GB2497515A

GB2497515A - Solenoid fuel injector system with needle position feedback

Info

Publication number: GB2497515A
Application number: GB1120854.3A
Authority: GB
Inventors: Massimiliano Melis; Antonio Arpaia
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2011-12-05
Filing date: 2011-12-05
Publication date: 2013-06-19
Also published as: GB201120854D0

Abstract

A solenoid fuel injector 160 for an internal combustion engine (ICE) comprises a needle 24 moved by a solenoid actuator 34,36 along an axial path 90. A limited portion 50 of the needle 24 is configured to intercept and concentrate flux lines of a magnetic field. The portion may be an enlarged part 54 made from ferromagnetic material. Solenoids 62, 66, 68 are positioned around the limited portion 50 of the needle; solenoid 62 is part of a primary circuit energized by a DC source and is positioned between solenoids 66 and 68 which are part of a secondary circuit 65 connected to the ECU. The ferromagnetic portion 50 intercepts and concentrates the magnetic field flux lines from solenoid 62 and induces in the secondary circuit 65 a signal, eg voltage, representative of the position of portion 50 of the needle allowing closed loop control of the injector and obviating end-of-line (EOL) compensations usually needed due to injectors production drift.

Description

A FUEL INJECT/ON SYSTEM FOR AN INTERNAL COMBUSTION ENGINE

TECHNICAL FIELD

The present disclosure relates to a fuel injection system for an internal combustion engine.

BACKGROUND

It is known that modern Diesel engines are provided with a fuel injection system for directly injecting fuel into the cylinders of the engine.

The fuel injection system generally comprises a fuel common rail and a plurality of electrically controlled fuel injectors, which are individually located in a respective cylinder of the engine and which are hydraulically connected to the fuel common rail through dedicated feeding conduits.

The fuel in the common rail is maintained at a high pressure by an high pressure pump and enters the injector through a fluid inlet and is directed towards a control chamber in the upper portion of the injector and to a lower portion of the injector where a nozzle and a movable needle are provided.

The needle is moved with the aid of a dedicated actuator, typically a solenoid actuator controlled by an engine control unit (ECU).

If the solenoid is not activated, the needle is closed because the pressure of the fuel in the control chamber balances the pressure that keeps the needle in the closed position.

An Engine Control Unit (ECU), which monitors engine operating parameters via various sensors calculates the appropriate amount of fuel to be injected as a function of various operating conditions of the engine.

When a certain quantity of fuel is to be injected, the solenoid is activated and an armature is lifted against the resistance of a spring to open one or more orifices that allows fuel to exit from the control chamber. Therefore the needle is lifted and the injector opens. If the solenoid is deactivated, the pressure in the control chamber increases until the needle closes again the injector.

A problem of solenoid injectors according to the known art is that there is no way to know the exact position of the needle of the injector as a function of time.

An object of an embodiment of the invention is to provide a fuel injector system for an internal combustion engine that can to send signals representative of the position of the needle to an Electronic Control Unit of the engine.

Another object of an embodiment of the invention is to provide a fuel injector for an internal combustion engine that can be controlled in closed loop by the Electronic Control Unit of the engine.

These and other objects are achieved by a solenoid injector having the features recited in the independent claim.

The dependent claims delineate preferred and/or especially advantageous aspects.

SUMMARY

An embodiment of the invention provides a solenoid injector for injecting fuel into a cylinder of an internal combustion engine, the solenoid injector comprising a needle and a solenoid actuator for moving the needle along an axial path, wherein a limited portion of the needle is configured to intercept and concentrate flux lines of a magnetic field.

An advantage of this embodiment is that the injector itself comprises at least an element that can be used to determine information representative of the injector needle position.

According to an embodiment of the invention, the limited portion of the needle comprises an enlarged part of the needle itself.

An advantage of this embodiment is that the enlarged part can be easily realized on the injector rod.

According to another embodiment of the invention, the limited portion of the needle is made from ferromagnetic material.

An advantage of this embodiment is that the limited portion can be realized in a suitable material for creating an element that can be used to determine information representative of the injector needle position.

A further embodiment of the invention provides a fuel injection system for an internal combustion engine, the engine having an engine block defining a cylinder, the fuel injection system comprising: -a solenoid injector according to any of the preceding claims for injecting fuel into the cylinder, -a primary electrical circuit configured to generate a magnetic field having magnetic field flux lines concatenated with the limited portion of the injector needle, -a secondary electrical circuit, inductively coupled to the primary electrical circuit so that the movement of the limited portion of the needle induces a variation of the mutual inductance between the primary and the secondary electrical circuit, thereby generating in the secondary electrical circuit a signal representative of the position of said limited portion of the needle.

An advantage of this embodiment is that it allows to read information representative of the injector needle position.

According to an embodiment of the invention, the primary electrical circuit comprises a first solenoid and the secondary electrical circuit comprises a second and a third solenoid, wherein each of the solenoids is wound around the solenoid injector, and wherein the first solenoid is positioned between the second and third solenoid with respect to the axial path of the limited portion of the solenoid injector needle.

An advantage of this embodiment is that it allows to create a structure around the path of the ferromagnetic portion of the injector needle that, when the ferromagnetic portion moves, the mutual inductances of the primary circuit and of the secondary circuit change, causing the voltages induced in the second and third solenoid to change respectively.

According to another embodiment of the invention, the movement of the limited portion of the needle generates in each of the second and third solenoid a respective voltage value that is proportional to the mutual inductance between the primary electrical circuit and the second and third solenoid, the second and third solenoid being connected in reverse series so that the signal representative of the position along the axial path of the limited portion of the injector needle is the difference between the two voltage values and of the second and third solenoid.

An advantage of this embodiment is that this configuration allows to generate automatically a signal that is representative of the position of the injector needle, at the same time, achieving a high measurement precision.

According to another embodiment of the invention, wherein in a closed position of the needle of the injector, the first solenoid of the primary electrical circuit is positioned in correspondence with the limited portion of the needle.

According to a further embodiment of the invention, wherein free ends of the second and third solenoid are connected to an Electronic Control Unit of the engine by a couple of electrical pins in the upper portion of the injector.

An advantage of this embodiment is that it allows to send a signal representative of the injector position to the Electronic Control Unit of the engine. This embodiment therefore -----allows to act ontothe injector using a closed ioop control based on the information on the position of the injector needle.

An embodiment of the invention provides an internal combustion engine comprising an engine block defining a cylinder and a fuel injection system according to the above disclosure arranged to inject fuel into the cylinder.

Another embodiment of the invention provides a method for operating an internal combustion engine, the method comprising the steps of: -moving the injector needle by powering the solenoid actuator of the injector with an electrical signal having a controllable parameter, -sensing a value of the signal generated in the secondary electrical circuit by the movement of the injector needle, -using the sensed value of the signal to determine a position of the solenoid injector needle, -adjusting a value of the controllable parameter of the electrical signal on the basis of a difference between the determined position of the needle and an expected position thereof, This embodiment allows to act onto the injector using a closed loop control based on the information on the position of the injector needle.

According to another embodiment of the invention, the electrical signal is a Power Width Modulation (PWM) signal and the controllable parameter is the duty cycle thereof.

An advantage of this embodiment is that the use of Power Width Modulation (PWM) techniques allow a faster and more precise control of the injector needle that is particularly useful in closed loop control of the injector methods.

Another advantage of this embodiment is that it allows to customize injector's needle lift actuation depending on calibration needs.

A further advantage is that it avoids End Of Line (EOL) compensations that are usually needed due to the injectors production drift.

Another embodiment of the invention provides an apparatus for operating an internal combustion engine according to the above disclosure, the apparatus comprising: -means for moving the injector needle by powering the solenoid actuator of the injector with an electrical signal having a controllable parameter, -means for sensing a value of the signal generated in the secondary electrical circuit by the movement of the injector needle, -means far using the sensed value of the signal to determine a position of the solenoid injector needle, -means for adjusting a value of the controllable parameter of the electrical signal on the basis of a difference between the determined position of the needle and an expected position thereof.

Another embodiment of the invention provides an automotive system comprising an internal combustion engine according to the above disclosure and an Electronic Control Unit, wherein the Electronic Control Unit is configured to: -move the injector needle by powering the solenoid actuator of the injector with an electrical signal having a controllable parameter, -sense a value of the signal generated in the secondary electrical circuit by the movement of the injector needle, -use the sensed value of the signal to determine a position of the solenoid injector needle1 -adjust a value of the controllable parameter of the electrical signal on the basis of a difference between the determined position of the needle and an expected position thereof The advantages of the apparatus and of the automotive system embodiments of the invention are substantially the same of those of the method for operation of the internal combustion engine provided with a fuel injection system according to the various embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments will now be described, by way of example, with reference to the accompanying drawings, wherein like numerals denote like elements, and in which: Figure 1 shows an automotive system; Figure 2 is a cross-section of an internal combustion engine belonging to the automotive system of figure 1; Figure 3 represents a cross-sectional view, with parts removed for reasons of clarity, of a fuel injection system according to an embodiment of the invention; Figure 4 is a cross-section view of a portion of a solenoid injector of Figure 3; Figure 5 is a schematic representation of a control logic that can be employed to control the fuel injection system of Figures 3-4.

DETAILED DESCRIPTION

Exemplary embodiments will now be described with reference to the enclosed drawings without intent to limit application and uses.

Some embodiments may include an automotive system 1001 as shown in Figures 1 and 2, that includes an internal combustion engine (ICE) 110 having an engine block 120 defining --at ieast one cylinder 125 having a piston 140 coupled to rotate a crankshaft 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 150 and ignited1 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 a fuel source 190.

More specifically, according to an embodiment of the invention, the internal combustion engine 110 may be provided with a fuel injection system 600, equipped with the injector 160 that will be described in more detail hereinafter.

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.

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 turbocharger 230, having a compressor 240 rotationally coupled to a turbine 250, may be provided. 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 catalysts, lean NOx traps 285, hydrocarbon adsorbers, selective catalytic reduction (SCR) systems, and particulate filters (DPF).

Oftiè éthb6dlthibfs yiclUdè haut äai r rdläiir coupled -between the exhaust manifold 225 and the intake manifold 200.

Another EGR system (not represented for simplicity) could be coupled between the pipes after turbine and the pipe before compressor (low pressure EGR or long-route EGR).

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 signals 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 410, a crank position sensor 420, exhaust pressure and temperature sensors 430, an EGR temperature sensor 440, and an accelerator pedal position sensor 445.

According to some embodiments of the invention, the ECU 450 may receive signals from the fuel injection system 600, as will be explained hereinafter.

Furthermore, the ECU 450 may generate output signals to various control devices that are arranged to control 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, or data carrier 460, and an interface bus.

The CPU is configured to execute instructions stored as a program in the memory system and send and receive signals to/from the interface bus, The memory system 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.

In Figure 3 a fuel injection system 600, according to an embodiment of the invention is represented, the fuel injection system 600 being equipped with an injector 160 having a body 10 that extends longitudinally and a side inlet 12 for connection to a fuel rail 170 of a iUl-'su5jiliystehiH ------The injector 160 is designed to be applied to the injection of fuel into a cylinder 125 of the Internal Combustion Engine (ICE) 110.

The fuel-supply system 600 is controlled by the Electrical Control Unit (ECU) 450 of the engine 110, the ECU 450 being configured to send electric activation signals to the injector 160, according to various conditions of the engine 110.

The injector 160 comprises a nozzle 14 communicating with the side inlet 12 through an injection chamber 16 by means of a fuel conduit 18. The nozzle 14 has a tip 20 generally of conical shape provided with holes 22 for injection of the fuel into a combustion chamber of the engine 110.

Normally, the nozzle 14 is held closed by a needle 24 that has a conical tip 26 designed to engage the conical tip 20 of the nozzle 14. The needle 24 is mobile in an axial seat 28 for opening or closing the nozzle 14 under the control of an actuator device 30. In particular, the conical tip 26 of the needle 24 is able to close holes 22 by engaging the conical tip 20 ofthenozzlel4.

The needle 24 has an active surface subject to the pressure of the fuel in the chamber 16, said active surface being formed by an annular surface 32 thereof.

Actuator device 30 comprises an electromagnet 34, an armature 36 axially slidable under the action of the electromagnet 34, and a preloaded spring 38, which acts on the armature 36 in a direction opposite to that of the attraction exerted by the electromagnet 34.

A rod 40 is housed in a seat 48 inside the shell 10 of the injector 160, the rod 40 being connected with the needle 24 for transmitting to the latter an axial thrust under the action of the pressure of the fuel. A second spring 42 is provided between the needle 24 and a shoulder 49 of the seat of the shell 10, the spring 42 contributing to keep the needle 24 in the position for closing the nozzle 14, Figure 4 represents in cross-section an enlarged portion of the solenoid injector 160 of Figure 3.

In Figure 4 it is visible a limited portion 50 of the needle 24 that is configured to intercept

and concentrate flux lines of a magnetic field.

The limited portion 50 of the needle 24 is defined by an enlarged part 54 of the needle 24 itself.

Moreover, the limited portion 50 of the needle 24 is made from ferromagnetic material.

The limited portion 50 is contained inside a chamber 52 that is enlarged in such a way to allow an upward or downward movement of the enlarged part 54 due to injector activation and consequently allowing the opening and closing of the nozzle 14.

The enlarged part 54 is connected to the axial portion 50 of the needle 24 by two annular surfaces 56,58 fhta}epreferbly synFnétrical. -----The annular surfaces 56,58 are suitable to create a balanced hydraulic pressure on both sides of the enlarged part 54.

In correspondence of the position of the enlarged part 54 of needle 24, a primary electrical circuit 60 (represented schematically in Figure 3 and in the enlarged view of Figure 4) is

B

provided.

The primary electrical circuit 60 comprises a first solenoid 62 that is energized (in 64) by an electrical energy source.

The electrical energy source may be a direct current (DC) source.

A couple of connectors 80 may be provided in the upper portion of the injector 160 to connect the first solenoid 62 to the electrical energy source 64.

A secondary electrical circuit 65, comprising a second and a third solenoid 66,68 that are coupled at each side of the energized solenoid 62, is also provided.

The second and third solenoid 6668 of the secondary circuit 65 are not energized and the free end thereof are connected to the ECU 450 of the engine 110 by a couple of electrical pins 82 in the upper portion of the injector 160.

The secondary electrical circuit 65 is inductively coupled to the primary electrical circuit 60.

Furthermore, the first solenoid 62 of the primary electrical circuit 60 is positioned between the second and third solenoid 66,68 of the secondary electrical circuit 65 in a mini-rail configuration 61 around the axial path 90 of the ferromagnetic limited portion 50 of the injector needJe 24.

Therefore the solenoids 62,6668 are positioned in correspondence of the limited portion of the needle 24.

Also, according to an embodiment of the invention, in a closed position of the needle 24 of the injector 160, the first solenoid 62 of the primary electrical circuit 60 is positioned in correspondence with the limited portion 50 of the needle 24.

The upper end of rod 40 defines with the end portion of the seat 48 a control chamber 46.

The control chamber 46 communicates permanently with the inlet 12, through a calibrated inlet duct (not represented for simplicity) which is designed to receive the fuel under pressure.

The fuel injector 160 carries out metering of the fuel by modulating opening of the needle 24 a function of the pressure of the fuel at the inlet 12.

During operation of the injector 160, when the actuator device 30 is energized under command by the Electrical Control Unit 450, the armature 36 is attracted against the resistance of the spring 38, so that the control chamber 46 is opened. The fuel of the control chamber 46 is discharged through a passages (not represented) reducing the présiürè ir the control chamber 46 so that the pressure of the fuel in the injectiQn chamber 16 pushes the needle 24 along an opening stroke upwards, opening the nozzle 14 and thus determining injection of the fuel.

The dimensions of the passages may be chosen in such a way to obtain a quick injector needle actuation.

When the actuator device 30 is de-energized, spring 38 brings armature 36 back downwards, so that the fuel entering from the inlet duct 12 restores the pressure of the control chamber 46. The action of said pressure on rod 40, assisted by the action of the spring 42, prevails again over the pressure of the fuel on the annular surface 32, so that the needle 24 performs a closing stroke for closing the nozzle 14.

The movement of the needle 24 can be detected by the sensing circuit 65 working as a movement sensor.

Since first solenoid 62 is energized by energy source 64 it creates a magnetic field 70 that invests the ferromagnetic limited portion 50 of the needle 24 of the injector 160, arid in particular the enlarged part 54 thereof.

The ferromagnetic portion 50 intercepts and concentrates magnetic field flux lines of the magnetic field 70 and induces in the secondary circuit 65 a variation of the mutual inductance between the primary 60 and the secondary electrical circuit 65 that generates, in the secondary electrical circuit 65, a signal E0 that is representative of the position of the ferromagnetic portion 50 of the needle 24.

The signal E0 may be a voltage.

More specifically in each of the second and third solenoid 66,66 secondary voltage values El and E2 are generated that are each proportional to the mutual inductance between the primary electrical circuit 60 and each of the second and third solenoid 66,6ft Preferably the secondary electrical circuit 65 is configured in order to have the second and third solenoid 66,68 connected in reverse series (Figures 3 and 4).

By reverse series connection it is intended that the second solenoid 66 is connected to the third solenoid 68 in such a way that the secondary voltage El generated in the second solenoid 66 has opposite sign with respect to the secondary voltage E2 generated in the third solenoid 68.

In that way the output voltage E01 is the difference between the two secondary voltages El and E2, in symbols: E0=E2-E1.

Each of the second and third solenoids 66,68 is connected through pins 82 to the ECU 450 that manages the internal combustion engine 110.

The ECU 450 therefore receives as input the signal E0 representative of a position of the --rromaetiboron5Qidthustthehibjfle24 In this way, the ECU 450 can be provided at each instant with information concerning the position of the needle 24 of the injector 160, According to a preferred embodiment of the invention, the actuator device 30 can be actuated by means of a Power Width Modulation (PWM) electrical signal in order to get the desired needle movement.

The duty cycle of the PWM electrical signal is properly regulated by the ECU 450.

More precisely, the ECU 450 is configured for using the duty cycle of the PWM electrical signal as a function of the determined quantity of fuel to be injected and of the desired shape of the injection in order to actuate the needle.

Figure 5 is a schematic representation of a control logic that can be employed to control the solenoid injector of Figures 1-2.

According to the various conditions of functioning of the engine 110, the ECU 450 determines, for a specific fuel injection into a cylinder 125 of the engine 110, a desired fuel quantity Q (block 502) and a desired shape (block 502) of the injection, namely a desired quantity of fuel as function of time for a particular fuel injection.

The desired fuel quantity Q and the desired injection shape information is passed to an electromagnetic actuation module (block 500) in the ECU 450 that in turn determines the required PWM shape and the required needle position (block 504) as a function of the desired fuel quantity Q and the desired injection shape.

A needle position feedback (block 505) is derived using the needle position information determined by sensing the needle position with the help of sensing circuit 65 and this information is used to calculate a correction factor to be added (block 506) to the required PWM shape and the required needle position (block 504) determined by the ECU 450.

This allows to control in closed loop the injector 160.

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 embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.

REFERENCE NUMBERS body

12 side iniet 14 nozzle 16 injection chamber 18 fuel conduit injector tip 22 tip hole 24 needle 26 needle tip 28 axial set of needle actuator device 32 annular surface of needle 34 electromagnet 36 armature 38 preloaded spring rod 42 second spring 46 control chamber 48 seat 49 shoulderof seat axial portion of rod 52 chamber for axial portion 54 enlarged pan of rod 56,58 annular surfaces electrical circuit 61 mini-rail 62 first solenoid 64 energy source 65 sensing circuit 66 second solenoid 68 thifdólehóid -

magnetic field

connectors 82 electrical pins axial path automotive system internal combustion engine (ICE) engine block cylinder 130 cylinder head camshaft piston crankshaft combustion chamber 155 cam phaser fuel injector fuel rail fuel pump fuel source 200 intake manifold 205 air intake duct 210 intakeairport 215 valves of the cylinder 220 exhaust gas port 224 exhaust line 225 exhaust manifold 230 turbocharger 240 compressor 250 turbine 260 intercooler 270 exhaust system 275 exhaust pipe 280 exhaust aftertreatment device 290 VGT actuator 300 EGR system 310 EGR cooler EGRvalve 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 lever sensors 400 fuel rail pressure sensor 410 cam position sensor 420 crank position sensor 430 exhaust pressure sensor 445 accelerator pedal position sensor 450 Electronic Control Unit (ECU) 460 data carrier 500 electromagnetic actuation module 501 desired injection shape 502 desired fuel injection quantity 504 required PWM and needle position module 505 needle position feedback 506 sum 600 fuel injection system

Claims

<claim-text>CLAIMS1. A solenoid injector (160) for injecting fuel into a cylinder (125) of an internal combustion engine (110), the solenoid injector (126) comprising a needle (24) and a solenoid actuator for moving the needle (24) along an axial path (90), wherein a limited portion (50) of the needle (24) is configured to intercept and concentrate fluxlines of a magnetic field.</claim-text> <claim-text>2. A solenoid injector according to claim 1, wherein the limited portion (50) of the needle (24) comprises an enlarged part (54) of the needle (24) itself.</claim-text> <claim-text>3. A solenoid injector according to claim 1, wherein the limited portion (50) of the needle (24) is made from ferromagnetic material.</claim-text> <claim-text>4. A fuel injection system (600) for an internal combustion engine (110), the engine (110) having an engine block (120) defining a cylinder (125), the fuel injection system (600) comprising: -a solenoid injector (160) according to any of the preceding claims for injecting fuel into the cylinder (125), -a primary electrical circuit (60) configured to generate a magnetic field having magnetic field flux Fines concatenated with the limited portion (50) of the injector needle (24), -a secondary electrical circuit (65), inductively coupled to the primary electrical circuit (60) so that the movement of the limited portion (50) of the needle (24) induces a variation of the mutual inductance between the primary (60) and the secondary electrical circuit (65), thereby generating in the secondary electrical circuit (65) a signal (E0) representative of the position of said limited portion (50) of the needle (24).</claim-text> <claim-text>5. A fuel injection system (600) according to claim 4, wherein the primary electrical circuit (60) comprises a first solenoid (62) and the secondary electrical circuit (65) comprises a second and a third solenoid (6668), wherein each of the solenoids is wound around the solenoid injector, and wherein the first solenoid (62) is positioned between the second and third solenoid (6668) with respect to the axial path (90) of the limited portion (50) of the solenoid injector needle (24).</claim-text> <claim-text>-afueiinjeatvonisfeth 6OO) théè6rdinj to claim 5, inwhiehthe movement of the limited portion (50) of the needle (24) generates in each of the second and third solenoid (66,68) a respective voltage value (E1,E2) that is proportional to the mutual inductance between the primary electrical circuit (60) and the second and third solenoid (6668), the second and third solenoid (66,65) being connected in reverse series so that the signal (E00) representative of the position along the axial path (90) of the limited portion (50) of the injector needle (24) is the difference between the two voltage values (El) and (E2) of the second and third solenoid (66,68).</claim-text> <claim-text>7. A fuel injection system (600) according to claims 5 or 6, wherein in a closed position of the needle (24) of the injector (160), the first solenoid (62) of the primary electrical circuit (60) is positioned in correspondence with the limited portion (50) of the needle (24).</claim-text> <claim-text>8. A fuel injection system (600) according any claim from 5 to 7, wherein free ends of the second and third solenoid (66,68) are connected to an Electronic Control Unit (450) of the engine (110) by a couple of electrical pins (82) in the upper portion of the injector (160).</claim-text> <claim-text>9. An internal combustion engine (110) comprising an engine block (120) defining a cylinder (125) and a fuel injection system (600) according to any of the claims from 4 to S arranged to inject fuel into the cylinder (125).</claim-text> <claim-text>10. A method for operating an internal combustion engine (110) according to claim 9, the method comprising the steps of: -moving the injector needle (24) by powering the solenoid actuator (30) of the injector (160) with an electrical signal having a controllable parameter, -sensing a value of the signal (E31) generated in the secondary electrical circuit (65) by the movement of the injector needle (24), -using the sensed value of the signal (E) to determine a position of the solenoid injector needle (24), -adjusting a value of the controllable parameter of the electrical signal on the basis of a difference between the determined position of the needle and an expected position thereof.</claim-text> <claim-text>11. A method according to claim 10, wherein the electrical signal is a Power Width Modulation (PWM) signal and the controllable parameter is the duty cycle thereof.</claim-text> <claim-text>12. An apparatus for operating an internal combustion engine (110) according to claim 9, the apparatus comprising: -means for moving the injector needle (24) by powering the solenoid actuator (30) of the injector (160) with an electrical signal having a controllable ---parañiétir, -means for sensing a value of the signal (E0) generated in the secondary electrical circuit (65) by the movement of the injector needle (24), -means for using the sensed value of the signal (E9) to determine a position of the solenoid injector needle (24), -means for adjusting a value of the controllable parameter of the electrical signal on the basis of a difference between the determined position of the needle and an expected position thereof.</claim-text> <claim-text>13. An automotive system (100) comprising an internal combustion engine (110) according to claim 9 and an Electronic Control Unit (450), wherein the Electronic Control Unit (450) is configured to: -move the injector needle (24) by powering the solenoid actuator (30) of the injector(160) with an electrical signal having a controllable parameter, -sense a value of the signal (E0) generated in the secondary electrical circuit (65) by the movement of the injector needle (24), -use the sensed value of the signal (E01) to determine a position of the solenoid injector needle (24), -adjust a value of the controllable parameter of the electrical signal on the basis of a difference between the determined position of the needle and an expected position thereof.</claim-text>