Injector for liquid or gaseous fuel and method for operating such injector

Abstract

The invention relates to an injector (1) for dispensing gaseous or liquid fuel in a metered manner, comprising a housing (2), which has a fuel chamber (11) that can be filled with fuel under injection pressure, and a valve body (3), which is surrounded by a sleeve (7), an intermediate space being formed between the valve body (3) and the sleeve (7), the intermediate space is part of the fuel chamber (11), and one end of the sleeve (7) and the valve body (3) form a sealing part (40) so as to seal the fuel chamber (11) outwards. A return chamber (45) is formed in the housing (2), which return chamber is connected to a return line (46) and is separated from the fuel chamber (11) by the sealing point (40).

Description

Field of the Invention

[0001] The present invention relates to an injector for metering the output of liquid or gaseous fuel, preferably for introducing fuel into the combustion chamber or the intake mechanism of an internal combustion engine. Background Art

[0002] In internal combustion engines operating with gaseous or liquid fuel, the fuel is either metered into the intake mechanism of the internal combustion engine or directly into the combustion chamber. For this purpose, the following injectors are used, which are supplied with compressed fuel and thus under injection pressure and meter out the fuel in an electronically controlled manner at the desired time and in the required amount. For this purpose, the injector has a movable valve element, which can be moved by an electromagnet or other electric actuator, and the metering opening is controlled to be opened or closed by the movement of the valve element. For example, such an injector is known from DE102021200689A1 and includes a piston-shaped nozzle needle as the valve element, which is arranged longitudinally displaceably in the injector housing. The fuel is guided through the fuel chamber in the injector and reaches the outlet-side end provided with the injection opening from the end where the fuel inlet is located. For low-friction support of the valve element, the valve element is surrounded by a lubricant chamber. To prevent the fuel from mixing with the lubricant, these two chambers of the injector are sealed from each other.

[0003] The injector consists of a plurality of components, which are connected to each other during assembly. Seals must be provided at the critical points where these components meet to reliably prevent fuel from leaking out of the injector on the one hand and to reliably prevent the lubricant from mixing with the fuel on the other hand. This is particularly laborious when using hydrogen as fuel, as hydrogen can also very easily penetrate into small gaps.

[0004] Injectors for large internal combustion engines are designed for long operating power and are accordingly costly. Therefore, when the function of such an injector deteriorates due to wear, the injector is usually repaired in order to be able to continue using it. For this purpose, the injector must be disassembled in order to either replace individual components or, if necessary, continue to use these components after cleaning. Since welded connections cannot be loosened without damage and thus make disassembly difficult or impossible, it is usually not feasible to achieve sealing between components and to the outside by welded connections. Summary of the Invention

[0005] The advantage of the injector according to the invention is that the injector can be disassembled into its individual components without damage and at the same time ensure reliable sealing of the fuel-guiding components of the injector. For this purpose, the injector has a housing which includes a valve body having a fuel inlet through which a fuel chamber constructed in the housing can be filled with fuel. The valve body is surrounded by a sleeve, and an intermediate space is constructed between the sleeve and the valve body, and this intermediate space is part of the fuel chamber, wherein one end of the sleeve and the valve body form a sealing portion for sealing the fuel chamber to the outside. In the housing, a return chamber is constructed, which is connected to a return line and is separated from the fuel chamber by the sealing portion.

[0006] The return chamber is used to receive the fuel flowing through the sealing portion due to the non-sealing property at the sealing portion or due to micro-leakage, as may especially occur when using hydrogen as fuel.

[0007] The fuel entering the return chamber is led out of the injector through the return line, so that the return chamber can always be kept at a low pressure. Since a certain amount of leakage can be tolerated at the sealing portion, the injector can be repaired by replacing or processing individual components. This function remains after disassembling and reassembling these components.

[0008] In a first advantageous configuration of the invention, the sealing portion includes a first sealing ring and a second sealing ring, which are arranged parallel to each other and are clamped between the sleeve and the valve body, wherein the annular space bounded by the sealing rings is connected to the return chamber. If fuel flows out of the fuel chamber through the first sealing ring, this fuel is guided into the return chamber and drained via the return line. The second sealing ring ensures that all the outflowing fuel is received by the return chamber in this way. Advantageously, such a sealing portion can also be constructed between the nozzle body and the sleeve, wherein the nozzle body forms the combustion chamber side end of the injector, and an injection opening is constructed in this combustion chamber side end.

[0009] In another advantageous expansion scheme of the invention, the sealing ring surrounds the valve body. Such a rotationally symmetric sealing portion can achieve great freedom in design, and thus the injector can be easily adapted to different installation conditions. The sealing ring is preferably made of an elastic material, especially an elastomer.

[0010] In an expansion scheme of the invention, it can be provided that a sealing portion is provided between the nozzle body and the magnet body, wherein the magnet body surrounds the electromagnet. Thereby, the internal region of the injector can be sealed against fuel in order to protect the components there from the influence of fuel.

[0011] In another advantageous configuration, the valve element is at least partially surrounded by a first bellows, and this bellows delimits a lubricant chamber that can be filled with lubricant. Through the sealing portion according to the invention, the lubricant chamber can be sealed against fuel, so that the lubrication of the valve element during its service life is retained.

[0012] In the method for operating the proposed injector according to the invention, the pressure in the return chamber is kept at a pressure below the pressure in the fuel chamber. This prevents gas or liquid from entering the fuel chamber from the return chamber and causing contamination or damage there. Here, the pressure in the return chamber is preferably the ambient pressure. Description of the Drawings

[0013] An embodiment of an injector according to the invention is shown in the drawings. The drawings show:

[0014] Figure 1 A longitudinal sectional view of the injector according to the invention is shown, in which only the main components of the injector are shown;

[0015] Figure 2 Shows Figure 1 An enlarged view of the part marked II. Detailed Description of the Invention

[0016] Figure 1 A longitudinal sectional view shows an injector for metering the output of liquid or gaseous fuel according to the invention, wherein the injector 1 is in particular configured to output fuel into the combustion chamber or the intake mechanism of an internal combustion engine. The injector 1 has a housing 2 which includes a valve body ३ with an attachment body 6, a magnet body 4 and a nozzle body 5, which adjoin one another and are clamped to one another in the longitudinal direction by a clamping device not shown in detail or are connected to one another by a threaded connection. The valve body ३ is surrounded by a hollow cylindrical sleeve 7, so that an annular space is formed between the valve body ३ and the sleeve 7. This annular space is part of the fuel chamber 11, which can be filled with gaseous or liquid fuel under injection pressure via the attachment body 6 screwed into the valve body ३ and the fuel inlet 10 configured therein. The injection pressure depends on the fuel used, the type and operating state of the internal combustion engine, and is for example 30 bar to 300 bar (3 MPa to 30 MPa) in the case of using gaseous fuels such as hydrogen or natural gas.

[0017] The fuel inlet 10 is connected through the connecting hole 17 to the portion of the fuel chamber 11 delimited by the sleeve 7, such that fuel can flow through the fuel chamber 11 and via the other connecting hole 18 into the nozzle body 5. The piston-shaped valve element 12 is arranged in the nozzle body 5 so as to be longitudinally displaceable, and this valve element has a valve disk 112 at its outlet-side end, which valve disk projects through the injection opening 15 constructed in the nozzle body 5. A sealing surface 14 is constructed on the valve disk 112, which sealing surface cooperates with the valve seat 13 surrounding the injection opening 15 for opening and closing the injection opening 15. If the valve element 12 moves out of the nozzle body 5, then the annular gap between the sealing surface 14 and the valve seat 13 is controlled to open, and fuel flows outwards from the fuel chamber 11 through this annular gap. If the valve element 12 abuts against the valve seat 13, then the injection opening 15 is closed.

[0018] The valve element 12 is received at its end facing away from the valve disk 112 in the guide sleeve 20. The closing spring 21 is received under pressure preloading between the guide sleeve 20 and the shoulder in the housing 2, and this closing spring acts on the valve element 12 with a closing force directed towards the nozzle body 5. The guide sleeve 20 abuts, facing away from the valve element 12, against the longitudinally displaceably supported bolt 22, which bolt is connected to the electromagnetic armature 24. In the extension of the bolt 22, a damping piston 25 is arranged in the valve body 3, which damping piston causes damping during the closing movement of the valve element 12, such that the valve disk 112 is placed on the valve seat 13 in a braked manner, thereby reducing the mechanical load.

[0019] In the magnet body 4, an electromagnet 26 is arranged at the height of the bolt 22, which electromagnet surrounds the electromagnetic armature 24 annularly, and whose magnetic field is strengthened and redirected by the inner pole 27. When the electromagnet 26 is energized, a force acts on the electromagnetic armature 24, which force pulls the electromagnetic armature in the direction of the outlet opening 15 against the force of the closing spring 21, such that the injection opening 15 is controlled to open, and fuel flows out of the fuel chamber 11.

[0020] If the energization of the electromagnet 26 is ended, then the closing spring 21 presses the valve element 12 back into its closed position, and the outlet opening 15 is closed again.

[0021] The valve element 12 is surrounded by a valve sleeve 31, which in turn is surrounded by a first bellows 30. The bellows 30 is sealingly connected to the valve sleeve 31 via a welded connection 32, and the valve sleeve 31 is sealingly connected to the valve element 12, so that the valve sleeve 31 moves along with the valve element 12 in the longitudinal direction. The other end of the bellows 30 is sealingly connected to the gasket 28. The first bellows 30 encloses a lubricant chamber 35, which extends through the closing spring 21, the electromagnetic armature 24, and the damping piston 25 into the area of the valve body 3 facing away from the valve element. There, the lubricant chamber 35 is bounded by a second bellows 36, which forms a compensation chamber. When the valve element 12 moves in the opening and closing directions, the volume of the lubricant chamber in the nozzle body 5 changes, which is compensated by the second bellows 36. To enable unimpeded flow of lubricant in the area of the electromagnetic armature 24, a plurality of longitudinal bores 124 are formed in the electromagnetic armature 24. The lubricant chamber 35 is filled with a liquid lubricant, for example a suitable mineral oil, in order to lubricate the guide region of the valve element 12 and thus enable a low-friction movement of the valve element 12 .

[0022] The sleeve 7 is Figure 1 The upper end of the sleeve 7 is sealed to the valve body 3 by forming a seal 40, consisting of a first sealing ring 41 and a second sealing ring 42, between the sleeve 7 and the valve body 3. The seal 40 prevents fuel from escaping from the fuel chamber 11, which must always be ensured, especially with gaseous fuels. The sealing rings 41 and 42 are made of an elastic material, such as an elastomer. An annular space 43 is formed between the sleeve 7 and the valve body 3, between the two sealing rings 41 and 42. This space is connected to a return chamber 45 via a connecting hole 47. Because even small micro-leakages are difficult to completely eliminate at the seal, any fuel that escapes is collected in the return chamber 45 and discharged from the injector 1 via a return line 46. The return chamber 45 is formed in the housing 2 as a plurality of interconnected holes and extends from the valve body 3, via the magnet body 4, to the nozzle body 5. A lower pressure, preferably ambient pressure, prevails in the return chamber 45, which is lower than the pressure in the fuel chamber 11.

[0023] The opposite second end of the sleeve 7 forms a second seal 50 with the nozzle body 5, which is also composed of two parallel sealing rings 51, 52, which delimit an annular space 53. Here, the annular space 53 is also connected to the return chamber 45 via the connecting hole 48, so that any fuel that may escape from the first sealing ring 51 can be discharged via the return chamber 45. For the purpose of explanation, Figure 2 by Figure 1 The enlarged view of the detail marked II again shows this region of the injector 1 .

[0024] The connection between the magnet body 4 and the nozzle body 5 is formed by a sealing section 60, which includes a first sealing ring 61 clamped between the magnet body 4 and the nozzle body 5. If fuel flows out of the fuel chamber 11 through the sealing ring 61, the fuel also enters the return chamber 45 here. A second sealing ring 62 is arranged on the inner side of the nozzle body 5, and the second sealing ring seals the return chamber 45 against the fuel present in the interior of the nozzle body 5. Other sealing sections are arranged between the magnet body 4 and the valve body 3 at the height of the damping piston 25 in the form of a sealing section 70 and between the interior of the valve body 3 and the attachment body 6 in the form of a sealing section 80, where the two sealing sections 70, 80 are composed of sealing rings.

[0025] The sealing sections 40, 50, 60, 70, 80 are arranged such that the fuel flowing out of the fuel chamber 11 is collected in the return chamber 45 and led away via a return line. Thus, the injector 1 can be disassembled without damage for maintenance and reassembled after processing or replacing individual components without affecting the sealing of the fuel chamber 11.

[0026] Since the fuel flowing away via the return line 46 is an indication of a leak at the injector 1, it can be used to identify the leak. A corresponding sensor is installed in the return line 46, which notifies of a functional failure when a predefinable concentration of fuel in the return line 46 is exceeded, so that the injector 1 concerned can be replaced or repaired.

Claims

1. An injector (1) for metering the output of gaseous or liquid fuel, having: a housing (2) which has a fuel chamber (11) that can be filled with fuel under injection pressure and having a valve body (3) which is surrounded by a sleeve (7), wherein, An intermediate space is formed between the valve body (3) and the sleeve (7), and the intermediate space is part of the fuel chamber (11). One end of the sleeve (7) and the valve body (3) form a sealing portion (40) to seal the fuel chamber (11) outward. It is characterized in that a return flow chamber (45) is formed in the housing (2). The return flow chamber is connected to a return flow pipeline (46) and is separated from the fuel chamber (11) by the sealing portion (40).

2. The injector (1) according to claim 1, characterized in that, The sealing portion (40) includes a first sealing ring (41) and a second sealing ring (42). The first sealing ring and the second sealing ring are arranged in parallel with each other and are clamped between the sleeve (7) and the valve body (3), so that an annular space (43) is defined between the first sealing ring (41) and the second sealing ring (42). The annular space (43) is connected to the return flow chamber (45).

3. The injector (1) according to claim 1 or 2, characterized in that, The housing (2) includes a nozzle body (5). The nozzle body forms the combustion chamber side end of the injector (1), and a valve element (12) for controlling the injection opening (15) is arranged in the nozzle body. The nozzle body (5) and the sleeve (7) form a second sealing portion (50), and the sealing portion includes two parallel sealing rings (51; 52). The two sealing rings are clamped between the sleeve (7) and the valve body (3). An annular space (53) between the two sealing rings (51; 52) is connected to the return flow chamber (45) formed in the valve body (3).

4. The injector (1) according to claim 2 or 3, characterized in that, The sealing rings (41; 42; 51; 52) surround the valve body (3).

5. The injector (1) according to one of claims 2 to 4, characterized in that, The sealing rings (41; 42; 51; 52) are made of an elastic material, preferably an elastomer.

6. The injector (1) according to one of claims 1 to 5, characterized in that, The valve body (5) and the magnet body (4) form another sealing portion (60), and the magnet body (4) surrounds the electromagnet (26).

7. The injector (1) according to any one of claims 1 to 6, characterized in that, The valve element (12) is at least partially surrounded by a first bellows (30), and the first bellows defines a lubricant chamber (35) that can be filled with lubricant.

8. The injector (1) according to one of claims 1 to 7, characterized in that, A fuel sensor for determining the fuel concentration is arranged in the return flow pipeline (46).

9. A method for operating an injector according to one of claims 1 to 8, characterized in that, The return flow chamber (45) is maintained at a pressure lower than the pressure in the fuel chamber (11).

10. The method according to claim 9, characterized in that, An ambient pressure (absolute pressure of 0.1 MPa) exists in the return flow chamber (45).

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