Gas injector with a damper

Abstract

The present invention relates to a gas injector for injecting gaseous fuel, comprising: a magnetic actuator (2) with an armature (20), a closing element (3) which has a valve needle (30) and is connected to the armature (20), wherein the closing element (3) releases and closes a gas path (11) at a sealing seat (8), a closed lubricant chamber (4), in which the armature (20) is arranged, and a flexible sealing element (40) which seals the lubricant chamber (4) and makes an axial movability of the valve needle (30) possible, wherein the lubricant chamber (4) is filled with a liquid lubricant (5) and a gas (6).

Description

[0001] Description

[0002] title

[0003] Gas injector with damper

[0004] State of the art

[0005] The present invention relates to a gas injector for injecting a gaseous fuel, in particular hydrogen or natural gas or the like, with improved damping properties and a short and compact axial design. The gas injector is designed in particular for direct injection into the combustion chamber of an internal combustion engine.

[0006] Gas injectors are known in various designs from the state of the art. One problem with gas injectors is that, due to the gaseous medium being injected, lubrication by the medium is not possible, as is the case with fuel injectors that inject gasoline or diesel, for example. This leads to excessive wear during operation of the gas injector. Furthermore, due to the increasing miniaturization of internal combustion engines, gas injectors also require as little installation space as possible.

[0007] Disclosure of the invention

[0008] The gas injector according to the invention for injecting a gaseous fuel with the features of claim 1, however, has the advantage that improved function is possible in conjunction with lubrication of moving parts of the gas injector. The gas injector according to the invention also has a very compact and short design, particularly in the axial direction of the gas injector. This is achieved according to the invention in that the gas injector comprises a magnetic actuator with an armature that is movable in the axial direction of the gas injector. The armature is connected to a closing element of the gas injector, which has a valve needle for opening and closing a gas path for the gaseous fuel at a valve seat. Furthermore, a sealed lubricant chamber is provided, which is filled with a liquid lubricant, wherein the axially movable armature is arranged in the lubricant chamber.The lubricant thus ensures lubrication of the armature during operation, preventing wear on the armature. The lubricant chamber comprises at least one flexible sealing element, in particular a bellows, which seals the lubricant chamber from the gas path. The flexible sealing element thus ensures axial mobility of the closing element and forms a housing part of the lubricant chamber. Furthermore, the lubricant chamber is filled with a gas in addition to the liquid lubricant. Thus, a defined gas volume exists in the lubricant chamber, which enables a volume compensation unit integrated into the lubricant chamber in the event of a temperature increase, which can lead to an expansion of the volume of the liquid lubricant.As a result, the flexible sealing element only needs to ensure the axial mobility of the closing element and does not need to provide additional temperature-related compensation for temperature-related volume changes of the liquid lubricant in the lubricant chamber. This results in a compact, flexible sealing element, for example, when using a bellows, resulting in a significantly reduced axial length of the bellows.

[0009] The subclaims show preferred developments of the invention.

[0010] The flexible sealing element is preferably a bellows, in particular a metal bellows. Due to the gas volume present in the lubricant chamber, the axial length of the bellows can be chosen to be very small, so that the bellows only has to ensure the axial mobility of the closing element of the gas injector. Alternatively, the flexible sealing element is a metal membrane, which can also be simplified due to the gas volume in the lubricant chamber.

[0011] Preferably, the gas injector further comprises a return element arranged within the lubricant chamber. The return element returns the closing element to a closed initial position. Thus, by arranging the closing element within the lubricant chamber, reduced wear on the closing element during operation can also be achieved.

[0012] The lubricant chamber further preferably comprises a deep-drawn part, which is designed as a housing part of the lubricant chamber. The deep-drawn part is preferably cup-shaped and further preferably has a central filling opening closed by a closure unit. The filling opening is preferably located along a central axis of the gas injector. The deep-drawn part is further preferably arranged at an end of the lubricant chamber facing away from the combustion chamber.

[0013] The gas used in the lubricant chamber is preferably air, CO2, or a noble gas. The lubricant is preferably an oil, a liquid fuel, a perfluoropolyether (PFPE), a heptane isomer, or a nonane.

[0014] The pressure in the lubricant chamber at a temperature of 20°C is preferably in a range of 1 to 4 x 10 5 Pa and is in particular 3 x 10 5Pa. The pressure in the lubricant chamber at 20°C is preferably always greater than ambient pressure.

[0015] At a temperature of 20°C, the volume of the liquid lubricant is greater than the volume of the gas in the lubricant chamber. The volume of the liquid lubricant at 20°C is more preferably at least twice the volume of the gas in the lubricant chamber.

[0016] Further preferably, a damping unit is arranged in the lubricant chamber. The damping unit preferably dampens the closing movement of the closing element to prevent so-called bounce, which can occur during rapid closing processes of the gas injector when the closing element hits a stop and briefly rebounds, which can lead to undesired opening of the sealing seat.

[0017] More preferably, the closing element is an outward-opening closing element. Preferably, the flexible sealing element is directly connected to the closing element, preferably by means of a welded connection.

[0018] Drawings

[0019] Preferred embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawing:

[0020] Figure 1 is a schematic sectional view of a gas injector according to a first embodiment of the invention, and

[0021] Figure 2 is a schematic partial sectional view of a gas injector according to a second embodiment of the invention.

[0022] Preferred embodiments of the invention

[0023] A gas injector 1 according to a first preferred embodiment of the invention is described in detail below with reference to Figure 1.

[0024] As can be seen from Figure 1, the gas injector 1 for injecting a gaseous fuel into a combustion chamber 10 comprises a magnetic actuator 2, which moves an outwardly opening closure element 3 from a closed state to an open state. Figure 1 shows the closed state of the gas injector.

[0025] The magnetic actuator 2 comprises an armature 20 and a coil 21, with the armature 20 being connected to the closing element 3. The closing element 3 comprises a valve needle 30 and a valve plate 31, which opens and closes a passage for injecting the gaseous fuel at a sealing seat 8. The sealing seat 8 is formed between the valve plate 31 and a valve body 9.

[0026] The gas injector 1 further comprises a gas connection 91 through which the gaseous fuel is supplied to the gas injector. Reference numeral 11 denotes a gas path that runs through the gas injector 1. The valve body 9 is connected to a housing sleeve 90, for example, by means of a welded connection. The gas path 11 runs radially outward from the gas connection 91, which is located centrally along a central axis XX of the gas injector, and flows around the magnetic actuator 2.

[0027] The gas injector 1 further comprises a sealed lubricant chamber 4, which accommodates several components of the gas injector 1. The lubricant chamber 4 is filled with a liquid lubricant 5 and a gas 6.

[0028] Furthermore, the gas injector 1 comprises a return element 7, which returns the closing element 3 to the closed position shown in Figure 1. The return element 7 is also arranged inside the lubricant chamber 4.

[0029] The lubricant chamber 4 comprises a flexible sealing element 40, which in this embodiment is a metallic bellows. Furthermore, the lubricant chamber 4 comprises a sleeve 41, which is fixedly connected to the coil 21. A shoulder 41a is provided inside the sleeve 41, against which a first end of the return element 7 rests. A second end of the return element 7 rests on a spring plate 32, which is fixedly connected to the valve needle 30.

[0030] As can be further seen from Figure 1, the closing element 3 has a guide element 33, which is formed on the valve needle 30 in the region of the valve body 9. The guide element 33 guides the closing element 3 along an inner circumference of the valve body 9 and has several openings for the gas path 11.

[0031] At an end of the lubricant chamber 4 facing away from the combustion chamber, a deep-drawn part 42 is arranged, which closes off the lubricant chamber 4. The deep-drawn part 42 is made of a thin metal material and has a substantially pot-shaped configuration. The deep-drawn part 42 has a filling opening 43, which is closed by a closure unit 44. The closure unit 44 comprises, for example, a sealing ring 44a and a cylindrical pin 44b.

[0032] Furthermore, a damping unit 12 is arranged in the lubricant chamber 4, which enables damping of the closing element 3 before it hits a stop when the closing element 3 is reset. The damping unit 12 is, for example, an elastic material at an end of the valve needle 30 facing away from the combustion chamber.

[0033] As can be seen from Figure 1, the volume of the liquid lubricant 5 is significantly larger than the volume of the gas 6 in the lubricant chamber 4. The gas volume in the lubricant chamber 4 enables the gas volume to be compressed when the volume of the liquid lubricant 5 expands upon a temperature increase. It has been determined that during operation, the liquid lubricant 5 can expand by up to 20% due to temperature increases. In this exemplary embodiment, at 20°C, the volume of the liquid lubricant 5 is twice the volume of the gas 6.

[0034] This makes it possible to design the flexible sealing element 40 so that it is solely responsible for the axial mobility of the closing element 3 for opening and closing. In other words, the flexible sealing element 40 does not have to compensate for temperature-related length changes due to expansion of the liquid lubricant. This allows the axial length of the gas injector to be significantly reduced.

[0035] The function of the gas injector according to the invention is as follows. When the magnetic actuator 2 is energized, the armature is moved toward the combustion chamber 10, causing the closing element 3 to open, as indicated by arrow A in Figure 1. This lifts the valve 31 from the sealing seat 8, and the gaseous fuel is injected through the released passage at the sealing seat 8. This is indicated by arrows B in Figure 1.

[0036] To terminate the injection, the current supply to the magnetic actuator 2 is terminated, so that the closing element 3 is returned to the closed position shown in Figure 1 by means of the return element 7. The damping unit 12 at the end of the closing element 3 facing away from the combustion chamber prevents so-called bounce when the closing element 3 reaches its end position against a stop.

[0037] The axial movement of the closing element 3 is realized exclusively by means of the flexible sealing element 40. Rising temperatures during operation, which can lead to an expansion of the volume of the liquid lubricant 5, are compensated by compressing the gas 6 in the lubricant chamber 4. This can result in a pressure increase in the lubricant chamber 4, which, however, has no negative impact on the function of the gas injector during opening and / or closing. Oil is preferably used as the liquid lubricant, and air is preferred as the gas 6.

[0038] Since the installation position of the gas injector 1 in an internal combustion engine is typically such that the sealing seat 8 faces downward, the gas 6, as indicated in Figure 1, is essentially located in the deep-drawn part 42. However, the installation position of the gas injector 1 in an internal combustion engine generally has no effect on the above-described function of the lubricant chamber 4 filled with liquid lubricant 5 and gas 6.

[0039] Thus, a large number of moving parts of the gas injector are arranged inside the lubricant chamber 4, allowing a significant reduction in wear on these moving components. This can significantly extend the service life of the gas injector.

[0040] The flexible sealing element 40 is connected to the valve needle 30, for example, by means of a welded connection. Preferably, a welded connection is also provided between the flexible sealing element 40 and the sleeve 41 of the housing of the lubricant chamber 4. This allows the lubricant chamber to be prefabricated and then filled via the filling opening 43, whereby filling with the gas 6 is also possible under pressure. After filling, the lubricant chamber 4 is then closed by the closure unit 44, for example, a cylindrical pin.

[0041] Figure 2 shows a gas injector 1 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.

[0042] In contrast to the first exemplary embodiment, the gas injector 1 of the second exemplary embodiment has a metal membrane as a flexible sealing element 40. The membrane is connected to the valve needle 30 via a sleeve 45 and to a radially outer circumference on a base body 12a of the damping unit 12. The damping unit 12 enables a fluid connection from a first chamber 4a of the lubricant chamber 4 to a second chamber 4b. The damper unit 12 enables damping both during an opening process of the closing element 3 and during a closing process of the closing element 3. As is clear from Figure 2, the use of the metallic membrane as a flexible sealing element 40 enables a further reduction in the axial length of the gas injector 1. This makes it possible to realize a particularly compact design. The use of a bellows is no longer necessary.The lubricant chamber 4 is formed at an end facing away from the combustion chamber with a pot 46, which essentially defines an absorbable volume of the lubricant chamber 4.

[0043] The volume of the lubricant chamber 4 is selected depending on the application. Filling of the lubricant chamber 4 can be achieved similarly to the first embodiment using a filling opening in the pot 46 or, as shown in Figure 2, through a filling opening 43 on the damper unit 12, which is closed by a closure ball 13. Otherwise, this embodiment corresponds to the previous embodiment, so reference can be made to the description given there.

Claims

Claims 1. Gas injector for injecting a gaseous fuel, comprising: a magnetic actuator (2) with an armature (20), a closing element (3) with a valve needle (30) which is connected to the armature (20), wherein the closing element (3) opens and closes a gas path (11) at a sealing seat (8), a closed lubricant chamber (4) in which the armature (20) is arranged, and a flexible sealing element (40) which seals the lubricant chamber (4) and enables axial mobility of the valve needle (30), wherein the lubricant chamber (4) is filled with a liquid lubricant (5) and a gas (6).

2. Gas injector according to claim 1, wherein the flexible sealing element (40) is a bellows or a membrane.

3. Gas injector according to one of the preceding claims, further comprising a return element (7), wherein the return element (7) is arranged in the interior of the lubricant chamber (4).

4. Gas injector according to one of the preceding claims, further comprising a deep-drawn part (42) which is a housing part of the lubricant chamber (4).

5. Gas injector according to claim 4, wherein the deep-drawn part (42) is pot-shaped and has a central filling opening (43) closed by a closure unit (44).

6. Gas injector according to one of the preceding claims, wherein the gas (6) is air or carbon dioxide or a noble gas and / or wherein the liquid lubricant (5) is oil or perfluoropolyether or a heptane isomer or a nonane.

7. Gas injector according to one of the preceding claims, wherein a pressure in the lubricant chamber (4) is greater than an ambient pressure.

8. Gas injector according to claim 7, wherein the pressure in the lubricant chamber (4) is in a range of 1 to 4 x 10 5 Pa is at 20°C.

9. Gas injector according to one of the preceding claims, wherein a volume of the liquid lubricant (5) is greater than a volume of the gas (6) in the lubricant chamber (4).

10. Gas injector according to one of the preceding claims, further comprising a damper unit (12), wherein the damper unit (12) is arranged in the lubricant chamber (4).

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