GB2526323A

GB2526323A - An electronic control unit for an internal combustion engine

Info

Publication number: GB2526323A
Application number: GB1408992.4A
Authority: GB
Inventors: Massimiliano Melis; Luca Lauritano; Francesco Concetto Pesce
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2014-05-20
Filing date: 2014-05-20
Publication date: 2015-11-25
Also published as: GB201408992D0

Abstract

Disclosed is an electronic control unit, ECU, for an internal combustion engine 110 having a crankshaft 145 coupled to a starter motor 195 and to a fuel pump 180 in fluid communication with a fuel rail 170. The electronic control unit is configured to activate the starter 195 to rotate the crankshaft 145 for a predetermined cranking time, monitor an engine speed during the cranking time, monitor an angular position of the crankÂshaft 145 during the cranking time, monitor 615 a pressure variation within the fuel rail 170 during the cranking time. The ECU uses the engine speed, the crankshaft angular position and the pressure variation to determine a crankshaft angular displacement between a top dead center position of a fuel pump piston and a reference angular position of the crankshaft 145.

Description

AN ELECTRONIC CONTROL UNIT FOR AN INTERNAL COMBUS-

TION ENGINE

TECHNICAL FIELD

The present disclosure generally relates to an electronic control unit for an internal corn-bustion engine, such as a compression-ignition engine (e.g. Diesel) or a spark-ignition engine (e.g. Gasoline) of a motor vehicle. In particular, the present disclosure relates to an electronic control unit configured to operate the internal combustion engine for determining an actual angular phasing of a fuel pump associated to the engine.

BACKGROUND

It is known that an internal combustion engine is generally equipped with a fuel pump that receives the fuel from a fuel tank and delivers it to a fuel rail in fluid communication with a plurality of fuel injectors. The fuel pump conventionally comprises a body defining at least an internal chamber that accommodates a reciprocating piston. The intemal chamber corn-municates with the fuel tank though an inlet valve and with the fuel rail though an outlet valve. The piston is coupled to a pump input shaft, whose rotation causes the reciprocating movements of the piston within the pump body. Each of these reciprocating movements comprises a suction stroke followed by a discharge stroke. During the suction stroke, the piston moves from a top death center position to a bottom death center position, thereby increasing the volume of the internal chamber to suck the fuel from the fuel tank via the intake valve. During the discharge stroke, the piston moves in the opposite direction, from the bottom death center position to the top death center position, thereby reducing the volume of the internal chamber to force the fuel into the fuel rail via the outlet valve.

The intake shaft of the fuel pump is conventionally rotated by the engine crankshaft through a timing system. The timing system may comprise a drive chain or belt, which is wound around a first sprocket keyed on the crankshaft and a second sprocket keyed on

I

the intake shaft of the fuel pump. Due to this coupling, there is a precise relation between the angular position of the engine crankshaft and the position of the reciprocating piston of the fuel pump, which implies that there is a precise relation between the angular position of the engine crankshaft and the pressure within the fuel rail. In particular, the fuel rail pressure is generally unstable any time the engine crankshaft is close to an angular posi-tion that corresponds to the top death center (TDC) position of the fuel pump piston, namely to the end of the discharge stroke.

The fuel rail pressure is an important parameter for controlling the operation of the internal combustion engine. For instance, the fuel rail pressure is periodically sampled and used to calculate the energizing time necessary for the fuel injectors to inject a desired quantity of fuel. In order to avoid fuel quantity errors, the sampling of the fuel rail pressure is sched-uled so as to happen when the engine crankshaft is in a defined angular position, which is presumed far from the angular position that corresponds to the TDC of the fuel pump pis-ton.

However, the crankshaft angular position that corresponds to the TDC of the fuel pump piston is not exactly the same for all the internal combustion engines, because the relative angular position of the fuel pump input shaft with respect to the engine crankshaft (fuel pump phasing) may be affected by production tolerances and/or errors during the mount- ing of the timing system, so that the fuel pump phasing may generally deviate by about +1- 150 from the prescribed reference value thereof. As a consequence, there may be engines for which the scheduled fuel rail pressure sampling is actually performed in an unstable pressure area, thereby causing fuel quantity errors and so increasing noise, fuel consump-tion and pollutant emissions.

SUMMARY

In view of the above, an object of an embodiment of the present invention is that of provid-ing a solution that allows to obviate to the negative effects caused by the phasing errors of the fuel pump.

Another object is that of reach this goal with a simple, rational and rather inexpensive solution.

These and other objects are achieved by the embodiments of the invention having the features recited in the independent claims. The dependent claims delineate secondary aspects of the invention.

An embodiment of the invention provides an electronic control unit for an internal combus- tion engine having a crankshaft coupled to a starter and to a fuel pump in fluid communi-cation with a fuel rail, wherein the electronic control unit is configured to: -activate the starter to rotate the crankshaft for a predetermined cranking time, -monitor an engine speed during the cranking time, -monitor an angular position of the crankshaft during the cranking time, -monitor a pressure variation within the fuel rail during the cranking time, -use the engine speed, the crankshaft angular position and the pressure variation to de-termine a crankshaft angular displacement between a top death center position of a fuel pump piston and a reference angular position of the crankshaft.

This embodiment of the invention allows to know, for each individual internal combustion engine, the actual angular position of the crankshaft that corresponds to the TDC position of the fuel pump, which can thus be used to prevent the negative effects caused by the fuel pump phasing errors.

According to an aspect of the invention, the electronic control unit may be configured to determine the crankshaft angular displacement by: -identifying a first instant when the crankshaft reaches the reference angular position, -identifying a second instant when the fuel rail pressure variation reaches a local maximum thereof, -calculating a time elapsed between the first instant and the second instant, -using the engine speed to convert the calculated elapsed time into an angular displace-ment of the crankshaft.

Since the local maxima of the fuel rail pressure generally corresponds to the TOC position of the fuel pump piston, this aspect of the invention provides a reliable solution to deter- mine the crankshaft angular displacement between the TDC position of the fuel pump pis-ton and the reference angular position of the crankshaft.

According to another aspect of the invention, the electronic control unit may be configured to determine the crankshaft angular displacement by: -identifying a plurality of first instants when the crankshaft reaches the reference angular position, -identifying a plurality of second instants when the fuel rail pressure variation reaches local maxima thereof, -calculating a time elapsed between each one of the first instants and a following second instant, -use the engine speed to convert each of the calculated elapsed time into a corresponding angular displacement of the crankshaft, -average the crankshaft angular displacements.

By averaging a plurality of crankshaft angular displacements, this aspect of the invention has the effect of yielding a final result that is less affected by possible measurement errors.

According to an aspect of the invention, the reference angular position of the crankshaft may correspond to a top death center position of an engine piston.

This aspect of the invention has the effect of yielding a crankshaft angular displacement which is ready to be used in most of the engine control procedures.

Another aspect of the invention provides that the electronic control unit may be configured to monitor the fuel rail pressure during the cranking time by sampling the fuel rail pressure with a crankshaft angular period comprised between 0.5 and 1 deg.

This pressure sampling is faster than during the normal operation of the engine, thereby allowing a more precise monitoring of the fuel rail pressure during the implementation of the method.

Another aspect of the invention provides that the cranking time may be shorter than or equal to a predetermined maximum value thereof.

This aspect of the invention has the effect of limiting the duration of the method and thus its impact on the normal engine operation.

According to an aspect of the invention, the electronic control unit may be configured to prevent any fuel injections during the cranking time.

This aspect of the invention has the effect of improving the accuracy of the result yielded by the method.

According to another aspect of the invention, the electronic control unit may be configured to calculate a deviation between the determined crankshaft angular displacement and a predetermined nominal value thereof.

This aspect of the invention allows to quantify the mounting error between the actual crank-shaft position corresponding to the TDC position of the fuel pump piston and a prescribed one.

According to an aspect of the invention, the electronic control unit may be configured to use the calculated deviation to correct a crankshaft angular position scheduled for sam-pling the fuel rail pressure during normal operations of the engine.

Thanks to this solution, during the normal engine operation, the fuel rail pressure may be actually sampled in a stable area, thereby contributing to reduce the fuel injected quantity errors.

Another aspect of the invention provides that the electronic control unit may be configured to perform the above mentioned activities at the end of a vehicle production line.

In this way, the activities can be performed only once and its results may be memorized in the engine control system to be used during the normal operation of the internal combus-tion engine.

Another embodiment of the invention provides a method of operating an internal combus- tion engine having a crankshaft coupled to a starter and to a fuel pump in fluid communi-cation with a fuel rail, wherein the method comprises the steps of: -activating the starter to rotate the crankshaft for a predetermined cranking time, -monitoring an engine speed during the cranking time, -monitoring an angular position of the crankshaft during the cranking time, -monitoring a pressure variation within the fuel rail during the cranking time, -using the engine speed, the crankshaft angular position and the pressure variation to determine a crankshaft angular displacement between a top death center position of a fuel pump piston and a reference angular position of the crankshaft.

This embodiment achieves the same effects of the method above, particularly that of al-lowing to know, for each individual internal combustion engine, the actual angular position of the crankshaft that corresponds to the TDC position of the fuel pump.

According to an aspect of the invention, the determination of the crankshaft angular dis-placement may comprise the steps of: -identifying a first instant when the crankshaft reaches the reference angular position, -identifying a second instant when the fuelrail pressure variation reaches a local maximum thereof, -calculating a time elapsed between the first instant and the second instant, -use the engine speed to convert the calculated elapsed time into an angular displacement of the crankshaft.

This aspect of the invention provides a reliable solution to determine the crankshaft angular displacement between the TOC position of the fuel pump piston and the reference angular position of the crankshaft.

According to another aspect of the invention, the determination of the crankshaft angular displacement may comprise the steps of: -identifying a plurality of first instants when the crankshaft reaches the reference angular position, -identifying a plurality of second instants when the fuel rail pressure variation reaches local maxima thereof, -calculating a time elapsed between each one of the first instants and a following second instant, -use the engine speed to convert each of the calculated elapsed time into a corresponding angular displacement of the crankshaft, -averaging the crankshaft angular displacements.

Another aspect of the invention provides that the monitoring of the fuel rail pressure during the cranking time may provide for sampling the fuel rail pressure with a crankshaft angular period comprised between 0.5 and 1 deg.

According to an aspect of the invention, the method may comprise the step of preventing any fuel injections during the cranking time.

According to another aspect of the invention, the method may comprise the step of calcu- lating a deviation between the determined crankshaft angular displacement and a prede-termined nominal value thereof This aspect of the invention allows to quantify the mounting error between the actual crank-shaft position corresponding to the TDC position of the fuel pump piston and a prescribed one.

According to an aspect of the invention, the method may comprise the step of using the calculated deviation to correct a crankshaft angular position scheduled for sampling the fuel rail pressure during normal operations of the engine.

Another aspect of the invention provides that the method may be performed at the end of a vehicle production line.

In this way, the method can be performed only once and its results may be memorized in the engine control system to be used during the normal operation of the internal combus-tion engine.

The method can be carried out with the help of a computer program comprising a program-code for carrying out all the steps of the method described above, and in the form of a computer program product comprising the computer program. The method can be also embodied as an electromagnetic signal, said signal being modulated to carry a sequence of data bits which represent a computer program to carry out all steps of the method.

Another embodiment of the invention provides an apparatus for operating an internal com- bustion engine having a crankshaft coupled to a starter and to a fuel pump in fluid com-munication with a fuel rail, wherein the apparatus comprises: -means for activating the starter to rotate the crankshaft for a predetermined cranking time, -means for monitoring an engine speed during the cranking time, -means for monitoring an angular position of the crankshaft during the cranking time, -means for monitoring a pressure variation within the fuel rail during the cranking time, -means for using the engine speed, the crankshaft angular position and the pressure var-iation to determine a crankshaft angular displacement between a top death center position of a fuel pump piston and a reference angular position of the crankshaft.

This embodiment achieves the same effects of the method above, particularly that of at-lowing to know, for each individual internal combustion engine, the actual angular position of the crankshaft that corresponds to the TOC position of the fuel pump.

According to an aspect of the invention, the means for determining of the crankshaft an-gular displacement may comprise: -means for identifying a first instant when the crankshaft reaches the reference angular position, -means for identifying a second instant when the fuel rail pressure variation reaches a local maximum thereof, -means for calculating a time elapsed between the first instant and the second instant, -means for using the engine speed to convert the calculated elapsed time into an angular displacement of the crankshaft.

This aspect of the invention provides a reliable solution to determine the crankshaft angular displacement between the TDC position of the fuel pump piston and the reference angular position of the crankshaft.

According to another aspect of the invention, the means for determining the crankshaft angular displacement may comprise: -means for identifying a plurality of first instants when the crankshaft reaches the reference angular position, -means for identifying a plurality of second instants when the fuel rail pressure variation reaches local maxima thereof, -means for calculating a time elapsed between each one of the first instants and a follow-ing second instant, -means for using the engine speed to convert each of the calculated elapsed time into a corresponding angular displacement of the crankshaft, -means for averaging the crankshaft angular displacements.

According to an aspect of the invention, the reference angular position of the crankshaft

B

may correspond to a top death center position of an engine piston.

Another aspect of the invention provides that the means for monitoring the fuel rail pres-sure during the cranking time may comprise means for sampling the fuel rail pressure with a crankshaft angular period comprised between 0.5 and I deg.

According to an aspect of the invention, the apparatus may comprise means for preventing any fuel injections during the cranking time.

According to another aspect of the invention, the apparatus may comprise means for cal- culating a deviation between the determined crankshaft angular displacement and a pre-determined nominal value thereof.

This aspect of the invention allows to quantify the mounting error between the actual crank-shaft position corresponding to the TDC position of the fuel pump piston and a prescribed one According to an aspect of the invention, the apparatus may comprise means for using the calculated deviation to correct a crankshaft angular position scheduled for sampling the fuel rail pressure during normal operations of the engine.

Another aspect of the invention provides that the above mentioned apparatus means are configured to operate at the end of a vehicle production line.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, with reference to the accompanying drawings.

Figure 1 schematically shows an automotive system.

Figure 2 is section A-A of figure 1.

Figure 3 shown a fuel pump of the automotive system of figure 1.

Figure 4 is a flowchart representing an operating strategy for an internal combustion en-gine of figure 1.

Figure 5 is a graph that show the variation of the fuel rail pressure over the time during the execution of the operating strategy of figure 4.

DETAILED DESCRIPTION

Some embodiments may include an automotive system 100 of a motor vehicle, as shown in figures 1 and 2, that includes an internal combustion engine (ICE) 110 having an engine block 120 defining at least one cylinder 125 having a piston 140 coupled to rotate a crank-shaft 145. A cylinder head 130 cooperates with the piston 140 to define a combustion chamber 150. A fuel and air mixture (not shown) is disposed in the combustion chamber and ignited, resulting in hot expanding exhaust gasses causing reciprocal movement of the piston 140. The fuel is provided by at least one fuel injector 160 and the air through at least one intake port 210. The fuel is provided at high pressure to the fuel injector 160 from a fuel rail 170 in fluid communication with a high pressure fuel pump 180 that increase the pressure of the fuel received from a fuel source 190. Each of the cylinders 125 has at least two valves 215, actuated by a camshaft 135 rotating in time with the crankshaft 145.

The valves 215 selectively allow air into the combustion chamber 150 from the port 210 and alternately allow exhaust gases to exit through a port 220. In some examples, a cam phaser 155 may selectively vary the timing between the camshaft 135 and the crankshaft 145. A starter 195, for example a small electric motor, may be coupled to rotate the engine crankshaft 145, before initiating the fuel injections, in order to start the engine's operation under its own power.

The air may be distributed to the air intake port(s) 210 through an intake manifold 200. An air intake duct 205 may provide air from the ambient environment to the intake manifold 200. In other embodiments, a throttle body 330 may be provided to regulate the flow of air into the manifold 200. In still other embodiments, a forced air system such as a turbo- charger 230, having a compressor 240 rotationally coupled to a turbine 260, may be pro-vided. Rotation of the compressor 240 increases the pressure and temperature of the air in the duct 205 and manifold 200. An intercooler 260 disposed in the duct 205 may reduce the temperature of the air. The turbine 250 rotates by receiving exhaust gases from an exhaust manifold 225 that directs exhaust gases from the exhaust ports 220 and through a series of vanes prior to expansion through the turbine 250. The exhaust gases exit the turbine 250 and are directed into an exhaust system 270. This example shows a variable geometry turbine (VGT) with a VGT actuator 290 arranged to move the vanes to alter the flow of the exhaust gases through the turbine 250. In other embodiments, the turbocharger 230 may be fixed geometry and/or include a waste gate.

The exhaust system 270 may include an exhaust pipe 275 having one or more exhaust aftertreatment devices 280. The aftertreatment devices may be any device configured to change the composition of the exhaust gases. Some examples of aftertreatment devices 280 include, but are not limited to, catalytic converters (two and three way), oxidation cat- alysts, lean NOx traps, hydrocarbon adsorbers, selective catalytic reduction (SCR) sys-tems, and particulate filters. Other embodiments may include an exhaust gas recirculation (EGR) system 300 coupled between the exhaust manifold 225 and the intake manifold 200. The EGR system 300 may include an EGR cooler 310 to reduce the temperature of the exhaust gases in the EGR system 300. An EGR valve 320 regulates a flow of exhaust gases in the EGR system 300.

The automotive system 100 may further include an electronic control unit (ECU) 450 in communication with one or more sensors and/or devices associated with the ICE 110. The ECU 450 may receive input signals from various sensors configured to generate the sig-nals in proportion to various physical parameters associated with the ICE 110. The sensors include, but are not limited to, a mass airflow and temperature sensor 340, a manifold pressure and temperature sensor 350, a combustion pressure sensor 360, coolant and oil temperature and level sensors 380, a fuel rail pressure sensor 400, a cam position sensor 4101 a crank position sensor 420, exhaust pressure and temperature sensors 430, an EGR temperature sensor 440, and an accelerator pedal position sensor 445. Furthermore, the ECU 450 may generate output signals to various control devices that are arranged to con-trol the operation of the ICE 110, including, but not limited to, the fuel injectors 160, the throttle body 330, the EGR Valve 320, the VGT actuator 290, and the cam phaser 155.

Note, dashed lines are used to indicate communication between the ECU 450 and the various sensors and devices, but some are omitted for clarity.

Turning now to the ECU 450, this apparatus may include a digital central processing unit (CPU) in communication with a memory system and an interface bus. The CPU is config-ured to execute instructions stored as a program in the memory system 460, and send and receive signals to/from the interface bus. The memory system 460 may include various storage types including optical storage, magnetic storage, solid state storage, and other non-volatile memory. The interface bus may be configured to send, receive, and modulate analog and/or digital signals to/from the various sensors and control devices. The program may embody the methods disclosed herein, allowing the CPU to carryout out the steps of such methods and control the ICE 110.

The program stored in the memory system 460 is transmitted from outside via a cable or in a wireless fashion. Outside the automotive system 100 it is normally visible as a com- puter program product, which is also called computer readable medium or machine read-able medium in the art, and which should be understood to be a computer program code residing on a carrier, said carrier being transitory or non-transitory in nature with the con- sequence that the computer program product can be regarded to be transitory or non-transitory in nature.

An example of a transitory computer program product is a signal, e.g. an electromagnetic signal such as an optical signal, which is a transitory carrier for the computer program code. Carrying such computer program code can be achieved by modulating the signal by a conventional modulation technique such as QPSK for digital data, such that binary data representing said computer program code is impressed on the transitory electromagnetic signal. Such signals are e.g. made use of when transmitting computer program code in a wireless fashion via a WiFi connection to a laptop.

In case of a non-transitory computer program product the computer program code is em-bodied in a tangible storage medium. The storage medium is then the non-transitory carrier mentioned above, such that the computer program code is permanently or non-perma-nently stored in a retrievable way in or on this storage medium. The storage medium can be of conventional type known in computer technology such as a flash memory, an Asic, a CD or the like.

Instead of an ECU 450, the automotive system 100 may have a different type of processor to provide the electronic logic, e.g. an embedded controller, an onboard computer, or any processing module that might be deployed in the vehicle.

As shown in figure 3, the fuel pump 180 may particularly comprise a pump body 500 de-fining an internal chamber 505 where a piston 510 is accommodated. The chamber 505 is in fluid communication with the fuel source 190 through a suction line 515 and with the fuel rail 170 through a discharge line 520. An inlet valve (not shown) is disposed in the suction line 515 and an outlet valve 525 is disposed in the discharge line 520. The inlet and the outlet valves may be check valves. The piston 510 has a cam follower 530, which is biased by a spring 535 against a cam 540. The cam 540 is integral with an input shaft 545 having a rotation axis orthogonal to the piston axis. In this way, the rotation of the input shaft 545 causes reciprocating movement of the piston 510. Each reciprocating movement of the piston 510 comprises a suction stroke followed by a discharge stroke. During the suction stroke, the piston 510 moves from a top death center position (TDC), shown in figure 3, towards a bottom death center position, thereby increasing the volume of the internal chamber 505. During this phase, the outlet valve 525 remain close while the inlet valve opens, letting the fuel into the chamber 505 via the suction line 515. During the following discharge stroke, the piston 510 moves from the BDC position to the TDC position, thereby reducing the volume of the chamber 505. During this phase, the inlet valve closes and the outlet valve 525 opens, so that the fuel contained in the chamber 505 is forced into the fuel rail 170 through the discharge line 520.

The input shaft 545 of the fuel pump 180 is usually driven by the engine crankshaft 145, to which the input shaft 545 is mechanically coupled by means of a timing system. The timing system may comprise a drive chain or a belt 550 (see fig.2) wound around a first sprocket 555 keyed on the crankshaft 145 and a second sprocket 560 (see fig.3) keyed on the pump input shaft 545. In other embodiments, the fuel pump 180 may be integrated in the engine body and the cam 540 may be directly keyed on the camshaft 135 or on the crankshaft 145.

Due to these coupling solutions, the inlet shaft 545 of the fuel pump 180 always rotates in time with the crankshaft 145, so that there is a precise and repetitive relation between the angular position of the engine crankshaft 145 and the position of the reciprocating piston 510 of the fuel pump 180. This relation is generally established by the constructional spec-ifications of the ICE 110 but it may vary due to mounting tolerances and/or mounting errors.

For this reason, the ECU 450 may be configured to implement a diagnostic procedure aimed to identify the actual angular position of the crankshaft 145 that corresponds to the TDC position of the pump piston 510. This procedure may be performed only once, for example at the end of the production line (EOL) of the motor vehicle which the automotive system 100 belongs.

As shown in the flowchart of figure 4, the ECU 450 may thus be configured to first check (block 600) whether the EOL line condition is met or not. If the EOL condition is not met, the diagnostic procedure is not performed and the ICE 110 is operated by means of the conventional control strategies. If conversely the EOL condition is met, the diagnostic pro-cedure (block 605) is triggered.

The diagnostic procedure provides for the ECU 450 to activate the starter 195 to rotate the engine crankshaft 145 for a predetermined cranking time (block 610). The cranking time may depend on the specific architecture of the ICE 110. It may thus be determined with a calibration activity and memorized in the memory system 460. In general, the cranking time may be shorter than a predetermined maximum value thereof. This maximum value may be a calibration value determined with an experimental activity.

During the cranking time, the diagnostic procedure further provides for the ECU 450 to monitor the pressure variation within the fuel rail 170 (block 615). To do so, the ECU may be configured to repeatedly sample the pressure within the fuel rail 170, during the crank-ing time. The fuel rail pressure may be sampled by means of the fuel rail pressure sensor 400. The fuel rail pressure sampling may be faster at this stage than during the normal operation of the engine. In other words, the sampling frequency of the fuel rail pressure may be higher than during the normal operation of the engine. For example, the fuel rail pressure may be sampled with an angular sampling period comprised between 0.5 and I deg. During the cranking time, the ECU 450 may be further configured to prevent any fuel injections into the engine combustion chambers 150 (block 620). In this way, the fuel rail pressure variation depends only on the operation of the fuel pump 180, which is driven by the starter 195 via the crankshaft 145.

Since the fuel rail 170 is initially almost empty, the variation of the fuel rail pressure over the cranking time should be represented by the curve A shown in the graph of figure 5. In greater details, the fuel rail pressure progressively increases, in a stepwise manner, from almost zero to a final value, wherein each step of increment is due to a discharge stroke of the fuel pump piston 510. As a consequence, during the cranking time, the fuel rail pressure reaches a plurality of local maxima B1, each of which corresponds to the TDC position of the fuel rail piston 510.

During the cranking time, the diagnostic procedure further provides for the ECU 450 to monitor the engine speed, namely the rotational speed of the crankshaft 145 (block 625).

The engine speed may be monitored for example by means of the crank position sensor 420.

During the cranking time, the diagnostic procedure further provides for the ECU 450 to monitor the angular position of the crankshaft 145 (block 630). In particular, the ECU 450 may be configured to monitor when the crankshaft 145 reaches a predetermined reference angular position thereof, for example the angular position that corresponds to the top death center (TDC) position of a piston 140 of the ICE 110. This monitoring of the crankshaft angular position may be performed with the aid of the crank position sensor 420.

The fuel rail pressure, the engine speed and the crankshaft angular position may then be used as inputs of a computational module 635, that yields an actual crankshaft angular displacement actuaI between the TDC center position of the fuel pump piston 510 and the above mentioned reference angular position of the crankshaft 145. Referring to figure 5, this computational module 635 may provide for the ECU 450 to identify the time instants Ci corresponding to when the crankshaft reaches the reference angular position (e.g. en-gine piston TDC), as well as the instants D1 corresponding to the local maxima of the fuel rail pressure. Then, the computational module 635 may provide for the ECU 450 to calcu- late the time period T1 elapsed between each instant C1 and the immediately following in-stant D1, and to use the monitored engine speed for converting each time period Ti into a crankshaft angular displacement pi. The actual crankshaft angular displacement pactuai may finally be calculated with the following average: Pactuat -N wherein N is the number of the angular displacements p. Consistently with the maximum cranking time of 500 ms, the maximum number N of calculated angular displacements p may be not bigger than 5.

The diagnostic procedure may further provide for the ECU 450 to use the actual crankshaft angular displacement Pactual for calculating (block 640) a deviation &p: = Pactuat -Pnomlnai between the actual crankshaft angular displacement actuaI and the nominal value Wncminai thereof, which may correspond to the crankshaft angular displacement of the fuel pump as defined by the engine constructional specifications.

The deviation Acp may finally be used by the ECU 450 to calculate (block 645) a corrected angular advance Dl, with respect to the reference angular position of the crankshaft 145, which will be used for scheduling the fuel rail pressure sampling during the normal opera-tions of the engine 110: Dl = Dinominat -wherein Dlnomjnai is a predetermined nominal value of the angular advance Dl, which can be the same for all the ICE 110 of the same kind and which may be determined by means of a calibration activity.

In this way, during the normal operations of the engine, the fuel rail pressure will be sam-pled when the crankshaft 145 is angularly in advance by the quantity Dl with respect to its reference position.

While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary em- bodiment, it being understood that various changes may be made in the function and ar-rangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.

REFERB4CES automotive system internal combustion engine 120 engine block cylinder cylinder head camshaft piston 145 crankshaft combustion chamber cam phaser fuel injector fuel rail 160 fuelpump fuelsource starter intake manifold 205 air intake duct 210 intake port 215 valves 220 exhaust port 225 exhaust manifold 230 turbocharger 240 compressor 250 turbine 260 intercooler 270 exhaust system 275 exhaust pipe 280 aftertreatment devices 290 VGT actuator 300 exhaust gas recirculation system 310 EGR cooler 320 EGR valve 330 throttle body 340 mass airflow and temperature sensor 350 manifold pressure and temperature sensor 360 combustion pressure sensor 380 coolant and oil temperature and level sensors 400 fuel rail pressure sensor 410 cam position sensor 420 crank position sensor 430 exhaust pressure and temperature sensors 440 EGR temperature sensor 445 accelerator pedal position sensor 450 ECU 460 memory system 500 pump body 505 internal chamber 510 fuel pump piston 515 suction line 520 discharge line 525 outlet valve 530 cam follower 535 spring 540 cam 545 input shaft 550 drive chain or belt 555 first sprocket 560 second sprocket 600 block 605 block 610 block 615 block 620 block 625 block 630 block 635 computational module 640 block 645 block

Claims

CLAIMS1. An electronic control unit (450) for an internal combustion engine (110) having a crankshaft (145) coupled to a starter (195) and to a fuel pump (180) in fluid communication with a fuel rail (170), wherein the electronic control unit (450) is configured to: -activate (610) the starter(195) to rotate the crankshaft (145) fora predetermined cranking time, -monitor (625) an engine speed during the cranking time, -monitor (630) an angular position of the crankshaft (145) during the cranking time, -monitor (615) a pressure variation within the fuel rail (170) during the cranking time, -use the engine speed, the crankshaft angular position and the pressure variation to de-termine (635) a crankshaft angular displacement between a top death center position of a fuel pump piston (510) and a reference angular position of the crankshaft (145).
2. An electronic control unit (450) according to claim 1, configured to determine the crankshaft angular displacement by: -identifying a first instant (C1) when the crankshaft (145) reaches the reference angular position, -identifying a second instant (Di) when the fuel rail pressure variation reaches a local maxi-mum thereof, -calculating a time (T1) elapsed between the first instant and the second instant, -using the engine speed to convert the calculated elapsed time into an angular displace-ment (pj) of the crankshaft (145).
3. An electronic control unit (450) according to claim 1, configured to determine the crankshaft angular displacement by: -identifying a plurality of first instants (Cj) when the crankshaft (145) reaches the reference angular position, -identifying a plurality of second instants (D1) when the fuel rail pressure variation reaches local maxima thereof, -calculating a time (T1) elapsed between each one of the first instants and a following second instant, -using the engine speed to convert each of the calculated elapsed time into a correspond-ing angular displacement (w') of the crankshaft (145), -averaging the crankshaft angular displacements (cp).
4. An electronic control unit (450) according to any of the preceding claims, wherein the reference angular position of the crankshaft (145) corresponds to a top death center position of an engine piston (140).
5. An electronic control unit (450) according to any of the preceding claims, configured to monitor the fuel rail pressure by sampling the fuel rail pressure with a crankshaft angular period of comprised between 0.5 and 1 deg.
6. An electronic control unit (450) according to any of the preceding claims, wherein the cranking time is shorter than or equal to a predetermined maximum value thereof.
7. An electronic control unit (450) according to any of the preceding claims, configured to prevent (620) any fuel injections during the cranking time.
8. An electronic control unit (450) according to any of the preceding claims, configured to calculate (640) a deviation between the determined crankshaft angular displacement and a predetermined nominal value thereof.
9. An electronic control unit (450) according to claim 8, configured to use the calculated deviation to correct (645) a crankshaft angular position scheduled for sampling the fuel rail pressure during normal operations of the engine (110).