Electromagnetic fuel injector

Abstract

An electromagnetic fuel injector (1) has: a tubular support body (4); a spray nozzle (3) arranged at one end of the support body (4); an injection valve (7) coupled to the injection nozzle (3); a plunger (8) movable so as to adjust the fuel flow through the injection nozzle (3) between a closed position and an open position of the injection valve (7); an electromagnetic actuator (6) provided with at least one primary electromagnet (11) and at least one secondary electromagnet (12); and a closing spring (10) configured to urge the plunger (8) toward a closed position of the injection valve (7). The secondary electromagnet (12) has a secondary coil (17) and a movable secondary armature (18) arranged inside the support body (4), movable, integral with the plunger (8) and magnetically coupled to the secondary coil (17), but not a fixed secondary armature arranged inside the support body (4) and magnetically coupled to the movable secondary armature (18) so as to magnetically attract the movable secondary armature (18).

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims the priority of Italian Patent Application No. 102023000014409 filed on July 10, 2023, and Italian Patent Application No. 102024000004939 filed on March 6, 2024, the entire disclosures of which are incorporated herein by reference. Technical Field

[0003] The invention relates to an electromagnetic fuel injector.

[0004] The invention is advantageously applied to electromagnetic hydrogen injectors, to which the following description will make explicit reference, without thereby losing generality. Background Art

[0005] Typically, an electromagnetic fuel injector (as described, for example, in patent application EP1619384A2) comprises a cylindrical tubular support equipped with a central supply channel, which serves as a fuel conduit and at the rear end is provided an injection nozzle regulated by an injection valve, which is controlled by an electromagnetic actuator. The injection valve is provided with a plunger, which is moved between a closed position and an open position of the nozzle by the action of the electromagnetic actuator, overcoming the action of a closing spring that pushes the plunger towards the closed position. At the rear end of the plunger is provided a shutter head, which is designed to closely rest against the valve seat of the injection valve.

[0006] The electromagnetic actuator comprises: (at least one) coil, which is arranged externally and in a fixed position around a support body; a movable armature made of ferromagnetic material, which is rigidly connected to a plunger and movably mounted in the support body; and a fixed armature (or bottom member) made of ferromagnetic material, which is arranged inside the support body in the area of ​​the coil and is designed to magnetically attract the movable armature when the coil is energized.

[0007] When liquid fuel is injected, the presence of liquid fuel inside the support body constitutes a significant obstacle to the movement of the movable armature, effectively generating a hydraulic damping that limits the speed of movement of the movable armature; moreover, liquid fuel (as opposed to gaseous fuel) has a lubricating effect, reducing the wear of the various parts that come into contact with each other during use, and limiting the noise generated by the various parts that come into contact with each other during use. On the contrary, when gaseous fuel is injected (especially when hydrogen, which is an extremely light gas), the presence of gaseous fuel inside the support body does not constitute a significant obstacle to the movement of the movable armature, so that the movable armature moves at a high speed and violently impacts the fixed armature at the end of the opening movement. This violent impact of the movable armature on the fixed armature at the end of the opening movement causes high noise and accelerated degradation (wear); moreover, the violent impact of the movable armature on the fixed armature at the end of the opening movement also causes a significant rebound phenomenon, which introduces a certain degree of randomness in the amount of fuel injected.

[0008] In this regard, it is worth noting that hydrogen has a low density (since 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 volume of hydrogen must be injected, which requires, among other things, a large passage area for the hydrogen to pass through the injection valve (i.e., the opening through which the hydrogen must pass in order to leave the hydrogen injector must be large). In order to have a large passage area for the hydrogen to pass through the injection valve, the plunger (and therefore the movable armature) needs to have a long stroke between the closed position and the open position, which further increases the impact speed of the movable armature on the fixed armature at the end of the opening movement.

[0009] In order to limit the impact speed of the movable armature against the fixed armature at the end of the opening movement, a specific profile of the current passed through the coil of the electromagnetic actuator is currently used, and the magnetic force that attracts the movable armature towards the fixed armature should be reduced when the movable armature approaches the fixed armature; however, when the movable armature approaches the fixed armature, controlling the magnetic force that attracts the movable armature towards the fixed armature is extremely complex and relatively inaccurate because, in this position, the magnetic force that attracts the movable armature towards the fixed armature is highly non-linear (i.e., the magnetic force increases exponentially when the air gap between the movable armature and the fixed armature becomes very small).

[0010] Patent applications EP3091219A1 and EP2975256A1 describe an electromagnetic fuel injector, in which the electromagnetic actuator includes two separate and independent electromagnets, each electromagnet including a coil, a movable armature made of ferromagnetic material and magnetically coupled to the coil, and a fixed armature (or bottom member) made of ferromagnetic material and magnetically coupled to the coil and the movable armature; that is, both electromagnets are provided with their own movable armatures integral with the plunger. 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 disadvantages, ie has low noise and moderate degradation (wear) and which is simple and cheap to manufacture.

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

[0013] Preferred embodiments of the invention are shown in the claims, which form an integral part of the present description. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0015] Figure 1 is a longitudinal section of a portion of a fuel injector manufactured according to the present invention;

[0016] Figure 2 yes Figure 1 enlarged scale views of details;

[0017] Figure 3 Shown by Figure 1 The time course of the current in the electromagnetic actuator of the fuel injector and Figure 1 The time course of the position of a movable plunger of a fuel injector in; and

[0018] Figure 4 , Figure 5 and Figure 6 The time courses of the current through the electromagnetic actuator and the voltage applied to the electromagnetic actuator according to three respective embodiments are shown. DETAILED DESCRIPTION

[0019] exist Figure 1 , reference numeral 1 generally denotes an electromagnetic injector for a gaseous fuel, in particular hydrogen, which has cylindrical symmetry about a longitudinal axis 2 and can be controlled to inject hydrogen through an injection nozzle 3 which terminates directly in a combustion chamber (not shown) of a cylinder of an internal combustion engine.

[0020] The electromagnetic injector 1 comprises a support body 4 having a tubular cylindrical shape with a variable cross section along a longitudinal axis 2 , and a supply channel 5 extending over the entire length of the support body 4 to supply pressurized hydrogen to the injection nozzle 3 .

[0021] The support body 4 accommodates an electromagnetic actuator 6 and an injection valve 7 ; in use, the injection valve 7 is driven by the electromagnetic actuator 6 to adjust the hydrogen flow rate obtained through the injection nozzle 3 in the region of the injection valve 7 .

[0022] The electromagnetic actuator 6 is configured to move a movable unit axially (i.e., along the longitudinal axis 2), and the movable unit is provided with a plunger 8 having a gate 9 at the rear end. The gate 9 cooperates with the valve seat of the injection valve 7 to regulate the flow of hydrogen through the injection nozzle 3. In other words, the rear of the support body 4 has (at least one) through hole, the valve seat is defined in the through hole, and the through hole is engaged by the gate 9. Specifically, the electromagnetic actuator 6 is configured to move the gate 9 between the closed position and the open position of the injection valve 7. In addition, the electromagnetic actuator 6 is connected to a closing spring 10, which keeps the electromagnetic injector 1 normally closed, that is, pushes the gate 9 towards the closed position of the injection valve 7. In other words, usually, due to the action of the closing spring 10, the closing spring 10 pushes the plunger 8 into the closed position, and the injection valve 7 is closed. In the closed position, the gate 9 of the plunger 8 presses on the valve seat of the injection valve 7.

[0023] In the embodiment shown in the drawings, the injection valve 7 opens axially inwards and the gate 9 is preferably spherical; according to a different embodiment not shown, the injection valve 7 opens axially outwards and in this embodiment the gate 9 may be, for example, truncated-conical.

[0024] like Figure 2 As shown, the electromagnetic actuator 6 includes a main (primary) electromagnet 11 and a secondary (slave) electromagnet 12, which are controlled together (i.e., controlled by the same current): the main electromagnet 11 is configured to apply a force to the plunger 8 (when it is activated) to open the injection valve 7 (thus, opposing the elastic force generated by the closing spring 10), and similarly, the secondary electromagnet 12 is also configured to apply a force to the plunger 8 (when it is activated) to open the injection valve 7 (thus, opposing 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 to push the plunger 8 to the open position of the injection valve 7.

[0025] The main electromagnet 11 comprises a main coil 13 externally housed in a support body 4 and a fixed main armature 14 (pole or bottom member or pole piece) made of ferromagnetic material, the fixed main armature 14 being housed inside the support body 4 in a fixed position in the region of the main coil 13 and having (at least one) central hole 15 to allow the fuel to flow to the injection nozzle 3 (alternatively, the hole 15 may not be arranged in a central position); i.e., the fixed main armature 14 is inserted inside the support body 4 and is integral with the support body 4 (usually, it is welded to the support body 4). Furthermore, the main electromagnet 11 includes a movable main armature 16, which is arranged inside the support body 4, is integral with the plunger 8 (i.e., it is part of the movable unit) and is therefore axially movable, is arranged near the fixed main armature 14, i.e., it is magnetically coupled to the fixed main armature 14 (and therefore faces the fixed main armature 14 to be close to the fixed main armature 14), and is magnetically attracted by the fixed main armature 14 (when the coil 13 is energized); i.e., the main movable armature 16 is magnetically coupled with the main coil 13 when the magnetic flux generated by the main coil 13 passes through it. In other words, the main electromagnet 11 is configured to generate a magnetic force that pushes the plunger 8 (integrated with the movable main armature 16) to the open position, mainly due to the magnetic attraction force generated between the movable main armature 16 and the fixed main armature 14.

[0026] The secondary electromagnet 12 comprises a secondary coil 17 housed outside the support 4, but does not comprise any fixed secondary armature (pole or bottom member or pole piece) made of ferromagnetic material, which is housed inside the support 4 in a fixed position in the region of the secondary coil 16. In addition, the secondary electromagnet 12 comprises a movable secondary armature 18, which is integral with the plunger 8 (i.e. it is part of the movable unit) and is therefore axially movable, which is arranged in the region of the secondary coil 17 and is magnetically attracted (when the secondary coil 17 is energized) towards a position of minimum magnetic resistance relative to the secondary coil 17; i.e. the movable secondary armature 18 is magnetically coupled to the secondary coil 17 when the magnetic flux generated by the secondary coil 17 passes through it. In other words, the secondary electromagnet 12 is configured to generate a magnetic force that pushes the plunger 8 (integral with the movable primary armature 16) towards the open position, mainly due to the force that attracts the movable secondary armature 18 towards the position of minimum magnetic resistance relative to the secondary coil 17.

[0027] In summary, the secondary electromagnet 12 does not have its own fixed secondary armature that is magnetically coupled to the movable secondary armature 18 (and therefore faces the movable secondary armature to be close to the movable secondary armature).

[0028] According to a preferred embodiment, the movable secondary armature 18 is constructed (i.e., shaped and positioned) so that throughout the entire stroke performed by the movable secondary armature 18 (which is integral with the plunger 8 and a part of the movable unit) between the closed position and the open position of the injection valve 7, the secondary electromagnet 12 always and exclusively generates a force that pushes the plunger 8 toward the open position of the injection valve 7; in other words, in this embodiment, the magnetic force generated by the secondary electromagnet 12 has the same direction throughout the entire stroke performed by the movable secondary armature 18 between the closed position and the open position of the injection valve 7.

[0029] According to different embodiments, the movable secondary armature 18 is constructed (i.e., shaped and positioned) so that along an initial portion of a stroke performed by the movable secondary armature 18 (which is integral with the plunger 8 and a portion of the movable unit) between the closed position and the open position of the injection valve 7, the secondary electromagnet 12 generates a force that pushes the plunger 8 toward the open position of the injection valve 7, while along a final portion of a stroke performed by the movable secondary armature 18 (which is integral with the plunger 8 and a portion of the movable unit) between the closed position and the open position of the injection valve 7, the secondary electromagnet 12 generates a force that pushes the plunger 8 toward the closed position of the injection valve 7; in other words, in this embodiment, the magnetic force generated by the secondary electromagnet 12 reverses its direction along the stroke performed by the movable secondary armature 18 between the closed position and the open position of the injection valve 7: initially (when the movable secondary armature 18 approaches the closed position) the magnetic force generated by the secondary electromagnet 12 pushes toward the open position, while at the end (when the movable secondary armature 18 approaches the open position), the magnetic force generated by the secondary electromagnet 12 pushes toward the closed position. However, such an embodiment, in which the magnetic force generated by the secondary electromagnet 12 reverses along the travel of the plunger 8 from the closed position to the open position, is generally avoided because it makes the position of the control plunger 8 unstable and therefore difficult to execute accurately.

[0030] According to another embodiment, the movable secondary armature 18 is constructed (i.e., shaped and positioned) so that throughout the stroke performed by the movable secondary armature 18 (which is integral with the plunger 8 and a part of the movable unit) between the closed position and the open position of the injection valve 7, the secondary electromagnet 12 always exclusively generates a force that pushes the plunger 8 toward the closed position of the injection valve 7, and thus always increases 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 stroke performed by the movable secondary armature 18 between the closed position and the open position of the injection valve 7, which direction is consistent with the closing force generated by the spring 10 and inconsistent with the magnetic force generated by the main electromagnet 11. Preferably, in this embodiment, when the injection valve 8 (i.e., the plunger 8) is in the closed position, the magnetic force generated by the secondary electromagnet 12 is zero, and when the injection valve 8 (i.e., the plunger 8) moves from the closed position to the open position, the magnetic force generated by the secondary electromagnet 12 increases (starting from zero).

[0031] The electromagnetic injector 1 comprises (is connected to) a control unit 19 (schematically shown in Figure 1 ), which supplies power to the two coils 13, 17 of the two electromagnets 11, 12 by applying a voltage v(t) that generates a current i(t) circulation to the series connection of the two coils 13, 17. Specifically, the two coils 13, 17 of the two electromagnets 11, 12 are connected in series with each other, and therefore, the same current flows through them. In other words, the electromagnets 11 and 12 are controlled by the same current.

[0032] In use, when the electromagnets 11, 12 are de-energized, the movable main armature 16 is not acted upon by any magnetic source force and is therefore only acted upon by the elastic force generated by the closing spring 10, which pushes the movable main armature 16 together with the plunger 8 to the closed position (i.e., downward), and in this case, the injection valve 7 is closed; the “end stop” of the closed position is established by the contact of the gate 9 against the valve seat of the injection valve 7 (or, more generally, by the contact of an element of the movable unit against a fixed element integral with the support body 4, i.e., the “end stop” of the closed position can be established independently of the contact of the gate 9 against the valve seat of the injection valve 7).

[0033] In use, in order to open the injection valve 7, both electromagnets 11, 12 are activated (i.e. both coils 13, 17 are energized), so that the two electromagnets 11, 12 generate a magnetic force that pushes the plunger 8 (i.e. the two movable armatures 16, 18) to the open position, overcoming the elastic force of the closing spring 10; as a result, the plunger 8 (i.e. the two movable armatures 16, 18) moves towards the open position, causing the injection valve 7 to gradually open. The (complete) open position of the injection valve 7 is reached when the movable main armature 16 abuts against the fixed main armature 14, because the "end stop" of the open position is established by the contact of the movable main armature 16 against the fixed main armature 14 (or, more generally, by the contact of an element of the movable unit against a fixed element integral with the support body 4). That is, at the end of the opening step, the movable main armature 16 ends its stroke against the fixed main armature 14.

[0034] Typically, once the movable main armature 16 has come into contact with the fixed main armature 14, to keep the injection valve 7 open, a lower intensity current i(t) is supplied to the coils 13, 17 of the electromagnets 11, 12, since the reduced magnetic force is sufficient to maintain the open position.

[0035] In use, to close the injection valve 7, the electromagnets 11, 12 are disconnected so that the plunger 8 (no longer subject to any magnetic source force) is pushed towards the closed position (ie downwards) by the spring force generated by the closing spring 10.

[0036] According to a possible embodiment, the electromagnets 11 , 12 remain open during the entire closing step.

[0037] According to an alternative embodiment, when the gate 9 approaches the valve seat of the injection valve 7 (at the end of the closing step), the electromagnets 11, 12 are briefly activated (reactivated) (i.e., the coils 13, 17 are energized) so that the electromagnets 11, 12 generate a magnetic force that pushes the plunger 8 toward the open position, thereby slowing down the movement of the plunger 8 toward the closed position. It is worth noting that the magnetic force generated by the electromagnets 11, 12 at the end of the closing step cannot (i.e., it is not sufficient) to prevent or reverse the movement of the plunger 8 toward the closed position, and only has the effect of slowing down (braking) the movement of the plunger 8 toward the closed position. Therefore, at the end of the closing step, when the gate 9 hits the valve seat of the injection valve 7, the movable main armature 16 ends its travel (the "end stop" of the closed position is established by the contact of the gate 9 against the valve seat of the injection valve 7), which hits at a relatively low speed due to the deceleration (braking) effect applied by the electromagnets 11, 12.

[0038] According to a preferred embodiment, the electromagnets 11, 12 are deactivated before the plunger 8 reaches the closed position, also taking into account electrical, magnetic and mechanical inertia (ie the magnetic force generated by the electromagnets 11, 12 is not immediately zero when they are deactivated).

[0039] Figure 3 An example of an opening and closing cycle of a fuel injector 1 starting from a closed position is shown: at time T0, a positive voltage v(t) is applied to cause a current i(t) to circulate in the electromagnets 11, 12, the current i(t) rapidly increases from a zero value to a peak effective value I1, the peak effective value I1 is reached from time T1, and is maintained until time T2 by cycling the voltage v(t) applied to the electromagnets 11, 12 between positive and zero values, so that the current i(t) is maintained within a range centered around the peak effective value I1.

[0040] At time T2, the current i(t) through the electromagnets 11, 12 decreases until, at time T3, it reaches a maintaining effective value I2 (i.e., a value less than the peak effective value I1) by applying a zero or negative voltage v(t) to the electromagnets 11, 12; the maintaining effective value I2 is maintained until time T4 by cycling the voltage v(t) applied to the electromagnets 11, 12.

[0041] At time T4, the current i(t) through the electromagnets 11, 12 decreases until, at time T5, it reaches a maintaining effective value I3 (i.e., a value less than the maintaining effective value I2) by applying a zero or negative voltage v(t) to the electromagnets 11, 12; the maintaining effective value I3 is maintained until time T6 by cycling the voltage v(t) applied to the electromagnets 11, 12.

[0042] The current i(t) circulating through the electromagnets 11, 12 generates a magnetic force that attracts the plunger 8 toward the open position, overcoming the elastic force generated by the spring 10; then, between time T0 and time T4, the plunger 8 moves from the closed position to the open position. After the plunger 8 has begun to move, the lower force is sufficient to continue the travel of the plunger 8, and in particular to maintain the plunger 8 in the open position, and therefore the current i(t) can be reduced from the initial peak effective value I1 to the maintaining effective value I2, I3.

[0043] At time T6, by applying zero voltage or negative voltage v(t) to the electromagnets 11, 12, the current i(t) gradually becomes zero; in particular, zero current i(t) is reached at time T7 and maintained from time T7 to time T8.

[0044] At time T8, a positive voltage v(t) is applied to circulate a current i(t) through the electromagnets 11 and 12, and the current i(t) increases rapidly from a zero value to a peak effective value I1, which is reached from time T9 and maintained by cyclically applying the voltage v(t) to the electromagnets 11, 12 until time T 10 .

[0045] At time T 10 , the current i(t) through the electromagnets 11, 12 decreases until at time T 11 , by applying a zero voltage or a negative voltage v(t) to the electromagnets 11 and 12, the effective value I3 is maintained; by cyclically applying the voltage v(t) to the electromagnets 11 and 12, the effective value I3 is maintained until the time T 12 .

[0046] At time T 12 , by applying zero voltage or negative voltage v(t) to the electromagnets 11 and 12, the current i(t) gradually becomes zero; specifically, at time T 13 reaches zero current i(t).

[0047] The return of the current i(t) to zero at time T7 causes the plunger 8 to move from the open position to the closed position under the action of the elastic force generated by the spring 10 (which is still the only force acting on the plunger 8); when the plunger 8 approaches (gets close to) the closed position, the electromagnets 11 and 12 are in contact with each other at times T8 and T9. 13 The reactivation between the two generates a force which slows down (but does not stop) the movement of the plunger 8 towards the closed position, so that the plunger 8 reaches the closed position at a relatively moderate speed (kinetic energy) (and therefore has a less violent impact when reaching the closed position).

[0048] Preferably, the patterns of voltage v(t) and current i(t) for opening the injection valve 7 and for decelerating the plunger 8 are similar in terms of simplicity of implementation (i.e. the control unit 19 only needs to store a single control profile) and provide the same effective values ​​I1, I2 and I3, which are maintained for different time intervals (obviously, in the initial phase, more energy needs to be supplied to the plunger 8, while just before closing less energy is needed to decelerate the plunger 8 and even the effective values ​​I2, I3 may not be reached).

[0049] In other words, when the plunger 8 moves from the open position to the closed position, the control unit 19 is configured to circulate a current i(t) through the electromagnets 11 , 12 that initially has a peak effective value I1 and subsequently has a maintaining effective value I3 that is lower than the peak effective value I1.

[0050] Therefore, the control unit 19 is configured to circulate a current i(t) having an effective opening value through the electromagnets 11, 12 to achieve the displacement of the plunger 8 from the closed position to the open position; and the control unit 19 is configured to circulate a current i(t) having an effective closing value (preferably, but not necessarily zero) through the electromagnets 11, 12 to achieve the displacement of the plunger 8 from the open position to the closed position; and the control unit 19 is configured to circulate a current i(t) having an effective deceleration value greater than the effective closing value through the electromagnets 11, 12 to slow down the displacement of the plunger 8 from the open position to the closed position without stopping it. Preferably, the effective deceleration value is equal to the effective opening value; in addition, the time interval of the effective deceleration value cycle is shorter than the time interval of the effective opening value cycle.

[0051] In other words, when the plunger 8 moves from the open position to the closed position, the control unit 19 activates the electromagnets 11, 12 so that the electromagnets 11, 12 generate a magnetic force that slows down the movement of the plunger 8 toward the closed position without stopping it. Preferably, the electromagnets 11, 12 are deactivated before the movable armature 19 reaches the closed position. In addition, when the plunger 8 moves from the open position to the closed position, a current i(t) initially having a peak effective value I1 and subsequently having a maintaining effective value I3 lower than the peak effective value I1 (with or without an effective value I2, according to different embodiments) circulates through the electromagnets 11, 12.

[0052] Figure 4 , Figure 5 and Figure 6 Three different possible patterns of the voltage v(t) applied to the electromagnets 11 , 12 and three corresponding patterns of the current i(t) circulating through the electromagnets 11 , 12 are shown.

[0053] According to a preferred embodiment, the electromagnets 11, 12 are controlled in open-loop mode by circulating a predetermined current i(t) pattern (profile) in the respective coils 13, 17; a self-calibration logic may be provided, which estimates the actual opening and / or closing moment of the injection valve 7 and, based on the actual opening and / or closing moment of the injection valve 7, the predetermined current pattern (profile) may be corrected (if necessary).

[0054] According to a preferred embodiment, the two coils 13, 16 differ from each other in that they must generate magnetic forces of different strengths and under different conditions; therefore, the two coils 13, 17 generally differ from each other in the number of turns and therefore in shape and / or size. Similarly, the movable armatures 16, 18 also differ from each other because they must generate magnetic forces of different strengths and under different conditions; therefore, the two movable armatures 16, 18 generally differ from each other in shape and / or size.

[0055] In the embodiment shown in the drawings, the electromagnetic actuator 6 comprises a single main electromagnet 11 (provided with a fixed main armature 14 arranged inside the tubular body 4 and coupled to its movable main armature 16) and a single secondary electromagnet 12 (without a fixed secondary armature arranged inside the tubular body 4 and coupled to a movable secondary armature 18). According to other embodiments not shown, the electromagnetic actuator 6 comprises a single main 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 another embodiment not shown, the electromagnetic actuator 6 comprises two (or more) main electromagnets 11 and one, two or more secondary electromagnets 12.

[0056] Where a plurality of sub-electromagnets 12 are provided, the various sub-electromagnets 12 may have different characteristics: for example, at least one sub-electromagnet 12 generates a magnetic force that is constantly positive (i.e., it constantly pushes the gate 9 toward the open position of the injection valve 7), at least one sub-electromagnet 12 generates a magnetic force that is constantly negative (i.e., it constantly pushes the gate 9 toward the closed position of the injection valve 7), at least one sub-electromagnet 12 generates a magnetic force that is initially positive and then negative, and / or at least one sub-electromagnet 12 generates a magnetic force that is initially negative and then positive.

[0057] In the above preferred embodiment, the electromagnetic injector 1 is configured to inject hydrogen, but alternatively, the electromagnetic injector 1 can be configured to inject any other type of gaseous fuel, such as methane, or it can also be configured to inject liquid fuel or water (usually, when a high injection flow rate is required, a particularly long plunger 8 stroke is required).

[0058] The embodiments described herein may be combined with each other without departing from the scope of protection of the present invention.

[0059] The electromagnetic fuel injector 1 described above has many advantages.

[0060] Firstly, the electromagnetic fuel injector 1 described above has low noise and moderate degradation (wear) due to the ability to control with sufficient precision the dynamics of the movable unit, i.e. the plunger 8 carrying the gate 9 and the movable armature 16, 18. This reduces, among other things, the rebound phenomenon which introduces a certain degree of randomness in the amount of fuel injected.

[0061] This is achieved by the presence of the secondary electromagnet 12 (or, more precisely, at least one secondary electromagnet 12), because, although the magnetic force generated by the main electromagnet 11 is highly non-linear, especially at the end of the opening (due to the approach of the movable main armature 16 to the fixed main armature 14, thereby gradually zeroing the air gap), the magnetic force generated by the secondary electromagnet 12 is more linear (the absence of a fixed secondary armature, i.e. a secondary bottom member, prevents the introduction of a "discontinuity" in the magnetic circuit), and therefore the total magnetic force acting on the plunger 8 (given by the sum of the magnetic forces generated by the two electromagnets 11, 12) is very linear (or, more precisely, much more linear than in the absence of the secondary electromagnet 12), making the dynamics of the movable unit controllable in a sufficiently precise manner.

[0062] Furthermore, the electromagnetic fuel injector 1 described above is simple and cheap to manufacture, since it has few design differences compared to similar known electromagnetic injectors which makes it easy to construct.

[0063] List of reference numerals

[0064] 1 Fuel Injector

[0065] 2 Vertical axis

[0066] 3 Spray nozzles

[0067] 4 Support

[0068] 5 Supply Channel

[0069] 6 Electromagnetic actuator

[0070] 7 Injection valve

[0071] 8 Plunger

[0072] 9. Gate

[0073] 10 Closing spring

[0074] 11 Electromagnet

[0075] 12 Electromagnet

[0076] 13 Main coil

[0077] 14 Fixed main armature

[0078] 15 Center hole

[0079] 16 Movable main armature

[0080] 17th coil

[0081] 18 Movable secondary armature

[0082] 19 Control Unit

[0083] i(t) current

[0084] v(t) voltage

[0085] T moment

Claims

1. An electromagnetic fuel injector (1), comprising: A tubular support (4); A spray nozzle (3) arranged at one end of the support body (4); an injection valve (7) connected to the injection nozzle (3); a plunger (8) movable to adjust the flow of fuel through the injection nozzle (3) between a closed position and an open position of the injection valve (7); an electromagnetic actuator (6) provided with at least one main electromagnet (11) and at least one secondary electromagnet (12), the main electromagnet (11) being configured to apply a force to the plunger (8) when it is activated, the force pushing the plunger (8) towards an open position of the injection valve (7); as well as a closing spring (10) configured to urge the plunger (8) toward a closed position of the injection valve (7); The main electromagnet (11) comprises: a fixed main armature (14) which is integrated with the support body (4) and arranged inside the support body (4); a main coil (13) which is arranged in the area of ​​the fixed main armature (14); and a movable main armature (16) which is arranged inside the support body (4) and is movable, the movable main armature (16) being connected to the fixed main armature (14) so ​​as to be magnetically attracted by the fixed main armature (14), the movable main armature (16) being integrated with the plunger (8) and magnetically coupled to the main coil (13); The secondary electromagnet (12) comprises: a secondary coil (17) and a movable secondary armature (18), wherein the movable secondary armature (18) is arranged inside the support body (4) and is movable, and the movable secondary armature (18) is integrated with the plunger (8) and is magnetically coupled to the secondary coil (17); The electromagnetic injector (1) is characterized in that the secondary electromagnet (12) has no fixed secondary armature, the fixed secondary armature is integrated with the support body (4), arranged inside the support body (4) and magnetically coupled to the movable secondary armature (18), thereby magnetically attracting the movable secondary armature (18).

2. The electromagnetic injector (1) according to claim 1, wherein: The secondary electromagnet (12) is configured to apply a force to the movable secondary armature (18) when activated, which force pushes the plunger (8) toward 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. The electromagnetic injector (1) according to claim 1, wherein: The secondary electromagnet (12) is constructed so that, when it is activated, it applies a first force and a second force to the movable secondary armature (18), the first force pushing the plunger (8) toward the open position of the injection valve (7) along an initial part of the stroke of the plunger (8) from the closed position to the open position, and the second force is opposite to the first force and pushes the plunger (8) toward the closed position of the injection valve (7) along a final part of the stroke of the plunger (8) from the closed position to the open position.

4. The electromagnetic injector (1) according to claim 1, wherein: The secondary electromagnet (12) is configured to apply a force to the movable secondary armature (18) when activated, which force pushes the plunger (8) toward 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. The electromagnetic injector (1) according to claim 4, wherein: The secondary electromagnet (12) is configured to apply zero force to the movable secondary armature (18) when it is activated when the plunger (8) is in the closed position.

6. The 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. 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) due to a force that attracts the movable secondary armature (18) towards a position of minimum magnetic resistance relative to the secondary coil (17).

8. The electromagnetic injector (1) according to any one of claims 1 to 7, wherein: A control unit (19) is provided, which is configured to activate the electromagnets (11, 12) when the plunger (8) moves from the open position to the closed position, so that the electromagnets (11, 12) generate a magnetic force that slows the movement of the plunger (8) to the closed position without stopping it.

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 electromagnetic injector (1) according to claim 8, wherein: The control unit (19) is configured to circulate a current (i) having initially a peak effective value (I1) and subsequently a holding effective value (I3) lower than the peak effective value (I1) through the electromagnets (11, 12) when the plunger (8) moves from the open position to the closed position.

11. The electromagnetic injector (1) according to any one of claims 1 to 7, wherein: A control unit (19) is provided, which is configured as follows: Circulating an electric current (i) having an effective opening value through the electromagnets (11, 12) to effect displacement of the plunger (8) from the closed position to the open position; Circulating an electric current (i) having an effective closing value through the electromagnets (11, 12) to effect displacement of the plunger (8) from the open position to the closed position; as well as A current (i) having an effective deceleration value greater than an effective closing value is circulated through the electromagnets (11, 12) to decelerate the displacement of the plunger (8) from the open position to the closed position without stopping it.

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

13. The electromagnetic injector (1) according to claim 11, wherein: The time interval of the effective deceleration value cycle is shorter than the time interval of the effective opening value cycle.

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

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

16. The control method according to claim 14, wherein: When the plunger (8) moves from the open position to the closed position, a current (i) initially having a peak effective value (I1) and subsequently having a maintaining effective value (I3) lower than the peak effective value (I1) circulates through the electromagnets (11, 12).

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