Gas injector with improved actuator

Abstract

The present invention relates to a gas injector for injecting a gaseous medium, comprising a closing element (2) with a valve needle (3) which opens and closes a gas path (8) at a sealing seat (6), an actuator for actuating the closing element (2), wherein the actuator comprises a first magnetic actuator (10) and a second magnetic actuator (20), wherein the first magnetic actuator (10) has a first coil (11), a first inner pole (12) and a first armature (13) and wherein the second magnetic actuator (20) has a second coil (21), a second inner pole (22) and a second armature (23), and wherein the first magnetic actuator (10) and the second magnetic actuator (20) are arranged in series in the axial direction (XX) of the gas injector, and a control unit (100) which is configured to control the first magnetic actuator (10) and the second magnetic actuator (22).

Description

Prior ArtThe present invention relates to a gas injector for blowing a gaseous medium, having an improved actuator which comprises two magnetic actuators.Gas injectors are known from the prior art in different configurations. One problem circle in gas injectors is that, as a result of the fact that the gaseous media have a larger volume compared to injectors for liquid media. As a result, gas injectors must open larger cross sections for injection, which also results in larger strokes. Furthermore, injection pressures are often significantly lower than in the case of liquid media, so that overall there is a greater force requirement for a gas injector for the opening process against the combustion chamber pressure. This increased force requirement could be achieved, for example, by using larger magnetic actuators. However, this has the disadvantage that more magnetic materials are necessary, which makes such magnetic actuators disproportionately expensive. Furthermore, especially when used in internal combustion engines in the case of directly blowing-in gas injectors, installation space problems are frequently present because of limited installation space. As such, in particular, diameters of gas injectors are limited with regard to their size.The invention further relates to a method for operating a gas injector.Disclosure of the InventionThe gas injector according to the invention having the features of claim 1 has the advantage over the related art that the gas injector can provide a high force development for an opening process of the gas injector, wherein an installation space of the gas injector, in particular an outer diameter of the gas injector, can be kept small. As a result, it is possible that the gas injector according to the invention can also be used for direct injection in internal combustion engines without changing a geometry of a cylinder head. The gas injector according to the invention can be adapted to a wide variety of cylinder heads of a wide variety of internal combustion engines. This results in great advantages in the production of the gas injector, which can be produced as a mass-produced component. Furthermore, by means of the gas injector according to the invention, an impact of components of the gas injector can be reduced in a targeted manner both during the opening process and during the closing process. As a result, a service life of the gas injector can be significantly extended and, in particular, operating noise can also be reduced.This is achieved according to the invention in that the gas injector comprises a closing element having a valve needle which opens and closes a gas path at a sealing seat. Furthermore, the gas injector comprises an actuator for actuating the closing element. The actuator includes first and second magnetic actuators. The first magnetic actuator includes a first coil, a first inner pole, and a first armature. The second magnetic actuator includes a second coil, a second inner pole, and a second armature. The first magnetic actuator and the second magnetic actuator are arranged in series one after the other and furthermore a control unit is configured to actuate the first and second magnetic actuators. Thus, according to the invention, instead of an enlargement of one magnetic actuator, two smaller, weaker magnetic actuators are used in series, whereby the forces of the two magnetic actuators add up. The smaller magnetic actuators do not unnecessarily increase an outer diameter of the gas injector, so that installation of the gas injector into already existing cylinder heads, which can be used further by the manufacturers of the internal combustion engines without any change, can be installed. The control unit is either arranged operatively connected to the gas injector as part of a control unit or is even provided directly integrated on the gas injector.The dependent claims show preferred developments of the invention.The first magnetic actuator preferably has a first armature pin which is fixedly connected to the first armature. The first armature pin is operatively connected to the valve needle. The second magnetic actuator includes a second armature pin operatively connected to the first armature pin. Preferably, the geometric dimensions of the two anchors and of the two anchor bolts are identical.The operative connection between the first armature pin and the valve needle is preferably realized by a planar contact of abutting surfaces which are perpendicular to a central axis of the gas injector. The operative connection between the first and the second anchor bolt is likewise preferably realized by a flat contact between the two anchor bolts.In order to realize a particularly compact construction, the first and second coils of the two magnetic actuators are preferably wound on a common winding carrier. The common winding carrier is preferably of hollow cylindrical construction and has recesses for receiving the windings of the first and second coils of the two magnetic actuators.Particularly preferably, the first and second coils are wound in a tension, wherein the first and second coils each have an even number of layers, for example "n=2 or 4 or 6 or 8". Particularly preferably, the two windings of the first and second coil are designed in such a way that the wire for the windings exits again on the same axial side of a coil after termination of the winding. This can be realized, for example, in such a way that in the first coil, an odd number of layers is first wound, for example three layers, then the second coil is wound with four layers using the same wire, and the wire is then fed back to the first coil again and the remaining last layer is wound onto the first winding. This allows a beginning and an end of the wire to enter and exit the same side of the spool. This further has the advantage that only one electrical connection has to be provided.Alternatively, the terminals for the two windings of the first and second coil can also be led separately to the outside. This has the advantage that the first and second coils can be controlled separately and individually. In this way, in particular a stroke profile of the two armatures of the gas injector can be actively influenced. In particular, an energization of the first and second coils can be started and / or ended at different points in time. Alternatively, energization of the first and second coils may be started at different times and ended at a same time.As the magnetic material for the first and second magnetic actuators, a mixture of an iron-cobalt material is preferably used.Further preferably, the first and the second magnetic actuator are of equal strength.As a result, the two magnetic actuators can provide identical forces for the opening process, which then add up during the opening process.According to a further preferred embodiment of the invention, a first armature stroke of the first armature is different from a second armature stroke of the second armature. Preferably, the first armature stroke is smaller than the second armature stroke. This makes it possible to ensure that a defined stop of the first armature is always made possible during an opening process of the gas injector. If the first armature stroke is smaller than the second armature stroke, it is also ensured that the armature of the second magnetic actuator has a small residual gap from the second inner pole in all operating states. This preferably makes it possible to dispense with surface hardening of the components of the second magnetic circuit. This makes it possible to achieve a significant reduction in the cost of the second magnetic actuator.Preferably, the first armature stroke operates about 200 μm and the second armature stroke operates about 220 μm.Further preferably, a guide element is arranged between the first and second magnetic actuators, wherein the guide element guides both the first armature bolt and the second armature bolt. The guide element is preferably a hollow cylinder. The guide element is further preferably made of a non-magnetic material.Further preferably, the two armature strokes of the two magnetic actuators are provided differently in such a way that the second armature stroke of the second magnetic actuator is significantly smaller than that of the first magnetic actuator. As a result of the smaller second armature stroke, the second magnetic actuator has significantly more force and can push the first armature bolt and thus also the valve needle more strongly via the second armature bolt until the second armature strikes. At this time, the first armature stroke of the first magnetic actuator has decreased to such an extent that an opening process is also possible without further participation of the second magnetic actuator.The present invention furthermore relates to a method for operating a gas injector according to the invention. According to the method according to the invention, during an opening process of the gas injector, the control unit controls the first and / or second magnetic actuator such that the first and / or second magnetic actuator is already switched off before a respective full stroke is reached. In this way, in particular, a so-called swing-through of the valve needle during opening can be reduced, since an opening force has already been reduced before a full stroke. Further preferably, in the method according to the invention, a magnetic actuator is actively operated already during a closing process of the gas injector in order to brake the valve needle before reaching the sealing seat. As a result, an impact impulse of the valve needle into the sealing seat can be reduced, which is advantageous with regard to wear of the gas injector and the occurrence of so-called bounces, in which the gas injector opens again briefly by rebound after reaching the sealing seat. A braking force can be easily controlled via a supplied current in the first and / or second coil.The gas injector according to the invention and the method according to the invention are particularly preferably used in the case of direct injection of a fuel into an internal combustion engine.Brief Description of the DrawingsA preferred embodiment of the invention will be described in detail below with reference to the accompanying drawings. In the drawing, the following is: FIG. 1 shows a schematic sectional view of a gas injector according to a preferred exemplary embodiment of the invention, FIG. 2 is a diagram showing a comparison of the magnetic forces of a single coil, a dual coil according to the invention having the same stroke and a dual coil according to the invention having a stroke offset, FIG. 3 shows a diagram which shows a comparison of the valve needle acceleration of a single coil, a dual coil according to the invention having the same stroke and a dual coil according to the invention having a stroke offset, and FIG. 4 is a graph showing a comparison of the valve needle speed of a single coil, a dual coil according to the invention having the same stroke and a dual coil according to the invention having a stroke offset.Preferred Embodiment of the InventionReferring now to Figs. 1 to 4, a preferred embodiment of the present invention will be described in detail.As can be seen from FIG. 1, the gas injector 1 comprises a closing element 2 with a valve needle 3, the valve needle 3 having a valve disk 30, which opens and closes a gas path 8 at a sealing seat 6 for blowing a gaseous medium into a combustion chamber 7.The gas injector 1 further comprises an actuator for actuating the closing element 2.The first magnetic actuator 10 has a first coil 11, a first inner pole 12, a first armature 13, a first armature pin 14 and a first electrical connection 15.The second magnetic actuator 20 has a second coil 21, a second inner pole 22, a second armature 23, a second armature pin 24 and a second electrical connection 25.As can be seen from FIG. 1, the first magnetic actuator 10 and the second magnetic actuator 20 are arranged in series in the axial direction X-X of the gas injector. In this case, the first magnetic actuator 10 is arranged in the axial direction between the second magnetic actuator 20 and the valve needle 3.The first coil 11 and the second coil 21 are arranged on a common winding carrier 80. The winding support 80 is made of a non-magnetic material, preferably a non-magnetic, austenitic material. The common winding carrier preferably has recesses on its outer periphery for receiving the windings of the first and second coil. The common winding support 80 furthermore forms a housing part of the lubricant chamber 4.Valve needle 3 has a contact surface 31 at an end facing away from sealing seat 6. This is in contact with a contact surface 140 of the first anchor bolt 14. The two contact surfaces are oriented perpendicular to the axial direction X-X of the gas injector.Furthermore, the first armature pin 14 has a further contact surface 141 at its end facing away from the sealing seat. This contact surface 141 is in contact with a contact surface 240 of the second anchor bolt 24. These contact surfaces are also oriented perpendicular to the axial direction X-X of the gas injector.FIG. 1 shows the closed state of the gas injector. In this case, the contact surfaces 31 and 140 and the contact surfaces 141 and 240 are in direct contact with one another. Thus, the valve needle 3, the first armature pin 14 and the second armature pin 24 are operatively connected in the axial direction, but can be moved independently of one another.A biasing element, not shown, maintains the valve needle 3 in the closed state.The gas injector 1 further comprises a lubricant chamber 4 which is filled with a lubricant. In the lubricant chamber 4, the two armatures 13, 23 are arranged in particular. This reduces friction during the movement of the anchors and of the anchor bolts on corresponding guides.In the lubricant chamber 4 there is provided a guide element 9 in which both the first armature pin 14 is guided at its end facing away from the sealing seat and the second armature pin 24 is guided at its end directed toward the sealing seat. It should be noted that still further guide members may be provided. Corresponding apertures are provided in the respective components, so that the lubricant located in the lubricant chamber 4, for example an oil or the like, can be distributed over the entire lubricant chamber 4.In order to produce the mobility of the valve needle 30, a bellows 5 is also provided, which is also a wall region of the lubricant chamber 4.The first magnetic actuator 10 has a first armature stroke H 1 until the first armature 13 strikes the inner pole 12. The second magnetic actuator 20 has a second armature stroke H 2 until the second armature 23 strikes the second inner pole 22. In this exemplary embodiment, the first armature stroke H 1 and the second armature stroke H 2 are the same.It should be noted, however, that it may also be advantageous if the armature strokes are different. In particular, the second armature stroke H 2 is smaller than the first armature stroke H 1.The function of the gas injector according to the invention is as follows. Starting from the closed state of the gas injector shown in FIG. 1, a control unit 100 energizes the first magnetic actuator 10 and the second magnetic actuator 20. The control unit 100 is either arranged operatively connected to the gas injector as part of a control unit or is even provided directly integrated on the gas injector.In the exemplary embodiment shown, in which the first armature stroke H 1 is equal to the second armature stroke H 2, the two coils of the magnetic actuators 10, 20 are preferably energized simultaneously and for the same length of time. As a result, the first armature 13 and the second armature 23 simultaneously move in the axial direction in the direction of the sealing seat 6. Since the two armatures are firmly connected to the respective armature bolts 14, 24 and are in operative connection on the contact surfaces, the valve needle 3 is also moved in the axial direction, so that the gas injector 1 opens. This results in a gaseous medium being blown directly into the combustion chamber 7.When the injection is to be ended, the energization of the two coils of the two magnetic actuators 10, 20 is ended, with the result that a restoring element, not shown, resets the valve needle 3 and therefore also the two armature bolts 14, 24 back into the closed starting position shown in FIG. 1.In FIGS. 2 to 4, three diagrams of different sizes of the first and second magnetic actuators are shown in comparison with a single magnetic actuator as in the prior art. In FIGS. 2 to 4, the individual magnetic actuator with single coil is shown in dashed curves and denoted by K1.The method according to the invention for operating the gas injector 1 can now be carried out in different methods. As described in the exemplary embodiment with reference to FIG. 1, in a gas injector 1 in which the first armature stroke H 1 is equal to the second armature stroke H 2, the curves in the diagrams of FIGS. 2 to 4 are each denoted as K 2. In an exemplary embodiment in which the first armature stroke H 1 is different from the second armature stroke H 2, the reference symbol K 3 is denoted in FIGS. 2 to 4.FIG. 2 schematically shows a comparison of the magnetic force. A single coil (curve K 1) has a magnetic force of 100% at a lifting hand strike H during the opening operation. The stroke of the armature in the case of only one coil begins at approximately 500 μm and ends at the stroke stop H at approximately 20 μm. Thus, the total stroke from the closed state to the fully open state is about 480 μm. For comparison, magnetic force when two magnetic actuators with the same stroke are used is represented in FIG. 2 by the curve K 2. Since both magnetic actuators are energized simultaneously in this case, the magnetic force at the beginning of the opening process amounts to approximately 22%, whereas only 13% was present in the case of the single coil. At the stroke stop H, the curve K 2 has a value of approximately 170% and thus significantly more than in the case of the single coil.A similar graph is shown in FIG. 3 which shows a comparison of the valve needle accelerations. The curve K 1 defines the value of 100% at the stroke stop H. The curve K2 in two magnetic actuators with the same stroke has a value of 120%.In FIG. 4, a comparison of the speeds of the valve needles is shown. The curve K 1 of the single coil again defines the comparison value of 100% at the stroke stop H. The curve K2 in two magnetic actuators with the same stroke has here about 150%.In FIGS. 2 to 4, an example is also drawn by curve K 3, in which a first armature stroke of the first magnetic actuator is greater than a second armature stroke of the second magnetic actuator. The second magnetic actuator has a stroke of approximately 280 μm, starting from the starting point at 500 μm up to approximately 220 μm. In this exemplary embodiment with different armature strokes, the energization of the second magnetic actuator is limited at the stroke stop II for the second magnetic actuator. Subsequently, only the first magnetic actuator is energized, wherein the curves in FIGS. 2 and 3 show here in each case a jump in the magnetic force (FIG. 2 ) and the acceleration of the valve needle (FIG. 3 ), and FIG. 4 shows a change in slope at the speeds of the valve needle 3.As can be seen from FIGS. 2 to 4, both the configuration of the gas injector according to the invention and the method according to the invention show, in the case of gas injectors with the same armature stroke height and with different armature stroke height, overall in each case a better performance than a magnetic actuator with only one coil as in the prior art. Although an overall length of the gas injector 1 is extended by the in-series connection of the two magnetic actuators 10, 20 in comparison with a gas injector having only one magnetic actuator, the opening forces provided are significantly greater by the series connection of the two magnetic actuators 10, 20. Since a construction space length is more non-critical than an increase in a diameter, which would be necessary if only a single magnetic actuator were used in order to obtain the same performance as in the case of the series connection of two magnetic actuators, the present invention offers distinct advantages compared to an exclusive increase in size of a single magnetic actuator.The different control methods also make it possible, furthermore, for braking processes to be implemented before the respective end positions of the valve needle 3 both during the opening process and during the closing process, as a result of which a strike against the respective stops or sealing seats both during the opening process and during the closing process is reduced, as a result of which a service life of the components is significantly extended. Improved noise behavior during operation can also be achieved.

Claims

Gas injector for blowing in a gaseous medium, comprising - a closing element (2) having a valve needle (3) which opens and closes a gas path (8) at a sealing seat (6), - an actuator for actuating the closing element (2), wherein the actuator comprises a first magnetic actuator (10) and a second magnetic actuator (20), - wherein the first magnetic actuator (10) has a first coil (11), a first inner pole (12) and a first armature (13), and wherein the second magnetic actuator (20) has a second coil (21), a second inner pole (22) and a second armature (23), and - wherein the first magnetic actuator (10) and the second magnetic actuator (20) are arranged in series in the axial direction (X-X) of the gas injector, and - a control unit (100) which is configured to, activating the first magnetic actuator (10) and the second magnetic actuator (22).Gas injector according to Claim 1, wherein the first magnetic actuator (10) has a first armature pin (14) which is fixedly connected to the first armature (13) and is operatively connected to the valve needle (3), and wherein the second magnetic actuator (20) has a second armature pin (24) which is connected to the second armature (23), wherein the second armature pin (24) is operatively connected to the first armature pin (14).Gas injector according to one of the preceding claims, wherein the first coil (11) and the second coil (21) are arranged on a common winding carrier (80).The gas injector according to any one of the preceding claims, wherein the first coil (11) and the second coil (21) are wound in a train and have an even number of layers.Gas injector according to Claim 3, wherein the first coil (11) and the second coil (21) have separate windings, wherein the control unit (100) is configured to drive the first coil (11) and the second coil (21) separately.Gas injector according to one of the preceding claims, wherein a first armature stroke (H1) of the first armature (13) is greater than a second armature stroke (H2) of the second armature (23).The gas injector of claim 6, wherein the first armature stroke (H1) is about 480 μm and the second armature stroke (H2) is about 280 μm.Gas injector according to one of the preceding claims, wherein a guide element (9) is arranged in the axial direction (X-X) of the gas injector between the first magnetic actuator (10) and the second magnetic actuator (20), wherein the guide element (9) guides both the first armature pin (14) and the second armature pin (24).Method for operating a gas injector according to one of the preceding claims, wherein, during an opening process of the gas injector, the control unit (100) actuates the first magnetic actuator (10) and the second magnetic actuator (20) in such a way that the first magnetic actuator (10) and / or the second magnetic actuator (20) are switched off before a full stroke is reached.Method according to Claim 9, wherein the control unit (100) is configured to actuate the first magnetic actuator (10) and / or the second magnetic actuator (20) in such a way during a closing operation that the closing element (2) is actively braked.

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