Electromagnetic fuel injector

Abstract

To provide an electromagnetic fuel injector that has a low noise level and modest degradation (wear), and is easy to manufacture.SOLUTION: An electromagnetic injector 1 for fuel has a tubular support body 4, an injection nozzle disposed at an end of the support body 4, an injection valve coupled to the injection nozzle, a plunger 8 that is movable between closed and open positions of the injection valve, an electromagnetic actuator 6 provided with at least one main electromagnet 11 and at least one secondary electromagnet 12, and a closing spring that pushes the plunger 8 towards the closed position of the injection valve. The secondary electromagnet 12 has a secondary coil 17 and a secondary movable armature 18, in which the secondary movable armature 18 is disposed inside the support body 4, is integral to the plunger 8 and is magnetically coupled to the secondary coil 17. The secondary electromagnet 12 is disposed inside the support body 4 and has no secondary fixed armature that is magnetically coupled to the secondary movable armature 18.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This patent application claims priority to Italian Patent Application No. 102023000014409, filed July 10, 2023, and Italian Patent Application No. 102024000004939, filed March 6, 2024, the entire disclosure of which is incorporated herein by reference.

[0002] The present invention relates to an electromagnetic fuel injector.

[0003] The present invention finds advantageous application in electromagnetic hydrogen injectors, and the following discussion makes explicit reference to electromagnetic hydrogen injectors, but without loss of generality. [Background technology]

[0004] Typically, an electromagnetic fuel injector (such as that described in US Pat. No. 5,399,363) comprises a cylindrical tubular support with a central supply channel, which serves as a fuel duct and ends in an injection nozzle adjusted by an injection valve controlled by an electromagnetic actuator. The injection valve comprises a plunger which is moved by the action of the electromagnetic actuator between the closed and open positions of the injection nozzle against the action of a closing spring which pushes the plunger towards the closed position. The plunger ends in a shutter head which is designed to seat tightly against the valve seat of the injection valve.

[0005] The electromagnetic actuator comprises (at least one) coil arranged in a fixed position outside and around the support, a movable armature made of ferromagnetic material that is firmly connected to a plunger and movably mounted inside the support, and a fixed armature (or bottom member) made of ferromagnetic material that is arranged inside the support in the region of the coil and designed to magnetically attract the movable armature when the coil is excited.

[0006] When liquid fuel is injected, the presence of the liquid fuel inside the support constitutes a significant obstacle to the movement of the movable armature, and in effect forms a hydraulic damper that limits the speed of movement of the movable armature. Furthermore, liquid fuel (as opposed to gaseous fuel) has a lubricating effect that reduces the wear of the various components that come into contact with each other during use, limiting the noise generated by the various components that come into contact with each other during use. Instead, when gaseous fuel is injected (especially when hydrogen, a very light gas, is injected), the presence of the gaseous fuel inside the support does not constitute a significant obstacle to the movement of the movable armature, and therefore the movable armature moves at high speed and at the end of the opening movement hits hard against the fixed armature. The hard hit of the movable armature against the fixed armature at the end of the opening movement causes both a high noise level and accelerated deterioration (wear). Furthermore, the hard hit of the movable armature against the fixed armature at the end of the opening movement also causes an important bounce phenomenon that introduces a certain randomness into the amount of fuel injected.

[0007] In this respect, it is important to note that hydrogen has a low density (because it has a very simple molecule consisting of only two hydrogen atoms), and therefore, in order to inject a sufficient amount (mass) of hydrogen into the combustion chamber, a correspondingly large amount of hydrogen must be injected, which in particular requires a large passage area for the hydrogen through the injector (i.e. the opening through which the hydrogen must pass to leave the hydrogen injector must be large). In order to have a large passage area for the hydrogen through the injector, it is necessary for the plunger (and therefore the movable armature) to have a long stroke between the closed and open positions, which causes a further increase in the impact velocity of the movable armature against the fixed armature at the end of the opening movement.

[0008] In order to limit the impact speed of the movable armature against the fixed armature at the end of the opening movement, a specific current profile is currently used through the coil of the electromagnetic actuator, which should enable the magnetic force attracting the movable armature towards the fixed armature to be reduced when the movable armature is close to the fixed armature. However, controlling the magnetic force attracting the movable armature towards the fixed armature when the movable armature is close to the fixed armature is very complicated and rather inaccurate, since in this position the magnetic force attracting the movable armature towards the fixed armature has a strong nonlinearity (i.e. it increases exponentially when the air gap between the movable armature and the fixed armature becomes very small).

[0009] Patent documents 2 and 3 describe an electromagnetic fuel injector whose electromagnetic actuator comprises two separate and independent electromagnets, each of which comprises a coil, a movable armature made of a ferromagnetic material and magnetically coupled to the coil, and a fixed armature (or bottom member) made of a ferromagnetic material and magnetically coupled to the coil and the movable armature, i.e., both electromagnets have their respective movable armatures integrated into the plungers. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] European Patent Application Publication No. 1619384 [Patent Document 2] European Patent Application Publication No. 3091219 [Patent Document 3] European Patent Application Publication No. 2975256 Summary of the Invention

[0011] The object of the present invention is to provide an electromagnetic fuel injector which does not have the above mentioned drawbacks, i.e. which has a low noise level and is subject to low deterioration (wear) whilst at the same time being easy and cheap to manufacture.

[0012] According to the present invention there is provided an electromagnetic fuel injector as claimed in the accompanying claims.

[0013] The appended claims exemplify preferred embodiments of the invention and form an integral part of this specification.

[0014] The present invention will now be described with reference to the accompanying drawings, which show non-limiting embodiments of the invention. [Brief description of the drawings]

[0015] [Figure 1] 1 is a longitudinal cross-sectional view of a portion of a fuel injector made in accordance with the present invention; [Diagram 2] FIG. 2 is a view on an enlarged scale of a detail of FIG. 1. [Diagram 3] 2 shows the time variation of current through an electromagnetic actuator of the fuel injector of FIG. 1 and the time variation of position of a moveable plunger of the fuel injector of FIG. 1. [Figure 4] 4 illustrates the current through and voltage applied to an electromagnetic actuator over time, according to one embodiment. [Diagram 5] 4 illustrates the current through and voltage applied to an electromagnetic actuator over time, according to one embodiment. [Figure 6] 4 illustrates the current through and voltage applied to an electromagnetic actuator over time, according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] In Figure 1, reference number 1 indicates as a whole an electromagnetic injector of a gaseous fuel, in particular of hydrogen, which has cylindrical symmetry about a longitudinal axis 2 and which can be controlled to inject hydrogen through an injection nozzle 3. The injection nozzle 3 terminates directly into the combustion chamber (not shown) of a cylinder of an internal combustion engine.

[0017] The electromagnetic injector 1 comprises a support 4 having a cylindrical tubular shape with a cross-section that varies along a longitudinal axis 2 and having a supply channel 5 extending along the entire length of the support 4 for supplying pressurized hydrogen towards an injection nozzle 3.

[0018] The support 4 houses an electromagnetic actuator 6 and an injector 7. In use, the injector 7 is actuated by the electromagnetic actuator 6 to regulate the flow of hydrogen through the injection nozzle 3 available in the region of the injector 7.

[0019] The electromagnetic actuator 6 is configured to move axially (i.e. along the longitudinal axis 2) a movable unit comprising a plunger 8 which ends in a shutter 9. The shutter 9 cooperates with a valve seat of the injector 7 in order to regulate the flow of hydrogen through the injection nozzle 3. In other words, the support 4 ends in a (at least one) through-hole, in which the valve seat is defined and which is engaged by the shutter 9. In particular, the electromagnetic actuator 6 is configured to move the shutter 9 between a closed position and an open position of the injector 7. Furthermore, the electromagnetic actuator 6 is coupled to a closing spring 10 which keeps the electromagnetic injector 1 normally closed. The closing spring 10, in other words, pushes the shutter 9 towards the closed position of the injector 7. In other words, the injector 7 is normally closed by the effect of the closing spring 10 which pushes the plunger 8 towards the closed position, in which the shutter 9 of the plunger 8 is pressed against the valve seat of the injector 7.

[0020] In the embodiment shown in the attached drawings, the injector 7 opens axially inwards and the shutter 9 preferably has a spherical shape. According to a different embodiment, not shown, the injector 7 opens axially outwards and in this embodiment the shutter 9 can for example have a frusto-conical shape.

[0021] As better shown in Fig. 2, the electromagnetic actuator 6 comprises a main (master) electromagnet 11 and a secondary (slave) electromagnet 12, which are controlled together (i.e. with the same current control). The main electromagnet 11 is configured to apply a force to the plunger 8 (when activated) that opens the injector 7 (thus in the opposite direction to the elastic force generated by the closing spring 10). Similarly, the secondary electromagnet 12 is configured to apply a force to the plunger 8 (when activated) that opens the injector 7 (thus in the opposite direction to the elastic force generated by the closing spring 10). In other words, the two electromagnets 11 and 12 are configured to apply mutually coordinated forces to the plunger 8, pushing the plunger 8 towards the open position of the injector 7.

[0022] The main electromagnet 11 comprises a main coil 13 housed outside the support 4 and a main fixed armature 14 (pole or bottom piece or pole piece) made of ferromagnetic material. The main fixed armature 14 is housed inside the support 4 in a fixed position in the region of the main coil 13 and has (at least one) central hole 15 that allows the fuel to flow towards the injection nozzle 3 (alternatively, the hole 15 may not be located in a central position). This main fixed armature 14 is thus inserted inside the support 4 and is integrated into it (typically it is welded to the support 4). Furthermore, the main electromagnet 11 comprises a main movable armature 16, which is arranged inside the support 4, integrated with the plunger 8 (i.e. it is part of the movable unit) and therefore axially movable, arranged close to the main fixed armature 14, i.e. it is magnetically coupled to the main fixed armature 14 (and therefore faces it in close proximity to it) and is magnetically attracted by the main fixed armature 14 (when the coil 13 is energized), i.e. the main movable armature 16 is magnetically coupled to the main coil 13, since it is passed by the magnetic flux generated by the main coil 13. In other words, the main electromagnet 11 is configured to generate a magnetic force that pushes the plunger 8 (integrated in the main movable armature 16) towards the open position, this is essentially due to the magnetic attraction generated between the main movable armature 16 and the main fixed armature 14.

[0023] The secondary electromagnet 12 comprises a secondary coil 17 housed outside the support 4, but does not comprise a secondary fixed armature (magnetic pole or bottom member or magnetic extension) made of ferromagnetic material and housed inside the support 4 in a fixed position in the region of the secondary coil 16. Furthermore, the secondary electromagnet 12 comprises a secondary movable armature 18, which is integrated in the plunger 8 (i.e. it is part of the movable unit) and is therefore axially movable, which is located in the region of the secondary coil 17 and which is magnetically attracted towards the position of least magnetic resistance to the secondary coil 17 (when the secondary coil 17 is energized), i.e. the secondary movable armature 18 is magnetically coupled to the secondary coil 17, since it is passed by the magnetic flux generated by the secondary coil 17. In other words, the secondary electromagnet 12 is configured to generate a magnetic force that pushes the plunger 8 (integrated in the main movable armature 16) towards the open position, which is essentially by a force that attracts the secondary movable armature 18 towards the position of least magnetic resistance against the secondary coil 17.

[0024] In summary, the secondary electromagnet 12 does not have its own secondary fixed armature that is magnetically coupled to (and therefore proximately facing) the secondary movable armature 18 .

[0025] According to a preferred embodiment, the secondary moving armature 18 is configured (i.e. shaped and positioned) in such a way that throughout the entire stroke made by the secondary moving armature 18 (integrated in the plunger 8 and part of the moving unit) between the closed and open positions of the injector 7, the secondary electromagnet 12 always generates only a force pushing the plunger 8 towards the open position of the injector 7. In other words, in this embodiment, the magnetic force generated by the secondary electromagnet 12 has the same direction throughout the entire stroke made by the secondary moving armature 18 between the closed and open positions of the injector 7.

[0026] According to a different embodiment, the secondary moving armature 18 is configured (i.e. shaped and positioned) in such a way that along the first part of the stroke between the closed and open positions of the injector 7, performed by the secondary moving armature 18 (integrated in the plunger 8 and part of the moving unit), the secondary electromagnet 12 generates a force pushing the plunger 8 towards the open position of the injector 7, while along the last part of the stroke between the closed and open positions of the injector 7, performed by the secondary moving armature 18 (integrated in the plunger 8 and part of the moving unit), the secondary electromagnet 12 generates a force pushing the plunger 8 towards the closed position of the injector 7. In other words, in this embodiment, the magnetic force generated by the secondary electromagnet 12 reverses its direction along the stroke between the closed and open positions of the injector 7, performed by the secondary moving armature 18. Initially (when the secondary movable armature 18 is close to the closed position), the magnetic force generated by the secondary electromagnet 12 pushes towards the open position, whereas at the end (when the secondary movable armature 18 is close to the open position), the magnetic force generated by the secondary electromagnet 12 pushes towards the closed position. However, this embodiment (where the magnetic force generated by the secondary electromagnet 12 is reversed along the stroke of the plunger 8 from the closed position to the open position) is generally avoided, as it makes controlling the position of the plunger 8 unstable and therefore very difficult to do accurately.

[0027] According to a further embodiment, the secondary moving armature 18 is configured (i.e. shaped and positioned) in such a way that, throughout the entire stroke between the closed and open positions of the injector 7 made by the secondary moving armature 18 (integrated in the plunger 8 and part of the moving unit), the secondary electromagnet 12 always generates only a force pushing the plunger 8 towards the closed position of the injector 7 and therefore always adds to the closing force generated by the spring 10 and opposes the force generated by the main electromagnet 11. In other words, in this embodiment, the magnetic force generated by the secondary electromagnet 12 has the same direction throughout the entire stroke between the closed and open positions of the injector 7 made by the secondary moving armature 18, which direction is harmonic with the closing force generated by the spring 10 but is anti-harmonic with the magnetic force generated by the main electromagnet 11. Preferably, in this embodiment, the magnetic force generated by the secondary electromagnet 12 is zero when the injector 8 (i.e., the plunger 8) is in a closed position and increases (starting from zero) as the injector 8 (i.e., the plunger 8) moves from the closed position to the open position.

[0028] The electromagnetic injector 1 is equipped with (connected to) a control unit 19 (schematically shown in FIG. 1). The control unit 19 controls the current i (t) The voltage v that generates the circulation (t) Applying a current of 0 V to both coils 13 and 17 of the two electromagnets 11 and 12 energizes both coils 13 and 17 of the two electromagnets 11 and 12. In particular, the two coils 13 and 17 of the two electromagnets 11 and 12 are connected in series with respect to each other, and therefore the same current flows through them. In other words, the electromagnets 11 and 12 are controlled by the same current.

[0029] In use, when the electromagnets 11 and 12 are de-energized, the main movable armature 16 is not subjected to any forces of magnetic origin and is therefore subjected only to an elastic force generated by the closing spring 10 which pushes it together with the plunger 8 towards the closed position (i.e. downwards). In this situation, the injector 7 is closed. The "end stop" of the closed position is established by the contact of the shutter 9 against the valve seat of the injector 7 (or, more generally, by the contact of an element of the movable unit against a fixed element integrated in the support 4; i.e. the "end stop" of the closed position may also be established independently of the contact of the shutter 9 against the valve seat of the injector 7).

[0030] In use, to open the injector 7, both main electromagnets 11 and 12 are activated (i.e. both coils 13 and 17 are energized) so that they generate a magnetic force that overcomes the elastic force of the closing spring 10 and pushes the plunger 8 (i.e. the two movable armatures 16 and 18) towards the open position. As a result, the plunger 8 (i.e. the two movable armatures 16 and 18) moves towards the open position, causing a gradual opening of the injector 7. The (fully) open position of the injector 7 is reached when the main movable armature 16 seats against the main fixed armature 14, since the "end stop" of the open position is established by the contact of the main movable armature 16 against the main fixed armature 14 (or, more generally, by the contact of an element of the movable unit against a fixed element integrated in the support 4). That is, at the end of the releasing step, the main movable armature 16 completes its stroke relative to the main fixed armature 14 .

[0031] Generally, when the main movable armature 16 contacts the main fixed armature 14, a low intensity current i is applied to keep the injector 7 open. (t) is supplied to the coils 13 and 17 of the electromagnets 11 and 12, since a reduced magnetic force is sufficient to maintain the open position.

[0032] In use, to close the injection valve 7, the electromagnets 11 and 12 are switched off and the plunger 8 is no longer subjected to any forces of magnetic origin and is pushed towards the closed position (i.e. downwards) by the elastic force generated by the closing spring 10.

[0033] According to a possible embodiment, the electromagnets 11 and 12 remain switched off throughout the closing step.

[0034] According to an alternative embodiment, when the shutter 9 is in the vicinity of the valve seat of the injector 7 (at the end of the closing step), the electromagnets 11 and 12 are briefly activated (reactivated) (i.e. the coils 13 and 17 are energized) and the electromagnets 11 and 12 generate a magnetic force which pushes the plunger 8 towards the open position, thereby slowing down the movement of the plunger 8 towards the closed position. It is important to note that the magnetic force generated by the electromagnets 11 and 12 at the end of the closing step is not (i.e. is not strong enough to) stop or reverse the movement of the plunger 8 towards the closed position, but only has the effect of slowing down (braking) the movement of the plunger 8 towards the closed position. Thus, at the end of the closing step, when the shutter 9 impacts the valve seat of the injector 7, the main movable armature 16 completes its stroke (the "end stop" of the closed position is established by the contact of the shutter 9 against the valve seat of the injector 7) and the shutter 9 impacts against the valve seat of the injector 7 at a significantly smaller speed as a result of the deceleration (braking) action exerted by the electromagnets 11 and 12.

[0035] According to a preferred embodiment, the electromagnets 11 and 12 are deactivated before the plunger 8 reaches the closed position (i.e., the magnetic force generated by the electromagnets 11 and 12 does not immediately become zero when the electromagnets 11 and 12 are deactivated) so as to create electrical inertia, magnetic inertia, and mechanical inertia.

[0036] FIG. 3 shows an example of a cycle of opening and closing the fuel injector 1 starting from a closed position. At time T0, a positive voltage v (t) is applied to the electromagnets 11 and 12, and a current i (t) is circulated. Current i (t) increases rapidly from zero to a peak effective value I1, which is reached at time T1, after which the voltage v applied to the electromagnets 11 and 12 (t) is periodically varied between positive and zero values, and the current i (t) is maintained within a range centered on the peak effective value I1 until time T2.

[0037] At time T2, the current i passing through the electromagnets 11 and 12 (t) is zero or negative voltage v (t) to the electromagnets 11 and 12 until a holding effective value I2 (i.e., a value less than the peak effective value I1) is reached at time T3. The holding effective value I2 is determined by applying the voltage v (t) is periodically changed until time T4.

[0038] At time T4, the current i passing through the electromagnets 11 and 12 (t) is zero or negative voltage v (t) to the electromagnets 11 and 12 until it reaches a hold effective value I3 (i.e., a value smaller than the hold effective value I2) at time T5. The hold effective value I3 is determined by applying the voltage v (t) is periodically changed until time T6.

[0039] Current i circulating through electromagnets 11 and 12 (t)creates a magnetic force that overcomes the elastic force created by the spring 10 and attracts the plunger 8 towards the open position. In so doing, between time T0 and time T4, the plunger 8 moves from the closed position to the open position. After the plunger 8 starts moving, a smaller force is sufficient to continue the movement of the plunger 8, in particular to keep the plunger 8 in the open position, and therefore the current i (t) can be reduced from an initial peak effective value I1 to hold effective values ​​I2 and I3.

[0040] At time T6, a zero or negative voltage v is applied to the electromagnets 11 and 12. (t) By applying a current i (t) is gradually reduced to zero. In particular, the zero current i (t) is reached at time T7 and is maintained from T7 to T8.

[0041] At time T8, the positive voltage v (t) is applied to the electromagnets 11 and 12, and a current i (t) is circulated. Current i (t) increases rapidly from zero to a peak effective value I1, which is reached at time T9, after which the voltage v applied to the electromagnets 11 and 12 (t) By periodically changing the time T 10 This is maintained until

[0042] Time T 10 Now, the current i passing through electromagnets 11 and 12 (t) is zero or negative voltage v (t) is applied to the electromagnets 11 and 12, at time T 11 The hold effective value I3 is reduced by the voltage v applied to the electromagnets 11 and 12. (t) By periodically changing the time T 12 This is maintained until

[0043] Time T 12 Now, apply zero or negative voltage v to electromagnets 11 and 12. (t) By applying a current i(t) is gradually reduced to zero. In particular, the zero current i (t) is time T 13 is reached.

[0044] At time T7, the current i (t) By making T zero, the plunger 8 is moved from the open position to the closed position under the elastic force generated by the spring 10, which remains the only force acting on the plunger 8. When the plunger 8 is close to the closed position, times T and T 13 Reactivation of electromagnets 11 and 12 between the start and end of the closed position creates a force that slows (but does not stop) the movement of plunger 8 towards the closed position. As a result, plunger 8 reaches the closed position with less velocity (kinetic energy) (and therefore less severe impact when it reaches the closed position).

[0045] Preferably, the voltage v for opening the injector 7 and for decelerating the plunger 8 is (t) and current i (t) are similar in terms of simplicity of implementation (i.e. the control unit 19 needs to store only one control profile) and provide the same effective values ​​I1, I2 and I3 that are only maintained for different times (obviously, more energy has to be supplied to the plunger 8 in the initial phase, while less energy is needed to decelerate the plunger 8 just before closing, and the effective values ​​I2 and I3 may not even be reached).

[0046] In other words, when the plunger 8 moves from the open position to the closed position, the control unit 19 controls the current i (t) is circulated through electromagnets 11 and 12.

[0047] Thus, the control unit 19 controls the current i having an opening effective value to achieve the displacement of the plunger 8 from the closed position to the open position. (t) current i having a closing effective value (preferably, but not necessarily zero) for achieving a displacement of the plunger 8 from the open position to the closed position, so as to circulate through the electromagnets 11 and 12. (t) through the electromagnets 11 and 12 and has a deceleration effective value greater than the closing effective value described above in order to decelerate the displacement of the plunger 8 from the open position to the closed position without stopping it. (t) through the electromagnets 11 and 12. Preferably, the deceleration effective value is equal to the opening effective value, and further, the deceleration effective value is cycled for a shorter time than the opening effective value is cycled.

[0048] In other words, the control unit 19 activates the electromagnets 11 and 12 such that, as the plunger 8 moves from the open position to the closed position, the electromagnets 11 and 12 generate a magnetic force that slows down the movement of the plunger 8 towards the closed position without stopping it. Preferably, the electromagnets 11 and 12 are deactivated before the moveable armature 19 reaches the closed position. Furthermore, as the plunger 8 moves from the open position to the closed position, a current i first has a peak effective value I1 and then has a hold effective value I3 less than the peak effective value I1 (with or without passing through an effective value I2, depending on the embodiment). (t) is circulated through electromagnets 11 and 12.

[0049] 4, 5, and 6 show the voltage v applied to the electromagnets 11 and 12. (t) and the current i circulating through the electromagnets 11 and 12. (t) and three corresponding patterns.

[0050] According to a preferred embodiment, the electromagnets 11 and 12 are driven by a predetermined current i (t)The current patterns (profiles) are controlled in an open loop mode by cycling the current patterns (profiles) through the respective coils 13 and 17. Self-calibration logic may be provided which estimates the actual opening and / or closing times of the injectors 7 and can make corrections (if necessary) to the pre-determined current patterns (profiles) based on the actual opening and / or closing times of the injectors 7.

[0051] According to a preferred embodiment, the two coils 13 and 16 differ from each other in that they need to generate magnetic forces of different strengths in different conditions. Thus, the two coils 13 and 17 differ from each other in terms of the number of turns and thus in shape and / or size. Similarly, the movable armatures 16 and 18 generally differ from each other in that they need to generate magnetic forces of different strengths in different conditions. Thus, the two movable armatures 16 and 18 generally differ from each other in terms of shape and / or size.

[0052] In the embodiment shown in the attached drawings, the electromagnetic actuator 6 comprises a single main electromagnet 11 (with a main fixed armature 14 arranged inside the tubular body 4 and coupled to its main movable armature 16) and a single secondary electromagnet (without a secondary fixed armature arranged inside the tubular body 4 and coupled to its secondary movable armature 18). According to other embodiments not shown, the electromagnetic actuator 6 comprises a single electromagnet 11 and two or more secondary electromagnets 12 (including up to four or five secondary electromagnets 12, or even more than five secondary electromagnets 12). According to further embodiments not shown, the electromagnetic actuator 6 comprises two (or more) main electromagnets 11 and one, two or more secondary electromagnets 12.

[0053] When multiple secondary electromagnets 12 are provided, the various secondary electromagnets 12 may have different characteristics: for example, at least one secondary electromagnet 12 generates a magnetic force that is always positive (i.e., the magnetic force always pushes the shutter 9 towards the open position of the injector 7), at least one secondary electromagnet 12 generates a magnetic force that is always negative (i.e., the magnetic force always pushes the shutter 9 towards the closed position of the injector 7), at least one secondary electromagnet 12 generates a magnetic force that is initially positive and then becomes negative, and / or at least one secondary electromagnet 12 generates a magnetic force that is initially negative and then becomes positive.

[0054] In the preferred embodiment described above, the electromagnetic injector 1 is configured to inject hydrogen, but alternatively the electromagnetic injector 1 may be configured to inject any other type of gaseous fuel, for example methane, or (typically when high injection flows are required, particularly requiring a long stroke of the plunger 8) liquid fuel or water.

[0055] The embodiments described herein may be combined with each other without departing from the scope of protection of the present invention.

[0056] The electromagnetic fuel injector 1 described above has many advantages.

[0057] Firstly, the electromagnetic fuel injector 1 described above has a low noise level and low deterioration (wear) due to the fact that the dynamics of the moving unit (i.e. the shutter 9 and the plunger 8 carrying the moving armatures 16 and 18) can be controlled with sufficient precision, in particular the bounce phenomenon that introduces a certain randomness in the amount of fuel injected is reduced.

[0058] This is achieved by the presence of a secondary electromagnet 12 (more precisely, of at least one secondary electromagnet 12), since while the magnetic force generated by the main electromagnet 11 has a strong nonlinearity, especially at the end of the opening (due to the approach of the main movable armature 16 to the main fixed armature 14 and thus the gradual zeroing of the air gap), the magnetic force generated by the secondary electromagnet 12 is much more linear (the absence of a secondary fixed armature, i.e. a secondary bottom member, prevents the introduction of a "discontinuity" in the magnetic circuit), and therefore the overall magnetic force acting on the plunger 8 (given by the sum of the magnetic forces generated by the two electromagnets 11 and 12) is fairly linear (more precisely, much more linear than in the situation without the secondary electromagnet 12), thus making it possible to control the dynamics of the movable unit with sufficient precision.

[0059] Furthermore, the above described electromagnetic fuel injector 1 is simple and cheap to manufacture as it has few easily manufacturable design differences compared to similar known electromagnetic injectors. [Explanation of symbols]

[0060] 1 Fuel Injector 2 Longitudinal axis 3. Injection nozzle 4 Support 5. Supply Channels 6 Electromagnetic Actuator 7 Injection valve 8 Plunger 9. Shutter 10 Closing spring 11 Electromagnet 12 Electromagnets 13 Main coil 14 Main fixed armature 15 Central Hall 16 Main moving armature 17 Secondary coil 18 Secondary moving armature 19 Control Unit i(t) current v (t) Voltage T time

Claims

1. An electromagnetic fuel injector (1), comprising: A tubular support (4), a spray nozzle (3) arranged at the end of said support (4); an injection valve (7) coupled to the injection nozzle (3); a plunger (8) movable between a closed position and an open position of the injector (7) to adjust the fuel flow through the injection nozzle (3); an electromagnetic actuator (6), the electromagnetic actuator (6) comprising at least one main electromagnet (11) configured to apply a force to the plunger (8) that, when activated, pushes the plunger (8) towards the open position of the injection valve (7), the electromagnetic actuator (6) comprising at least one secondary electromagnet (12); a closing spring (10) configured to urge the plunger (8) towards the closed position of the injection valve (7); the main electromagnet (11) comprises a main fixed armature (14) integrated into the support (4) and arranged inside the support (4), a main coil (13) arranged in the area of ​​the main fixed armature (14), and a main movable armature (16) arranged inside the support (4), movable and coupled to the main fixed armature (14) so ​​as to be magnetically attracted by the main fixed armature (14), integrated into the plunger (8) and magnetically coupled to the main coil (13), The secondary electromagnet (12) comprises a secondary coil (17) and a secondary movable armature (18), the secondary movable armature (18) being arranged inside the support (4), being movable, being integrated into the plunger (8) and being magnetically coupled to the secondary coil (17), Electromagnetic injector (1), characterized in that the secondary electromagnet (12) does not have a secondary fixed armature, which is integrated into the support (4), is arranged inside the support (4) and is magnetically coupled to the secondary movable armature (18) for magnetically attracting the secondary movable armature (18).

2. 2. The electromagnetic injector (1) of claim 1, wherein the secondary electromagnet (12) is configured to apply a force to the secondary movable armature (18) when activated, urging the plunger (8) towards the open position of the injection valve (7) along the entire stroke of the plunger (8) from the closed position to the open position.

3. 2. The electromagnetic injector (1) of claim 1, wherein the secondary electromagnet (12) is configured, when activated, to apply a first force to the secondary movable armature (18) along an initial portion of the stroke of the plunger (8) from the closed position to the open position, urging the plunger (8) towards the open position of the injector (7), and to apply a second force to the secondary movable armature (18) in a direction opposite to the first force and urging the plunger (8) towards the closed position of the injector (7) along a final portion of the stroke of the plunger (8) from the closed position to the open position.

4. 2. The electromagnetic injector (1) of claim 1, wherein the secondary electromagnet (12) is configured to apply a force to the secondary movable armature (18) when activated, urging the plunger (8) towards the closed position of the injection valve (7) along the entire stroke of the plunger (8) from the closed position to the open position.

5. 5. The electromagnetic injector (1) of claim 4, wherein the secondary electromagnet (12), when activated, is configured to apply zero force to the secondary movable armature (18) when the plunger (8) is in the closed position.

6. 2. An electromagnetic injector (1) according to claim 1, wherein the two coils (13, 17) of the two electromagnets (11, 12) are connected in series with each other so that the same current (i) flows through them.

7. 2. The electromagnetic injector (1) according to claim 1, wherein the secondary electromagnet (12) is configured to generate a magnetic force that pushes the plunger (8) by attracting the secondary movable armature (18) towards a position where the magnetic resistance against the secondary coil (17) is minimum.

8. 8. An electromagnetic injector (1) according to any one of claims 1 to 7, further comprising a control unit (19) configured to activate the electromagnets (11, 12) such that, when the plunger (8) moves from the open position to the closed position, the electromagnets (11, 12) generate a magnetic force that slows down the movement of the plunger (8) towards the closed position without stopping it.

9. 9. The electromagnetic injector (1) according to claim 8, wherein the control unit (19) is configured to deactivate the electromagnets (11, 12) before the movable armature (19) reaches the closed position.

10. The control unit (19) first measures the peak effective value (I １ ) and then the peak effective value (I １ Hold effective value (I ３ 9. The electromagnetic injector (1) according to claim 8, configured to circulate a current (i) having a magnitude (I) of 100 .mu.m through the electromagnets (11, 12).

11. A control unit (19) is provided, the control unit (19) comprising: to circulate through said electromagnets (11, 12) a current (i) having an opening effective value for achieving a displacement of said plunger (8) from said closed position to said open position; circulating a current (i) through said electromagnets (11, 12) having a closing effective value for achieving a displacement of said plunger (8) from said open position to said closed position; and 8. An electromagnetic injector (1) according to any one of claims 1 to 7, configured to circulate a current (i) through the electromagnets (11, 12) having a deceleration effective value greater than the closing effective value for decelerating the displacement of the plunger (8) from the open position to the closed position without stopping it.

12. Electromagnetic injector (1) according to claim 11, wherein the deceleration effective value is equal to the opening effective value.

13. 12. The electromagnetic injector (1) according to claim 11, wherein the deceleration effective value is cycled for a time that is shorter than the time that the opening effective value is cycled.

14. 8. A method for controlling an electromagnetic injector (1) according to any one of claims 1 to 7, comprising the step of activating the electromagnets (11, 12) such that, when the plunger (8) moves from the open position to the closed position, the electromagnets (11, 12) generate a magnetic force that slows down the movement of the plunger (8) towards the closed position without stopping it.

15. 15. The control method according to claim 14, wherein the electromagnets (11, 12) are deactivated before the movable armature (19) reaches the closed position.

16. When the plunger (8) moves from the open position to the closed position, the first peak effective value (I １ ) and then the peak effective value (I １ Hold effective value (I ３ 15. The method of claim 14, wherein a current (i) having a magnitude of 0.1 V is circulated through the electromagnets (11, 12).

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