GAS INJECTOR WITH HYDRAULIC DAMPING DEVICE WITH FREE TRAVEL

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 hydraulic damping device with free travel in order to dampen a movement of a valve needle, in particular both during an opening process and during a closing process.

[0002] Gas injectors are known in various designs from the prior art. For example, DE 102016205358 A1 discloses a gas injector with a hydraulic damping device.

[0003] Due to the gaseous medium injected by gas injectors, gas injectors must execute a very large stroke compared to injectors for liquid media, such as fuel injectors. However, this can lead to significant wear on components, particularly on the sealing seat and stroke limiter, in gas injectors. The high switching forces required for gas injectors further increase wear on components during operation. Disclosure of the invention

[0004] The gas injector according to the invention for injecting a gaseous medium, in particular for injecting hydrogen or natural gas, with the features of claim 1, has the advantage that, despite the large stroke due to the large volume of gas to be injected, a damping device can be provided in a very compact and cost-effective manner. The damping device also reduces wear on components of the gas injector. Furthermore, the gas injector according to the invention has significantly improved noise behavior, in particular when encountering an end stop during an opening process and when closing a sealing seat during a closing process. This is achieved according to the invention in that the gas injector has a closing element that opens and closes a through-opening on a sealing seat.The gas injector further comprises a return element which returns the closing element from the open state to a closed initial state. Furthermore, an actuator is provided which actuates the closing element, as well as a hydraulic damping device. The hydraulic damping device is designed to dampen a movement of the closing element. The damping is achieved by means of a fluid which, in a sealed hydraulic chamber of the damping device, carries out a damping process when the closing element is opened and / or closed. Furthermore, a free-travel arrangement is provided which is functionally arranged between the closing element and the hydraulic damping device. The free-travel arrangement is designed to dampen the movement of the closing element, both during the opening process and during the closing process, only after a predetermined free travel has been traveled.This enables a very cost-effective and compact design of the damping device. Due to the free travel of the free-travel arrangement, the opening and closing processes initially occur without damping, and only after the free travel has been covered does the damping device engage. This prevents excessive wear on the contact components of the gas injector, particularly on the sealing seat and / or on a stop that limits the opening stroke of the gas injector. Furthermore, the hydraulic damping provided by the damping device results in significantly improved noise behavior during the opening and closing processes of the gas injector.

[0005] The subclaims show preferred developments of the invention.

[0006] More preferably, a complete opening stroke of the closing element comprises the free travel of the free-travel arrangement and a damping travel of the hydraulic damping device. The damping travel of the hydraulic damping device is smaller than the free travel. Thus, for example, during the opening process, very rapid opening with correspondingly large injection quantities is achieved before the damping device dampens the opening movement after the free travel has been covered, which slows the opening process somewhat. Similarly, during a closing movement of the closing element, a large part of the closing travel of the closing element is first covered by covering the free travel, until the hydraulic damping device then engages and enables damping to prevent wear and noise when the closing element hits the sealing seat.

[0007] A ratio of the damping travel to the free travel is preferably in a range of 0.06 to 0.12, in particular in a range of 0.08 to 0.10 and is particularly preferably 0.9.

[0008] More preferably, the free-path arrangement comprises a free-path housing, a control element arranged in the free-path housing, and a stop element, in particular a stop ring, fixed to the free-path housing. The free path is formed between the control element and the stop element, or alternatively, between the control element and the free-path housing. This allows the free-path arrangement to be very compact and small-sized.

[0009] Further preferably, the free-travel housing is connected to the hydraulic damping device, and the control element is connected to the closing element. Alternatively, the free-travel housing is connected to the closing element, and the control element is connected to the hydraulic damping device. Thus, the free-travel arrangement is integrated between the closing element and the hydraulic damping device in the axial direction of the gas injector.

[0010] Further preferably, the hydraulic damping device comprises a base body and a centering pin arranged axially movable within the base body, which is connected to the free-travel arrangement. This allows a simple connection between the hydraulic damping device and the free-travel arrangement via the centering pin. The centering pin preferably extends into the hydraulic damping device.

[0011] To ensure the simplest possible design, the hydraulic damping device has a first control chamber and a second control chamber, which are connected to each other via a fluid connection. This creates two control chambers, one of which is responsible for damping the opening movement of the closing element, and the other for damping the closing movement of the closing element.

[0012] The fluid connection between the first and second control chambers preferably comprises a throttle. The throttle is preferably arranged in a control cylinder that separates the first and second control chambers. The throttle dampens the closing element during the opening and closing processes by changing the volume in the first and second control chambers. The throttle can, for example, be formed as a small bore in the control cylinder or, alternatively or additionally, can be provided via radial gaps on the control cylinder.

[0013] Further preferably, the first and second control chambers are formed in the base body, in particular in a bore or the like that is open on one side and lies in a central axis of the gas injector.

[0014] To achieve the most compact design possible, the damping device preferably comprises a base body, a first flexible element, and a second flexible element. The closing element is connected to the first flexible element, and the first and second flexible elements form housing areas of the enclosed hydraulic chamber. The first flexible element thus enables the movement of the closing element.

[0015] The first and second flexible elements are preferably a metal membrane. Alternatively, the first and second flexible elements are metallic bellows.

[0016] Further preferably, the first flexible element is arranged on the base body of the damping device in such a way that a first sub-chamber of the hydraulic chamber is formed between the base body and the first flexible element. Furthermore, the second flexible element is arranged on the base body in such a way that a second sub-chamber of the hydraulic chamber is formed between the base body and the second flexible element. The first and second sub-chambers are fluidly connected to one another via a connecting region, preferably a groove or a bore or the like.

[0017] Further preferably, the first and second control chambers are connected to the connecting region by means of a transverse bore.

[0018] To minimize the temperature influence on the damping device during operation, the damping device and the free-path arrangement are preferably arranged in the axial direction XX of the gas injector on a side of the actuator facing away from the sealing seat. Thus, the actuator protects the damping device and the free-path arrangement from potential thermal influences, especially when the gas injector is designed for direct injection into the combustion chamber of an internal combustion engine.

[0019] The gas injector is further preferably an outward-opening gas injector. The gas injector is preferably designed for direct injection of a gaseous fuel into a combustion chamber of an internal combustion engine.

[0020] In order to provide the most compact, pre-assembled unit possible, the hydraulic damping device is preferably designed with the free-travel arrangement as a pre-assembled module. The pre-assembled module is preferably arranged in an actuator module housing through which the closing element is passed.

[0021] To prevent significant leakage from the first and second control chambers into the hydraulic chamber, the centering pin is preferably guided by the first flexible element, in particular a metal diaphragm, and a sealing disc. The sealing disc is preloaded in the axial direction by a spring washer. This measure allows the radial gaps in the damping device to be designed very small, thus minimizing leakage through these radial gaps.

[0022] The spring washer is preferably cup-shaped and includes a retaining edge, axially projecting cams, and axial openings. The spring washer is preferably arranged in the second control chamber of the hydraulic damping device. The spring washer preferably exerts an axial force on the sealing washer, thereby sealing the sealing washer against the base body of the hydraulic damping device.

[0023] Alternatively, the sealing disc described above is preferably pressed against the base body of the hydraulic damping device by means of a pressed-in disc. This allows for very good sealing, particularly in the contact area between the sealing disc and the base body. The sealing disc, together with the first flexible element, in particular a metal membrane, guides the centering bolt. A radius is preferably formed on the inner circumference of the sealing disc. This allows radial gaps to be made very small, so that leakage via these radial gaps from the hydraulic chamber into the first and second control chambers can be minimized. The pressed-in disc is connected to the base body by a press connection.

[0024] Preferably, a compensation chamber filled with liquid is provided on the radial outer circumference of the sealing disc.

[0025] Furthermore, the present invention relates to an internal combustion engine with a gas injector according to the invention. The gas injector preferably injects hydrogen, natural gas, or another fuel gas, in particular directly into a combustion chamber of the internal combustion engine. Short description of the drawings

[0026] Preferred embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawing: Figure 1 is a schematic sectional view of a gas injector according to a first preferred embodiment of the invention, Figure 2 is a schematic, enlarged partial sectional view of a damping device and a free-path arrangement of the gas injector of Figure 1 in the closed state of the gas injector, Figure 3 a schematic, enlarged partial sectional view of a damping device and a free-path arrangement of the gas injector of Figure 1in the partially opened state after covering the free path, Figure 4 a schematic, enlarged partial sectional view of a damping device and a free path arrangement of the gas injector of Figure 1 in the fully opened state after covering the free path, Figure 5 a schematic, enlarged partial sectional view of a damping device and a free path arrangement of the gas injector of Figure 1in the partially closed state after covering the free path, Figure 6 shows a schematic partial sectional view of a damping device and a free path arrangement of a gas injector according to a second embodiment of the invention in the closed state, Figure 7 shows a schematic partial sectional view of a damping device and a free path arrangement of a gas injector according to a third embodiment of the invention in the closed state, Figure 8 shows a schematic partial sectional view of a damping device and a free path arrangement of a gas injector according to a fourth embodiment of the invention in the closed state, Figure 9 shows a schematic sectional view of the spring washer of Figure 8 , Figure 10 a schematic plan view of the spring washer of Figure 9, and Figure 11 is a schematic partial sectional view of a damping device and a free-path arrangement of a gas injector according to a fifth embodiment of the invention in the closed state.

[0027] The following is based on the Figures 1 to 5 a gas injector 1 according to a first preferred embodiment of the invention is described in detail.

[0028] As from Figure 1 As can be seen, the gas injector for injecting a gaseous medium into a combustion chamber 30 of an internal combustion engine comprises a closing element 2 and an actuator 5 for actuating the closing element 2. The closing element 2 is a valve needle. The actuator 5 is a magnetic actuator with an inner pole 50 and an armature 51 connected to the closing element 2. A stop 52 is formed on the inner pole 50 to limit an opening stroke of the closing element.

[0029] The closing element 2 thereby exposes and closes a through-opening 4 at a sealing seat 3. In the open state, the through-opening 4 is an annular passage, with the gas injector 1 being an outward-opening injector. This means that, to open, the closing element 2 is moved outward in the direction of arrow A toward the combustion chamber 30.

[0030] At the opposite end of the sealing seat 3, a gas inlet 31 is provided. As can be seen from Figure 1 As can be seen, the gas inlet 31 is arranged in line with the closing element 2 on a central axis which defines an axial direction XX of the gas injector.

[0031] In Figure 1 the arrows B indicate the gas flow through the gas injector 1 starting from the gas inlet 31 to the sealing seat 3.

[0032] How to continue Figure 1As can be seen, the actuator 5 is sealed against the gaseous medium by means of a metal membrane 9. The metal membrane 9 is connected to the closing element 2 by means of a welded joint. The metal membrane 9 has a central opening through which the closing element 2 is guided.

[0033] The gas injector 1 further comprises a return element 6, which in this embodiment is a cylindrical coil spring. The return element 6 returns the closing element 2 from the open state to its initial closed state. The return element 6 is supported by a spring plate 60 and a housing component 10a.

[0034] The gas injector 1 further comprises a hydraulic damping device 7, which is described in particular in detail with reference to the Figures 2 to 5 described.

[0035] The hydraulic damping device 7 is configured to dampen a movement of the closing element 2. Movements are damped during both the opening and closing processes. The hydraulic damping device is configured to perform the damping by means of a fluid in a sealed hydraulic chamber 8 of the damping device 7.

[0036] The hydraulic damping device 7 comprises a first control chamber 80 and a second control chamber 88. The two control chambers 80, 88 are arranged in a base body 17 of the hydraulic damping device 7. The first control chamber 80 serves to dampen a return movement of the closing element, and the second control chamber 88 serves to dampen an opening movement of the closing element.

[0037] As from Figure 2As can be seen, a control cylinder 13 is arranged on a centering pin 18. The control cylinder 13 has a plurality of bores 13a, which connect the first control chamber 80 to the second control chamber 88. A throttle 14 is formed in each of the bores, wherein the strength of the damping during the opening and closing process can be adjusted by selecting a bore diameter for the throttles 14.

[0038] Furthermore, the damping device 7 comprises a first flexible element 11 and a second flexible element 12. The first and second flexible elements 11, 12 are a metal membrane in this embodiment. As can be seen from Figure 2As can be seen, the enclosed hydraulic chamber 8 is formed by cavities in the base body 17 and the first and second flexible elements 11, 12. The first flexible element 11 is provided with a central opening through which the centering pin 18 is passed. The first flexible element 11 is connected to the centering pin 18 by means of a welded joint.

[0039] The enclosed hydraulic chamber 8 is filled with a liquid, for example oil. As can be seen from Figure 2 As can be seen, the centering bolt 18 is formed with a through hole 18a, which is closed by a ball 86. This allows for easy filling of the enclosed hydraulic chamber 8.

[0040] The second flexible element 12 is arranged in a fluid-tight manner on the end face of the base body 17 facing the gas inlet 31. Since the first and second flexible elements 11, 12 are preferably metal membranes, fluid tightness with the base body 17 can be easily achieved by welded connections.

[0041] A first sub-chamber 81 of the hydraulic chamber is formed between the base body 17 and the first flexible element 11. A second sub-chamber 82 is formed between the base body 17 and the second flexible element 12. The first and second sub-chambers are fluidly connected to one another via a connecting region 83, which is a connecting bore.

[0042] Furthermore, the gas injector 1 comprises a free-path arrangement 20. The free-path arrangement 20 is arranged in the axial direction XX between the hydraulic damping device 7 and the actuator 5 (cf. Figure 1 ).

[0043] The free-way arrangement 20 comprises a free-way housing 21, a control element 22, which in this embodiment is a control disc, and a stop element 23. As can be seen from Figure 2 As can be seen, the stop element 23 is firmly connected to the free-travel housing 21 by means of a welded connection. The control element 22 is arranged on a side of the closing element 2 facing away from the combustion chamber 30. A fixed connection is provided between the control element 22 and the end of the closing element 2. This can be, for example, a welded connection, a press connection, or any other fixed mechanical connection.

[0044] The free-travel housing 21 is connected to the centering pin 18, whereby the free-travel housing 21 and the centering pin 18 are formed, for example, as a single, common component. However, the free-travel housing 21 and the centering pin can also be constructed in multiple parts.

[0045] The gas injector 1 further comprises a pot-shaped actuator module housing 100, in which the free-path arrangement 20 and, in part, the damping device 7 are arranged. The actuator module housing is welded to an outer periphery of the base body 17 of the damping device 7.

[0046] The function of the gas injector 1 according to the invention with path-optimized damping function is as follows. Based on the Figure 1 and 2 In the closed position of the gas injector 1 shown, the actuator 5 is actuated. This attracts the armature 51 toward the inner pole 50, so that the closing element 2 lifts off the sealing seat 3 and releases the through opening 4. The return element 6 is thereby preloaded.

[0047] In Figure 2The opening process for the closing element 2 is indicated by the arrow C. In the closed state of the gas injector, a free path S1 exists between the stop element 23 and the control element 22 in the axial direction. Since the control element 22 is connected to the closing element 2, this free path S1 is covered during the opening process until the control element 22 strikes the stop element 23. This state is in Figure 3 shown.

[0048] Until the Figure 3 In the state shown, no damping occurs during the opening process of the gas injector. However, the gas injector is not yet fully open. For the remaining opening stroke of the gas injector, damping is now provided by the hydraulic damping device 7.

[0049] There, as in Figure 3indicated by the arrow C, the closing element 2 is moved further in the opening direction, the contact between the control element 22 and the stop element 23 also moves the free-travel housing 21 and thereby also the centering bolt 18 in the direction of the arrow C. This is shown in Figure 4 indicated by the arrow D on the centering pin 18. Since the control cylinder 13 is firmly connected to the centering pin 18, this is also moved in the opening direction, as indicated by the arrows E. However, this changes the volume of the first control chamber 80 and the second control chamber 88. More precisely, the volume of the first control chamber 80 increases and the volume of the second control chamber 88 decreases. Since the two control chambers 80, 88 are fluidly connected to one another via the bore 13 and the throttle 14, this results in a dampening of the movement of the closing element until the armature 51 finally strikes the inner pole 50.

[0050] In Figure 4A damping travel S2, which is traveled by the control cylinder 13, is shown here. Thus, the maximum opening stroke of the closing element 2 is the sum of the free travel S1 and the damping travel S2. The damping strength can be easily adjusted by selecting the bore diameter for the throttles 14.

[0051] How to continue Figure 4 As can be seen, the volume of the first sub-chamber 81 and the second sub-chamber 82 also changes, since the first flexible element 11 is directly connected to the centering bolt 18 moving in the axial direction XX. More precisely, the volume of the first sub-chamber 81 increases and the volume of the second sub-chamber 82 decreases accordingly (cf. Figure 4 ).

[0052] For the closing process of the gas injector, the current supply to the actuator 5 is stopped, so that a restoring force is exerted on the closing element 2 by the prestressed restoring element 6. Figure 5 shows the first movement path for the reset process, whereby the control element 22 connected to the locking element 2 first travels the free path S1 until it rests against a shoulder 21a of the free path housing 21. This state is shown in Figure 5 shown. Up to this point during the return process, the hydraulic damping device 7 remains without damping effect.

[0053] As soon as the control element 22 rests against the shoulder 21a of the free-travel housing 21, the return movement of the return element 6 also moves the free-travel housing 21 and thus also the centering bolt 18 connected to the free-travel housing 21. This also moves the control cylinder 13 into the Figure 2 The return movements of the components are shown in Figure 5 marked by the arrows F.

[0054] As soon as the control element 22 rests against the free-travel housing 21, the movement of the centering bolt 18 results in damping by means of the hydraulic damping device 7, since the volumes in the first control chamber 80 and second control chamber 88 are again adjusted to the Figure 2 Adjust the starting position shown. The dashed line shows Figure 5 The maximum damping travel S2 is indicated, which must be covered until the closing element 2 completely seals against the sealing seat 3. Thus, only the final movement during the return of the gas injector is dampened.

[0055] According to the invention, by cleverly providing the free travel S1 by means of the free travel arrangement 20, damping during the opening process can be limited to the last opening travel of the closing element. In the same way, during the closing process, a damping effect by the hydraulic damping device 7 is limited to the last axial travel of the closing element 2 (damping travel S2). This makes it possible for the hydraulic damping device 7 to be very compact and particularly cost-effective, with only one flexible element 11, 12 at each end of the base body. Furthermore, the inner and outer diameters of the first and second control chambers 80, 88 are the same. This allows the base body 17 in particular to be of very simple construction. By appropriately designed radial gaps between the centering bolt 18 and the base body 17 orThe mobility of the centering bolt 18 can be ensured by the control element 22 and the base body 17. By selecting the gap height of the radial gap on the centering bolt 18 or the control element 22, a further possibility for influencing the damping effect is also provided.

[0056] Thus, according to the invention, the damping can be limited to the last section of the gas injector's travel during opening and closing. The free travel S1 is greater than the damping travel S2. This allows for fast switching times, and the first undamped movement of the closing element during opening allows for rapid, large-scale gas injection. The same applies to the closing process, which is largely possible due to the first undamped closing travel.

[0057] Figure 6schematically shows a partial sectional view of a gas injector according to a second embodiment of the invention. Identical or functionally identical parts are designated by the same reference numerals as in the first embodiment.

[0058] In contrast to the first embodiment, in the second embodiment, the free-travel housing 21 is directly connected to the locking element 2. Furthermore, the free-travel arrangement 20 comprises a control pin 24, which has a head 24a arranged in the free-travel housing 21 and a shaft 24b connected to the centering bolt 18. The connection between the control pin 24 and the centering bolt 18 can be realized, for example, by means of a welded connection. Thus, in the second embodiment, during the opening process, the free-travel housing 21 is first moved together with the locking element 2 until the free travel S1 has been covered. The head of the control pin 24 then rests against the stop element 23, so that during the further opening movement of the locking element 2, the control pin 24 is also moved in the axial direction.Since the control pin 24 is firmly connected to the centering bolt 18, damping then occurs during the remaining opening travel by the hydraulic damping device 7, as described in the first embodiment. During the closing process, the control pin 24, as in the first embodiment, first travels the free travel S1 until the head of the control pin 24 rests against the free travel housing 21 with a stop surface 21b, and then a resetting of the centering bolt 18 is enabled via the control pin 24. The final closing travel of the locking element 2 is then also dampened by the damping device 7. Otherwise, this embodiment corresponds to the first embodiment, so that reference can be made to the description given there.

[0059] Figure 7shows a partial sectional view of a gas injector according to a third embodiment of the invention. Identical or functionally identical parts are again designated by the same reference numerals as in the previous embodiments.

[0060] The third embodiment essentially corresponds to the second embodiment, wherein the free-path arrangement 20 also comprises a control pin 24. However, the centering pin 18 in the third embodiment is formed in two parts, wherein a sleeve 28 is provided for connecting the centering pin 18 to the control pin 24. Furthermore, in the third embodiment, the control cylinder present in the first two embodiments is formed in one piece with the centering pin 18, which in Figure 7indicated by reference numeral 18b. Otherwise, this embodiment corresponds to the previous embodiment, so that reference can be made to the description given there.

[0061] The Figures 8 to 10 show a gas injector according to a fourth embodiment of the invention. Identical or functionally identical parts are designated by the same reference numerals as in the previous embodiments.

[0062] The fourth embodiment, in comparison to the previous embodiments, enables a reduction in leakage from the first control chamber 80 and the second control chamber 88 into the hydraulic chamber 8. Thus, a reliable function of the hydraulic damping device 7 can be ensured, particularly over a very long operating period. For this purpose, the fourth embodiment, in contrast to the previous embodiments, has a modified guide for the centering bolt 18. As can be seen from Figure 8 As can be seen, the centering pin 18 is guided by a sealing disc 19. The sealing disc 19 has a radius R1 on an inner circumferential area, creating a contact line between the sealing disc 19 and the centering pin 18 for guidance. This allows the gap in the area between the sealing disc 19 and the centering pin 18 to be kept very small.

[0063] Furthermore, a spring washer 110 is provided, which exerts a spring force F on the sealing washer 19 in the axial direction XX. This results in an axial seal between the sealing washer 19 and the base body 17 of the hydraulic damping device 7.

[0064] As shown in detail in the Figures 9 and 10 can be seen, which shows the spring washer 110 in sectional view ( Figure 9 ) and in top view ( Figure 10), the spring washer 101 has a substantially pot-shaped configuration, wherein the bottom has a central opening through which the centering bolt 18 is passed. The spring washer 101 comprises a holding region 102, which is arranged on an outer circumference of the spring washer 101 and is non-positively fixed to the base body 17. Furthermore, three cams 103 are provided, which are arranged at equal intervals (cf. Figure 10 ) of 120° and are in contact with the sealing disc 19. The spring force F is exerted on the sealing disc 19 via the cams 103. Openings 104 are provided between the cams to allow sufficient movement of the centering pin when the centering pin 18 moves in the axial direction XX.

[0065] The control cylinder 13 is arranged at least partially in the cup-shaped spring washer 101. As can be seen in particular from Figure 8As can be seen, the control cylinder 13 has a radially outwardly directed flange 113, wherein a throttle gap 14 is formed between the flange 113 and the base body 17. The fluid can flow from the first control chamber 80 into the second control chamber 88 and vice versa via this throttle gap 14.

[0066] Furthermore, a sealing ring 15 is provided, on the inner circumference of which a second radius R2 and a cone 15a are formed. This seals the first control chamber 80 relatively well from the hydraulic chamber 8.

[0067] How to continue Figure 8 As can be seen, a cone 17a is formed on the base body 17 between the base body and the centering pin 18, so that fluid from the hydraulic chamber 8 reaches the sealing disc 19. This ensures, in particular, good mobility of the centering pin 18.

[0068] The first flexible element 11, which is connected to the centering pin 18, has a relatively high radial stiffness. Therefore, the first flexible element 11 cannot compensate for radial tolerances, or can only do so to a limited extent. According to the fourth embodiment, the centering pin 18 is now guided radially on the sealing disc 19. This allows for a very small radial gap.

[0069] By providing the cone 17a on the base body 17 and the cone 15a on the sealing ring 15, any inclination of the centering bolt 18 that may occur during operation can be very effectively compensated. The cone angle preferably lies in a range of 0.5° to 30°, in particular 1° to 10°. Otherwise, this embodiment corresponds to the previous embodiments, so reference can be made to the description given there.

[0070] The following is based on reference to Figure 11A gas injector according to a fifth embodiment of the invention is described in detail. Identical or functionally identical parts are designated by the same reference numerals as in the previous embodiments.

[0071] The fifth exemplary embodiment essentially corresponds to the fourth exemplary embodiment, whereby instead of the spring washer used in the fourth exemplary embodiment, a pressed-in washer 119 is used in the fifth exemplary embodiment to press the sealing washer 19 against the base body 17 of the hydraulic damping device 7. A press connection is formed between the pressed-in washer 119 and the base body 17. As in the fourth exemplary embodiment, the sealing washer 19 guides the centering bolt 18 on an inner circumferential region which has the radius R1. A fluid-filled space 120 remains on the sealing washer 19 radially on the outer circumference, so that the centering bolt can also execute compensating movements directed in the radial direction if necessary. Otherwise, this exemplary embodiment corresponds to the previous exemplary embodiments, so that reference can be made to the description given there.

Claims

1. Gas injector for injecting a gaseous medium, comprising: - a closing element (2) which opens up and closes off a passage opening (4) at a sealing seat (3), - a restoring element (6) which returns the closing element (2) into a closed starting position, - an actuator (5) which actuates the closing element (2), - a hydraulic damping device (7) for damping a movement of the closing element (2), wherein the hydraulic damping device (7) is configured to provide damping by means of a liquid in a closed-off hydraulic space (8), characterized by - a free-travel arrangement (20) which is arranged between the closing element (2) and the hydraulic damping device (7) and is configured to perform the damping of the movement of the closing element (2) only after a predetermined free travel (S1) has been covered.

2. Gas injector according to Claim 1, wherein a complete opening stroke of the closing element (2) comprises the free travel (S1) and a damping travel (S2) of the hydraulic damping device (7).

3. Gas injector according to Claim 2, wherein the damping travel (S2) is shorter than the free travel (S1).

4. Gas injector according to Claim 3, wherein a ratio of the damping travel (S2) to the free travel (S1) lies in a range from 0.06 to 0.12, and in particular in a range from 0.08 to 0.10.

5. Gas injector according to one of the preceding claims, - wherein the free-travel arrangement (20) comprises a free-travel housing (21), a control element (22) arranged in the free-travel housing (21) and a stop element (23) fixed to the free-travel housing (21), wherein the free travel (S1) is formed between the control element (22) and the stop element (23), or - wherein the free travel (S1) is formed between the control element (22) and the free-travel housing (21).

6. Gas injector according to Claim 5, wherein the free-travel housing (21) is connected to the hydraulic damping device (7) and the control element (22) is connected to the closing element (2), or wherein the free-travel housing (21) is connected to the closing element (2) and the control element (22) is connected to the hydraulic damping device (7).

7. Gas injector according to one of the preceding claims, wherein the hydraulic damping device (7) comprises a main body (17) and a centring pin (18) arranged in an axially movable manner in the main body (17), wherein the centring pin (18) is operatively connected to the free-travel arrangement (20).

8. Gas injector according to one of the preceding claims, wherein the hydraulic damping device (7) has a first control space (80) and a second control space (88), which are connected to one another via a fluid connection.

9. Gas injector according to Claim 8, wherein the fluid connection comprises a throttle (14) which is arranged in a control cylinder (13) that separates the first control space (80) from the second control space (88), wherein, via the throttle (14), the closing element (2) is damped during the opening process and during the closing process by way of a change in volume in the first and second control spaces.

10. Gas injector according to one of the preceding claims, wherein the damping device (7) has a main body (17), a first flexible element (11) and a second flexible element (12), wherein the closing element (2) is connected to the first flexible element (11) and the first flexible element (11) and the second flexible element (12) form housing regions of the closed-off hydraulic space (8).

11. Gas injector according to Claim 10, wherein the first flexible element and / or second flexible element are metal membranes / is a metal membrane, and / or wherein the first and second flexible elements are corrugated bellows.

12. Gas injector according to Claim 10 or 11, wherein the first flexible element (11) is arranged on the main body (17) in such a way that a first sub-space (81) of the hydraulic space (8) is formed between the main body (17) and the first flexible element (11), and wherein the second flexible element (12) is arranged on the main body (17) in such a way that a second sub-space (82) of the hydraulic space (8) is formed between the main body (17) and the second flexible element (12), wherein the first and second sub-spaces (81, 82) are fluidically connected to one another via a connecting region (83).

13. Gas injector according to one of the preceding claims, wherein the free-travel arrangement (20) and the damping device (7) are arranged on a side of the actuator (5) that faces away from the sealing seat (3) in the axial direction (X-X) of the gas injector.

14. Gas injector according to Claim 13, wherein the free-travel arrangement (20) and the hydraulic damping device (7) are formed as a pre-assembled module (100).

15. Gas injector according to one of Claims 7 to 14, wherein the centring pin (18) is guided by means of the first flexible element (11) and a sealing disc (19), wherein the sealing disc (19) is preloaded by means of a spring disc (101).

16. Gas injector according to Claim 15, wherein the spring disc (101) is designed in a pot-shaped manner with a retaining edge (102), cams (103) protruding in the axial direction (X-X) and axial apertures (104).

17. Gas injector according to one of Claims 7 to 14, wherein the centring pin (18) is guided by means of the first flexible element (11) and a sealing disc (19), wherein the sealing disc (19) is preloaded in the axial direction by means of a pressed-in disc (119) which is connected by means of a press-fit connection to the main body (17) of the hydraulic damping device.

18. Gas injector according to Claim 17, wherein a fluid-filled compensation space (120) is present at the radially outer periphery of the sealing disc (19).