TECHNICAL FIELD The invention relates to a method for diagnosing a crankshaft rotational position sensor unit of a crankshaft according to the preamble of claim 1 . The invention also relates to a system for diagnosing a crankshaft rotational position sensor unit of a crankshaft. The invention also relates to a vehicle. The invention in addition relates to a computer program and a computer program product.

BACKGROUND ART

When controlling the operation of an internal combustion engine of a vehicle it is important to know the crank angle of the crankshaft of the engine to know the position of the pistons of the set of cylinders arranged along the crankshaft for fuel injection or generation of an ignition spark when the pistons is at the top dead centre position for combustion.

In order to determine the top dead centre position for combustion, crankshaft rotational position sensor unit for determining the rotational speed of said crankshaft so as to determine crankshaft angle values are provided.

During an engine cycle of two revolutions of the crankshaft the piston of the cylinder will also be in the top dead centre for gas exchange and it is important to know whether the piston of the cylinder is in the top dead centre for combustion or top dead centre for gas exchange since a fuel injection in the top dead centre for gas exchange could result in an engine breakdown. In order to diagnose the plausibility of the crankshaft rotational position sensor unit a camshaft rotational position sensor unit for determining the rotational speed of the camshaft is provided.

The camshaft is engaged with the crankshaft and performs one revolution during a four stroke cycle of a piston of a cylinder. By using the rotational position determined by means of the crankshaft rotational position sensor unit and the rotational position determined by means of said camshaft rotational position sensor unit the top dead centre for combustion can be determined.

If the results of a comparison of the rotational speed of the camshaft rotational position sensor unit is essentially half of the rotational speed of the crankshaft rotational position sensor unit it is plausible that the both the camshaft and crankshaft rotational position sensor units are functioning correctly. However, if there is a difference it is not possible to tell which of the sensor units that is not functioning correctly. A non-functioning crankshaft rotational position sensor unit is a severe incident requiring an immediate stop of the vehicle whereas a non-functioning cam shaft rotational position sensor unit is less severe not requiring an immediate stop but rather a trip to a workshop.

US2002092499 discloses a method providing reference values of the camshaft and crankshaft positions provided by analysis from values from a vibration sensor, the analysis identifying a series of combustion events. The reference values are being compared with values from a camshaft rotational sensor and crankshaft rotational sensor.

US2005159877 discloses a method for diagnosing a camshaft sensor and a crankshaft sensor, sensor values being compared with the time of peaks in in cylinder pressure measurements.

There is however a need for improving for diagnosing a crankshaft rotational position sensor. OBJECTS OF THE INVENTION

An object of the present invention is to provide a method for diagnosing a crankshaft rotational position sensor unit which facilitates easy and efficient determination of the function of the crankshaft rotational position sensor unit.

Another object of the present invention is to provide a system for diagnosing a crankshaft rotational position sensor which facilitates easy and efficient determination of the function of the crankshaft rotational position sensor unit.

SUMMARY OF THE INVENTION

These and other objects, apparent from the following description, are achieved by a method, a system, a vehicle, a computer program and a computer program product, as set out in the appended independent claims. Preferred embodiments of the method and the system are defined in appended dependent claims.

Specifically an object of the invention is achieved by a method for diagnosing a crankshaft rotational position sensor unit of a crankshaft of an internal combustion engine. The internal combustion engine further comprises a flywheel connected to said crankshaft, and a set of cylinders distributed along the crankshaft for rotating said crankshaft during engine operation. The method comprises the steps of: determining a course of change of crankshaft rotational speed as a function of crankshaft angle by means of said crankshaft rotational position sensor unit; identifying the different cylinders based upon peak height and/or peak width of said determined course of change of crankshaft rotational speed as a function of crankshaft angle; and deciding on the function of said crankshaft rotational position sensor unit based upon the identification of the different cylinders. By thus identifying the different cylinders an easy and efficient determination of the function of the crankshaft rotational position sensor unit is facilitated. By thus determining whether the crankshaft rotational position sensor unit is functioning unnecessary stops can be avoided due to uncertainty which sensor unit is malfunctioning by a comparison between the values obtained by the crankshaft rotational position sensor unit and a the camshaft rotational position sensor unit. If the identification of the different cylinders differs compared with an expected identification for a functioning crankshaft rotational sensor unit the sensor unit being diagnosed is likely malfunctioning. If the identification of the different cylinders matches with an expected identification for a functioning crankshaft rotational sensor unit the sensor unit being diagnosed is likely to function. Deciding on the function of said crankshaft rotational position sensor unit based upon the identification of the different cylinders may comprise comparing the order in which the identified cylinders are ignited/are in the top dead centre for combustion with such an order for a functioning crankshaft rotational sensor unit. If the compared order does differs the sensor unit being diagnosed is likely malfunctioning and if the order is the same the diagnosed sensor unit is likely to function correctly.

According to an embodiment of the method the step of deciding on the function of said crankshaft rotational position sensor unit comprises the step of comparing peak height pattern and/or peak width pattern of said determined course of change of crankshaft rotational speed with a known such pattern for a functioning crankshaft rotational position sensor unit. Hereby an easy and efficient determination of the function of the crankshaft rotational position sensor unit is obtained. If the peak height pattern and/or peak width pattern of said determined course of change of crankshaft rotational speed determined by the crankshaft rotational sensor unit being diagnosed differs to a certain extent from such pattern for a functioning crankshaft rotational position sensor unit the sensor unit being diagnosed is likely malfunctioning and if the patterns match to a certain extent the diagnosed sensor unit is likely to function correctly. According to an embodiment of the method said engine further comprises a camshaft having a camshaft rotational position sensor unit, the method further comprising the steps of: comparing the rotational speed determined by means of said crankshaft rotational position sensor unit and the rotational speed determined by means of said camshaft rotational position sensor unit; and/or comparing the rotational position determined by means of said crankshaft rotational position sensor unit and the rotational position determined by means of said camshaft rotational position sensor unit and deciding the function of said crankshaft rotational position sensor unit based upon said comparison. By thus first comparing the rotational positions determined by said sensor units the top dead centre for combustion can be determined for each cylinder. If there is a certain difference it will be possible to determine which of the sensor units that is not functioning correctly by means of said identification of the cylinders, and by thus comparing the peak patterns obtained with peak patterns for a functioning crankshaft rotational position sensor unit. If there is no such certain difference in the rotational speeds and/or positions determined by the respective sensor units it can be assumed that both sensor units are functioning correctly. Checking the function of the crankshaft rotational position sensor unit by means of said identification of the cylinders and by comparing the peak patterns obtained with peak patterns for a functioning crankshaft may still be performed as a redundancy.

Specifically an object of the invention is achieved by a system for diagnosing a crankshaft rotational position sensor unit of a crankshaft of an internal combustion engine. The internal combustion engine further comprises a flywheel connected to said crankshaft, and a set of cylinders distributed along the crankshaft for rotating said crankshaft during engine operation. The system comprises means for determining a course of change of crankshaft rotational speed as a function of crankshaft angle by means of said crankshaft rotational position sensor unit; means for identifying the different cylinders based upon peak height and/or peak width of said determined course of change of crankshaft rotational speed as a function of crankshaft angle; and means for deciding on the function of said crankshaft rotational position sensor unit based upon the identification of the different cylinders.

According to an embodiment of the system the means for deciding on the function of said crankshaft rotational position sensor unit comprises means for comparing peak height pattern and/or peak width pattern of said determined course of change of crankshaft rotational speed with a known such pattern for a functioning crankshaft rotational position sensor unit.

According to an embodiment of the system said engine further comprises a camshaft having a camshaft rotational position sensor unit, the system further comprising means for comparing the rotational speed determined by means of said crankshaft rotational position sensor unit and the rotational speed determined by means of said camshaft rotational position sensor unit; and means for deciding the function of said crankshaft rotational position sensor unit based upon said comparison. The system according to the invention has the advantages according to the corresponding method.

Specifically an object of the invention is achieved by a vehicle comprising a system as set out herein.

Specifically an object of the invention is achieved by a computer program for diagnosing a crankshaft rotational position sensor unit of a crankshaft of an internal combustion engine, said computer program comprising program code which, when run on an electronic control unit or another computer connected to the electronic control unit, causes the electronic control unit to perform the methods as set out herein. Specifically an object of the invention is achieved by a computer program product comprising a digital storage medium storing the computer program. BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention reference is made to the following detailed description when read in conjunction with the accompanying drawings, wherein like reference characters refer to like parts throughout the several views, and in which:

Fig. 1 schematically illustrates a side view of a vehicle according to the present invention;

Fig. 2 schematically illustrates a combustions engine according to an embodiment of the present invention; Fig. 3 schematically illustrates course of change of crankshaft rotational speed as a function of crankshaft angle during engine operation according to an embodiment of the present invention;

Fig. 4 schematically illustrates a system for diagnosing a crankshaft rotational position sensor unit of a crankshaft of an internal combustion engine according to an embodiment of the present invention;

Fig. 5 schematically illustrates a method for diagnosing a crankshaft rotational position sensor unit of a crankshaft of an internal combustion engine according to an embodiment of the present invention; and

Fig. 6 schematically illustrates a computer according to an embodiment of the present invention.

DETAILED DESCRIPTION

Hereinafter the term "link" refers to a communication link which may be a physical connector, such as an optoelectronic communication wire, or a non- physical connector such as a wireless connection, for example a radio or microwave link. Hereinafter the term "course of change of crankshaft rotational speed" refers to the acceleration of a crankshaft during engine operation, i.e. during an engine cycle. The term "course of change of crankshaft rotational speed" thus refers to the derivative of the angular speed of the crankshaft. The engine according to the present invention could be any suitable internal combustion engine with any suitable number of cylinders. The internal combustion engine according to the present invention could for example be a 5-cylinder engine, a 6-cylinder engine or an 8-cylinder engine. The cylinders could be in any suitable alignment, for example inline engine or a V-engine. In fig. 3 an embodiment for a 6-cylinder engine is described.

Fig. 1 schematically illustrates a side view of a vehicle 1 according to the present invention. The exemplified vehicle 1 is a heavy vehicle in the shape of a truck. The vehicle according to the present invention could be any suitable vehicle such as a bus or a car. The vehicle 1 comprises an internal combustion engine E for operating the vehicle 1 . The vehicle 1 comprises a system I for diagnosing a crankshaft rotational position sensor unit of a crankshaft of an internal combustion engine.

Fig. 2 schematically illustrates an internal combustions engine E according to an embodiment of the present invention. The engine E comprises a crankshaft CS connected to a flywheel FW, and a set of cylinders of which one cylinder C is shown, distributed along said crankshaft CS for rotating said crankshaft CS during operation of the engine.

The cylinder C is connected to the crankshaft via a connecting rod R connected to a piston P of the cylinder C. The engine E comprises fuel injectors F for injecting fuel into the cylinder C for combustion. The engine E further comprises a camshaft CAM for regulating the valves of the engine during engine operation. The camshaft CAM is in mesh with the crankshaft CS via gears G1 , G2 arranged on the respective shaft CS, CAM, the camshaft thus being rotated by means of the crankshaft. The engine E is arranged to provide a four stroke cycle. The complete four stroke cycle forms a single thermodynamic cycle from which mechanical work will be extracted for operating a vehicle. For a complete four stroke cycle the crankshaft CS will turn two revolutions, this being the engine cycle.

When the piston is farthest from the crankshaft CS is known as the top dead centre TDC and when the piston P is closest to the crankshaft CS is known as the bottom dead centre BDC. A dead centre is when the connecting rod R and the crankshaft CS align.

The strokes comprise an intake stroke (TDC to BDC) filling the cylinder C with air, a compression stroke (BDC to TDC) where the air is compressed and at the end of which fuel is injected for combustion, an expansion stroke (TDC to BDC) where the combustion is completed and an exhaust stroke (BDC to TDC).

A crankshaft rotational position sensor unit 1 12 is arranged to determine rotational speed and position of the crankshaft CS. The crankshaft rotational position sensor unit 1 12 is arranged in connection to the flywheel FW as explained below in connection to e.g. fig. 5.

A camshaft rotational position sensor unit 150 is arranged to determine rotational speed and position of the camshaft CAM.

In order to provide efficient control of the operation of the engine the injection of fuel needs to be executed at the correct moment in the engine cycle, i.e. in connection to when the piston of the respective cylinder is in the top dead centre for combustion. Therefore the crankshaft angle a is important to know. The crankshaft angle a is according to a variant determined by means of the crankshaft rotational position sensor unit 1 12 arranged in connection to the flywheel FW.

By combining the rotational position determined by means of the crankshaft rotational position sensor unit 1 12 and the rotational position determined by means of said camshaft rotational position sensor unit 150 the top dead centre for combustion can be determined. By comparing rotational speed and/or position of the crankshaft CS and camshaft CAM the function of the sensor units 1 12, 150 can be determined. If the results of the comparison are essentially the same it is plausible that both the camshaft and crankshaft rotational position sensor units 1 12, 150 are functioning correctly.

The crankshaft rotational position sensor unit 1 12 and the camshaft rotational position sensor unit 150 are operably connected to an electronic control unit ECU. The electronic control unit ECU is arranged to process signals from said sensor units for comparison. However, if there is a difference it is not possible to tell which of the sensor units that is not functioning correctly.

The present invention facilitates improvement in deciding on the function of said crank shaft rotational position sensor unit as explained below.

Fig. 3 schematically illustrates course of change of crankshaft rotational speed as a function of crankshaft angle during engine operation according to an embodiment of the present invention.

The example illustrated in fig. 2 is for an internal combustion engine with six cylinders, 1 , 2, 3, 4, 5 and 6.

The course of change of crankshaft rotational speed as a function of crankshaft angle during engine operation is determined based on the rotational speed detected by means of a sensor unit arranged in connection to the flywheel connected to the crankshaft. The course of change of crankshaft rotational speed as a function of crankshaft angle provides peaks corresponding to the piston of the cylinder being in the top dead centre for combustion. The order in which the piston of the cylinders are in the top dead centre for combustion and thus the order in which the cylinders are injected with fuel during engine operation is 1 , 5, 3, 6, 2 and finally 4.

The first cylinder 1 provides a peak height H1 and a peak width W1 , the second cylinder 2 provides a peak height H2 and a peak width W2, the third cylinder 3 provides a peak height H3 and a peak width W3, the fourth cylinder 4 provides a peak height H4 and a peak width W4, the fifth cylinder 5 provides a peak height H5 and a peak width W5, and the sixth cylinder 6 provides a peak height H6 and a peak width W6.

The cylinders 1 -6 are arranged along the crankshaft such that the first cylinder 1 is furthest away from the flywheel, the second cylinder 2 is second furthest from the flywheel and so on to the sixth cylinder being closest to the flywheel and hence the sensor unit.

As can be seen the peak height is higher and width smaller for the cylinders furthest from the flywheel. The reason for this is that an increased distance from the flywheel generally results in a greater torsional effect. Therefore the cylinder being furthest from the flywheel, i.e. the first cylinder 1 , has the highest peak H1 and the smallest width.

Hereby it is possible to determine when the different pistons of the cylinders 1 - 6 of said set of cylinders are in a top dead centre position for combustion by identifying the different cylinders based upon peak height and/or peak width of said determined course of change of crankshaft rotational speed as a function of crankshaft angle. The peaks and widths thus differ depending on the distance from the sensor unit and flywheel.

If the identification of the different cylinders differs compared with an expected identification for a functioning crankshaft rotational sensor unit the sensor unit being diagnosed is likely malfunctioning. If the identification of the different cylinders matches with an expected identification for a functioning crankshaft rotational sensor unit the sensor unit being diagnosed is likely to function. Deciding on the function of said crankshaft rotational position sensor unit based upon the identification of the different cylinders may comprise comparing the order in which the identified cylinders are ignited/are in the top dead centre for combustion with such an order for a functioning crankshaft rotational sensor unit. If the compared order does differs the sensor unit being diagnosed is likely malfunctioning and if the order is the same the diagnosed sensor unit is likely to function correctly.

In order to decide on the function of the crank shaft rotational position sensor unit peak height pattern and/or peak width pattern of a course of change of crank shaft rotational speed determined with the crank shaft rotational position sensor is compared with a known such pattern for a functioning crank shaft rotational position sensor unit.

If the peak height pattern and/or peak width pattern of said determined course of change of crankshaft rotational speed determined by the crankshaft rotational sensor unit being diagnosed differs to a certain extent from such pattern for a functioning crankshaft rotational position sensor unit the sensor unit being diagnosed is likely malfunctioning and if the patterns match to a certain extent the diagnosed sensor unit is likely to function correctly.

The course of change of crankshaft rotational speed as a function of crankshaft angle for a known such pattern for a functioning crank shaft rotational position sensor unit is according to an embodiment provided in a workshop, during manufacture of the engine or the like and stored in storage means, e.g. in an electronic control unit.

The course of change of crankshaft rotational speed as a function of crankshaft angle for a known such pattern for a functioning crank shaft rotational position sensor unit is according to an embodiment modelled by modelling means and stored in storage means, e.g. in the electronic control unit 100.

The course of change of crankshaft rotational speed as a function of crankshaft angle for the crank shaft rotational position sensor unit for which the function is to be decided is thus determined during engine operation during actual drive of the vehicle.

Thus, the course of change of crankshaft rotational speed as a function of crankshaft angle illustrated in fig. 3 could be either the course of change of crankshaft rotational speed as a function of crankshaft angle determined by means of the rotational position sensor unit for which the function is to be decided or for a functioning crank shaft rotational position sensor unit stored in an electronic control unit and used for comparison.

Fig. 4 schematically illustrates a system I for diagnosing a crankshaft rotational position sensor unit of a crankshaft of an internal combustion engine according to an embodiment of the present invention.

The internal combustion engine further comprises a flywheel connected to said crankshaft, and a set of cylinders distributed along the crankshaft for rotating said crankshaft during engine operation.

The system comprises an electronic control unit 100. The electronic control unit 100 could according to a variant be provided by the electronic control unit ECU in fig. 2.

The system I comprises means 1 10 for determining a course of change of crankshaft rotational speed as a function of crankshaft angle by means of the crankshaft rotational position sensor unit. The means 1 10 for determining a course of change of crankshaft rotational speed as a function of crankshaft angle by means of said crankshaft rotational position sensor unit comprises the crankshaft rotational position sensor unit 1 12. The crankshaft rotational position sensor unit 1 12 is arranged to detect the rotational speed of said crankshaft. The crankshaft rotational position sensor unit 1 12 is arranged to detect the rotational speed of said crankshaft so as to determine crankshaft angle values. The crankshaft rotational position sensor unit 1 12 is arranged to detect the rotational position of said crankshaft. The crankshaft rotational position sensor unit 1 12 may comprise any suitable sensor unit. According to an embodiment the sensor unit 1 12 is a conductive sensor unit. The pulses from the sensor unit is according to an embodiment received a certain number of times during a revolution of the crankshaft based on encoder settings. According to an embodiment the rotational speed of the flywheel is determined for determining the rotational speed of the crankshaft and hence the crankshaft angle values.

The crankshaft rotational position sensor unit 1 12 is according to an embodiment arranged in connection to the flywheel of the internal combustion engine, radial holes being arranged with a certain equidistant angle, e.g. six degrees, around the periphery of the flywheel. The sensor unit is arranged to register when hole passes by detecting changes in the magnetic field. The time difference between two holes is measured. The sensor signal from the sensor unit 1 12 is synchronous with the crank angle degree, wherein the rotational speed of the crankshaft can be determined. Holes, e.g. two holes, are according to an embodiment omitted on the flywheel so that the sensor unit can determine when the crankshaft has turned one revolution. Thus, by dead reckoning, position can also be determined.

The system I comprises means 120 for identifying the different cylinders based upon peak height and/or peak width of said determined course of change of crankshaft rotational speed as a function of crankshaft angle. The peaks and widths differ depending on the distance from the flywheel. By comparing peak height and/or peak width with of a determined change of crankshaft rotational speed as a function of crankshaft angle for a peak the piston being in the top dead centre for combustion may be determined and hence that cylinder. The means 120 could according to an embodiment be comprised in the electronic control unit 100.

The system I comprises means 130 for determining a course of change of crankshaft rotational speed as a function of crankshaft angle for obtaining a known such pattern for a functioning crank shaft rotational position sensor unit.

The system I comprises means 140 for deciding on the function of said crankshaft rotational position sensor unit based upon the identification of the different cylinders.

The means 140 for deciding on the function of said crank shaft rotational position sensor unit comprises means 142 for comparing peak height pattern and/or peak width pattern of said determined course of change of crank shaft rotational speed with a known such pattern for a functioning crank shaft rotational position sensor unit.

The means 140 could according to an embodiment be comprised in the electronic control unit 100.

Fig. 3 shows an example of a course of a change of crankshaft rotational speed as a function of crankshaft angle for an engine with six cylinders which may be provided by the means 130 for determining a course of change of crankshaft rotational speed as a function of crankshaft angle according to an embodiment. The means 130 for determining a course of change of crankshaft rotational speed as a function of crankshaft angle for obtaining a known such pattern for a functioning crank shaft rotational position sensor unit is according to an embodiment provided in a workshop, during manufacture of the engine or the like and stored in storage means, e.g. in the electronic control unit 100. The means 130 for determining a course of change of crankshaft rotational speed as a function of crankshaft angle for obtaining a known such pattern for a functioning crank shaft rotational position sensor unit is according to an embodiment modelled by modelling means and stored in storage means, e.g. in the electronic control unit 100.

The engine further comprises a camshaft having a camshaft rotational position sensor unit 150. The camshaft rotational position sensor unit 150 is arranged to determine the rotational speed and position of the camshaft.

The system I comprises according to an embodiment the camshaft rotational position sensor unit 150.

According to an embodiment the system I comprises means 160 for comparing the rotational speed determined by means of said crankshaft rotational position sensor unit 1 12 and the rotational speed determined by means of a camshaft rotational position sensor unit 150 and/or comparing the rotational position determined by means of said crankshaft rotational position sensor unit 1 12 and the rotational position determined by means of a camshaft rotational position sensor unit 150. The means 160 could according to an embodiment be comprised in the electronic control unit 100.

The system I comprises means 170 for deciding the function of said crankshaft rotational position sensor unit based upon the comparison of the rotational speed and/or position determined by means of said crankshaft rotational position sensor unit 1 12 and the rotational speed and/or position determined by means of a camshaft rotational position sensor unit 150. The means 170 could according to an embodiment be comprised in the electronic control unit 100.

The system I comprises according to an embodiment means 180 for warning the operator of a vehicle of a non-functioning sensor unit 1 12, 150. The means 180 for warning the operator of the vehicle comprises visual means for visual warning such as a light of certain colour such as red or yellow and/or acoustic means for audible warning such as a sound alarm or a voice message and/or tactile means for tactile warning such as vibrations in steering wheel, seat or the like. The degree of warning is according to an embodiment arranged to differ if the warning represents a warning for a non-functioning crankshaft rotational position sensor unit 1 12 requiring immediate stop of the vehicle or a warning for a non-functioning camshaft rotational position sensor unit 150 allowing the vehicle to continue driving to e.g. a workshop for taking care of the non-functioning sensor unit. 150. Visual warning may be a red light for nonfunctioning sensor unit 1 12 and a yellow light for a non-functioning sensor unit 150.

The electronic control unit 100 is operably connected to the means 1 10 for determining a course of change of crankshaft rotational speed as a function of crankshaft angle by means of the crankshaft rotational position sensor unit via a link 10. The electronic control unit 100 is via the link 10 arranged to receive a signal from the means 1 10 representing data for a course of change of crankshaft rotational speed determined by means of data for rotational speed of the crankshaft from the sensor unit 1 12. The electronic control unit 100 is operably connected to the crankshaft rotational position sensor unit 1 12 via a link 12. The electronic control unit 100 is via the link 12 arranged to receive a signal from the crankshaft rotational position sensor unit 1 12 representing data for rotational speed of the crankshaft. The electronic control unit 100 is operably connected to the means 120 for identifying the pistons of the different cylinders at top dead centre based upon peak height and/or peak width of said determined course of change of crankshaft rotational speed as a function of crankshaft angle via a link 20a. The electronic control unit 100 is via the link 20a arranged to send a signal to the means 120 representing data for peak height and/or peak width of cylinders during course of change of crankshaft rotational speed as a function of crankshaft angle.

The electronic control unit 100 is operably connected to the means 120 for identifying the different cylinders based upon peak height and/or peak width of said determined course of change of crankshaft rotational speed as a function of crankshaft angle via a link 20b. The electronic control unit 100 is via the link 20b arranged to receive a signal from the means 120 representing data for identified cylinders based upon peak height and/or peak width of said determined course of change of crankshaft rotational speed as a function of crankshaft angle.

The electronic control unit 100 is operably connected to the means 130 for determining a course of change of crankshaft rotational speed as a function of crankshaft angle for obtaining a known such pattern for a functioning crank shaft rotational position sensor unit via a link 30. The electronic control unit 100 is via the link 30 arranged to receive a signal from the means 130 representing data for course of change of crankshaft rotational speed as a function of crankshaft angle for obtaining a known such pattern for a functioning crank shaft rotational position sensor unit. The electronic control unit 100 is operably connected to the means 142 for comparing peak height pattern and/or peak width pattern of said determined course of change of crank shaft rotational speed with a known such pattern for a functioning crank shaft rotational position sensor unit via a link 42a. The electronic control unit 100 is via the link 42a arranged to send a signal to the means 142 representing data for peak height pattern and/or peak width pattern of the course of change of crank shaft rotational speed determined by means of the sensor unit 1 12.

The electronic control unit 100 is operably connected to the means 142 for comparing peak height pattern and/or peak width pattern of said determined course of change of crank shaft rotational speed with a known such pattern for a functioning crank shaft rotational position sensor unit via a link 42b. The electronic control unit 100 is via the link 42b arranged to send a signal to the means 142 representing data for peak height pattern and/or peak width pattern of the course of change of crank shaft rotational speed a known such pattern for a functioning crank shaft rotational position sensor. The electronic control unit 100 is operably connected to the means 142 for comparing peak height pattern and/or peak width pattern of said determined course of change of crank shaft rotational speed with a known such pattern for a functioning crank shaft rotational position sensor unit via a link 42c. The electronic control unit 100 is via the link 42c arranged to receive a signal from the means 142 representing data for comparison of peak height pattern and/or peak width pattern of said determined course of change of crank shaft rotational speed with a known such pattern for a functioning crank shaft rotational position sensor unit for deciding upon the function of the sensor unit 1 12.

The electronic control unit 100 is operably connected to the camshaft rotational position sensor unit 150 via a link 50. The electronic control unit 100 is via the link 50 arranged to receive a signal from the camshaft rotational position sensor unit 150 representing data for rotational speed of the camshaft. The electronic control unit 100 is operably connected to the means 160 for comparing the rotational speed determined by means of said crankshaft rotational position sensor unit 1 12 and the rotational speed determined by means of a camshaft rotational position sensor unit 150 and/or comparing the rotational position determined by means of said crankshaft rotational position sensor unit 1 12 and the rotational position determined by means of said camshaft rotational position sensor unit 150via a link 60a. The electronic control unit 100 is via the link 60a arranged to send a signal to the means 160 representing data for rotational speed of the crank shaft rotational position sensor unit 1 12. The electronic control unit 100 is operably connected to the means 160 for comparing the rotational speed determined by means of said crankshaft rotational position sensor unit 1 12 and the rotational speed determined by means of a camshaft rotational position sensor unit 150 and/or comparing the rotational position determined by means of said crankshaft rotational position sensor unit 1 12 and the rotational position determined by means of said camshaft rotational position sensor unit 150 via a link 60b. The electronic control unit 100 is via the link 60b arranged to send a signal to the means 160 representing data for rotational speed and/or position of the cam shaft rotational position sensor unit 150. The electronic control unit 100 is operably connected to the means 160 for comparing the rotational speed and/or position determined by means of said crankshaft rotational position sensor unit 1 12 and the rotational speed and/or position determined by means of a camshaft rotational position sensor unit 150 via a link 60c. The electronic control unit 100 is via the link 42c arranged to receive a signal from the means 160 representing data for comparison of the rotational speed and/or position determined by means of said crankshaft rotational position sensor unit 1 12 and the rotational speed and/or position determined by means of a camshaft rotational position sensor unit 150.

The electronic control unit 100 is operably connected to the means 170 for deciding the function of said crankshaft rotational position sensor unit 1 12 based upon the comparison of the rotational speed and/or position determined by means of said crankshaft rotational position sensor unit 1 12 and the rotational speed and/or position determined by means of a camshaft rotational position sensor unit 150 via a link 70a. The electronic control unit 100 is via the link 70a arranged to send a signal to the means 170 representing data for comparison of rotational speeds and/or positions determined by the sensor units 1 12 and 150.

The electronic control unit 100 is operably connected to the means 170 for deciding the function of said crankshaft rotational position sensor unit 1 12 based upon the comparison of the rotational speed and/or position determined by means of said crankshaft rotational position sensor unit 1 12 and the rotational speed and/or position determined by means of a camshaft rotational position sensor unit 150 via a link 70b. The electronic control unit 100 is via the link 70b arranged to receive a signal from the means 170 representing data for decided function crankshaft rotational position sensor unit. The electronic control unit 100 is operably connected to the means 180 for warning the operator of a vehicle of a non-functioning sensor unit 1 12, 150 via a link 80. The electronic control unit 100 is via the link 80 arranged to send a signal to the means 180 representing data for warning the operator of a vehicle of a non-functioning sensor unit 1 12, 150.

Fig. 5 schematically illustrates a method for diagnosing a crankshaft rotational position sensor unit of a crankshaft of an internal combustion engine. The internal combustion engine further comprises a flywheel connected to said crankshaft, and a set of cylinders distributed along the crankshaft for rotating said crankshaft during engine operation.

According to the embodiment the method for diagnosing a crankshaft rotational position sensor unit of a crankshaft of an internal combustion engine comprises a step S1 . In this step a course of change of crankshaft rotational speed as a function of crankshaft angle by means of said crankshaft rotational position sensor unit is determined.

According to the embodiment the method for diagnosing a crankshaft rotational position sensor unit of a crankshaft of an internal combustion engine comprises a step S2. In this step the different cylinders are identified based upon peak height and/or peak width of said determined course of change of crankshaft rotational speed as a function of crankshaft angle.

According to the embodiment the method for diagnosing a crankshaft rotational position sensor unit of a crankshaft of an internal combustion engine comprises a step S3. In this step the function of said crankshaft rotational position sensor unit is decided on based upon the identification of the different cylinders.

If the identification of the different cylinders differs compared with an expected identification for a functioning crankshaft rotational sensor unit the sensor unit being diagnosed is likely malfunctioning. If the identification of the different cylinders matches with an expected identification for a functioning crankshaft rotational sensor unit the sensor unit being diagnosed is likely to function. Deciding on the function of said crankshaft rotational position sensor unit based upon the identification of the different cylinders may comprise comparing the order in which the identified cylinders are ignited/are in the top dead centre for combustion with such an order for a functioning crankshaft rotational sensor unit. If the compared order does differs the sensor unit being diagnosed is likely malfunctioning and if the order is the same the diagnosed sensor unit is likely to function correctly.

According to an embodiment of the method the step of deciding on the function of said crankshaft rotational position sensor unit comprises the step of comparing peak height pattern and/or peak width pattern of said determined course of change of crankshaft rotational speed with a known such pattern for a functioning crankshaft rotational position sensor unit. Hereby an easy and efficient determination of the function of the crankshaft rotational position sensor unit is obtained.

If the peak height pattern and/or peak width pattern of said determined course of change of crankshaft rotational speed determined by the crankshaft rotational sensor unit being diagnosed differs to a certain extent from such pattern for a functioning crankshaft rotational position sensor unit the sensor unit being diagnosed is likely malfunctioning and if the patterns match to a certain extent the diagnosed sensor unit is likely to function correctly.

According to an embodiment of the method said engine further comprises a camshaft having a camshaft rotational position sensor unit, the method further comprising the steps of: comparing the rotational speed determined by means of said crankshaft rotational position sensor unit and the rotational speed determined by means of said camshaft rotational position sensor unit and/or comparing the rotational position determined by means of said crankshaft rotational position sensor unit and the rotational position determined by means of said camshaft rotational position sensor unit; and deciding the function of said crankshaft rotational position sensor unit based upon said comparison. By thus first comparing the rotational positions determined by said sensor units the top dead centre for combustion can be determined for the piston of each cylinder. If there is a certain difference it will be possible to determine which of the sensor units that is not functioning correctly by means of said identification of the cylinders, and by thus comparing the peak patterns obtained with peak patterns for a functioning crankshaft rotational position sensor unit. If there is no such certain difference in the rotational speeds and/or positions determined by the respective sensor units it can be assumed that both sensor units are functioning correctly. Checking the function of the crankshaft rotational position sensor unit by means of said identification of the cylinders and by comparing the peak patterns obtained with peak patterns for a functioning crankshaft may still be performed as a redundancy.

With reference to figure 6, a diagram of an apparatus 500 is shown. The control unit ECU, 100 described with reference to fig. 2 and 4 may according to an embodiment comprise apparatus 500. Apparatus 500 comprises a non-volatile memory 520, a data processing device 510 and a read/write memory 550. Non-volatile memory 520 has a first memory portion 530 wherein a computer program, such as an operating system, is stored for controlling the function of apparatus 500. Further, apparatus 500 comprises a bus controller, a serial communication port, l/O-means, an A/D-converter, a time date entry and transmission unit, an event counter and an interrupt controller (not shown). Non-volatile memory 520 also has a second memory portion 540.

A computer program P is provided for diagnosing a crankshaft rotational position sensor unit of a crankshaft of an internal combustion engine according to the innovative method. The program P comprises routines for determining a course of change of crankshaft rotational speed as a function of crankshaft angle by means of said crankshaft rotational position sensor unit. The program P comprises routines for identifying the different cylinders based upon peak height and/or peak width of said determined course of change of crankshaft rotational speed as a function of crankshaft angle. The program P comprises routines for deciding on the function of said crankshaft rotational position sensor unit based upon the identification of the different cylinders. The routines for deciding on the function of said crank shaft rotational position sensor unit comprises routines for comparing peak height pattern and/or peak width pattern of said determined course of change of crank shaft rotational speed with a known such pattern for a functioning crank shaft rotational position sensor unit. The engine further comprises a cam shaft configuration having a cam shaft rotational position sensor unit. The program P comprises routines for comparing the rotational speed determined by means of said crank shaft rotational position sensor unit and the rotational speed determined by means of said cam shaft rotational position sensor unit and/or comparing the rotational position determined by means of said crankshaft rotational position sensor unit and the rotational position determined by means of said camshaft rotational position sensor unit. The program P comprises routines for deciding the function of said crank shaft rotational position sensor unit based upon said comparison. The computer program P may be stored in an executable manner or in a compressed condition in a separate memory 560 and/or in read/write memory 550.

When it is stated that data processing device 510 performs a certain function it should be understood that data processing device 510 performs a certain part of the program which is stored in separate memory 560, or a certain part of the program which is stored in read/write memory 550.

Data processing device 510 may communicate with a data communications port 599 by means of a data bus 515. Non-volatile memory 520 is adapted for communication with data processing device 510 via a data bus 512. Separate memory 560 is adapted for communication with data processing device 510 via a data bus 51 1 . Read/write memory 550 is adapted for communication with data processing device 510 via a data bus 514. To the data communications port 599 e.g. the links connected to the control unit 100 may be connected. When data is received on data port 599 it is temporarily stored in second memory portion 540. When the received input data has been temporarily stored, data processing device 510 is set up to perform execution of code in a manner described above. The signals received on data port 599 can be used by apparatus 500 for determining a course of change of crank shaft rotational speed as a function of crank shaft angle by means of said crank shaft rotational position sensor unit. The signals received on data port 599 can be used by apparatus 500 for identifying the different cylinders based upon peak height and/or peak width of said determined course of change of crank shaft rotational speed as a function of crank shaft angle. The signals received on data port 599 can be used by apparatus 500 for deciding on the function of said crank shaft rotational position sensor unit based upon the identification of the different cylinders. The signals used for deciding on the function of said crank shaft rotational position sensor unit comprises signals used for comparing peak height pattern and/or peak width pattern of said determined course of change of crank shaft rotational speed with a known such pattern for a functioning crank shaft rotational position sensor unit. The engine further comprises a cam shaft configuration having a cam shaft rotational position sensor unit. The signals received on data port 599 can be used by apparatus 500 for comparing the rotational speed determined by means of said crank shaft rotational position sensor unit and the rotational speed determined by means of said cam shaft rotational position sensor unit and/or comparing the rotational position determined by means of said crankshaft rotational position sensor unit and the rotational position determined by means of said camshaft rotational position sensor unit. The signals received on data port 599 can be used by apparatus 500 for deciding the function of said crank shaft rotational position sensor unit based upon said comparison.

Parts of the methods described herein can be performed by apparatus 500 by means of data processing device 510 running the program stored in separate memory 560 or read/write memory 550. When apparatus 500 runs the program, parts of the methods described herein are executed. The foregoing description of the preferred embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated.