WO2019112503A1

WO2019112503A1 - Method and system for diagnosing supply of air to an internal combustion engine of a vehicle

Info

Publication number: WO2019112503A1
Application number: PCT/SE2018/051112
Authority: WO
Inventors: Martin Kågebjer
Original assignee: Scania Cv Ab
Priority date: 2017-12-07
Filing date: 2018-10-30
Publication date: 2019-06-13
Also published as: SE1751508A1

Abstract

The present invention relates to a method for diagnosing an air intake conduit for supplying air to an internal combustion engine (101) of a vehicle (100), the vehicle (100) comprising: an internal combustion engine (101) comprising at least one combustion chamber (201); an air intake conduit configured supply air to said at least one combustion chamber (201); the air intake conduit comprising an air filter (205); the method comprising, when the vehicle (100) is standing still: controlling a mass flow (formula I) of the air being supplied to said at least one combustion chamber (201) to a first mass flow (formula II); when said mass flow (formula I) is controlled to said first mass flow (formula II), determining a differential pressure (Δp) over at least a portion of said intake air conduit, said portion comprising said air filter (205); based on said determined differential pressure (Δp) and said first mass flow (formula II), estimating at least one parameter (c 1 ; c 2 ) value being dependent on an airflow resistance of said air intake conduit, said at least one parameter (c 1 ; c 2 ) value being a parameter (c 1 ) value being dependent on a degree of filling of said air filter (205), and being independent from variations in said air flow (formula I); and diagnosing the function of the air intake conduit based on said estimated at least one parameter (c 1 ; c 2 ) value.

Description

METHOD AND SYSTEM FOR DIAGNOSING SUPPLY OF AIR TO AN INTERNAL COMBUSTION ENGINE OF A VEHICLE

Field of the invention

The present invention relates to vehicles, and in particular to a method and system for diagnosing supply of air to an internal combustion engine. The present invention also relates to a vehicle, as well as a computer program and a computer program product that implement the method according to the invention.

Background of the invention

Vehicles may be propelled through the use of an internal combustion engine that directly or indirectly provides propelling power to the vehicle drive wheels. As is well known, internal combustion relies on a sufficient amount of air being supplied to the combustion chambers of the internal combustion engine. The combustion air is in general drawn from the surroundings of the internal combustion engine, such as ambient air of a vehicle.

Oftentimes, as is in general the case with regard to vehicles, the air being supplied to the combustion chambers is arranged to pass through an air intake conduit, consisting, inter alia, of suitable piping for channelling ambient air to the combustion chambers, and an air filter.

The air filter cleans the air entering the internal combustion engine and also prevents e.g. debris from entering the internal combustion engine and possibly causing damage. An adverse effect of using air filters, however, is that the cleanliness of the air filter affects the airflow. The air filter becomes filled from filtering the air passing through it, and as time progress the filtering capacity is reduced and also the flow through the filter may also be reduced thereby affecting engine operation.

In relation to a filled (clogged) filter, a clean, i.e. empty, air filter may improve internal combustion engine operation e.g. with regard to, for example, gas mileage, vehicle acceleration, engine life, emission levels etc. A clogged filter may, for example, have the consequence that the desired volume of clean air to be supplied to the combustion may not reach the combustion chambers, which in turn may affect emission and/or result in too rich air/fuel ratios. Air filters of e.g. vehicles are therefore replaced at regular intervals, where such intervals may be determined e.g. by the vehicle manufacturer. However, the rate at which the filter is becoming filled with particles collected from the air passing through may differ substantially in dependence on the environmental conditions in which the vehicle is travelling. The filter exchange interval may be set beforehand e.g. according to a worst-case scenario, thereby resulting in unnecessarily frequent filter exchanges, and service stops associated therewith, than that in reality may be accounted for.

Therefore, in addition to regular service intervals, vehicles may comprise an onboard diagnostics system that may determine whether an air filter is clogged and should be subject for replacement.

Summary of the invention

It is an object of the present invention to provide a method and system for diagnosing the supply of combustion air to an internal combustion engine of a vehicle that allows a service mechanic to search for faults and verify the system following repair when the vehicle is still under service. This object is achieved by a method according to claim 1.

According to the present invention, it is provided a method for diagnosing supply of air to an internal combustion engine of a vehicle,

the vehicle comprising:

an internal combustion engine comprising at least one combustion chamber; an air intake conduit configured supply air to said at least one combustion chamber;

the air intake conduit comprising an air filter;

the method comprising, when the vehicle is standing still:

controlling a mass flow of the air being supplied to said at least one combustion chamber to a first mass flow, which may be a predetermined mass flow; when said mass flow is controlled to said first mass flow, determining a differential pressure over at least a portion of said intake air conduit, said portion comprising said air filter;

based on said determined differential pressure and said first mass flow, estimating at least one parameter value being dependent on an airflow resistance of said air intake conduit, said at least one parameter value being a parameter value being dependent on a degree of filling of said air filter, and being independent from variations in said air flow; and

diagnosing the function of the air intake conduit based on said

estimated at least one parameter value.

As was mentioned above, proper supply of air for the combustion in an internal combustion engine is essential to ensure proper operation. As was also mentioned, the air intake conduit of a vehicle in general comprises an air filter for cleaning the intake air and preventing debris from entering the internal combustion engine. The air filter needs to be regularly replaced by an empty filter to prevent air cleaning capacity from becoming too low and/or flow restriction from becoming too high.

The environments in which a vehicle is operating may differ substantially from one vehicle to another even if the vehicles otherwise are similar. Also, vehicles may be used in highly different areas of application. These differences in operating

environment and/or application gives rise to variations in the rate at which the air filter fills up and becomes clogged. According to the invention, it may be determined a filter status, e.g. with regard to degree of filling, and/or the status of the air intake conduit e.g. in terms of presence of a leak.

The method according to the invention is carried out when the vehicle is standing still. The mass flow of the air being supplied to the at least one combustion chamber of the internal combustion engine is controlled to a first mass flow. This first mass flow may be a predetermined mass flow. The first mass flow is further preferably a mass flow exceeding a mass flow that prevails when the internal combustion engine is idling and disconnected from the vehicle drive wheels.

The mass flow may be increased in various manners as is exemplified below.

Controlling the mass flow to a mass flow exceeding the mass flow that prevails when the internal combustion engine is idling may increase accuracy in estimations performed according to the invention. In particular, the differential pressure may be low for low air flows, which may have an impact on the accuracy in the estimations.

For example, the air mass flow may be set to an air mass flow being at least twice the air mass flow that prevail when the engine is idling. The air mass flow may also be set to an air mass flow corresponding to at least 15%, or at least 20% or at least 30% of the maximum mass flow that the particular internal combustion engine configuration is capable of delivering

When the airflow has been controlled to said first mass flow, a differential pressure over at least a portion of the air intake conduit is determined, where the portion of the air intake conduit at least includes the air filter and hence the differential pressure (pressure drop) over the air filter, i.e. the pressure drop that the flow of air undergoes when passing through the air filter is taken into account. The differential pressure may be determined e.g. using a pressure sensor upstream the air filter and a pressure sensor downstream the air filter. According to embodiments of the invention the differential pressure may represent the pressure drop that the flow of air undergoes when passing through further parts of the air intake conduit. For example, the differential pressure may represent the pressure drop that the air undergoes from the inlet for intake of air, such as e.g. a nozzle/snorkel, to the upstream side of a compressor for compressing the intake air prior to being supplied to the at least one combustion chambers of the internal combustion engine. The differential pressure may be determined through the use of any suitable kind of pressure sensors, such as differential pressure sensors and/or gauge pressure sensors measuring in relation to the ambient pressure.

When the differential pressure has been determined, this determined differential pressure together with said first mass flow, i.e. the mass flow for which the differential pressure has been determined, is used to estimate at least one parameter being dependent on the airflow resistance of the air intake conduit. The supply of air to the internal combustion engine is then diagnosed based on the estimated at least one parameter.

The estimated parameter value is further a parameter value being dependent on a degree of filling of the air filter. The inventor has realised that a parameter value that will vary with varying degrees of filling of the air filter may be determined, where the parameter value will act as a constant for variations in air mass flow. In this way e.g. a degree of filling can be determined irrespective of the air mass flow prevailing when the determination is made. The determined differential pressure will vary in

dependence on the mass flow, and the differential pressure may be expressed as a function of the determined parameter value and the mass flow.

The parameter value being dependent on a degree of filling of said air filter may in addition be based on a predetermined parameter value representing a flow restriction of said air intake conduit when the air filter is clean, i.e. empty. Again, the inventor has realised that such a parameter value may be determined which acts as a constant in regard of changes in air mass flow, and also to the degree of filling of the air filter. With regard to the flow restriction, the determined differential pressure will vary in dependence on the mass flow taken to the second power, and the differential pressure may be expressed as a function of the parameter value and the mass flow taken to the second power. In this way the parameter representing the flow restriction will be independent from changes in degree of filling.

The determined differential pressure may therefore be represented by a portion being dependent on the degree of filling and a portion being dependent on the general flow restriction of the portion of the air intake conduit for which the differential pressure is determined. The diagnosing of the function of the air intake conduit may include generating a signal indicating a status of the air intake conduit, where the signal may indicate e.g. a leak in the air intake conduit, a need for replacing the air filter and/or a degree of filling of the air filter.

The diagnosing may include to determine, based on said estimated parameter, if the differential pressure over the at least a portion of the air intake conduit, for a predetermined higher air mass flow than the said first air mass flow, will exceed a predetermined limit. A signal may then be generated when the differential pressure at said predetermined higher mass flow will exceed said predetermined limit. In this way it can be determined whether higher mass flows may result in differential pressures that potentially may damage engine operation and/or components. According to embodiments of the invention, the at least one estimated parameter may be compared with a limit value of said at least one parameter, and a signal may be generated when said estimated value exceeds a maximum limit or is below a minimum limit value. For example, since the parameter value may be dependent on the degree of filling of the air filter, the parameter value may increase with increasing degree of filling, and when the parameter value reaches an upper limit it may be determined that the filter needs replacement to avoid undesired pressure levels from arising.

According to embodiments of the invention, a signal representing the current degree of filling of said air filter may be generated, and e.g. indicated to a driver of the vehicle.

Furthermore, in case the parameter value represents the flow restriction in a system where a clean (empty) air filter is fitted, a signal may be generated when said estimated value is below a minimum limit since this may indicate a leak in the system.

The parameter value representing the flow restriction may oftentimes be considered constant and hence be determined beforehand, e.g. during manufacturing of the vehicle. Flowever, as was mentioned, this parameter value may be used to detect a leak in the system and according to embodiments of the invention, a first value of the differential pressure over said at least a portion of the air intake conduit is determined when said airflow is controlled to a first mass flow. A second value of the differential pressure over said at least a portion of the air intake conduit may then be determined when said airflow is controlled to a second mass flow being different from said first mass flow.

These values of the differential pressure and associated mass flows may then be used to estimate both said first parameter value representing a degree of filling of said air filter, and being independent of the air flow, and said second parameter value representing a flow restriction of said air intake conduit when the air filter is empty. In this way, it can be determined e.g. whether there is a leak in the system, which may influence the determination of the degree of filling of the air filter. The mass flow may be controlled to a mass flow exceeding the mass flow when the internal combustion engine is idling, and the mass flow may be increased by increasing by, for example, actions according to the below and/or increasing a load on the internal combustion engine when the vehicle is standing still.

For example, the mass flow may be increased by increasing the speed of rotation of the internal combustion engine to thereby increase the mass flow of air being taken in by the air intake conduit.

Furthermore, the timing of the injection of fuel into the combustion chambers may be changed and be advanced or retarded to increase energy in the exhaust gases which may be used to increase work produced by a turbine of a turbocharger.

If the vehicle comprises a turbo charger, the turbocharger can be controlled to increase compression of intake air. For example, if the vehicle comprises a Variable- Geometry Turbocharger (VGT), the turbine of the Variable-geometry turbocharger may be controlled to increase the amount of exhaust gas energy being used to compress intake air so that air flow is increased, where the exhaust gas energy may be further increased e.g. by increasing speed of rotation of the internal combustion engine and advancing/retarding fuel injection.

If the vehicle comprises a fixed geometry turbocharger and a waste gate, the waste gate may be throttled to increase exhaust gases passing the turbine to thereby increase compression of intake air to increase the air flow, where the exhaust gas energy also may be further increased as above.

The exhaust gas energy may also be increased by injecting fuel into the exhaust gas stream downstream the internal combustion engine but upstream a turbine. Such injections may be utilised to increase exhaust gas temperature to increase the temperature of exhaust gas components, and may also be utilised to increase mass flow according to embodiments of the invention.

A further method to increase the flow of air through the internal combustion engine is to control the pressure over the internal combustion engine such that the pressure at the intake manifold exceeds the pressure of the exhaust manifold. In this way, intake air can be controlled to pass through an exhaust gate recirculation (EGR) valve from intake manifold to exhaust manifold to thereby increase mass flow.

If the vehicle comprises an exhaust brake, activation, e.g. by throttling, of the exhaust brake may be used to increase load on the internal combustion engine to thereby further increase the air being supplied to the combustion, hence increasing the mass flow.

According to embodiments of the invention, the mass flow is increased by one or more from increasing speed of rotation of the internal combustion engine, controlling ignition to increase exhaust gas energy, controlling a turbocharger to increase compression of intake air, increasing load of the internal combustion engine and passing air from intake manifold to exhaust manifold through an EGR circuit.

The diagnose may be utilized to determine if and when an air filter needs to be changed and/or the air intake conduit for other reasons need service, e.g. due to a leakage.

The diagnose according to embodiments of the invention may prevent e.g. a service mechanic from doing unnecessary air filter changes, and may also minimize the risk for vehicle is being driven in dusty environments without changing the air filter even when necessary.

The degree of filling may also be monitored over time by estimating a parameter value at subsequent times, and, for example, be utilised to predict a remaining travel distance and/or remaining time of operation to a time of replacement of the air filter.

The invention is carried out in a vehicle, and the invention also relates to a system corresponding to the method set forth above. The system is characterised in means carrying out features of the invention. Such means for carrying out features of the invention can consist of any suitable means, and the means can be specifically adapted to perform the features set forth in the system claim. Such means can consist of one or more control units, one or more computer programs, or other electrical, mechanical and/or electromechanical elements or arrangements. Further characteristics of the present invention and advantages thereof are indicated in the detailed description of exemplary embodiments set out below and the attached drawings.

Brief description of the drawings

Fig. 1 A illustrates a power train of an exemplary vehicle;

Fig. 1 B illustrates an example of a control unit/means in a vehicle control system;

Fig. 2 illustrates an exemplary air intake conduit of a vehicle;

Fig. 3 illustrates an exemplary method according to embodiments of the invention.

Fig. 4 illustrates differential pressure as a function mass flow for various flow resistances in an air intake conduit.

Detailed description of exemplary embodiments

Fig. 1A schematically depicts a power train of an exemplary vehicle 100. The power train of the vehicle in Fig. 1A comprises an internal combustion engine 101 which, in a conventional manner, is connected, via an output shaft of the engine 101 , to a gearbox 103 via a clutch 106. The engine 101 is controlled by the vehicle's control system via a control unit/means 115. The clutch 106, which, for example, can be an automatically operated clutch, and the gearbox 103 are also controlled by the vehicle's control system by means of a control unit/means 1 16.

An output shaft 107 of the gearbox 103 drives drive wheels 1 13, 1 14 through a final drive 108 such as, for example, a conventional differential gear, and drive shafts 104,

105 connected to the said final drive 108.

Fig. 1 A discloses a powertrain of a specific kind, but the invention is applicable for any kind of power train comprising an internal combustion engine, and hence embodiments of the invention are also applicable e.g. for hybrid vehicles. The disclosed vehicle further comprises one or more exhaust treatment components 130 for exhaust treatment (purifying) of exhaust gases that results from combustion in the internal combustion engine 101.

The exhaust treatment components 130 may be of various kinds and designs. For example, in a manner known per se, the exhaust treatment components 130 may include one or more diesel oxidation catalytic converters (DOC), which, inter alia, may be used to oxidize remaining hydrocarbons and carbon monoxide in the exhaust gas stream. The oxidation catalytic converter may also oxidize nitrogen monoxide (NO) occurring in the exhaust gas stream to nitrogen dioxide (N02). Further, the exhaust treatment components may include one or more Selective Reduction

Catalytic (SCR) converters. Such catalytic converters may be utilised to reduce presence of nitrogen monoxide (NO) and nitrogen dioxide (N02) occurring in the exhaust gas stream. Further, the exhaust treatment components 130 may include one or more particle filters being arranged to capture particles occurring in the exhaust gas stream. There exist various exhaust treatment components and configurations of combinations of such components, and, in principle, any such combination may be utilised according to embodiments of the invention. The exhaust treatment will therefore not be discussed further herein.

Fig. 2 discloses an exemplary air intake conduit of the internal combustion engine 101 according to embodiments of the invention.

The internal combustion engine 101 is schematically illustrated as a six-cylinder Diesel engine, i.e. the internal combustion engine 101 comprises six combustion chambers 201. According to embodiments of the invention, the internal combustion engine may comprise any number of cylinders/combustion chambers 201.

Combustion engines of the disclosed kind in general also comprise at least one fuel injector (not shown) for each combustion chamber 201 , where the fuel injectors, in a conventional manner, injects fuel into the combustion chambers 201 for combustion.

The internal combustion engine 101 further comprises an intake manifold,

schematically indicated by 202 which may form part of an air intake conduit, for distributing intake air, i.e. vehicle ambient air, to the combustion chambers 201.

The air intake conduit, according to the present example, further comprises an air inlet hose/pipe 203 having an opening/snorkel 204 towards the surroundings of the vehicle 101 for intake of ambient air. The air intake conduit further comprises an air filter 205 for cleaning air being taken in through opening snorkel 204 to be supplied to the combustion chambers 201. The filtering of the air is performed to avoid e.g. particles in the air from negatively impacting the operation of the internal combustion engine 101.

Following combustion in the internal combustion engine 101 , exhaust gases (the exhaust gas flow) that are generated during the combustion passes through an exhaust conduit comprising a turbine 21 1 forming part of a turbocharger unit 210 and the one or more exhaust treatment components 130 for treatment of the exhaust gases discussed above. According the present example the exhaust conduit also comprises an exhaust gas brake system 215 which e.g. may be utilised to increase internal combustion engine 101 back-pressure by throttling the exhaust gases.

The use of a turbocharger unit 210 according to fig. 2 hence means that the combustion engine 101 may become supercharged, i.e. the pressure of the intake air being supplied to the combustion chambers 201 may exceed the pressure of the ambient air that surrounds the vehicle 100.

This supercharging using the turbocharger unit 210 is achieved, according to the present example, by a compressor 212 being driven by the turbine 21 1 through a shaft 207. The compressor 212 compresses, i.e. pressurizes, the air that is supplied via the inlet 204, possibly also together with conventional recirculation of exhaust gases, known as EGR (not shown in the drawings), for subsequent supply to the intake manifold 202. The ability of the compressor 212 to compress air is controlled by the force, or speed of rotation, by means of which the turbine 21 1 rotates. Since the turbine 21 1 is driven by the exhaust gas flow, the force, or speed of rotation, is dependent, and controlled, by the passing exhaust gas flow.

The turbocharger unit 210 according to the exemplary embodiment disclosed in fig. 2 is of a type having a variable geometry, i.e. the turbocharger unit is a Variable Geometry Turbocharger (VGT), which means that the fraction of the exhaust gas flow that is actually used to propel the turbine may be controlled. This can be

accomplished, for example, by the turbine 211 in a conventional manner being provided with several adjustable guide rails for controlling the amount of exhaust gases that is used to influence the turbine wheel, and the amount of exhaust gases that is allowed to pass the turbocharger unit without the energy being exploited for compression of the combustion air. Thus, the operation of the turbine 21 1 can be controlled with the aid of the adjustable guide rails, whereby also the pressure to which the compressor 212 compresses the air that is supplied to the combustion process can be controlled through the aid of the guide rails.

The turbocharger unit 210 can be used, according to embodiments of the present invention, to assist in obtaining a desired predefined flow of the intake air to allow proper diagnose of the air intake conduit. For example, if the internal combustion engine 101 is idling, the airflow may not be sufficient to perform the diagnose with a desired level of accuracy, and/or the accuracy may be improved if the airflow is increased.

Further with regard to the air filter 205, the air filter 205 will, in time, become filled (clogged) by the particles and other possible substances being collected from the air passing through the filter 205. As the air filter 205 fills up, the flow restriction that the air passing through the filter exhibits will increase, and at some point in time the filter must be replaced to ensure proper supply of air to the combustion to thereby ensure proper operation of the internal combustion engine 101.

The time it takes for the air filter to fill and become clogged depends greatly on the environment in which the vehicle is travelling. An air filter of a vehicle travelling in surroundings being more subjected to pollution will fill up more quickly than an air filter of a vehicle travelling in areas where the ambient air in general is cleaner.

According to embodiments of the present invention, the air intake conduit can be diagnosed to reduce the risk that the vehicle is being driven with an air filter being clogged to an extent that may negatively impact the operation of the internal combustion engine 101. According to embodiments of the invention, instead or in addition, possible air leaks in the air intake conduit may be detected through the diagnose.

An exemplary method 300 according to embodiments of the invention is illustrated in fig. 3, where the method 300 according to the present example is arranged to be carried out by the engine control unit 1 15 shown in Figures 1 A and 1 B.

The person skilled in the art will appreciate that a method for diagnosing the air intake conduit of a vehicle according to the present invention may be implemented in a computer program, which, when it is executed in a computer, instructs the computer to execute the method. The computer program is usually constituted by a computer program product stored on a non-transitory/non-volatile digital storage medium, in which the computer program is incorporated in the computer-readable medium of the computer program product. The computer-readable medium

comprises a suitable memory, such as, for example: ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically Erasable PROM), a hard disk unit, etc., and be arranged in or in connection with a control unit/system/means, whereupon the computer program is executed by the control unit/system/means.

A plurality of the functions of a vehicle, such as controlling the internal combustion engine and turbocharger unit are, in general, controlled by control means such as e.g. a control system and/or a control unit. Control systems in modern vehicles commonly comprise communication bus systems comprising one or more

communication buses for linking a number of electronic control units (ECU's), or means or controllers, and various components located on the vehicle. Such a control system can comprise a large number of control units/means and the responsibility for a specific function can be divided amongst more than one control unit. Vehicles of the shown type thus often comprise significantly more control units than the control units shown in fig. 1 A, which is well known to the person skilled in the art within this technical field. The control units/means 1 15, 1 16 of fig.1 A may hence communicate with one another via the communication bus system, partly indicated by

interconnecting lines in fig. 1 A. When a method according to embodiments of the invention is implemented in a control unit/means e.g. of the exemplified kind this may hence be accomplished using a computer program stored on storage means of the control unit/means and being executed by executing means of the control

unit/means. A method according to embodiments of the invention may also be implemented using a combination of a plurality of computer programs, which may be implemented in a same or different control units/means. A vehicle control system may also comprise only a single control unit/means carrying out the various control system functions of the vehicle. The present invention can be implemented in any suitable control unit/control means, and, according to the illustrated example, the invention is implemented in control unit/means 1 15 for controlling the internal combustion engine 101. The invention may, however, also be implemented in any other suitable control unit/means and/or combination of control units/means. The diagnosing of the air intake conduit according to embodiments of the invention will usually depend on signals being received from other control units/means and/or vehicle components, and it is generally the case that control units/means of the disclosed type are normally adapted to receive sensor signals from various parts of the vehicle 100. The control unit/means 1 15 will, for example, receive control signals representing engine parameters and temperatures and pressures of sensors. Control units/means of the illustrated type are also usually adapted to deliver control signals to various parts and components of the vehicle, e.g. to control the turbine 21 1 and/or other means for increasing the airflow being supplied to the combustion chambers, and/or other control units/means of the control system of the vehicle.

An exemplary control unit/means (the control unit/means 1 15) forming part of, or constituting, the vehicle control system is schematically shown in Fig. 1 B, wherein the control unit/means comprise a computing unit 120, which can comprise, for example, any suitable type of processor or microcomputer, such as a circuit for digital signal processing (Digital Signal Processor, DSP) or a circuit having a predetermined specific function (Application Specific Integrated Circuit, ASIC). The computing unit 120 is connected to a memory unit 121 , which provides the processing unit 120, with e.g. the stored program code 126 and/or the stored data that the computing unit 120 requires to be able to perform calculations. The computing unit 120 is also arranged so as to store partial or final results of computations in the memory unit 121.

Furthermore, the control unit/means 1 15 is provided with devices 122, 123, 124, 125 for receiving and transmitting input and output signals. These input and output signals can comprise waveforms, impulses or other attributes that can be detected as information and can be converted into signals which can be processed by the computing unit 120. These signals may then be made available to the computing unit 120. The devices 123, 124 for transmission of output signals are arranged to convert signals received from the processing unit 120 in order to create output signals by, for example, modulating the signals, which can be transmitted to other parts of and/or systems of the vehicle. Each of the connections to the devices for receiving and transmitting input and output signals may comprise 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 Transport) or any other bus configuration, or a wireless

connection. A person skilled in the art will appreciate that the claimed system, or part of the claimed system may comprise the control unit/means 115 where means of the claimed system may comprise the computing unit 120.

Further to the method 300 in fig. 3, the method starts in step 301 , where it is determined whether the air intake conduit is to be diagnosed. This may be arranged to be performed at regular intervals and/or in case, for example, there is an indication that a diagnosis should be performed, upon such indication. As is realized by the person skilled in the art, other and/or additional criteria for performing the diagnose may also be utilized. For example, it may be determined that no intermittent loads that only temporary applies a load to the internal combustion engine 101 are active to ensure that airflow does not abruptly change if such loads are suddenly stopped. The method remains in step 301 for as long as no diagnosis to be performed. When it is determined that the air intake conduit is to be diagnosed, the method continues to step 302.

According to the present example, the air intake conduit is diagnosed when the vehicle is standing still. It is therefore determined in step 302 whether the vehicle is, in fact, standing still. If this is not the case the method returns to step 301 while otherwise the method continues to step 303. According to embodiments of the invention the criterion that the vehicle is standing still may, instead, be a criterion for the transition from step 301 -302 (which then e.g. would correspond to step 303 of the present example).

In step 303, the airflow to pass the air intake conduit for supplying the combustion chambers 201 is set to a predetermined air mass flow m_x. As was mentioned above, it may be preferred to set the airflow to an air mass flow that exceeds the air mass flow that prevails when the vehicle is idling. The airflow may therefore be controlled, according to the present example, e.g. through the use of the turbo unit 210, where the turbine 21 1 may be controlled to extract more, or even as much energy from the exhaust gases as possible so that the compressor 212 compresses the intake air to a higher extent to thereby increase the amount of air being supplied each combustion cycle and hence increasing the airflow. Furthermore, the internal combustion engine 101 may e.g. be further loaded e.g. by throttling the exhaust brake 215 and/or activating other loads that can be applied to the internal combustion engine when the vehicle is standing still to thereby further increase the amount of fuel being injected into the combustion chambers 201 , thereby further increasing the air intake flow.

When it is determined, step 304, that the actual air mass flow equals the

predetermined desired air mass flow m_x, the method continues to step 305, while otherwise the method returns to step 303. The current airflow can be determined, for example, using a flow sensor 220 (see fig. 2). The flow sensor 220 is, in the present example arranged downstream the compressor 210 hence measuring the

compressed airflow and possibly also recirculated exhaust gases. According to embodiments of the invention, the flow sensor 220 may, instead, be arranged upstream the compressor 212, hence measuring the air being drawn from the exterior of the vehicle 100. There may also be more than one flow sensor present at the vehicle 100. The air mass flow m_x further need not be predetermined, but it may e.g. only be increased to an essentially arbitrary air mass flow, since the airflow may then determined using the flow sensor/meter 220. Alternatively, the air mass flow may be calculated using a mathematical model. The model may, for example, be used to calculate air mass flow from speed of rotation of the internal combustion engine, cylinder volume and pressure and temperature of the intake manifold and pressure and temperature of the exhaust manifold.

When it has been determined that the desired airflow has been obtained, a differential pressure Dr over a desired portion of the air intake conduit is determined in step 305, where this differential pressure Dr at least takes into account the differential pressure over the air filter 205, Ap _iiter. The differential pressure Dr may be determined using two pressure sensors 221 , 222 arranged upstream and downstream, respectively, of the air filter 205. The pressure sensors 221 , 222 may be arranged in the immediate vicinity upstream and downstream of the air filter 205 to only evaluate the air filter 205 or at any other suitable location in the air intake conduit for as long as at least the differential pressure over the air filter 205 is accounted for, i.e. included in the measurement. The evaluation of the air filter 205 may be performed irrespective of the locations of the pressure sensors for as long as the air filter 205 is included in the airflow path between the sensors. Hence, it is sufficient to determine e.g. the ambient pressure of the air be in taken in by the air intake conduit and a further pressure using a pressure sensor downstream the air filter 205. The differential pressure may also be determined e.g. using a single pressure sensor 222, which may then be e.g. a gauge pressure sensor designed to measure a relative pressure such as pressure relative to the ambient pressure and hence in relation to the air inlet 204. Hence a single pressure sensor arranged downstream the air filter 205 may be sufficient to determine the differential pressure. The differential pressure Dr is further preferably determined for a portion of the air intake conduit upstream the compressor 212, because the pressure increase that the air undergoes in the compressor may reduce the accuracy of the determination of the differential pressure Dr. It is, however, also possible to perform a measurement downstream the compressor, but then the speed of rotation of the compressor/turbine is required to determine the pressure increase imposed by the compressor.

Furthermore, a temperature T of the ambient air being drawn from the surroundings of the vehicle 100 through nozzle/snorkel 204 may also be determined, e.g. using a temperature sensor 223 or using other suitable means, where the temperature sensor 223 may be located at any location on the vehicle 100 for as long as the sensed temperature is representative of the ambient air temperature.

When the measurements have been performed the air intake conduit is diagnosed in step 306. According to embodiments of the invention, any, or both, of two different conditions of the air intake conduit can be diagnosed using the described method. According to embodiments of the invention the air filter 205 can be diagnosed in terms of e.g. degree of filling so that it can be determined e.g. whether it is time to replace the air filter 205. According to the invention, the diagnose can be performed for essentially any air mass flow while still determining the degree of filling. Furthermore, according to embodiments of the invention, the air intake conduit can alternatively or in addition be diagnosed with regard to possible leakage, where a presence of a present leakage in the system may also be detected. When the diagnose in step 306 indicates a fault e.g. that the air filter 205 has reached a degree of filling where it should be scheduled for replacement, or a leakage is detected, a signal may be generated in step 308, e.g. alerting a driver or setting one or more diagnostic trouble codes to be attended to e.g. at an upcoming service of the vehicle. The method may be then ended in step 309.

The diagnose according to embodiments of the invention is performed by estimating a parameter that depends on either the flow restriction through the filter caused by the degree of filling, and/or a parameter representing the flow restriction through the air intake conduit when the filter is clean (empty), where the parameter being estimated in this case is not affected by an increase in the degree of filling of the air filter. In dependence of which characteristic (degree of filling of the air filter or possible leakage) that is to be determined a selected, or both, of these parameters are estimated.

As was mentioned, when estimating the parameter value a differential pressure is determined, and the difference in static pressure, such as, for example, between the intake nozzle/snorkel 204, i.e. the pressure of the air surrounding the vehicle, and the compressor inlet depends on the inlet pipes, air filter degree of filling, air mass flow and density of the air. The difference in static pressure can be modelled as:

where

(eq. 2)

And where C, T₀ and m₀ are physical constants for which the following values may be used: C = 120, T₀ = 291,15 and m₀ = 18,27 * 10^-6 c represents the parameter that depends on the restriction caused by air filter degree of filling and c₂ represents the parameter that depends on the restriction of the air intake conduit piping when a clean (empty) air filter is fitted. p represents the density of the air, which may be determined from temperature of the air, which may be determined by a temperature sensor, and pressure which is determined by pressure sensor according to the above. The density p may be stored in a memory for various combinations of pressure and temperature, or be expressed by a mathematical expression.

rh is the air mass flow.

Other models for representing the flow restriction through the air filter and air intake conduit, respectively, may also be utilized. However, the impact of the clogging on the differential pressure will be dependent on the air mass flow, and the impact of the general restriction in the air intake conduit on the differential pressure will depend on the air mass flow raised to the second power as is exemplified in eq. 1.

Reference values of the parameters c_x and c₂ may be predetermined e.g. for a particular air intake conduit or even a particular vehicle e.g. during a construction or design stage, where the parameters may be determined through the use of a mathematical model of the air intake conduit or through actual measurements of the system. The parameter c_± may further be determined, for example, for various degrees of clogging (degrees of filling) of the air filter. For example, a value representing a full filter, or a degree of filling at which the filter should be replaced may be used as the predetermined reference parameter value. Since parameter c₂ in general is independent on the degree of filling, a single measurement may be sufficient, but this measurement is preferably, or perhaps even should, be performed when the air filter is clean (empty). When performing a diagnose of the air intake conduit according to the invention the estimated one or two parameters c_x and/or c₂ that has determined according to the above can be compared with the expected predetermined parameter values of c and/or c₂. When the parameter values being estimated during the diagnose indicates e.g. that the filter should be replaced, e.g. because the parameter value of c exceeds a maximum value and/or it is indicated that the system comprises a possible leakage, e.g. because the parameter value of c₂ is below a minimum value, a suitable signal can be generated, e.g. to alert a driver and/or set one or more diagnostic trouble codes to assist/alert e.g. service personnel at an upcoming service, and/or even activate an indicator alerting the driver to take the vehicle in for service.

The estimation of a parameter being dependent on e.g. the degree of filling of the air filter, or the flow restriction through the air intake conduit has the advantage that the parameter value may be estimated at an arbitrary air flow, but the estimated parameter value will still be valid for other air flows. That is, the parameter values of c is constant irrespective of the air flow for a particular degree of filling of the air filter 205 and only changes with the change in degree of filling. The parameter value of parameter c₂ is constant irrespective of air flow and degree of filling of the air filter 205 for as long as e.g. no leak arises in the system. Hence, when the parameter value has been estimated, a differential pressure may also be estimated for any other airflows than the current air mass flow at which the parameter is actually being estimated. This further means that a maximum parameter value of e.g. c_x can be determined for a worst case, and by comparing the estimated parameter value with the limit value it can be determined whether there is a risk for the differential pressure becoming too high at other air flows. This will be explained further with reference to fig. 4.

If the pressure drop that the intake air undergoes when passing the air intake conduit on its way to the combustion chambers 201 , or when a compressor is present as in the present example, in general to the upstream side of the compressor, becomes too large there is a potential risk of damage to components of the internal combustion engine. For example, if there is a high pressure drop, and hence pressure below atmospheric pressure, i.e. negative pressure, upstream the compressor 212 inlet, this may result in a turbo malfunction due to overspeed caused by reduced compressor load. A high pressure difference may also result in excess stress on air intake conduit components which may be subjected to a high pressure difference between the interior and exterior of the components. Furthermore, a high pressure drop may also lead to high exhaust temperatures due to low lambda combustion with potential damage e.g. to aftertreatment components.

Therefore, when designing an internal combustion engine, tests may be performed to determine the highest pressure drop of the intake air that a particular internal combustion engine may be subjected to while still ensuring proper operation. Such tests may, for example be performed in test cells. The results from these tests may be stored in memory and used as upper limits imposing conditions regarding when to exchange the air filter since it is, in principle, the air filter that will give rise to the differences in differential pressure that the system undergoes for a particular point of operation as time progress.

Oftentimes there exist limitations regarding the maximum differential pressure of the air intake conduit and/or air filter. For example, there may exist a maximum

differential pressure for a particular air mass flow. There may also exist maximum differential pressures for a number of different air mass flows that should not be exceeded in order to ensure proper engine operation. Such one or more points of operation may then be used to determine upper limits of the parameter c and/or or c₂ so that the estimated parameter may be compared to this maximally allowed parameter to thereby diagnose the system. The value of the parameter c_x may also be used e.g. to determine a current degree of filling of the air filter 205. Fig. 4 illustrates an example of the variation of differential pressure Dr as a function of the air mass flow passing through the air intake conduit.

Oftentimes there are in particular two or three operating points that are likely to give rise to the most unfavourable situations. A first of these points is an operating point where maximum torque is produced at a low speed of rotation of the internal combustion engine 101. This is illustrated by point 403 in figure 4. A second operating point is when the internal combustion engine produces maximum power. This is represented by point 404. A third operating point (not shown) may constitute an operating point where engine load is low and/or fuel injection being turned off, e.g. when so called dragging prevails. The turbine may be only very slowly rotating in situations of this kind, with the result that oil seals of the turbine shaft may not provide optimal sealing. A negative pressure caused by a clogged air filter may result in oil leak in situations of this kind, hence providing a further limitation regarding allowable pressure drop over the air filter.

The obtained results from these tests, i.e. point 403 represented by N , m and point 404 represented by Ap₂, rn₂, may then be used to calculate parameter c for the two situations. The operating point resulting in a parameter c_x having the lowest value may then be selected as the maximum allowable value of parameter c when performing the assessment according to the invention. In the present case, the value of c obtained in point 404 is selected. As can be seen from the figure, this point results in a lower maximum differential pressure as a function of air mass flow, represented by solid line 405, than point 403 (represented by dotted line 406). Solid line 405, representing a plot using eq. 1 at with parameter c determined from operating point 404, hence represents the maximum allowable degree of filling of the air filter 205. According to the example shown in fig. 4 it is hence the operating point representing maximum delivered power by the internal combustion engine that is limiting the upper value of parameter c . For other systems the situation may be different.

When performing the determination of the parameter c_t in this manner, the parameter c₂ may preferably first been determined for the system when a clean (empty) air filter is fitted as explained above. With regard to the parameter c₂, this may be determined for a number of air intake conduits beforehand and stored in memory, so that when determining the limiting values of parameter c_± tests need not actually be performed to determine parameter c₂. Since the c_x portion of eq. 1 is used to only represent a degree of the filling of the air filter, this part may be assumed to be zero, that is the parameter c may be assumed to be zero, when a fresh air filter is fitted. This further means that the airflow restriction through the system when the air filter is newly replaced will have an exponential dependency. This is illustrated by line 401 , which represents the differential pressure between two points of measurement in the air intake conduit, such as, in the present example, from the intake nozzle 204 to pressure sensor 222 downstream of the air filter 205. The dash-dotted line 401 hence represents the pressure loss from intake nozzle 204 to pressure sensor 222 as a function of the air mass flow for a system where the air filter is freshly replaced. This is hence a minimum differential pressure (as a function of air mass flow) that will prevail when there is no leakage in the system, and which determines parameter c₂. When the differential pressure is below line 401 , such as is the case with line 409, it can be assumed that there is a leak in the system. In time, as particles/compositions occurring in the intake air is captured by the air filter 205, and the air filter 205 pose an increasingly higher flow resistance the pressure loss that the air mass flow undergoes when passing through the filter 205 increases. Dashed line 402 in fig. 4 exemplifies the reduction in pressure, differential pressure Dr, as a function of air mass flow m that the intake air undergoes in a situation where the air filter 205 is filled approximately to 50% of the maximum degree of filling that should not be exceeded in order to ensure proper operation of the internal combustion engine 101. The pressure loss that the intake air undergoes, and hence the differential pressure that the intake air is subjected to will hence increase both as a function of air mass flow but also as a function of the degree of filling of the air filter 405. Line 407 represents a situation where the air filter is filled to a too high extent, where high mass flows may result in too high differential pressures.

The parameter values of parameter c_x and c₂ will hence act as constants irrespective of the air flow, parameter c_± only being dependent on degree of filling of the air filter, and may therefore also be determined from any set air mass flow such as, for example, air mass flow m_x of fig. 4. Hence, in principle any air mass flow may be set when performing the diagnose according to the invention. However, e.g. lines 401 and 409 of fig. 4 may be close to each other for low air mass flows, and any measurement error and/or model error may have a greater impact on the result of the estimation if low air mass flow are used.

Therefore, according to embodiments of the invention the mass flow is set to a mass flow that is at least higher than the mass flow that prevails when the internal combustion engine 101 is idling and the vehicle is standing still. The particular minimum mass flow that should be set when performing the evaluation according to the invention may differ from vehicle to vehicle, and a suitable minimum mass flow may be determined e.g. during design or manufacturing stage.

Tests have been performed, however, for a number of systems, and these tests have revealed that a high level of accuracy is obtained already at mass flows in the order of 20-30% of the maximum mass flow that the particular internal combustion engine configuration is capable of delivering. Hence tests can be performed with a considerably lower mass flow than the maximum mass flow being represented e.g. by point 404 in fig. 4.

The system may be designed to generate a warning signal when the degree of filling of the air filter 205 reaches a degree of filling e.g. being a predetermined percentage of the determined maximally allowable parameter c_x.

For example, when this level is reached a warning may be set in the vehicle control system e.g. to alert service personnel at the next service and/or the driver may be notified about the need for placing the air filter. As was mentioned above, estimations of parameter c at different points in time and monitoring the progress of the increase of parameter c may allow suitable time of replacement of the air filter 205 to be predicted so that a replacement of the air filter 205 may e.g. be scheduled for any service occasion occurring in the vicinity of this predicted point in time so that the air filter may be replaced even if the level represented by line 406 has not been yet reached. In this way, a next service operation caused solely by the need for replacement of the air filter may be avoided.

Furthermore, in case the system is operational as expected and no leaks are occurring, the parameter c₂ will remain essentially constant over time, and an estimation of this parameter that was performed e.g. during the manufacturing stage may be utilized when assessing degree of filling of the air filter 205 according to the above. In general the air intake conduit should be subjected to only little or no degree of degradation of over time, and in principle, re-estimation of the parameter c₂ would therefore not be necessary for such reasons. The vehicle may, however, be subject to a rebuild which may change physically e.g. the location of the air intake nozzle, thereby rendering a need to re-estimate the parameter c₂.

The parameter c₂ may, however, be arranged to be re-estimated at regular intervals to determine a possible presence of leaks because leaks in the system may be detected by estimating the parameter c₂. According to embodiments of the invention, therefore, the parameter c₂ is instead or in addition estimated. In case the parameter c is known with a high accuracy, this may be the case, for example, if the air filter has recently been replaced and hence the parameter c may be assumed to be zero, the parameter c₂ may be estimated in a straightforward manner using eq. 1 above using the known value of parameter c_x. However, if the parameter c_x is not known with sufficient accuracy it may be necessary to estimate both parameters. This may still be performed using eq. 1 above. However, if both parameters are to be estimated, measurements of the differential pressure need to be performed for two different mass flows to allow the two unknown variables to be solved.

This may be accomplished in a straightforward manner by first setting the mass flow to a first mass flow at which a first differential pressure is determined followed by setting the mass flow to a second, different from the first, mass flow to determine a second differential pressure. For example, measurements may be performed at mass flows m_x and ni_y resulting in differential pressures Ap_x and p_y in fig. 4. The parameters c_{l t} c₂ may then be solved using eq. 1 , where the solving of eq. 1 may be performed in any suitable manner. For example, a Kalman filter or any other suitable method may be used as is known to the person skilled in the art. Hence, in this way, it is possible to simultaneously estimate both a degree of filling of the air filter as well as determining whether there is a leak in the system.

More particularly, if the estimated value of parameter c₂ is below the value that was obtained when the parameter was first determined, hence the parameter giving rise to line 401 in fig. 4, it is highly likely that a leakage in the system is present. A suitable diagnostic trouble code may then be set to alert e.g. service personnel about the problem. The determination of the c_x and the c₂ parameter has the advantage that the reason for e.g. a system operating in an undesired manner may more easily be detected since e.g. reduction in combustion engine performance caused by a filled air filter can be detected and separated from e.g. reduction in performance caused by a leakage in the system.

Furthermore, according to embodiments of the invention, the diagnose may be performed e.g. by a service technician when the vehicle is taken in for service to thereby reduce the risk for e.g. an air filter being replaced only to subsequently realize that the vehicle still is not operating properly and therefore needs to be taken in for service once again. The diagnose may also be performed any suitable time that the vehicle is standing still, where, as was mentioned above, diagnostic trouble codes may be set when required for subsequent attending to. The invention has the advantage that it may be determined whether there is a risk for a maximum allowable pressure drop in the air intake conduit occurring without actually setting the air mass flow to a mass flow resulting in such a pressure drop, so that the risk for potentially damaging pressure drops may be detected prior to such pressure drops actually arise.

The invention may also be utilized to predict at which point in time the air filter will become full, and hence the point in time at which it can be assumed that the filter will need replacement. For example, the degree of filling can be determined at different periods of time, where a driven distance and/or time of utilization of the vehicle between the determinations of degree of filling so that a future point in time at which the filter will become clogged, e.g. in the terms of driven distance and/or hours of use can be estimated to thereby proactively determine a suitable time for replacement of the filter.

The driver may also be presented, e.g. upon a driver request or service personnel request, a degree of filling of the air filter expressed e.g. in percent, e.g. in the instrument cluster of the vehicle. In this way the current status of the air filter may be immediately available on request e.g. to rule out or confirm the air filter being a possible cause for a current undesired behaviour of the of the vehicle, or simply to inform about the current status.

The present invention is not limited to the above described embodiments. Instead, the present invention relates to, and encompasses all different embodiments being included within the scope of the independent claims.

Claims

1. Method for diagnosing an air intake conduit for supplying air to an internal combustion engine (101 ) of a vehicle (100),

said vehicle (100) comprising:

an internal combustion engine (101 ) comprising at least one combustion chamber (201 );

an air intake conduit configured supply air to said at least one combustion chamber (201 );

said air intake conduit comprising an air filter (205);

said method comprising, when said vehicle (100) is standing still:

controlling a mass flow (; m ) of said air being supplied to said at least one combustion chamber (201 ) to a first mass flow ( rh_x );

when said mass flow (m) is controlled to said first mass flow ( rh_x ), determining a differential pressure (Dr) over at least a portion of said intake air conduit, said portion comprising said air filter (205);

based on said determined differential pressure (Dr) and said first mass flow ( rh_x ), estimating at least one parameter (q; c₂) value being dependent on an airflow resistance of said air intake conduit, said at least one parameter (q; c₂) value being a parameter (c_x) value being dependent on a degree of filling of said air filter (205), and being independent from variations in said air flow ( m ) ; and

diagnosing the function of said air intake conduit based on said estimated at least one parameter (c_x; c₂) value.

2. Method according to claim 1 , further comprising:

estimating said parameter (q) value being dependent on a degree of filling of said air filter (205) based on, in addition, a predetermined parameter (c₂) value representing a flow restriction of said air intake conduit when said air filter (205) is empty.

3. Method according to any one of the preceding claims, the diagnosing

comprising:

based on said estimated at least one parameter (q; c₂) value determining if said differential pressure (Dr) over said at least a portion of said air intake conduit will exceed a predetermined limit (Dr₁; Dr₂) at a

predetermined mass flow

being higher than said first mass flow ( rh_x ), and generate a signal when said differential pressure (Dr) will exceed said predetermined limit (Dr₁; Dr₂) at said predetermined mass flow

4. Method according to any one of the preceding claims, further comprising:

controlling said first mass flow ( rh_x ) to a mass flow exceeding the mass flow {rh) prevailing when said internal combustion engine (101 ) is idling.

5. Method according to any one of the preceding claims, further comprising:

determining a first value (Dr ) of said differential pressure (Dr) over said at least a portion of said air intake conduit when said mass flow (rh) is controlled to said first mass flow (rh ); and

determining a second value {Ap_y) of said differential pressure (Dr) over said at least a portion of said air intake conduit, when said mass flow (rh) is controlled to a second mass flow (rh_y), being different from said first mass flow (rh ); and

based on said determined first and second values (Dr ; Ap_y) and said first and second mass flows (rh ,rh_y), estimating a first parameter (q) value representing a degree of filling of said air filter (205) and a second parameter (c₂) value representing a flow restriction of said air intake conduit when said air filter (205) is empty.

6. Method according to claim 5, further comprising:

when controlling said mass flow (rh) of said air being supplied to said at least one combustion chamber (201 ) to said first (rh_x) and said second (rh_y) mass flow, controlling said first (rh_x) and second (rh_y) mass flow to a mass flow exceeding said mass flow (rh) prevailing when said internal combustion engine (101 ) is idling.

7. Method according to any one of the preceding claims, the diagnosing

comprising:

comparing said at least one estimated parameter (q; c₂) value with a predetermined limit value of said at least one parameter (q; c₂), and generating a signal when said estimated parameter (q; c₂) value exceeds a maximum limit value or is below a minimum limit value.

8. Method according to any one of the preceding claims, further comprising:

estimating said at least one parameter (c_x; c₂) value as a parameter (q) value representing a degree of filling of said air filter (205) and,

generating a signal representing the current degree of filling of said air filter (205).

9. Method according any one of the preceding claims, further comprising, when controlling said mass flow (m):

increasing said mass flow ( m ) from a mass flow (m) prevailing when said internal combustion engine (101 ) is idling by increasing a load on said internal combustion engine (101 ).

10. Method according to any one of the preceding claims, further comprising:

increasing said mass flow (m) using one or more from the following: increasing a speed of rotation of said internal combustion engine (101 ); when said vehicle (100) comprises a turbocharger, controlling said turbocharger to increase an amount of exhaust gas energy being used to compress intake air;

when said vehicle comprises an exhaust brake, activating said exhaust brake;

control pressure over said internal combustion engine (101 ) such that an intake manifold pressure exceeds an exhaust manifold pressure to allow intake air to pass through an exhaust gate recirculation (EGR) passage from said intake manifold to said exhaust manifold to thereby increase said mass flow ( m );

controlling a fuel injection timing to increase exhaust gas energy.

11. Method according to any one of the preceding claims, wherein:

the diagnosing of said function of said air intake conduit includes generating a signal indicating a status of said air intake conduit.

12. Computer program comprising instructions which, when said program is executed by a computer, cause said computer to carry out the method according to any one of the preceding claims.

13. Computer-readable medium comprising instructions which, when executed by a computer, cause said computer to carry out the method according to any one of the claims 1 -12.

14. System for diagnosing an air intake conduit for supplying air to an internal combustion engine (101 ) of a vehicle (100),

said vehicle (100) comprising:

said air intake conduit comprising an air filter (205);

said system being characterised in:

means configured to, when said vehicle (100) is standing still, controlling a mass flow (m) of said air being supplied to said at least one combustion chamber (201 ) to a first mass flow ( m_x );

means configured to, when said mass flow (m) is controlled to said first mass flow ( rh_x ), determining a differential pressure (Dr) over at least a portion of said intake air conduit, said portion comprising said air filter (205);

means configured to, based on said determined differential pressure (Dr) and said first mass flow ( rh_x ), estimating at least one parameter (q; c₂) value being dependent on an airflow resistance of said air intake conduit, said at least one parameter (q; c₂) value being a parameter (c_x) value being dependent on a degree of filling of said air filter (205), and being independent from variations in said air flow (m); and

means configured to diagnose the function of said air intake conduit based on said estimated at least one parameter (c_x; c₂) value.

15. Vehicle (100) comprising a system according to claim 14.