N is stopped, where these additional injection devices 132...13N comprise the total number of injection devices, except the special injection device 131. The special injection device 131 here injects an original amount of fuel M predet . The special injection device is herein referred to, for illustrative reasons, with the figure reference 131. However, the special injection device 131 may consist of any of the N injection devices 131...13N

In a second step 302 of the method according to the present invention, at least one additional spin-down time T 2 ...T N is determined, e.g. by a second determination device 142, by repeating the determination of the spin-down time carried out in the first step, here with each of the additional injection devices 132...13N selected as the special injection device. According to one embodiment of the present invention, spin- down times T2... T N are here determined for each of the

additional injection devices 132...13N.

After the first 301 and the second step 302 of the method, a first 1 and at least a second T2...T N spin-down time has thus been determined. These spin-down times are used, according to the present invention, at the analysis of the function for the at least one injection device 131...13N.

According to the present invention, adaptation and

determination steps shall be carried out if at least one spin- down time of the determined spin-down times Ti...T N differs from a spin-down time interval T predet 1 · · · T predet N for the corresponding injection device. The respective spin-down time intervals T predet 1 · · · T predet is here related to the original amount M predet of fuel which is supplied to the respective cylinder by the respective injection devices 131. . .13N. Thus, one or several differing spin-down times Ti...T N may be

identified, if applicable, following which the adaptation and determination steps described below are carried out for each one of the injection devices having such a differing spin-down time . According to one embodiment of the invention, the spin-down time interval T predet 1 · · · T predet N constitutes an interval

T mean interval around a mean spin-down time T mean for the determined spin-down times Τ 1 ...Τ Ν . According to another embodiment, the spin-down interval T predet 1... T predet N constitutes a nominal spin- down interval T nominal 1... T nominal N for the respective injection devices 131. . .13N.

In a third step 303 of the method according to the present invention, the original amount M predet of fuel injected into the cylinders by the injection devices 131. . .13N is adjusted. Such adjustment occurs in accordance with an iterative algorithm, until an adjusted differing spin-down time T adj ust 1 · · · T adjust N for the respective injection devices reaches the spin-down time interval T predet _1...T prede _N T adjust _1... 1 · · · T redet _N ·

In a fourth step 404 of the method according to the present invention, an adjusted amount M adjust i. . .M adjust of fuel is determined, which is related to the adjusted spin-down time T ad ust ··· T adj ust · Thus, here the adjusted amount

M ad ust 1 · · · M ad ust of fuel for the respective cylinders is determined, which means that the adjusted differing spin-down time T ad ust 1 ··· T ad ust for the respective injection device reaches the respective spin-down time interval

T predet _1 · · · -T predet _N; T ad ust _1 · · · J- ad ust _N = T predet _1 · · · -T predet _N-

The adjusted amount M ad ust 1 · · · adjust N of fuel for the respective cylinder, which is obtained with the use of the present invention, may then be used to diagnose at least one of the injection devices 131...13N. This diagnosis may determine whether one or several of the injection devices 131...13N has a substandard function. Thus, defective injection devices may be identified through the analysis according to the present invention. This identification is fast, exact and robust, and may provide a fast indication as to whether any, and if so which, injection device should be replaced in the fuel

injection system 130. Since adjusted amounts M adjust 1... M adjust N of fuel for the respective cylinders are obtained through the method according to the present invention, the analysis provides a comprehensive indication for each one of the injection devices 131...13N, which means that defective injection devices, if any, may be identified easily and with high precision. Thus, replacements of non-defective injection devices may be avoided, which replacements have been relatively common when prior art solutions have been used, since the prior art methods provide unreliable and inexact indications as to the condition/state of the injection devices. It is costly to replace an injection device, which means that the present invention may reduce the operating and/or maintenance costs of the vehicle considerably.

The present invention may be implemented in the software, e.g. in the control device 140, which means that the contribution to the vehicle's complexity and/or manufacturing cost is minor . According to one embodiment of the present invention, the special injection device 131 is deemed to be defective if its adj usted amount M adju st 1 · · · M adj ust N of fuel di f fers from the corresponding original amount M predet by more or the same as the original amount M predet multiplied by a factor k, |M adjust 1 N - predet Ι≥ k*M predet , where k>0. The factor k may here thus assume different values which are greater than zero; k>0.

Table 1 below shows a non-limiting example of what this assessment of the injection devices may look like for an engine with 5 cylinders; N=5. Here, the original amount of fuel M predet is 10 mg/stroke and the factor k is 0.5, which means that the adjusted amount M adjust 1 ...M adjust N may differ from the original amount of fuel M predet by 5 mg/stroke

Table 1

As shown in table 1, according to this example the injection devices 131, 132, 133, 134 for four of the cylinders are deemed to be functional; since |M adjust ± - M predet = 2 5,

|M asjust _2 - M Predet = 0 ≤ 5, M adjust _ 3 - M predet = 2 < 5, and

|M ad j ust 4 - Mpredet = 0 ≤ 5; while one injection device 135 is deemed to be defective; since |M adj ust 5 - M predet = |10 | ≥ 5. Naturally, the same table may be prepared for substantially all suitable numbers of cylinders that a combustion engine may have, and for any suitable values of M predet and the factor k.

Tables such as table 1 may be calculated in advance and stored in the control device 140, so that a very fast and reliable diagnosis of the injection devices may be obtained.

According to one embodiment of the present invention, the method is repeated for analysis of a function for at least one injection device 131...13N for different values of the

original fuel amount M predet . Thus, the first 301, second 302, third 303 and fourth 304 steps described in connection with Figure 3 are repeated for different fuel amounts M predet .

Here, the analysis may, according to the method, first be carried out for one relatively smaller amount of fuel supplied to each one of the cylinders, e.g. around 10 mg of injected fuel per stroke, so that adjusted amounts M adjust 1... adjust N of fuel for the respective cylinder is obtained for this

relatively smaller amount of fuel supplied. Subsequently, the analysis may, according to the method, be carried out for at least one relatively greater original amount of fuel supplied to each cylinder M predet , e.g. around 20 mg of injected fuel per stroke, possibly followed by one or several additional relatively greater amounts of supplied fuel M predet , so that adjusted amounts M adju s t 1 · · · M adjust of fuel for the respective cylinders are obtained for this at least one relatively greater amount of fuel supplied.

By performing the analysis according to the present invention for several values of the original amount of fuel M predet , non- linearities in the relationship between a fuel amount

requested by the fuel/injection system and an actually

injected fuel amount may be compensated for. Thus, the reliability and exactitude of the analysis according to the present invention increase further if it is repeated for different values of the original fuel amount M pre det -

According to one embodiment of the present invention, the analysis of the function of the injection devices 131...13N is comprised in a garage test.

According to one embodiment of the present invention, the analysis, which may be comprised in the garage test mentioned above, is performed when the vehicle 100 is at a standstill and when the combustion engine 101 is disconnected from a driveline in the vehicle 100, e.g. by a neutral gear having been selected in the gearbox 103, or by the clutch 106 being open .

Thus, according to one embodiment of the present invention, the analysis of the function of the injection devices

131...13N may e.g. be used by a garage before they replace one or several injection devices, to ensure that specifically the defective injection device (s) are replaced and that well- functioning injection devices are not replaced. Thus

considerable savings may be achieved for the owner/user of the vehicle. In addition, the risk that the vehicle is standing still unnecessarily in a garage, instead of being in

operation, due to a deficient analysis is minimised.

According to one embodiment of the present invention, the analysis of the function of the injection devices 131...13N is used to correct at least one of the injection devices

131...13N. Here, the adjusted amounts M ac ij ust ι · · · Hadj ust N of fuel determined during the analysis for the respective cylinder may thus be used as a basis for an adj ustment/adaptation of one or several of the injection devices 131...13N. After one or several adjustments/adaptations of one or several of the injection devices 131...13N has been carried out, the analysis of the function of the injection devices 131...13N may then be repeated, to determine the impact that the

adj ustment/adaptation has had on the function of the injection devices 131...13N. Thus, according to this embodiment, an uneven torque from the engine 101 may be compensated through adj ustment/adaptation of one or several of the injection devices 131...13N, where such adj ustment/adaptation is based on the analysis of the function of the injection devices

131...13N, according to the present invention. Thus, in some cases a replacement of one or several injection devices may be avoided, since minor diverging features of injection devices may be compensated for through such adj ustment/adaptation .

The analysis according to the present invention may also be used for diagnosis and/or correction, i.e.

adj ustment/adaptation, of at least one of the injection devices 131...13N, where the selection of whether a diagnosis or a correction should be performed depends on how much the adjusted amount M ac ijust ι · · · Hadjust N of fuel differs from the respective said original amount of M pre det-

According to one embodiment, the special injection device 131 is corrected if the adjusted amount M ac ijust i-M a djust N of fuel differs from the original amount M pre det of fuel by less or the same as the original amount M pre det of fuel multiplied by a first factor ki; I adjust _i... adjust _ N - pre det I ≤ ki*M pred et. This first factor ki is greater than zero; ki>0.

If, instead, the adjusted amount M ad j USt i-M ad US t N of fuel differs from the original amount M pre det of fuel by more or the same as the original amount M pre det of fuel multiplied by a second factor k 2 ; I adjust _i... adjust _ N - M pred et I ≥ k 2 *M pre det, the special injection device 131 is instead deemed to be defective, which means that a replacement of this special injection device is recommended. The second factor ]¾ is greater than the first factor ki, and is thus also greater than zero; k 2 >ki>0.

According to a non-limiting example, the first factor ki may have a value of 0.2 and the second factor k 2 may have a value of 0.4. The values of these factors depend on the size of the relevant fuel amounts.

If the adjusted amount M ac ijust i-M a djust N of fuel differs from the original amount M pre det of fuel by a value between the values for the first factor ki and the second factor ]¾, according to one embodiment, a correction is then performed up to the value for the first factor k 1 . Here, the correction is limited to an area within which a robust and controlled correction may be performed safely, to reduce the risk that the correction does more harm than good.

According to one embodiment of the present invention, the iterative algorithm, which is used in the analysis according to the invention to determine the adjusted fuel amount

Mad ust l-Madjust r comprises a bisection method. The bisection method may be viewed as an iterative bisection method. According to the bisection method, in a first step a first change of the original amount M pre det of fuel is

performed, and subsequently the impact of such first change of the original amount M pre det of fuel on the adjusted spin-down time T a d ust ι · · · T a djust N is analysed. Subsequently, the previous change of the original amount M pre det of fuel is halved in at least one subsequent step. Consecutive parting in halves of previous changes of the original amount M pre det of fuel are then performed until the adjusted spin-down time T a d ust i-T a djust N is within the spin-down time interval T pre det i-T r edet N;

Tadjust_i-Tadjust_N=T P redet_i-Tpredet_N. As described above, in this document T pre ciet i-T r edet constitutes time intervals for spin- down times for the respective injection devices/cylinders.

The bisection method is a robust numerical equation solution method, which always converges if the solution is within the examined interval, and which may be implemented with little added complexity.

According to one embodiment of the present invention, the iterative algorithm, which is used during the analysis according to the invention, to determine the adjusted amount Mad ust l · · · Mad ust N , comprises a secant method.

The secant method uses one or several secant lines to change the original amount M predet of fuel until the adjusted spin-down time Tad ust l · · · Tadjust is within the spin-down time interval

Tpredet_l—Tpredet_N ' · The Secant method often converges faster than the bisection method, and may be implemented with little added complexity. However, convergence may not always be guaranteed for the secant method.

A person skilled in the art will realise that other equation solution algorithms may also be used to adjust the original amount M pre det of fuel, so that the corresponding adjusted diverging spin-down time T a djust i-T a djust N for the injection device is controlled toward the spin-down time interval

T redet i-Tpredet · Preferably, robust numerical equation solution algorithms may be used to find the adjusted amount

Madjust_l—M a djust_N '

The fuel injection system 130, injection devices 131. . .13N and their function may also be impacted by one or several ambient parameters . A pressure P of the fuel supplied to the injection devices 131...13N constitutes such an ambient parameter. The fuel temperature T fue i of the fuel and/or its chemical composition Kmix may also constitute ambient parameters that may impact the injection.

Another ambient parameter that may impact the injection consists of the number of fuel injections performed by the injection devices 131...13N for the respective cylinders during a compression stroke and a combustion stroke. In some engines, it is possible to perform several, e.g. three, injections per stroke.

Another ambient parameter consists of the crank angle when the fuel injections performed by the injection devices 131...13N are about to start. A crank angle interval between the starts of two consecutive fuel injections performed by the injection devices 131...13N may constitute such an ambient parameter.

According to one embodiment of the present invention, the method of the analysis, i.e. the steps described in connection with Figure 3, is repeated for different values in one or several of the ambient parameters mentioned above. Since these ambient parameters may impact the function of one or several of the injection devices 131...13N, and also do this in different ways, the repetition of the method for these

different values results in an even more reliable and exact analysis.

Thus, different adaptations/corrections are determined based on different values in the ambient parameters. For example, an adaptation which is suitable at a low fuel pressure P and another adaptation suitable at a high fuel pressure P are determined. Similarly, different adaptations/corrections may be determined for different values in the other ambient parameters mentioned above.

A person skilled in the art will realise that a method for the analysis of a function for at least one injection device in a combustion engine according to the present invention may also be implemented in a computer program, which when executed in a computer will cause the computer to carry out the method. The computer program usually consists of a part of a computer program product 403, where the computer program product comprises a suitable digital storage medium on which the computer program is stored. Said computer readable medium consists of a suitable memory, e.g.: ROM (Read-Only Memory), PROM (Programmable Read-Only Memory) , EPROM (Erasable PROM) , Flash, EEPROM (Electrically Erasable PROM) , a hard disk device, etc.

Figure 4 schematically shows a control device 400. The control device 400 comprises a calculation device 401, which may consist of essentially a suitable type of processor or

microcomputer, e.g. a circuit for digital signal processing (Digital Signal Processor, DSP) , or a circuit with a

predetermined specific function (Application Specific

Integrated Circuit, ASIC) . The calculation device 401 is connected to a memory unit 402 installed in the control device 400, providing the calculation device 401 with e.g. the stored program code and/or the stored data which the calculation device 401 needs in order to be able to carry out

calculations. The calculation device 401 is also set up to store interim or final results of calculations in the memory device 402. Further, the control device 400 is equipped with devices 411, 412, 413, 414 for receiving and sending of input and output signals. These input and output signals may contain wave shapes, pulses or other attributes, which may be detected as information by the devices 411, 413 for the receipt of input signals and may be converted into signals that may be

processed by the calculation device 401. These signals are then provided to the calculation device 401. The devices 412, 414 for sending output signals are arranged to convert the calculation result from the calculation unit 401 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 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.

A person skilled in the art will realise that the above- mentioned computer may consist of the calculation device 401, and that the above-mentioned memory may consist of the memory device 402.

Generally, control systems in modern vehicles consist of a communications bus system, consisting of one or several communications buses to connect a number of electronic control devices (ECUs) , or controllers, and different components localised on the vehicle. Such a control system may comprise a large number of control devices, and the responsibility for a specific function may be distributed among more than one control device. Vehicles of the type shown thus often comprise significantly more control devices than what is shown in

Figure 4, which is well known to a person skilled in the art within the technology area. The present invention, in the embodiment displayed, is

implemented in the control device 400. The invention may, however, also be implemented wholly or partly in one or several other control devices already existing in the vehicle, or in a control device dedicated to the present invention.

According to one aspect of the present invention, a system arranged for analysis of a function for at least one injection device 131...13N is provided in a combustion engine 101. The combustion engine 101 comprises a number of cylinders 1...N which are supplied with fuel by injection through a number of injection devices 131...13N.

The system also comprises a first determination device 141, which is arranged for the determination of a spin-down time Τχ related to a special injection device 131, where the spin-down time Τχ represents the time it takes for the combustion engine 101 to reduce its engine speed ω from a first engine speed coi to a second lower engine speed ( 2 by interrupting the injection of fuel for all additional injection devices 132...13N. The additional injection devices 132...13N here comprise all the injection devices, except the special injection device 131. The special injection device 131 here injects the original amount of fuel M pre ciet -

The system also comprises a second determination device 142, which is arranged for the determination of at least one additional spin-down time T2...T N . At such determination of additional spin-down times, the determination of the spin-down time is repeated with each one of the additional injection devices 132...13N as special injection devices.

According to the present invention, an adjustment device 144 is arranged to perform an adjustment of the original amount Mpre d et of fuel supplied to the respective cylinders by the respective injection devices 131...13N, if at least one spin- down time of the determined spin-down times ΊΊ ... N differs from a spin-down time interval T pre ciet i-T r edet N for the

corresponding injection device, where the spin-down time interval T pre ciet i-T r edet N is related to the original amount M pre ciet of fuel. The adjustment, which is performed by the adjustment device for each one of the injection devices with a divergent spin-down time is performed in accordance with an iterative algorithm, until an adjusted diverging spin-down time

adjust l-Tadjust for the injection device reaches the spin-down time interval T pre det_l---T p redet_N; *

The system also comprises a third determination device 143, which is arranged for the determination of the adjusted amount M ad ust l-Hadjust of fuel related to the adjusted spin-down time T ad j USt i...T ad j USt N, obtained with the use of the iterative

algorithm.

The system according to the present invention has the same advantages as described above for the method according to the present invention. The system according to the present invention may be arranged to perform all of the method embodiments described above and in the claims, so that the system for the respective

embodiments obtains the above described advantages for the respective embodiments. A person skilled in the art will also realise that the above system may be modified according to the different embodiments of the method according to the invention. Additionally, the invention pertains to a motor vehicle 100, e.g. a truck or a bus, comprising at least one system for analysis of a function for at least one injection device in a combustion engine. The present invention is not limited to the above described embodiments of the invention, but pertains to and comprises all embodiments within the scope of the enclosed independent claims .