Fuel injector

Abstract

A fuel injector 1 for gaseous fuel, extending along an axial direction (A) from a proximal side (P) to a distal side (D). The injector comprises a body 2 and uses an outward opening pintle (10,fig.1) and an armature element 15. The armature element is axially movable from a proximal position to a distal position in a distal armature movement, in which it moves the pintle into a distal pintle position, and from the distal armature position towards the proximal side in a proximal armature movement. The fuel injector further comprises at least one damper element 20 received in the injector body. The first damper element is axially movable between a proximal first-damper position and a distal first-damper position. The armature element has a primary armature surface 15.1 that is spaced from a primary first-damper surface 20.1 of the first damper element when the armature element is in the distal armature position, and that is adapted to engage the primary first-damper surface from the distal side during the proximal armature movement in order to move the first damper element from the distal first-damper position towards the proximal first-damper position in a proximal first-damper movement.

Description

Technical Field [0001 ] The invention relates to a fuel injector. Background Art

[0002] For automotive applications, hydrogen engines are considered as a promising alternative to gasoline or diesel engines since the emissions from a hydrogen engine consist mainly of water. However, using hydrogen as a fuel in a combustion engine brings about several difficulties as compared to liquid fuels like gasoline or diesel. Specifically, while liquid fuel provides a considerable damping effect, in particular due to squeeze damping, such damping is negligible for a gaseous fuel. Accordingly, when a moving part of the injector engages another part during its movement in the injection cycle, the resulting impact is much more severe than in a comparable injector for liquid fuel. Also, the mass of the moving elements is oftentimes greater than in a liquid-fuel injector, which also increases the forces acting during impact. Over time, this may lead to deformation or even failure of a component. In particular, the injector valve may lose its sealing properties due to deformations of the injector pintle or the valve seat which the pintle engages during each injection cycle. The resulting injector leakage normally necessitates the replacement of the injector.

[0003] Furthermore, as the injector is closed, a pintle moves towards and engages a valve seat. The closing movement can be initiated by the biasing force of a spring acting on the pintle. The opening movement, on the other hand is commonly initiated by an armature element that engages the pintle and that, e.g., can be moved by a magnetic force. During the closing movement, this armature element is moved by the pintle, i.e., kinetic energy is transferred to the armature element. When the pintle reaches its closed position, the armature may continue to move. It may finally collide with the injector body. While some energy is dissipated due to the impact and some kinetic energy may be transferred to the injector body, a considerable amount of kinetic energy remains with the armature element. Thus, the armature element subsequently moves towards the pintle, which may be described as a “rebound” of the armature element. When it hits the pintle, kinetic energy is transferred to the pintle, which may eventually lead to an unwanted reopening of the injector. Technical Problem

[0004] It is thus an object of the present invention to minimize the risk of unwanted re-opening of a fuel injector for gaseous fuel.

[0005] This problem is solved by a fuel injector according to claim 1. General Description of the Invention

[0006] The invention provides a fuel injector for gaseous fuel. In other words, the fuel injector is designed for an engine that is adapted for gaseous fuel. “Gaseous fuel” normally refers to a fuel that is gaseous under standard conditions, i.e., 15°C and 101,325 Pa. Specifically, the gaseous fuel may be hydrogen (H2). The fuel injector is adapted for injection, e.g., direct injection, of the gaseous fuel into a combustion chamber of a cylinder of the respective engine. However, the fuel injector could also be used for indirect injection.

[0007] The fuel injector extends along an axial direction from a proximal side to a distal side. The axial direction can correspond to an injector axis, which may be a symmetry axis of at least some parts of the fuel injector. When the fuel injector is installed to the engine, the proximal side is the side that faces away from the engine, while the distal side faces the engine. The general flow direction of the fuel is from the proximal side to the distal side. In some embodiments, the proximal side is designed to be the upper side with respect to the direction of gravity, while the distal side is the lower side.

[0008] The fuel injector comprises an injector body defining a fuel passage and having a distally disposed end portion that defines a valve seat extending around an outlet opening. The fuel passage extends through the injector body and communicates with the outlet opening, which is disposed on the distal side of the injector body. During operation, fuel is ejected from the fuel passage through the outlet opening. The end portion of the injector body at the distal side defines a valve seat that extends around the outlet opening. As a rule, the injector body comprises several components that are connected to each other. Several components or portions of the injector body may be made of metal, normally stainless steel. The fuel passage can be symmetric with respect to the abovementioned symmetry axis of the fuel injector. Usually, at least the end portion of the injector body is adapted to be inserted into a through-opening of a cylinder head, with the outlet opening being disposed near the inside of the cylinder head, i.e., near the combustion chamber.

[0009] The fuel injector further comprises an outward opening pintle received in the injector body to be axially movable between a proximal pintle position, in which it engages the valve seat to close the outlet opening, and a distal pintle position, in which it disengages from the valve seat to release the outlet opening (which is then opened, i.e. gas can flow therethrough). The pintle is normally received in the injector body so that it can slide along the axial direction. The term “outward opening” refers to a pintle that moves outward with regard to the fuel passage as it opens, i.e., towards the cylinder. In the proximal pintle position, the pintle engages the abovementioned valve seat (in a gastight manner) to prevent fuel from exiting the fuel passage. In the distal pintle position, it disengages from the valve seat, thereby opening the fuel passage via the outlet opening. The proximal pintle position can therefore be referred to as a closed position and the distal pintle position can be referred to as an open position. As a rule, the pintle is also made of metal like stainless steel.

[0010] Further, the injector comprises an armature element being axially movable from a proximal armature position to a distal armature position in a distal armature movement, in which it moves the pintle into the distal pintle position, and from the distal armature position towards the proximal side in a proximal armature movement. The armature element may be made of a single piece or of several pieces which are fixedly connected. It is movable within the injector body. As it is moved from the proximal armature position to the distal armature position, which movement is herein referred to as the distal armature movement, it moves the pintle into the distal pintle position (i.e., the open position). This includes the possibility that it permanently engages the pintle or may even be fixedly connected thereto. As it moves from the distal armature position towards the proximal side in the proximal armature movement, the pintle can move back to the proximal pintle position (i.e., the closed position). In the proximal armature movement, the armature element preferably at least moves to the proximal armature position. However, during the proximal armature movement, the armature element may also overshoot the proximal armature position, i.e., it may move further to the proximal side than from where it started at the beginning of the distal armature movement. The most proximal position of the armature element can be referred to as an overshoot position.

[0011] The injector also comprises a magnetic actuator adapted to initiate / operate the distal movement. The magnetic actuator is activatable to generate a magnetic field. This, in turn, moves the armature element from the proximal armature position towards the distal armature position, and possibly into the distal armature position. As a rule, the magnetic field magnetizes at least some components of the injector body, thereby creating magnetic attraction. Specifically, the armature element can be pulled towards the distal side. The injector body may comprise a pole piece that is designed to be magnetized and thus enhance and / or redirect the magnetic field created by the magnetic actuator. By way of example, the magnetic actuator can be a solenoid.

[0012] Furthermore, the fuel injector comprises at least one damper element received in the injector body to be axially movable, wherein a first damper element is axially movable between a proximal first-damper position and a distal first-damper position, and wherein the armature element has a primary armature surface that is spaced from a primary first-damper surface of the first damper element when the armature element is in the distal armature position, and that is adapted to engage the primary first-damper surface from the distal side during the proximal armature movement in order to move the first damper element from the distal first-damper position towards the proximal first-damper position in a proximal first-damper movement. Each damper element is received in the injector body, e.g., inside the fuel passage and / or adjacent to the fuel passage. It is axially movable and may be adapted for a guided movement parallel to the axial direction. However, it is possible that at least one damper element is adapted to move oblique to the axial direction. The first damper element may be the only damper element, and therefore the designation “first” is not to be construed in that there have to be several damper elements. It can be moved between the proximal first-damper position and the distal first-damper position. These are positions of the first damper element relative to the injector body. They may be the end positions of a range of motion of the first damper element, thereby defining a range of motion. However, in some embodiments, at least one end position may depend e.g., on the current position of another movable element, specifically the armature element. The damper element may at least partially be made of metal, e.g., stainless steel. However, it may at least partially be made of a material with a higher density, e.g. a metal or a metal compound.

[0013] The armature element has a primary armature surface, and the first damper element has a primary first-damper surface. Optionally, these surfaces may have a complementary shape in order to provide a contact over a greater surface area. During the proximal armature movement, the primary armature surface contacts the primary first-damper surface from the distal side. “During” is not to be understood in that there is a permanent contact during the entire proximal armature movement, but in that the contact occurs at some time during the proximal armature movement. One could also say that the primary armature surface contacts the primary first-damper surface at least temporarily during the proximal armature movement. Specifically, the primary armature surface is spaced from the primary first-damper surface when the armature element is in the distal armature position and the proximal armature movement leads to the contact with the primary first-damper surface. This contact could occur in various positions, e.g. between the distal armature position and the proximal armature position, in the proximal armature position, or possibly even beyond the proximal armature position, if the armature element moves further to overshoot the proximal armature position. Since the armature element is moving, the contact corresponds to an impact of the armature element on the first damper element. Accordingly, momentum and kinetic energy are transferred to the first damper element. This serves to move the first damper element from the distal first-damper position towards the proximal first-damper position in a proximal first-damper movement. In other words, the first damper element is accelerated, while the armature element is decelerated and possibly even stopped or accelerated towards the distal side. Moreover, a certain portion of the kinetic energy will be dissipated due to the impact, i.e., it will be transformed into vibrational energy and / or heat. In fact, while an impact of the armature element with the injector body would basically lead to an inversion of the proximal armature movement, the impact with the first damper element significantly reduces the speed of the armature element.

[0014] It should be noted that designations like “primary”, “secondary”, “tertiary” and “quaternary” are only used for distinction. Therefore, one embodiment may e.g. not comprise a “tertiary surface” as designated here but comprise a “quaternary surface". Also, any of these designations could be interchanged.

[0015] The further movement of the first damper element depends on the embodiment. Eventually, it will move towards the distal first-damper position in a distal first-damper movement, and the primary first-damper surface may again contact the primary armature surface, i.e., another impact may occur. This impact also leads to dissipation of energy. Also, the kinetic energy of the first damper element can be reduced in between the two impacts, e.g., due to friction or additional impacts. In any case, even if some kinetic energy that was transferred to the first damper element is finally retransferred to the armature element, the total process reduces the kinetic energy of the armature element significantly. This dissipation of kinetic energy is a main benefit of the inventive fuel injector. Accordingly, the armature element is less likely to move the pintle back into the distal pintle position before the magnetic actuator initiates another distal armature movement. An unwanted re-opening of the outlet valve, which is due to a rebound of the armature element and the pintle, is unlikely and / or insignificant. Accordingly, the inventive fuel injector works reliably, and the amount of fuel released during one injection can be determined with a high precision.

[0016] The armature element preferably comprises an armature shaft and an armature that is circumferentially disposed around the armature shaft and fixedly connected thereto. The general shape of the armature may be annular. It is also received in the injector body and is axially movable. The armature shaft can be elongate in the axial direction. The armature may be attracted by the abovementioned pole piece when the magnetic actuator is activated. The pole piece is normally circumferentially and fixedly disposed around the fuel passage. When the magnetic actuator is activated, the pole piece is magnetized, thereby magnetically attracting the armature. According to one embodiment, the armature shaft comprises a hollow sleeve portion disposed around a shaft channel, wherein the primary armature surface is disposed on the proximal side of the sleeve portion. The overall shape of the sleeve portion can be cylindrical. The abovementioned armature can be fixed to an outside of the sleeve portion. The proximal side of the sleeve portion may form the primary armature surface.

[0017] The injector body preferably comprises a guide element circumferentially disposed around the armature shaft. The overall shape of the guide element is annular, and it may protrude radially inwards from an adjacent portion of the injector body. As the name suggests, the guide element is preferably adapted to axially guide the armature shaft and thus the armature element as a whole. For assembly reasons, the guide element is usually a separately manufactured element that is connected to the rest of the injector body, e.g., by press-fitting or welding. While it may at least partially be made of metal, e.g., stainless steel, it may comprise a guide bearing that is disposed next to the armature shaft and that is made of a different material, e.g., a ceramic, a polymer or the like.

[0018] Preferably, the pintle is biased towards the proximal pintle position by a pintle spring. The pintle spring may be a coil spring circumferentially disposed around the pintle. It is normally a pressure spring that is interposed between the pintle and the injector body. It should be understood that the closing of the injector is caused by the action of the pintle spring. Also, during at least a part of the proximal armature movement, the pintle spring may act, through the pintle, on the armature element. In other words, the armature element can be biased towards the proximal armature position by the pintle spring.

[0019] While the armature element and the pintle could be fixedly connected or could even be made of a single piece, it is preferred that the armature element and the pintle are separate elements and the armature element is adapted to engage the pintle and move it distally during the distal armature movement and the pintle is adapted to engage the armature element and move it proximally during the proximal armature movement. During the injection cycle, the pintle and the armature element may be in permanent contact, or they may temporarily disengage. During the distal armature movement, the armature element pushes the pintle (normally against the force of the above-mentioned pintle spring) towards the distal pintle position. The proximal movement, on the other hand, is caused by the pintle (impelled by the pintle spring) pushing the armature element towards the proximal armature position.

[0020] One embodiment provides that the first damper element comprises a primary damper stop surface adapted to engage a primary injector-body stop surface of the injector body from the proximal side, whereby the distal first-damper position is defined. As mentioned above, the proximal first-damper movement will eventually be reversed, i.e., the first damper element will move distally. In this embodiment, the distal movement is stopped when the primary damper stop surface makes contact with the primary injector-body stop surface. Therefore, the distal first-damper position is well defined. Also, any remaining kinetic energy of the first damper element is not transferred to the armature element, which would be undesirable. Rather, such kinetic energy is at least partially dissipated or transferred to the injector body. The primary injector-body stop surface may be disposed on the abovementioned guide element.

[0021] In one embodiment, at least one damper element, preferably the first damper element, comprises a secondary damper stop surface adapted to engage a secondary injector-body stop surface of the injector body from the distal side, whereby a proximal damper position of this damper element is defined. It will be understood that the contact between the secondary damper stop surface and the secondary injector-body stop surface corresponds to another impact, which dissipates kinetic energy and may also reverse the movement of the damper element.

[0022] Preferably, at least one damper element is biased towards the distal side by an elastic damper-bias element. The damper-bias element acts directly or indirectly on the damper element. The force exerted on the damper element is directed towards the distal side. The term “elastic” means that the damper-bias element can be deformed by an external force but will return to its original shape when the external force is removed. It can therefore store energy. Depending on the characteristics of the damper-bias element, a certain portion of the energy is dissipated, i.e., it cannot be transformed back into kinetic energy. One function of the damper-bias element can be to ensure that the damper element returns to its distal damper position, e.g., in case of the first damper element, to the distal first-damper position. It may also serve to slow down a proximal damper movement of the damper element, thereby reducing the severity of an impact with another element.

[0023] According to one embodiment at least one damper-bias element is an elastomeric element. This may specifically be an elastomeric O-ring, but it could have a different shape. Elastomeric foams are also an option. One advantage of an elastomeric element is that it inherently dissipates a relatively large amount of energy, being somewhat more viscous than a conventional plastic O-ring (rather purely elastic behavior). The elastomeric element is preferably an elastomer having a hardness between 60 and 90 Shore A, preferably 75-80 Shore A. This is only an example and those skilled in the art will know how to select appropriate materials. According to another embodiment, at least one damper-bias element is a spring element. This may also be referred to as a damperbias spring. Preferably, the spring element is a coil spring made of spring steel, but other materials or designs are possible, too. As compared to an elastomeric element, the spring element dissipates less energy. A major portion (e.g., over 95%) of the kinetic energy stored in the spring element can be retrieved. In case of several damper-bias elements, all of them can be elastomeric, all of them can be spring elements, or at least one can be elastomeric and at least one can be a spring element.

[0024] According to one embodiment, at least one damper-bias element is interposed between a damper element and the injector body. “Interposed” means that the damper-bias element acts between the damper element and the injector body and creates a pair of equal but opposite forces. It may be in direct contact with the damper element and the injector body. However, there could be an additional element in between. Of course, if there is only the first damper element, the damper-bias element is interposed between the first damper element and the injector body. According to another embodiment, at least one damper-bias element is interposed between two damper elements. In this case, the damper-bias element biases one damper element towards the distal side and the other one towards the proximal side.

[0025] On the one hand, energy can be dissipated by impacts between elements like the armature element and the first damper element, or by deformation of an elastomeric element. There are other options, though. According to one embodiment, at least one damper element comprises internal cavity which is partially filled with a plurality of movable filler bodies. This may specifically be the first damper element. The internal cavity is formed within an outer shell of the damper element. This outer shell may be closed, but it could also be provided with at least one opening that is smaller than any of the filler bodies. The filler bodies are preferably made of a material with a density of at least 5 g / cm3, at least 7 g / cm3 or at least 10 g / cm3. Possible materials include, but are not limited to, metals and metal compounds. E.g., tungsten carbide is a suitable material, which has a density of about 15 g / cm3. The filler bodies may be spherical, i.e., ballshaped, but could have other shapes, even irregular, random shapes. They partially fill the cavity, with the remainder normally being filled by air or another gas like hydrogen fuel. However, it would be conceivable to fill the remainder of the cavity with a liquid. The outer shell can be rigid so that it does not significantly deform during operation of the injector, or it can be elastic / resilient. Either way, in case of an impact between the respective damper element and another element, momentum is first transferred to the shell, but from the shell also to the filler bodies. Also, collisions may occur between the filler bodies as well as between filler bodies and the shell. All of these collisions lead to a transfer of momentum and energy, but in each collision, energy is dissipated. Moreover, while the damper element may be axially guided within the injector body, the filler bodies may be able to move in a random manner. Therefore, some kinetic energy is transferred to non-axial motion, which reduces the energy for axial motion. In comparison to a solid damper element, the damper element with the filler bodies can absorb a considerably greater amount of kinetic energy.

[0026] The interaction between the first damper element and the armature element and / or the injector body, as well as the movement of the first damper element, could potentially be impaired by any misalignment of the first damper element. In order to prevent such misalignment, one embodiment provides that the injector body comprises a first ball-joint surface cooperating with a second ball-joint surface of the first damper element, wherein the second ball-joint is spherical around a center point so that the first damper element is tiltable about the center point. In other words, the second ball-joint surface represents a portion of a sphere around said center point. The center point is normally located on a symmetry axis of the fuel passage. Due to the spherical design of the second ball-joint surface, the first damper element can be tilted in any direction about the center point. Thus, any misalignment in relation to the armature element or the injector body is prevented. The term “ball-joint surface” indicates that the two surfaces cooperate in a way comparable to a ball joint. The first and second ball-joint surfaces are preferably in sliding contact with each other. The sliding contact does not have to be gas-tight or liquid-tight, but it may be close enough so that the first damper element is guided inside the injector body. While the second ball-joint surface is spherical, the first ball-joint surface is preferably cylindrical with the axial direction corresponding to the cylinder axis, thus enabling the movement of the first damper element in the axial direction. Specifically, it may correspond to the lateral surface of a circular cylinder.

[0027] In embodiments, to minimize rebound of the armature element after the contact with the first damper element, it can be advantageous if these elements have at least a similar mass. Thus, the energy transfer during the collision is maximized. According to such an embodiment, a damper-element mass of the first damper element is between 60% and 140%, preferably between 80% and 120%, more preferably between 90% and 110% of an armature-element mass of the armature element. This is however not mandatory, as the damper-bias element assists in slowing down a proximal damper movement of the damper element.

[0028] In other embodiments, it may be advantageous, though, if the damperelement mass is somewhat greater than the armature-element mass, e.g , corresponding to between 100% and 120% thereof, or 105 to 115%. When using a damper element with a higher damper-element mass, it is possible to omit the the damper-bias element. When it by the armature element, the damper element of greater mass will nevertheless continue its proximal movement.

[0029] In some embodiments, the armature element is biased by an armature spring towards the distal armature position. This embodiment is usually combined with an embodiment in which the pintle is biased by a pintle spring towards the proximal pintle position. Then, pintle spring and the armature spring act in opposite directions and can press the pintle and the armature element against each other. The action of the armature spring helps to decelerate the armature element during the proximal armature movement, but to accelerate the armature element during the distal armature movement. It also helps to maintain contact between armature element in the proximal position, such that the two are already in contact when the actuator is energized to operate the distal movement. Although reference is made to “an armature spring”, it will be understood that a plurality of armature springs could be employed. Preferably, the armature spring is a coil spring made of spring steel, but other materials or designs are possible, too. The armature spring may act against the above-mentioned pintle spring. In this case, the force of the pintle spring has to be considerably greater than that of the armature spring in order to guarantee a reliable closing of the fuel injector.

[0030] According to one embodiment, the armature spring is interposed between the armature element and the first damper element. Therefore, the armature spring transfers kinetic energy between the armature element and the first damper element. This may e.g., postpone the contact between the armature element and the first damper element during the proximal armature movement, and it may reduce the severity of the impact. Depending on various factors, this effect may be desirable or not. In some cases, a more severe impact can be advantageous to dissipate energy, while in other cases, a less severe impact may be desirable to prevent damage to the armature element and / or the first damper element. According to another embodiment, the armature spring is interposed between the armature element and the injector body, e.g. the abovementioned guide element of the injector body. Specifically, the armature spring may be interposed between the guide element and the armature. Without direct contact with the first damper element, the armature spring does not transfer energy between the armature element and the first damper element. However, it also decelerates the armature element during the proximal armature movement, thus reducing the severity of the impact between the armature element and the first damper element. It should be noted that these embodiments could be combined, with one armature spring being interposed between the armature element and the injector body and another one being interposed between the armature element and the first damper element.

[0031] The armature spring stores mechanical energy that is released in the further process and accelerates the armature towards the distal side. This could increase the risk of an unwanted re-opening of the injector. Therefore, the deformation of the armature spring should preferably be limited. According to one embodiment, an axial distance between the primary armature surface and the primary first-damper surface corresponds to less than 50%, less than 40% or less than 30% of a stroke length of the armature element. If the armature spring is interposed between the armature element and the first damper element, it can only be deformed while the armature element moves within the axial distance, i.e., before the primary armature surface hits the primary first-damper surface. The stroke length of the armature element is the axial distance between the extreme positions of the armature element. It can be the distance between the proximal armature position and the distal armature position, or between the abovementioned overshoot position and the distal armature position. In this embodiment, the armature element can only deform the armature spring over a portion of the stroke length, namely less than 50%, less than 40% or less than 30% thereof. Therefore, the amount of energy stored in the armature spring is limited.

[0032] In some embodiments, the first damper element is the only damper element and therefore could also be referred to as the damper element. In other embodiments, there is at least one additional damper element. One such embodiment provides that a second damper element is axially movable relative to the first damper element, and the first damper element has a secondary first-damper surface adapted to engage a primary second-damper surface of the second damper element from the distal side during the proximal first-damper movement in order to move the second damper element towards the proximal side in a proximal second-damper movement. In some embodiments, the secondary first-damper surface is spaced from the primary second-damper surface when the first damper element is in the distal first-damper position. In other embodiments, these surfaces may be in contact when first damper element is in the distal first-damper position. The second damper element is movable relative to the first damper element. While it is moved towards the proximal side by the contact of the two abovementioned surfaces, it at least temporarily moves independently of the first damper element. I.e., the two surfaces temporarily disengage. There may be one or several contacts between the two damper elements, each contact coinciding with dissipation of kinetic energy. These may serve to further reduce the amount of kinetic energy that may be re-transferred to the armature element.

[0033] In one embodiment, the first damper element has a tertiary first-damper surface adapted to engage a secondary second-damper surface of the second damper element from the proximal side to limit the proximal second-damper movement. In this embodiment, the secondary and tertiary first-damper surfaces define a possible range of motion of the second damper element in relation to the first damper element. As the tertiary first-damper surface engages the secondary second-damper surface, kinetic energy is transferred between the first and second damper elements. The proximal second-damper movement may be stopped and possibly reversed by this contact. If the first damper element is moving distally before the contact, its movement may be slowed. In any case, the contact leads to at least some dissipation of energy, which is beneficial.

[0034] The armature element may have a secondary armature surface adapted to engage a quaternary first-damper surface of the first damper element from the proximal side to limit the proximal first-damper movement. In this embodiment, the primary and secondary armature surfaces define a possible range of motion of the first damper element in relation to the armature element. As the secondary armature surface engages the quaternary first-damper surface, kinetic energy is transferred between the armature element and the first damper element. The proximal first-damper movement may be stopped and possibly reversed by this contact. If the armature element is moving distally before the contact, its movement may be slowed or even stopped or reversed. The contact also leads to at least some dissipation of energy.

[0035] In some embodiments, the armature element is adapted to engage the injector body when it reaches its most proximal position, like the abovementioned overshoot position. In such a case, the armature element comprises an armature stop surface that is adapted to engage the secondary injector-body stop surface from the distal side. The armature stop surface can be disposed on the armature shaft or on the armature.

[0036] Optionally, the fuel injector may comprise a third damper element that is axially movable relative to the first and second damper element, wherein the second damper element has a tertiary second-damper surface adapted to engage a primary third- damper surface of the third damper element from the distal side during the proximal second-damper movement in order to move the third damper element towards the proximal side in a proximal third-damper movement. The third damper element may be disposed proximal of the first damper element and / or the second damper element. As the tertiary second-damper surface makes contact with the primary third-damper surface during the proximal second-damper movement, kinetic energy is transferred between the second and third damper elements. The proximal second-damper movement may be slowed, stopped or reversed. On the other hand, the proximal third-damper movement is initiated by the contact. Again, energy is dissipated. The proximal third-damper movement will finally be reversed, e.g., after a contact with the injector body. This may lead to another contact between the tertiary second-damper surface and the primary third-damper surface. This impact will also reduce the total kinetic energy. All in all, the addition of the third damper element helps to reduce the chance of any significant rebound of the armature element and / or the pintle. Brief Description of the Drawings

[0037] Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a sectional view of a first embodiment of an inventive fuel injector; Fig.2A-2C are detail views of the fuel injector from fig. 1 during various stages of an injection cycle; Fig.3 is a sectional view of a second embodiment of an inventive fuel injector; Fig.4 is detail view of a third embodiment of an inventive fuel injector; Fig.5A-5F are detail views of the fuel injector from fig.4 during various stages of an injection cycle; Fig.6 is detail view of a fourth embodiment of an inventive fuel injector; Fig.7 is detail view of a fifth embodiment of an inventive fuel injector; Fig.8 is detail view of a sixth embodiment of an inventive fuel injector; Fig.9 is detail view of a seventh embodiment of an inventive fuel injector; Fig. 10 is detail view of an eighth embodiment of an inventive fuel injector; and Fig. 11 is detail view of a ninth embodiment of an inventive fuel injector. Description of Preferred Embodiments

[0038] Figs. 1 - 2C show a fuel injector 1 according to a first embodiment of the present invention. The fuel injector 1 is adapted to inject a gaseous fuel, in particular H2, into a cylinder head of a combustion engine (not shown). The fuel injector 1 is mostly symmetrical to an axial direction A. It comprises an injector body 2 that is at least partially made of stainless steel. When installed to the engine, at least an end portion 3 of the injector body 2 is inserted into a through-opening of the cylinder head. The injector body 2 defines a fuel passage 4, which extends axially from a proximal side P towards a distal side D, where it communicates with an outlet opening 5. A pintle 10 is movably received inside the injector body 2. In a closed position, which is shown in fig. 1, a pintle head 10.2, which radially protrudes from a pintle shaft 10.1, closes the outlet opening 5. Specifically, the pintle head 10.2 rests against a valve seat 3.1 that is formed by the end portion 3 around the outlet opening 5. The pintle 10 is also made of stainless steel. The pintle 10 is biased by a pintle spring 11 towards a proximal pintle position shown in fig.1 (closed injector configuration). The pintle spring 11 engages a pintle perch 10.3 that protrudes from the pintle shaft 10.1.

[0039] Proximally of the pintle 10, an armature element 15 is disposed inside the injector body 2. The armature element 15 comprises an elongate, roughly cylindrical armature shaft 16 and an annular armature 17 that circumferentially surrounds the armature shaft 16 and is fixedly connected thereto, e.g. by press-fitting or by welding. To the distal side D, the armature 17 faces a pole piece 6 which is part of the injector body 2 (fixed by welding). The pole piece 6 is magnetizable by a magnetic actuator, in this case a solenoid 7, which generates a magnetic field when it is activated / energized. By the magnetization of the pole piece 6, the armature 17 and the entire armature element 15 can be pulled towards the distal side D in a distal armature movement. Figs. 1 and 2B show the armature element 15 in a proximal armature position, in which the armature 17 and the pole piece 6 are axially spaced apart.

[0040] The armature shaft 16 comprises an elongate, hollow sleeve portion 16.1 that circumferentially surrounds a shaft channel 16.2. During operation, gaseous fuel flows through the shaft channel 16.2. The armature shaft 16 is guided by an annular guide element 8 of the injector body 2. Proximally of the guide element 8, a first damper element 20 is received in the injector body 2. The first damper element 20, which may also be made of stainless steel, has a generally annular shape and surrounds the fuel passage 4. In this variant, the first damper element 20 has an annular wall and a bottom flange. The first damper element 20 is axially movable between a distal first-damper position shown in figs. 1, 2A and 2B, and a proximal first-damper position shown in fig. 2C. The first damper element 20 comprises a primary first-damper surface 20.1 which is adapted to cooperate with a primary armature surface 15.1 that is formed on a proximal end of the armature shaft 16. [0041 ] The first damper element 20 also comprises a primary damper stop surface 20.5 which engages a primary injector-body stop surface 2.1 that is disposed on the proximal side P of the guide element 8. An armature spring 18 is interposed between the first damper element 20 and the armature element 15. It biases the first damper element 20 towards the proximal side P and the armature element 15 towards the distal side D. Since the armature shaft 16 is in contact with the pintle 10, the pintle spring 11 and the armature spring 18 act against each other and create opposing forces on the armature element 15. Furthermore, a damper-bias element 25, namely an elastomeric damper-bias O-ring 27 is interposed between the injector body 2 and the first damper element 20. It is adapted to bias the first damper element 20 towards the distal side D. The injector body 2 comprises a cylindrical first ball-joint surface 2.3 that surrounds a portion of the first damper element 20. A second ball-joint surface 20.7 of the first damper element 20 is in sliding contact with the first ball-joint surface 2.3. The second ball-joint surface 20.7 is spherical about a center point C, wherefore the first damper element 20 is tiltable about the center point C. Therefore, any misalignment with respect to the armature element 15 or the guide element 8 can be avoided. The second ball-joint surface 20.7 is arranged at the proximal side of the annular wall of the first damper element 20. The O-ring 27 is arranged around the annular wall, on the proximal side of the first damper flange.

[0042] By the contact of the primary injector-body stop surface 2.1 and the primary damper stop surface 20.5, a distal first-damper position of the first damper element 20 is defined. In a similar way, a proximal first-damper position is defined by the contact of a secondary injector-body stop surface 2.2 and the secondary damper stop surface 20.6, as is shown in fig.2C. When the solenoid 7 is activated and magnetizes the pole piece 6, the armature element 15 is pulled towards the distal armature position in a distal movement. Since the armature shaft 16 engages the pintle 10, the pintle 10 is also pushed towards the distal pintle position and the injector 1 starts to open. The armature element 15 moves further to the distal side D until the armature 17 engages the pole piece 6, thereby defining the distal armature position shown in fig. 2A.

[0043] When the solenoid 7 is deactivated, the armature 17 is no longer attracted towards the pole piece 6. Accordingly, the force of the pintle spring 11 pushes the pintle 10 towards the proximal pintle position, and accordingly, the armature element 15 is pushed towards the proximal armature position in a proximal armature movement. During the first phase of the proximal armature movement, there is no contact between the armature shaft 16 and the first damper element 20. The first damper element 20 remains in its distal first-damper position, because the force exerted by the armature spring 18 is smaller than the force exerted by the damper-bias O-ring 27. At this stage, the proximal armature movement is influenced - apart from friction forces - only by the force of the pintle spring 11 and the armature spring 18. This changes, however, when the armature element 15 reaches the proximal armature position and the primary armature surface 15.1 engages the primary first-damper surface 20.1 from the distal side D, as shown in fig.2B. Now, a portion of the kinetic energy of the armature element 15 is dissipated by the impact, while another portion is transferred to the first damper element 20, the latter being promoted by the abovementioned mass ratio.

[0044] In the further process, as the armature element 15 moves to an overshoot position shown in fig. 2C, kinetic energy is absorbed by the deformation of the O-ring 27. Due to the properties of the elastomeric material, a major portion of the energy is dissipated, i.e. it is transformed into heat or vibrational energy and therefore cannot be recovered when the O-ring 27 expands again. The O-ring 27 may be made of an elastomer having a hardness between 60 and 90 Shore A, preferably 75-80 Shore A. Elastomeric foams can also be envisaged. Since an axial distance between the primary armature surface 15.1 and the primary first-damper surface 20.1 corresponds to less than 50% of a stroke length of the armature element 15, the maximum compression of the armature spring 18 is limited and therefore also the amount of energy stored therein. In other embodiments, the axial distance could correspond to less than 40% or less than 30% of the stroke length. Also, some energy is dissipated when the secondary damper stop surface 20.6 engages the secondary injector-body stop surface 2.2. Afterwards, the O-ring 27 expands and the first damper element 20 and the armature element 15 move towards the distal side D. After some time, the armature element 15 again reaches the proximal armature position, which corresponds to the proximal pintle position in which the injector is closed. Due to the dissipated energy, the armature element 15 is unlikely to push the pintle further towards the distal pintle position. Accordingly, the fuel injector 2 can remain closed until the solenoid 7 initiates another distal armature movement.

[0045] Fig.3 shows a second embodiment of an inventive fuel injector 1, which is largely identical to the first embodiment and will insofar not be described again. However, in this embodiment, there is no armature spring, wherefore the armature element 15 is biased towards the proximal side P by the pintle 10 and the pintle spring 11 acting thereon. Also, the first damper element 20 has a simple annular disc shape without the ball-joint surface of the first embodiment.

[0046] Figs. 4 and 5A - 5F show a third embodiment of an inventive fuel injector 1. In this embodiment, the armature spring 18 is interposed between the guide element 8 of the injector body 2 and the armature 17 of the armature element 15. Again, the first damper element 20 does not comprise any ball-joint surface. Most importantly, an additional second damper element 21 is provided, which has the shape of an annular disc. It is circumferentially disposed around a portion of the first damper element 20 and is in sliding contact therewith. Its range of motion is defined by a secondary first-damper surface 20.2, which engages a primary second-damper surface 21.1 from the distal side, and a tertiary first-damper surface 20.3, which is adapted to engage a secondary second-damper surface 21.2 from the proximal side. A damper-bias element 25, in this case a damper-bias spring 26, is interposed between the second damper element 21 and the injector body 2. It biases the second damper element 21 towards the distal side D. While the primary second-damper surface 21.1 is in contact with the secondary first-damper surface 20.2, the force exerted by the damper-bias spring 26 also biases the first damper element 20 towards the distal side D.

[0047] The working principle of the fuel injector 1 from fig. 4 will now be explained with reference to figs. 5A - 5F. Fig. 5A shows the armature element 15 in the distal armature position, in which the pintle 10 is also in the distal pintle position. The armature shaft 17 is axially spaced from the first damper element 20. Accordingly, the first damper element 20 is resting on the guide element 8. As the solenoid 7 is deactivated, the pintle 10 and the armature element 15 are pushed towards the proximal side P by the pintle spring 11 against the force of the armature spring 18. After some time, the armature 15 reaches the proximal armature position shown in fig. 5B, in which the primary armature surface 15.1 engages the primary first-damper surface 20.1 from the distal side D. By the impact, some kinetic energy is dissipated, while another portion is transferred to the first and second damper elements 20, 21. The first damper element 20 begins a proximal first-damper movement and the second damper element 21 begins a proximal second-damper movement. As the armature element 15 pushes the damper elements 20, 21 towards the proximal side P, energy is stored in the armature spring 18 and the damper-bias spring 26.

[0048] The proximal first-damper movement is stopped when the secondary damper stop surface 20.6 engages the secondary injector-body stop surface 2.2 as shown in fig. 5C. By the impact, some kinetic energy is transferred to the injector body to, while another portion is dissipated. The proximal armature movement is also stopped as the armature element 15 reaches the overshoot position shown in fig. 5C. As a consequence of the impact with the injector body 2, the first damper element 20 reverses its direction of motion and begins a distal first-damper movement. Correspondingly, the armature element 15 begins its distal armature movement. However, due to its inertia, the second damper element continues its proximal second-damper movement, wherefore the primary second-damper surface 21.1 disengages from the secondary first-damper surface 20.2, which is shown in fig. 5D. It will be understood that at this stage, the damper-bias spring 26 does not exert any force on the first damper element 20. Therefore, during this phase, the first damper element 20 and the armature element 15 are slowed down by the action of the pintle spring 11.

[0049] The proximal second-damper movement is stopped when the secondary second-damper surface 21.2 engages the tertiary first-damper surface 20.3 as shown in fig. 5E. The one hand, this impact dissipates more kinetic energy. On the other hand, it reverses the proximal second-damper movement into a distal second-damper movement, wherefore the secondary second-damper surface 21.2 disengages from the tertiary first-damper surface 20.3, as shown in fig. 5F. Since the first damper element 20 is slowed by the impact with the second damper element 21 and then stopped by the contact with the guide element 8, the primary armature surface 15.1 disengages from the primary first-damper surface 20.1, which can also be seen in fig. 5F. As the first damper element 20 hits the guide element 8, more kinetic energy is dissipated. In addition, kinetic energy is dissipated when the second damper element 21 finishes its distal second-damper movement and hits the first damper element 20. Although this embodiment does not include an elastomeric O-ring but only the damper-bias spring 26, which dissipates considerably less energy, it leads to more impacts between the various elements 2, 15, 20, 21. Since each impact leads to a dissipation of energy, the kinetic energy of the armature element 15 is also effectively reduced.

[0050] Fig. 6 shows a fourth embodiment of an inventive fuel injector 1, which is mostly identical to the third embodiment. However, the damper-bias spring 26 has been removed. Accordingly, while the movement of the damper elements 20, 21 is basically the same as in the third embodiment, the impact of the secondary damper stop surface 20.6 on the secondary injector-body surface 2.2 is more severe. The same goes for the impact of the secondary second-damper surface 21.2 on the tertiary first-damper surface 20.3. Since the damper elements 20, 21 are not biased by any spring or any other damper-bias element 25, this embodiment may only work effectively if the proximal side P corresponds to an upper side with respect to the direction of gravity.

[0051] Fig. 7 shows a fifth embodiment of an inventive fuel injector 1. In this embodiment, the first and only damper element 20 has an annular disc shape similar to the second damper element 21 in the third and fourth embodiment. The range of motion of the first damper element 20 is defined by the primary armature surface 15.1 and a secondary armature surface 15.2. In fig. 7, the primary first-damper surface 20.1 engages the first armature surface 15.1 with a damper-bias spring 26 biasing the first element 20 towards the distal side D. Fig. 7 shows the armature element 15 in the proximal armature position. Like the other embodiments, the armature element 15 can move towards the proximal side into an overshoot position in which an armature stop surface 15.3 engages the secondary injector-body stop surface 2.2. At this point, the proximal armature movement is reversed into the distal armature movement, while the first damper element 20 continues its proximal first-damper movement until a quaternary first-damper surface 20.4 engages the secondary armature surface 15.2 from the distal side D. It will be understood that each impact between the first damper element 20 and the armature element 15 dissipates energy.

[0052] Fig. 8 shows a sixth embodiment of an inventive fuel injector 1, which is very similar to the first embodiment. However, this embodiment does not include the balljoint surfaces. Also, the damper-bias O-ring 27 has been replaced by a damper-bias spring 26. The first damper element 20 is shaped as a flanged ring, the ring wall hence extends axially and defines, on the distal side, the primary first-damper surface 20.1. and primary damper stop surface 20.5, and on the proximal side, the secondary damper stop surface 20.6. The ring wall laterally maintains coil spring 26. The distal flange allows radial guiding of the first damper element 20 in the injector body. The inner diameter of the ring here substantially corresponds to the inlet diameter of the injector, but could be lower or greater.

[0053] The damper-element mass of the first damper element 20 may be between 95% and 120%, or between 105% and 110% of the armature-element mass of the armature element 15. This is however only an example and other options are possible.

[0054] Fig. 9 shows a seventh embodiment of an inventive fuel injector 1, which comprises 3 damper elements 20, 21, 22. One damper-bias spring 26 is interposed between the first damper element 20 and the second damper element 21. A second damper-bias spring 26 is interposed between the second damper element 21 an a third damper element 22, while a third damper-bias spring 26 is interposed between the third damper element 22 and the injector body 2. The armature spring 18 has been omitted in this embodiment. During the proximal armature movement, as the armature element 15 moves from the proximal armature position shown in fig. 9 towards its overshoot position, it makes contact with the first damper element 20 through the primary armature surface 15.1 and the primary first-damper surface 20.1. Thus, the proximal first-damper movement is initiated. At this time, since the damper elements 20, 21, 22 are coupled via the damper-bias springs 26, the second damper element 21 and the third damper element 22 also begin to move towards the proximal side P, although considerably slower than the first damper element 20.

[0055] After some time, the first damper element 20 makes contact with the second damper element 21 via the secondary first-damper surface 20.2 and the primary second-damper surface 21.1. This leads to an acceleration of the second element 21 and a corresponding deceleration of the first damper element 20 and the armature element 15. The accelerated movement of the second damper element 21 then leads to a contact with the third damper element 22 via a tertiary second-damper surface 21.3 and a primary third-damper surface 22.1. Accordingly, the third damper element 22 is accelerated while the second damper elements 21, the first element 20 and the armature element 15 are decelerated. All the proximal movements are stopped when the secondary damper stop surface 20.6, which is disposed on the third damper element 22, engages the secondary injector-body stop surface 2.2. As the armature element 15 begins its distal armature movement, the damper elements 20, 21, 22 disengage from each other. The distal first-damper movement of the first damper element 20 is stopped when the primary damper stop surface 20.5 engages the primary injector-body stop surface 2.1. Depending on the speed of the damper elements 20, 21, 22 at this point and the characteristics of the damper-bias springs 26, the second and third damper elements 21, 22 may continue their distal movement until the second element 21 engages the first element 20 and / or until third damper elements 22 engages the second damper element 21. These additional impacts will also dissipate kinetic energy.

[0056] Fig. 10 shows an eighth embodiment of an inventive fuel injector 1, which is largely identical to the seventh embodiment. In this case, the armature spring 18 has been reintroduced. Also, the damper-bias springs 26 have been replaced by damper-bias O-rings 27. The working principle is very similar to the seventh embodiment, with one important difference being that the elastomeric O-rings 27 dissipate considerably more energy during their compression and expansion.

[0057] Fig. 11 shows a ninth embodiment of an inventive fuel injector 1, which is mostly identical to the first embodiment. One difference is that this embodiment does not include the elastomeric O-ring. Also, the first element 20 is not solid but comprises internal cavity 23. The cavity 23 is partially filled with ball-shaped filler bodies 24. While the remainder of the cavity 23 is filled with gas, the filler bodies are made of a material with a high density, e.g. tungsten carbide. They are freely movable within the cavity 23. When the armature element 15 hits the first damper element 20 during its proximal armature movement, momentum and kinetic energy are transferred to the shell around the cavity 23, but also to the filler bodies 24. Specifically, a multitude of impacts can occur among the filler bodies 24 and between the filler bodies 24 and the shell of the cavity 23. Every impact dissipates kinetic energy which is transformed into vibrational energy and heat. Also, the complex, unpredictable interactions between the filler bodies 24 give rise to non-axial movement, which also reduces the kinetic energy for the axial movement. Legend of Reference Numbers: 1 fuel injector 2 injector body 2.1 primary injector-body stop surface 2.2 secondary injector-body stop surface 2.3 first ball-joint surface 3 end portion 3.1 valve seat 4 fuel passage 5 outlet opening 6 pole piece 7 solenoid 8 guide element 10 pintle 10.1 pintle shaft 10.2 pintle head 10.3 pintle perch 11 pintle spring 15 armature element 15.1 primary armature surface 15.2 secondary armature surface 15.3 armature stop surface 16 armature shaft 16.1 sleeve portion 16.2 shaft channel 17 armature 18 armature spring 20 first damper element 20.1 primary first-damper surface 20.2 secondary first-damper surface 20.3 tertiary first-damper surface 20.4 quaternary first-damper surface 20.5 primary damper stop surface 20.6 secondary damper stop surface 20.7 second ball-joint surface 21 second damper element 21.1 primary second-damper surface 21.2 secondary second-damper surface 21.3 tertiary second-damper surface 22 third damper element 22.1 primary third-damper surface 22.2 secondary third-damper surface 23 cavity 24 filler body 25 damper-bias element 26 damper-bias spring 27 damper-bias O-ring A axial direction D distal side L axial length P proximal side S stroke length

Claims

1. A fuel injector (1) for gaseous fuel, extending along an axial direction (A) from a proximal side (P) to a distal side (D) and comprising:an injector body (2) defining a fuel passage (4) and having a distally disposed end portion (3) that defines a valve seat (3.1) extending around an outlet opening (5);an outward opening pintle (10) at least partially received in the injector body (2) to be axially movable between a proximal pintle position, in which it engages the valve seat (3.1) to close the outlet opening (5), and a distal pintle position, in which it disengages from the valve seat to release the outlet opening (5);an armature element (15) being axially movable from a proximal armature position to a distal armature position in a distal armature movement, in which it moves the pintle (10) into the distal pintle position, and from the distal armature position towards the proximal side (P) in a proximal armature movement; anda magnetic actuator (7) adapted to operate the distal armature movement, the fuel injector (1) further comprising at least one damper element (20-22) received in the injector body (2) to be axially movable, wherein a first damper element (20) is axially movable between a proximal first-damper position and a distal first-damper position, and wherein the armature element (15) has a primary armature surface (15.1) that is spaced from a primary first-damper surface (20.1) of the first damper element (20) when the armature element (15) is in the distal armature position, and that is adapted to engage the primary first-damper surface (20.1) from the distal side (D) during the proximal armature movement in order to move the first damper element (20) from the distal first-damper position towards the proximal first-damper position in a proximal first-damper movement.

2. The fuel injector according to claim 1, wherein the first damper element (20) comprises a primary damper stop surface (20.5) adapted to engage a primary injector-body stop surface (2.1) of the injector body (2) from the proximal side (P), whereby the distal first-damper position is defined.

3. The fuel injector according to any of the preceding claims, wherein at least one damper element (20-22), preferably the first damper element (20), comprises a secondary damper stop surface (20.6) adapted to engage a secondary injector-body stop surface (2.2) of the injector body (2) from the distal side (D), whereby a proximal damper position of this damper element (20-22) is defined.

4. The fuel injector according to any of the preceding claims, wherein at least one damper element (20-22) is biased towards the distal side (D) by an elastic damper-bias element (25).

5. The fuel injector according to any of the preceding claims, wherein at least one damperbias element (25) is an elastomeric element (27) or a spring element (26).

6. The fuel injector according to any of the preceding claims, wherein at least one damperbias element (25) is an elastomeric element (27) with a hardness of between 60 and 90 shore A.

7. The fuel injector according to any of the preceding claims, wherein at least one damperbias element (25) is interposed between a damper element (20-22) and the injector body (2) or between two damper elements (20-22).

8. The fuel injector according to any of the preceding claims, wherein the first damper element comprises an annular wall with a distal flange, a proximal end portion of the annular wall being slideably guided in a cylindrical section of the injector body, the elastomeric O-ring being arranged around the annular wall and between the flange and a facing body surface.

9. The fuel injector according to any of the preceding claims, wherein the injector body (2) comprises a first ball-joint surface (2.3) cooperating with a second ball-joint surface (20.7) of the first damper element (20), wherein the second ball-joint surface (20.7) is spherical around a center point (C) so that the first damper element (20) is tiltable about the center point (C).

10. The fuel injector according to claim 8 depending on claim 7, wherein the second balljoint surface (20.7) is provided on the proximal end portion of the annular wall.

11. The fuel injector according to any of the preceding claims, wherein the armature element (15) is biased by an armature spring (18) towards the distal armature position.

12. The fuel injector according to any of the preceding claims, wherein the armature spring (18) is interposed between the armature element (15) and the first damper element (20) or the injector body (2).

13. The fuel injector according to any of the preceding claims, wherein the first damper element comprises an annular wall with a distal flange, the first damper element comprises being radially guided in the injector body by the distal flange, the damper-bias element (25) being a spring element (26) that is arranged around the annular wall and between the flange and a facing body surface.

14. The fuel injector according to any of the preceding claims, wherein an armature spring (18) is interposed between the armature element (15) and the injector body (2), in particular a guide element (8).

15. The fuel injector according to any of the preceding claims, wherein an axial distance between the primary armature surface (15.1) and the primary first-damper surface (20.1) corresponds to less than 50%, less than 40% or less than 30% of a stroke length of the armature element (15).

16. The fuel injector according to any of the preceding claims, wherein the armature element (15) comprises a hollow armature shaft (16) and an armature (17) that is circumferentially disposed around the armature shaft and fixedly connected thereto, the armature shaft coming into contact with the pintle at its distal end.

17. The fuel injector according to any of the preceding claims, wherein a second damper element (21) is axially movable relative to the first damper element (20), and wherein the first damper element (20) has a secondary first-damper surface (20.2) adapted to engage a primary second-damper surface (21.1) of the second damper element (21) from the distal side (D) during the proximal first-damper movement in order to move the second damper element (21) towards the proximal side (P) in a proximal second-damper movement.

18. The fuel injector according to any of the preceding claims, wherein the first damper element (20) has a tertiary first-damper surface (20.3) adapted to engage a secondary second-damper surface (21.2) of the second damper element (21) from the proximal side (P) to limit the proximal second-damper movement.

19. The fuel injector according to any of the preceding claims, wherein the armature element (15) has a secondary armature surface (15.2) adapted to engage a quaternary first-damper surface (20.4) of the first damper element (20) from the proximal side (P) to limit the proximal first-damper movement.

Images