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), wherein the closing element (3) comprises a valve needle (30) and an armature bolt (31) rigidly connected to the armature (20), a sealed lubricant chamber (4) in which the armature (20) and the armature bolt (31) are arranged, a return element (6) which returns the closing element (3) to a closed initial position, a bellows (42) which is part of a housing of the lubricant chamber (4), wherein a first end of the bellows (42) is connected to the valve needle (30), and a braking device (7) which is configuredto prevent the armature (20) from striking the inner pole (21) during an opening process and to prevent the valve needle (30) from striking the sealing seat (5) during a closing process, wherein the braking device (7) comprises a brake piston (70) arranged in the lubricant chamber (4) with a through-opening (70a), wherein the armature bolt (31) is guided through the through-opening (70a), and wherein a first stop (71) and a second stop (72) are arranged on the armature bolt (31), wherein the brake piston (70) is arranged with an axial clearance (A) in the axial direction (XX) between the first stop (71) and the second stop (72).

Description

State of the art

[0001] The present invention relates to a gas injector for injecting a gaseous medium, in particular hydrogen or natural gas or the like, with a damping device for an opening process and a closing process of the gas injector.

[0002] Gas injectors are known in various designs from the prior art. Due to the non-lubricating properties of the injected gas compared to fuel injectors for liquid fuels, it has been proposed to provide a so-called lubrication chamber in which moving parts of the gas injector can be located and lubricated. This significantly extends the service life of the gas injector. Bellows are known for sealing the lubrication chamber against the injected medium. A problem with such gas injectors is that a bellows can be excited to longitudinal vibrations during the opening and / or closing of the gas injector. Such longitudinal vibrations place additional stress on the bellows during continuous operation and can lead to damage, even complete destruction of the bellows. Therefore, it is desirable to reduce the stress on the bellows. Disclosure of the invention

[0003] The gas injector according to the invention for injecting a gaseous medium, comprising the features of claim 1, has the advantage that improved protection of the gas injector's bellows is possible. In particular, the service life of a gas injector's bellows can be significantly extended. Specifically, during the opening and closing processes of the gas injector, damping of impacts between components of the gas injector is possible. During the opening process, impacts of an armature against an inner pole can be dampened, and during a closing process, impacts of a valve needle against a sealing seat can be dampened. Thus, according to the invention, vibration excitation of the bellows can be reduced or completely prevented during both the opening and closing processes.

[0004] According to the invention, this is achieved by the gas injector comprising a magnetic actuator with an armature, an inner pole, and a coil. Furthermore, the gas injector includes a two-part closing element comprising a valve needle and an armature bolt rigidly connected to the armature. The closing element opens and closes a sealing seat of a gas path. A sealed lubricant chamber is also provided, containing a liquid lubricant, in particular oil or the like, in which the armature and the armature bolt are arranged. A return element is also provided, which returns the closing element to a closed initial position of the gas injector after an opening operation. The gas injector further includes a bellows, which is part of a housing of the lubricant chamber, with a first end of the bellows being connected to the valve needle.The gas injector further comprises a braking device configured to decelerate the armature against an inner pole during an opening operation and to decelerate the closing element against the sealing seat during a closing operation. The braking device includes a brake piston with a through-hole located in the lubrication chamber. The armature bolt passes through the through-hole of the brake bolt and has a first and a second stop. The brake piston is arranged with axial play between the first and second stops.

[0005] According to the invention, a hydraulic braking device can be provided which can provide damping before impact during both the opening and closing processes of the gas injector. The brake piston, arranged with axial play between the first and second stops, forms an additional damping mass which is activated shortly before components impact the anchor bolt via the first and second stops. This leads to a reduction in the movement speed of the closing element and thus to a lower impact velocity. Consequently, the stress on the bellows can be significantly reduced during both the opening and closing processes.

[0006] The dependent claims describe preferred embodiments of the invention.

[0007] For a particularly compact and simple design, the brake device also features a cylinder with a base located in the lubrication chamber. A throttle bore is incorporated in the base, which provides additional damping of the closing movement, especially during the closing process. The brake piston is located within the cylinder.

[0008] The cylinder preferably has a cover with an opening through which the anchor bolt passes. The opening preferably serves as a guide for the anchor bolt. The cover creates a sealed cylinder that is only in fluid contact with the rest of the lubricant chamber via the throttle bore. If the cover is designed as a guide component, a separate guide for the anchor bolt may be unnecessary.

[0009] Preferably, the cover is designed as a guide disc, which in particular has openings on an outer circumference for the fluid in the lubricant chamber.

[0010] Preferably, the brake piston in the cylinder has a first radial clearance to the cylinder on an outer circumference and a second radial clearance to the anchor bolt on an inner circumference. This allows the brake piston to move freely within the cylinder, providing a damping mass during the opening and closing processes. This mass must be moved, thus providing damping and additionally displacing fluid within the cylinder, which also dampens the opening and closing movement of the gas injector's locking element.

[0011] The first radial clearance on the outer circumference of the brake piston is preferably smaller than the second radial clearance of the brake piston to the anchor bolt.

[0012] Preferably, the axial play of the brake piston, which is freely movable in the cylinder, is smaller than the armature gap between the armature and the inner pole when the gas injector is closed. The axial play of the brake piston is preferably in the range of 20% to 80%, and particularly 30% to 70%, of the armature gap.

[0013] For particularly simple and cost-effective manufacturing, the first and / or second stop of the brake device is each designed as a stop ring, which is fixed to the anchor bolt, for example by means of a welded connection.

[0014] Alternatively, the first and / or second stop can be formed as a single unit with the anchor bolt. The anchor bolt can, for example, be a turned part.

[0015] Preferably, a liquid, in particular oil, and a gas, in particular air, are present in the lubrication chamber, wherein the brake device is completely immersed in the liquid when the gas injector is installed. The gas enables compensation for temperature-related volume changes of components and / or the liquid in the lubrication chamber.

[0016] The brake device is preferably arranged in a pot-shaped housing component of the lubricant chamber, which is located at an end of the lubricant chamber facing away from the sealing seat. Brief description of the drawings

[0017] Preferred embodiments of the invention are described in detail below with reference to the accompanying drawing. The drawing shows: Fig. 1 a schematic sectional view of a gas injector according to a first embodiment of the invention in the closed state, Fig. 2 a schematic partial sectional view of a braking device of the gas injector of Fig. 1 in the closed state, Fig. 3 a schematic partial sectional view of a braking device of the gas injector of Fig. 1 in the open state, Fig. 4 a diagram showing the stroke of a valve needle over the time of the gas injector from Fig. 1 shows, Fig. 5 a schematic partial sectional view of a braking device of a gas injector according to a second embodiment of the invention, and Fig. 6 a schematic partial view of a braking device of a gas injector according to a third embodiment of the invention. Preferred embodiments of the invention

[0018] The following refers to the Fig. 1 to 4 a gas injector 1 according to a first preferred embodiment of the invention is described in detail.

[0019] Fig. Figure 1 shows the closed state of the gas injector 1. The gas injector 1 is set up to inject a gaseous medium, for example hydrogen, into a combustion chamber 13.

[0020] The gas injector 1 includes a magnetic actuator 2, which moves an outwardly opening closing element 3 from the closed state to an open state.

[0021] The magnetic actuator 2 comprises an armature 20, an inner pole 21 and a coil 22.

[0022] The closing element 3 is two-part and comprises a valve needle 30, which seals against a sealing seat 5 in the closed state, and an anchor bolt 31. The anchor bolt 31 is fixedly connected to the anchor 20. The valve needle 30 and the anchor bolt 31 are arranged in series and can move independently of each other. In the closed state, a first contact area 30a of the valve needle rests against a second contact area 31a of the anchor bolt.

[0023] The gas injector 1 further comprises a reset element 6, which is in operative connection with the valve needle 30 in order to reset this element from the open to the closed state.

[0024] Furthermore, the gas injector 1 comprises a main body 10 with a gas inlet 11, through which pressurized gas is supplied into the interior of the gas injector. A gas path 14 is indicated by the arrows in Fig. Figure 1 is shown schematically. The gas path 14 runs from the gas inlet 11 along the inner circumference of a housing sleeve 12 to the sealing seat 5 of the gas injector. Corresponding passages and openings for supplying the gas from the gas inlet 11 to the valve plate of the valve needle 30 are provided in the components of the gas injector.

[0025] 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 configuration, such that the gas 41, as shown in Fig. 2 shown schematically, in an upper area of ​​the lubricant chamber 4 when assembled.

[0026] Lubrication chamber 4 is a sealed hydraulic chamber filled with a lubricating fluid to lubricate moving parts of gas injector 1. As shown in the diagram... Fig. As can be seen in Figure 1, the anchor 20 and the anchor bolt 31 are arranged in the lubricant chamber 4. The return element 6 is also arranged in the lubricant chamber 4.

[0027] The lubricant chamber 4 is sealed off from the gas path 40. Components present in the gas injector form a housing for the lubricant chamber 4. Furthermore, a bellows 42 is arranged at an end of the lubricant chamber 4 facing the combustion chamber, which allows axial movement of the closing element 30. As shown from Fig. As can be seen in Figure 1, the bellows 42 is connected to the valve needle 30 at one end facing 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.

[0028] The lubricant chamber 4 further comprises a damping housing 43, which is in Fig. 2 is shown and is located at an end of the lubricant chamber 4 facing away from the combustion chamber. The damping housing 43 is essentially pot-shaped and is also connected, for example, by means of welded connections to other sleeve-like housing components of the lubricant chamber 4.

[0029] A braking device 7 is also arranged in the lubricant chamber 4. The braking device is designed to slow down both the opening and closing movements of the closing element 3. This allows the braking device 7 to reduce the impact velocity during both the opening and closing movements, thereby significantly extending the service life of the gas injector.

[0030] The brake device 7 is arranged in the lubricant chamber 4 and comprises a brake piston 70, which has an axial through-opening 70a. The anchor bolt 31 is guided through the through-opening 70a of the brake piston 70.

[0031] A first stop 71 and a second stop 72 of the brake device 7 are arranged on the anchor bolt 31. As shown from Fig. As can be seen in Figure 2, which also shows the closed state of the gas injector, the brake piston 70 is arranged in the axial direction XX between the first stop 71 and the second stop 72. The brake piston 70 has an axial play A in the axial direction XX. The brake piston 70 is arranged to move freely between the first stop 71 and the second stop 72.

[0032] The brake device 7 further comprises a cylinder 73 with a cylinder base 73a. A throttle bore 8 is provided in the cylinder base 73a.

[0033] What's next? Fig. As can be seen in Figure 2, the brake device 7 is completely located in a region filled with fluid 40. The region filled with gas 41 is located in the pot-shaped damper housing 43 at the bottom of the damper housing 43.

[0034] The brake device 7 further comprises a cover 74, which is designed as a guide disc. The cover 74 is fixedly connected to the cylinder 73, for example by means of a welded connection. Openings 75 are provided on the outer circumference of the disc-shaped cover 74 to allow unimpeded movement of the fluid 40 in the lubricant chamber 4. The cover 74 has a central through opening 76 as a guide area for the anchor bolt 31.

[0035] As from Fig. As can be seen in Figure 2, the anchor bolt 31 is designed in such a way that it extends in axial direction XX beyond the anchor 20 to the braking device 7.

[0036] Furthermore, the brake piston 70 has a first radial clearance C on its outer circumference towards the cylinder 73 and a second radial clearance D on its inner circumference towards the anchor bolt 31. The first radial clearance C is smaller than the second radial clearance D.

[0037] When the gas injector is closed, as described in the Fig. 1 and Fig. As shown in Figure 2, the armature 20 is spaced from the inner pole 21 by the armature gap B in the axial direction XX. In the closed state of the gas injector, the brake piston 70 is spaced from the first stop 71, which is located at the end of the armature bolt 31 facing away from the combustion chamber, by the axial clearance A. The axial clearance A is smaller than the armature gap B.

[0038] Starting from the closed state, the magnetic actuator 2 is energized, causing the armature 20 to be pulled towards the inner pole 21. This is in Fig. 2, indicated by arrow E. This also moves the anchor bolt 21, which is rigidly connected to the anchor 20, towards the combustion chamber 13. Since the valve needle 30 rests directly against the anchor bolt 31, it is also moved in the opening direction, so that an outlet for the injected gas is present at the sealing seat 5, allowing gas to be injected into the combustion chamber 13.

[0039] What's next? Fig. As can be seen in Figure 2, the opening movement of the anchor bolt 31 also moves the first and second stops 71, 72, which are fixedly connected to the anchor bolt 31. This overcomes the axial gap A, since the brake piston 70 does not move at the beginning of the opening process due to inertia. Because the axial clearance A is smaller than the anchor gap B, the first stop 71 then comes into contact with the brake piston 70 before the anchor 20 strikes the inner pole 21. The axial clearance A is in a range of 20% to 80% of the anchor gap B and preferably lies between 45% and 55% of the anchor gap B.

[0040] As soon as the first stop 71 contacts the brake piston 70 during the opening process, the movement speed of the closing element 3 is reduced, since the brake piston 70 must displace fluid in a first sub-chamber 77 in the cylinder 73. The displaced lubricant volume escapes through the relatively small gaps between the brake piston 70 and the cylinder 73 and through the gap between the anchor bolt 31 and the guide disc. Optionally, the guide disc or the cover 74 can also be provided with a throttle bore through which displaced lubricant also escapes. Hardly any lubricant flows through the relatively large gap D between the anchor bolt 31 and the inner circumference of the brake piston 70, because the gap A between the brake piston 70 and the first stop 71 is largely closed.Thus, the movement of the brake piston 70 creates a pressure in the first sub-space 77, which causes a damping effect and a reduction in the movement speed of the closing element 3.

[0041] This is also shown again in the diagram of Fig. Figure 4 shows the valve needle stroke H over time t. At the beginning of the energization of the magnetic actuator 2 at time t1, the opening process of the valve needle 30 begins first slowly and then essentially exponentially. This is shown in Fig. 4 is marked by section A1. At time t2, the first stop 71 then comes into contact with the brake piston 70. This is in Fig. 4 is defined by area A2, which extends to time t3. At this point, due to the braking effect of the braking device 7, the opening speed of the closing element 3 is reduced and essentially constant. From time t3 to time t4 (area A3), the gas injector is fully open at its full stroke. At time t4, the current to the magnetic actuator is cut off, so that the closing process of the closing element 3 begins due to the restoring force of the restoring element 6 (area A4). At time t5 (area A5), the closing brake of the braking device 7 then begins to act, until at time t6 the gas injector is fully closed again.

[0042] The closing process is described in detail in Fig. Figure 3 illustrates this. The return element 6 exerts a return force on the valve needle 30, which is in operative connection with the anchor bolt 31. This causes the anchor bolt 31 to move back towards its closed initial position. This is shown in Fig. 3 indicated by the arrow F. Fig. Figure 3 shows the gas injector in its fully open state. In this fully open state, the axial gap A exists between the second stop 72 and the brake piston 70. The axial gap A is the same size as in the Fig. 2 shows the closed starting position of the gas injector. Due to its inertia, the brake piston 70 remains in the position shown at the beginning of the closing process. Fig. 3 position shown. By resetting the anchor bolt 31, the second stop 72 also moves towards the still stationary brake piston 70 until the axial gap A is overcome. Then the damping effect by the brake device 7 begins, with the return speed being as shown in Fig. As shown in section A5, the process is essentially linear again until time t6. Since the fluid from the lubricant chamber 4 is located in a second subchamber 78, it is displaced from the cylinder 73 via the throttle bore 8. This reduces the closing speed of the closing element 3, so that the impact of the valve needle 30 on the sealing seat 5 occurs at a lower speed. This results in reduced impact of the closing element 3, thus preventing damage to the sealing seat 5 or the valve needle 30.

[0043] Thus, the movement speed of the closing element can be reduced during both the opening and closing processes. This results in reduced impact forces 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. This significantly reduces wear on these components. Furthermore, the load on the bellows 42 is also considerably reduced, as the reduced impact forces generate less axial vibration on the bellows 42. Additionally, the deceleration process during both the opening and closing processes results in reduced pressure pulsations in the fluid within the lubricant chamber 4. Overall, this significantly extends the robustness and service life of the gas injector.

[0044] During the opening and closing processes, the brake device 7 is always located in the liquid region below the boundary line between the liquid and the gas. Accordingly, a gas space must be dimensioned within the lubricant chamber 4 so that the brake device 7 is always located in the liquid under all operating conditions. The gas 41 can compensate for temperature-related volume changes of the liquid and / or of components located in the lubricant chamber 4.

[0045] It should also be noted that by selecting a length and diameter for the throttle bore 8, braking behavior during the closing process can be directly adjusted.

[0046] Should gas bubbles ever enter cylinder 73 or be generated undesirably during operation, they can be released via the large second radial clearance D and the throttle bore 8 towards the gas-filled area of ​​the lubrication chamber 4 while the gas injector is held open. The second radial clearance D, which is significantly larger than the first radial clearance C, also prevents the anchor bolt from jamming in the brake device 7. Furthermore, the second large radial clearance D ensures that no friction occurs between the anchor bolt 31 and the brake piston 70. This allows the anchor bolt 31 to perform a first partial stroke in both the opening and closing directions without any braking action. The integration of the brake device 7 into the lubrication chamber 4 also results in a very compact and, in particular, axially short design of the gas injector.A slim gas injector can also be achieved in the radial direction by integrating the brake device 7 into the lubrication chamber 4. This is particularly important when, for example, only limited installation space is available in internal combustion engines where the gas injector is to be used.

[0047] Fig. Figure 5 shows a gas injector with a braking device 7 according to a second embodiment of the invention. Identical or functionally equivalent parts are designated with the same reference numerals as in the first embodiment. In contrast to the first embodiment, in the second embodiment the second stop 72 is formed by a thickening 72a on the anchor bolt 31. Thus, the thickening 72a takes over the function of the stop ring in the first embodiment. Otherwise, this embodiment corresponds to the first embodiment, so reference can be made to the description given therein.

[0048] Fig.Figure 6 shows a gas injector with a braking device 7 according to a third embodiment of the invention. Identical or functionally equivalent parts are designated with the same reference numerals as in the preceding embodiments. In contrast to the first embodiment, the braking device 7 of the third embodiment does not have a gas cushion. Instead, volume compensation is achieved via a spring-loaded second bellows 80 that is completely filled with lubricant. A spring 81 pre-tensions the bellows 80. Thus, volume compensation can be achieved in the lubricant chamber 4 without a gas cushion.

Claims

[1] 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), wherein the closing element (3) comprises a valve needle (30) and an anchor bolt (31) firmly connected to the armature (20), - a closed lubricant chamber (4) in which the armature (20) and the armature bolt (31) are arranged, - a return element (6) which returns the closing element (3) to a closed initial position, - a bellows (42) which is part of a housing of the lubricant chamber (4), wherein a first end of the bellows (42) is connected to the valve needle (30), and - a braking device (7) which is designed to brake the armature (20) from striking the inner pole (21) during an opening process and to brake the valve needle (30) from striking the sealing seat (5) during a closing process, - wherein the braking device (7) comprises a brake piston (70) arranged in the lubricant chamber (4) with a through-opening (70a), - wherein the anchor bolt (31) is guided through the through opening (70a), and - wherein a first stop (71) and a second stop (72) are arranged on the anchor bolt (31), wherein the brake piston (70) is arranged with an axial play (A) in the axial direction (XX) between the first stop (71) and the second stop (72). [2] Gas injector according to claim 1, wherein the braking device (7) further comprises a cylinder (73) with a cylinder bottom (73a), wherein the cylinder (73) is arranged in the lubricant chamber (4) and a throttle bore (8) is introduced into the cylinder bottom (73a), wherein the braking piston (70) is arranged in the cylinder (73). [3] Gas injector according to claim 2, wherein the cylinder (73) further comprises a cover (74) with an opening (76), wherein the anchor bolt (31) is passed through the opening. [4] Gas injector according to claim 3, wherein the cover (74) is designed as a guide disc for guiding the anchor bolt in the opening. [5] Gas injector according to one of claims 2 to 4, wherein the brake piston (70) has a first radial clearance (C) to the cylinder (73) on an outer circumference and a second radial clearance (D) to the anchor bolt (31) on an inner circumference. [6] Gas injector according to claim 5, wherein the first radial clearance (C) is smaller than the second radial clearance (D). [7] Gas injector according to one of the preceding claims, wherein the axial play (A) is smaller than an armature gap (B) between the armature (20) and the inner pole (21) in the closed state, wherein the axial play (A) is in particular in a range of 20% to 80% of the armature gap (B). [8] Gas injector according to one of the preceding claims, wherein the first stop (71) and / or the second stop (72) is a stop ring which is fixed to the anchor bolt (31). [9] Gas injector according to one of claims 1 to 7, wherein the first stop (71) and / or the second stop (72) is formed integrally with the anchor bolt (31). [10] Gas injector according to one of the preceding claims, wherein a liquid (40) and a gas (41) are present in the lubricant chamber (4), wherein the braking device (7) is arranged entirely in the liquid (40).

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