Gas injector with stop brake

Abstract

The present invention relates to a gas injector for injecting a gaseous medium, comprising: a magnetic actuator (2) with an armature (20), an inner pole (21) and a coil (22), a closing element (3) which opens and closes a gas path (14) at a sealing seat (5), a closed lubricant chamber (4) in which the armature (20) and a part of the closing element (3) are arranged, and a braking device (7) which is designed to brake the armature from striking the inner pole (21) by means of an opening brake (8) during an opening process and to brake the closing element (3) from striking the sealing seat (5) by means of a closing brake (9) during a closing process, wherein the braking device (7) comprises a brake piston (70) arranged in the lubricant chamber (4) and operatively connected to the closing element (3), wherein the brake piston (70) is arranged in a brake housing (71) which has a cover (72),a bottom (73) and a wall region (74), is arranged to be axially movable, wherein the opening brake (8) comprises a first damping chamber (80) on a first end face (70a) of the brake piston (70), a first control slot (81) in the wall region (74) of the brake housing (71), at least one first bore (82) connecting the first damping chamber (80) to the lubricant chamber (4), and a first valve arrangement (83) for opening and closing the first bore (82), wherein the closing brake (9) comprises a second damping chamber (90) on a second end face (70b) of the brake piston (70), a second control slot (91) in the wall region (94) of the brake housing (91), at least one second bore (92) connecting the second damping chamber (90) to the lubricant chamber (4), and a second valve arrangement (93) for opening and closing the second bore (92) includes.,

Description

Prior ArtThe present invention relates to a gas injector for blowing in a gaseous medium, in particular hydrogen or natural gas or the like, having a damping device for an opening process and a closing process of the gas injector.Gas injectors are known from the prior art in different configurations. Due to the non-lubricating properties of the gas to be injected in comparison with fuel injectors for liquid fuels, it has been proposed to provide a so-called lubricant space in which movable parts of the gas injector can be arranged and lubricated. This significantly extends a service life of the gas injector. Bellows are known for sealing the lubricant chamber with respect to the medium to be blown in. A problem with such gas injectors is that a bellows can be excited to longitudinal oscillations during an opening process and / or closing process of the gas injector. Such longitudinal oscillations additionally load the bellows during continuous operation and can lead to damage up to complete destruction of the bellows. As such, it is desirable to reduce a load on the bellows.Disclosure of the InventionThe gas injector according to the invention for blowing in a gaseous medium having the features of claim 1 has the advantage that improved protection of bellows of the gas injector is possible. In particular, a service life of a bellows of a gas injector can be significantly extended. In this case, in particular during an opening process and a closing process of the gas injector, damping of a striking of components of the gas injector is possible. During the opening process, in particular, a striking of an armature on an inner pole can be damped, and during a closing process, in particular, a striking of a valve needle on a sealing seat can be damped. Thus, according to the invention, both during the opening process and during the closing process, an excitation of oscillations of the bellows can be reduced or completely prevented.This is achieved according to the invention in that the gas injector comprises a magnetic actuator having an armature, an inner pole and a coil. Furthermore, the gas injector comprises a closing element which releases and closes a sealing seat of a gas path. Furthermore, a closed-off lubricant chamber is provided, which has a liquid lubricant, in particular oil or the like, and in which the armature is arranged. Furthermore, a restoring element is provided, which returns the closing element after an opening process into a closed starting position of the gas injector. The gas injector further comprises a bellows, which is part of a housing of the lubricant chamber, wherein a first end of the bellows is connected to the closing element. The gas injector further comprises a braking device which is configured to brake a strike of the armature on an inner pole during an opening process with an opening brake and to brake a strike of the closing element on the sealing seat during a closing process with a closing brake. The brake device comprises a brake piston arranged in the lubricant chamber, which is operatively connected to the closing element. The brake piston is arranged in a brake housing so as to be axially movable. The brake housing comprises a cover, a base and a wall region, in particular a cylindrical wall region. Furthermore, the opening brake comprises a first damping chamber on a first end face of the brake piston, a first control slot in the wall region of the brake housing, at least one first bore which connects the first damping chamber to the lubricant chamber, and a first valve arrangement for opening and closing the first bore. The closing brake comprises a second damping chamber on a second end face of the brake piston and a second control slot in the wall region of the brake housing. Furthermore, the closing brake comprises at least one second bore, which connects the second damping chamber to the lubricant chamber, and a second valve arrangement for releasing and closing the second bore. During an opening process, the second valve arrangement of the closing brake is configured to release the second bore, so that the second damping chamber is connected to the lubricant chamber and the first valve arrangement remains in a closed state. During a closing process, the first valve arrangement is configured to open the first bore, so that the first damping chamber is connected to the lubricant chamber and the second valve arrangement remains in a closed state. Thus, during an opening process of the gas injector after the brake piston has closed the first control slot, the first damping chamber is a closed chamber which provides damping during the opening process. As a result, a strike of the armature on an inner pole is damped. During a closing process, after the brake piston passes over the second control slot, the second damping chamber is provided as a closed chamber, so that a contact of the closing element with a sealing seat is damped.Due to the damping effect both during the opening process and during the closing process, further movable components, in particular a bellows on a lubricant housing of the lubricant chamber, are saved and can thus have a long service life.The dependent claims show preferred developments of the invention.Particularly preferably, the first and second valve arrangements each comprise a plate-shaped valve element, in particular a valve ring, which are each held in the closed state by means of a prestressing device. As a result of the movement of the brake piston during the opening process and during the closing process, a negative pressure is generated in each case in one of the two damping spaces, with the result that the first or second valve arrangement is preferably automatically opened, the damping effect being made possible in a slot-controlled manner. The first and second valve arrangement can thus be constructed very simply and cost-effectively. Preferably, the first and second valve arrangements are of technically identical construction.Particularly preferably, the first and second valve arrangement comprises a flap valve with a movable valve element. The movable valve element is preferably automatically reset and is preferably reset to the closed starting state by a biasing device. Preferably, the flap valve comprises a main body, in particular an annular main body, and the movable valve element is formed by a movable arm portion projecting from the main body. In the closed state, the arm region covers the first or second bore of the opening or closing brake.Preferably, the opening brake and closing brake have a plurality of bores which are each simultaneously released or closed by the first and second valve arrangements.Particularly preferably, the first and second valve arrangements are reset by means of a reset element, in particular one or more springs.Further preferably, the opening brake has a first throttle on the first damping chamber, which throttle establishes a connection between the first damping chamber and the lubricant chamber. The first and second restrictors are preferably bores.With a selection of a minimum diameter of the throttles, a damping effect during the closing process can be set exactly. According to a further preferred embodiment of the invention, the locking brake has a second throttle on the second damping chamber, which throttle connects the second damping chamber to the lubricant chamber.In order to reduce components and to improve compactness, the cover of the brake housing is preferably a guide component with a guide region for the closing element.Further preferably, the first bore of the opening brake is formed in the cover of the brake housing and the second bore is formed in the base of the brake housing. In this case, a plurality of bores are preferably provided in the cover or in the base.Particularly preferably, the closing element is a two-part closing element with a valve needle and an anchor bolt. The anchor bolt is firmly connected to the anchor. Further preferably, the brake piston is also fixed to the anchor bolt. The valve needle and the armature pin are arranged in such a way that they each lie against one another on an end face in the closed state. The valve needle is preferably connected to a bellows, which is part of the lubricant housing of the lubricant chamber.The lubricant chamber preferably contains a liquid, in particular oil, and a gas, preferably air. In this way, in particular temperature-induced changes in length of components can be compensated.Further preferred is a partial stroke for closing the first and / or second control slot about 20 to 90% of the total stroke of the armature, in particular 50 to 90% of the total stroke, further in particular 60 to 85% of the total stroke and in particular 80% of the total stroke.The flap valve is preferably made of a sheet metal material, in particular spring sheet metal. As a result, the first and second valve arrangements can be reset automatically, so that additional reset elements for the first and second valve arrangements can be dispensed with.Further preferably, the brake piston has a radial clearance with respect to the brake housing with respect to the wall region. A size of the play also has an influence on the damping behavior both during the opening process and during the closing process. Via the radial play of the brake piston, there is always an open connection between the first and second damping chambers.The brake device is further preferably arranged in a pot-shaped housing component of the lubricant chamber, which is arranged at an end of the lubricant chamber facing away from the sealing seat.Brief Description of the DrawingsPreferred embodiments 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 first exemplary embodiment of the invention in the closed state, FIG. 2 shows a schematic partial sectional view of a brake device of the gas injector of FIG. 1 in the closed state, FIG. 3 shows a valve element of the gas injector of FIG. 1, FIG. 4 shows a schematic partial sectional view of a brake device of a gas injector according to a second exemplary embodiment of the invention, and FIG. 5 shows a valve element of the gas injector of FIG. 4.Preferred Embodiments of the InventionIn the following, a gas injector 1 according to a first preferred exemplary embodiment of the invention is described in detail with reference to FIGS. 1 to 3.FIG. 1 shows the closed state of the gas injector 1. the gas injector 1 is configured to blow a gaseous medium, for example hydrogen, into a combustion chamber 13.The gas injector 1 comprises a magnetic actuator 2 which moves an outwardly opening closing element 3 from the closed state into an open state.The magnetic actuator 2 comprises an armature 20, an inner pole 21 and a coil 22.The closing element 3 is in two parts and comprises a valve needle 30, which seals at a sealing seat 5 in the closed state, and an armature pin 31. The valve needle 30 and the armature pin 31 are arranged in series and are movable independently of one another. In the closed state, a first contact region 30 aof the valve needle abuts a second contact region 31 aof the armature bolt.The gas injector 1 further comprises a restoring element 6, which is operatively connected to the valve needle 30 in order to restore this element from the open to the closed state.The gas injector 1 further comprises a main body 10 with a gas inlet 11 via which pressurized gas is supplied into the interior of the gas injector. A gas path 14 is schematically illustrated by the arrows in FIG. 1. The gas path 14 extends from the gas inlet 11 on an inner circumference of a housing sleeve 12 as far as the sealing seat 5 of the gas injector. In this case, passages and apertures for supplying the gas from the gas inlet 11 to the valve disk of the valve needle 30 are correspondingly provided in the components of the gas injector.The gas injector 1 further comprises a lubricant chamber 4 which is filled with a liquid 40 and a gas 41. The gas injector 1 is arranged in a substantially vertical arrangement, such that the gas 41, as schematically illustrated in FIG. 2, is located in an upper region of the lubricant chamber 4 in the assembled state.The lubricant space 4 is a closed hydraulic space filled with a lubricating liquid to lubricate moving parts of the gas injector 1. As can be seen from FIG. 1, in this case the armature 20 and the armature pin 31 are arranged in particular in the lubricant chamber 4. The restoring element 6 is also arranged in the lubricant chamber 4.The lubricant chamber 4 is closed off from the gas path 14. In this case, components present in the gas injector form a housing of the lubricant chamber 4. a bellows 42 is furthermore arranged at an end of the lubricant chamber 4 directed toward the combustion chamber, which bellows creates an axial movability of the closing element 30. As can be seen from FIG. 1, the bellows 42 is connected to the venil needle 30 by an end directed toward the combustion chamber 13, for example by means of a welded connection, and a second end of the bellows 42 facing away from the combustion chamber is connected to a housing component 15 of the lubricant chamber 4.The lubricant chamber 4 further comprises a damping housing 43, which is shown in FIG. 2 and is arranged at an end of the lubricant chamber 4 facing away from the combustion chamber. The damping housing 43 is substantially cup-shaped and, for example, likewise connected by means of welded connections to sleeve-like further housing components of the lubricant chamber 4.A brake device 7 is also arranged in the lubricant chamber 4. The braking device is configured to brake an opening operation of the closing element 3 and a closing operation of the closing element 3. As a result, the brake device 7 enables a reduced impact speed both during an opening operation and during a closing operation, as a result of which a service life of the gas injector can be significantly extended.The brake device 7 is arranged in the lubricant chamber 4 and comprises a brake piston 70.The brake device 7 further comprises an opening brake 8 and a closing brake 9. The bottom 73 and the wall region 74 are made of one component in the shape of a pot. The cover 72 also forms a guide element for the anchor bolt 31 with a guide region 72 a.The brake piston 70 is arranged in the brake housing 71, wherein a first damping chamber 80 is formed on a first end face 70 adirected toward the combustion chamber 13 and a second damping chamber 90 is formed on an opposite second end face 70 b.The opening brake 8 comprises the first damping chamber 80, a first control slot 81, a plurality of first bores 82 and a first valve arrangement 83. the first valve arrangement 83 comprises a valve element 84, which can be seen in detail from FIG. 3, and a biasing device 85.As can be seen from FIG. 3, the valve element 84 is a closed ring. Four bores 82 of the opening brake, which are formed in the cover 72 of the brake housing 71, are indicated in dashed lines in FIG. 3.The closing brake 9 comprises the second damping chamber 90, a second control slot 91 and a plurality of second bores 92 and a second valve arrangement 93.The second valve arrangement 93 comprises a valve element 94 and a biasing device 95. the second valve arrangement 93 is designed the same as the first valve arrangement 83. Four second bores 92 are also formed in the bottom 73 of the brake housing 71.The opening brake 8 comprises a first throttle 86 which, in this exemplary embodiment, is formed in the wall region 74 of the brake housing 71. The first throttle 86 connects the first damping chamber 80 to the lubricant chamber 4.The closing brake 9 further comprises a second throttle 96, which is formed in the floor 73 in this exemplary embodiment. The second throttle 96 connects the second damping chamber 90 to the lubricant chamber 4.Thus, the first embodiment has a slot-controlled opening brake 8 and a slot-controlled closing brake 9. During the opening process of the gas injector, the armature 20 is moved in the direction of the inner pole 21, as a result of which the armature pin 31 moves the brake piston 70 along. As a result, a negative pressure arises in the second damping chamber 90, so that the second valve arrangement 93 opens against the prestressing force of the prestressing device 95. Fluid is displaced from the first damping chamber 80 via the first control slot 81 from the first damping chamber into the lubricant chamber 4 until the brake piston 70 covers the first control slot 81 due to its axial movement. This state is then reached shortly before the armature 20 strikes the inner pole 21. Damping of the opening process by the opening brake 8 now begins, since liquid can only escape from the first damping chamber 80 via the first throttle 86 and a gap 70 con the circumference of the brake piston 70 between the brake piston 70 and the wall region 74 of the brake housing. It should be noted in principle that the first throttle 86 can be dispensed with if the gap 70 cis formed on the outer circumference of the brake piston 70 with corresponding play with respect to the wall region 74.During the closing process, the restoring element 6 restores the closing element 3 again in the direction of the closed position shown in FIGS. 1 and 2, wherein the valve needle 30 comes into contact with the armature pin 31 and restores the armature pin and the brake piston 70 again in the direction of the closed starting position. This creates a negative pressure in the first damping chamber 80, so that the first valve arrangement 83 opens. A damping effect is then achieved as soon as the brake piston 70 travels axially over the second control slot 71 and a damping pressure is built up in the second damping chamber 90. The second valve arrangement 93 is closed and the second damping chamber 90 is only still connected to the lubricant chamber 4 via the second throttle 96 and the gap 70 con the brake piston 70 to the wall region 74. In particular, corresponding to the play and the diameter of the second throttle 96, a damping effect takes place during the closing process. Thus, an undesired hard impact of the closing element 3 in the sealing seat 5 can be prevented.Thus, both during an opening process and during a closing process, a movement speed of the closing element 3 can be reduced. This results in reduced stops of the armature 20 on the inner pole 21 during the opening process and of the closing element 3 on the sealing seat 5 during the closing process. Wear on these components is thereby significantly reduced. In addition, a load on the bellows 42 is likewise significantly reduced, since low axial oscillations are generated on the bellows 42 by reduced stop forces. Furthermore, the braking process results in reduced pressure pulsations in the liquid in the lubricant chamber 4 both during the opening process and during the closing process.During the opening process and the closing process, the brake device 7 is always located in the liquid region below the separating line between the liquid 40 and the gas 41. accordingly, a gas space in the lubricant space 4 must be dimensioned, so that in all operating states the brake device 7 is always arranged in the liquid. The gas 41 can compensate for temperature-induced volume changes of the liquid and / or of components which are arranged in the lubricant chamber 4.Alternatively, instead of the gas cushion, a volume compensation can also be made by means of a spring-loaded second bellows which is completely filled with lubricant. The second bellows filled with lubricant is then used instead of the damping housing 43.The damping effect of the opening brake 8 and the closing brake 9 can be adjusted in particular by selecting a length and a diameter of the throttles 86, 96 and / or of the gap 70c.FIGS. 4 and 5 show a gas injector 1 with a brake device 7 according to a second exemplary embodiment of the invention. Identical or functionally identical parts are denoted by the same reference numerals as in the first exemplary embodiment. In contrast to the first exemplary embodiment, in the second exemplary embodiment, the first and second valve arrangements 83, 93 are configured differently. As can be seen in particular from FIG. 5, the first valve arrangement 83 comprises a valve element 84 in the form of a closed ring which forms a main body of the first valve arrangement 83. Four movable arm portions 84a projecting radially inward from the main body as valve elements are formed, which close and open the first bores 82 of the opening brake 8. In FIG. 4, schematically, broken lines show an open state of arm portions 84a'. The first valve arrangement 83 is preferably made of spring steel. Thus, the first valve arrangement 83 has arm regions which open and close automatically as a result of pressure conditions between its front side and rear side for opening and closing the first bores 82.The second valve arrangement 93 of the closing brake 9 is designed in the same way as the first valve arrangement 83. The broken line indicates the open state of the second bores 92 with the reference symbol 94a'. Otherwise, the second exemplary embodiment corresponds to the first exemplary embodiment, so that reference can be made to the description given there.

Claims

Gas injector for blowing in a gaseous medium, comprising: - a magnetic actuator (2) having an armature (20), an inner pole (21) and a coil (22), - a closing element (3) which opens and closes a gas path (14) at a sealing seat (5), - a closed lubricant chamber (4) in which the armature (20) and a part of the closing element (3) are arranged, - a restoring element (6) which restores the closing element (3) into a closed starting position, - a bellows (42) which is a part of a housing of the lubricant chamber (4), wherein a first end of the bellows (42) is connected to the closing element (3), and - a braking device (7) which is configured, in an opening process, a stop of the armature at the inner pole (21) is braked with an opening brake (8) and in a closing process a stop of the closing element (3) at the sealing seat (5) is braked with a closing brake (9), - wherein the brake device (7) comprises a brake piston (70) arranged in the lubricant chamber (4) and operatively connected to the closing element (3), - wherein the brake piston (70) is arranged in an axially movable manner in a brake housing (71) which has a cover (72), a base (73) and a wall region (74), - wherein the opening brake (8) comprises a first damping chamber (80) at a first end face (70a) of the brake piston (70), a first control slot (81) in the wall region (74) of the brake housing (71), at least one first bore (82), which connects the first damping chamber (80) to the lubricant chamber (4) and comprises a first valve arrangement (83) for releasing and closing the first bore (82), - wherein the closing bore (9) comprises a second damping chamber (90) on a second end face (70b) of the brake piston (70), a second control slot (91) in the wall region (94) of the brake housing (91), at least one second bore (92) which connects the second damping chamber (90) to the lubricant chamber (4), and a second valve arrangement (93) for releasing and closing the second bore (92), - wherein, during an opening operation, the second valve arrangement (93) is configured to release the second bore (92), such that the second damping chamber (90) is connected to the lubricant chamber (4) and the first valve arrangement (83) is configured to close the first bore (82), and - wherein during a closing process the first valve arrangement (83) is configured to release the first bore (82), such that the first damping chamber (80) is connected to the lubricant chamber (4) and the second valve arrangement (93) is configured to close the second bore (92).Gas injector according to Claim 1, wherein the first valve arrangement (83) and the second valve arrangement (93) each comprise a plate-shaped valve element, in particular a valve ring, wherein the plate-shaped valve element is held in the closed state by means of a prestressing device (85, 95).The gas injector of claim 1, wherein the first valve assembly (83) and the second valve assembly (93) comprise a flapper valve having a movable valve element (84a, 94a).Gas injector according to Claim 3, wherein the movable valve element (84a, 94a) can be automatically reset.The gas injector of claim 4, wherein the flapper valve comprises a main body and the valve element projecting from the main body and having movable arm portions providing opening and closing of the first and second valve assemblies.Gas injector according to one of the preceding claims, wherein the first valve arrangement (83) and the second valve arrangement (93) are resettable by means of prestressing devices (85, 95).Gas injector according to one of the preceding claims, wherein the opening brake (8) comprises a first throttle (86) on the first damping chamber (80) for connecting the first damping chamber (80) to the lubricant chamber (4).Gas injector according to one of the preceding claims, wherein the closing brake (9) comprises a second throttle (96) at the second damping chamber (90) for connecting the second damping chamber (90) to the lubricant chamber (4).Gas injector according to one of the preceding claims, wherein the cover (72) of the brake housing (71) is designed as a guide component with a guide region (72a) for the closing element (3).Gas injector according to one of the preceding claims, wherein the closing element (3) is formed in two parts with a valve needle (30) and an armature pin (31).Gas injector according to one of the preceding claims, wherein a partial stroke during the opening process up to a closing of a first control slot (81) in the wall region (84) of the brake housing and / or a partial stroke for closing of a second control slot (91) in the wall region (74) of the brake housing is 20 to 90% of a total stroke of the closing element (3).

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