Injector for liquid or gaseous fuels and method for operating such an injector

Abstract

Disclosed is an injector (1) for metered dispensing of a gaseous or liquid fuel, having a housing (2), which has a fuel chamber (11) which can be filled with fuel at an injection pressure, and a valve body (3) which is surrounded by a casing tube (7), wherein an intermediate space is formed between the valve body (3) and the casing tube (7), which is a part of the fuel chamber (11), wherein one end of the casing tube (7) forms a sealing point (40) with the valve body (3), in order to seal the fuel chamber (11) from the outside. A return chamber (45) is formed in the housing (2), which is connected to a return line (46) and is separated from the fuel chamber (11) by the sealing point (40).

Description

[0001] title

[0002] Injector for liquid or gaseous fuels and method for operating such an injector

[0003] The invention is based on an injector for metered delivery of a liquid or gaseous fuel, as is preferably used to introduce fuel into a combustion chamber or an intake tract of an internal combustion engine.

[0004] State of the art

[0005] In internal combustion engines powered by gaseous or liquid fuels, the fuel is metered either into the intake tract of the internal combustion engine or directly into a combustion chamber of the internal combustion engine. Injectors are used for this purpose. These are supplied with the compressed fuel, which is thus subject to injection pressure, and which deliver it electrically at the desired time and in the required quantity. For this purpose, the injectors have a movable valve element that can be moved via an electromagnet or other electrical actuator, with the movement of the valve element opening or closing a metering opening. Such an injector is known, for example, from DE 10 2021 200 689 A1 and comprises a piston-shaped nozzle needle as the valve element, which is arranged so as to be longitudinally displaceable in the injector housing.The fuel is guided through a fuel chamber within the injector and thus reaches the outlet end where the injection opening is located. To ensure low-friction support for the valve element, it is surrounded by a lubricant chamber. To prevent mixing of fuel and lubricant, both chambers of the injector are sealed off from one another. The injector consists of several components that are joined together during assembly. Seals must be formed where the components adjoin one another to reliably prevent fuel from escaping from the injector and to prevent lubricant and fuel from mixing. This is particularly complex when hydrogen is used as the fuel, as hydrogen can easily diffuse into even small gaps.

[0006] Injectors for large internal combustion engines are designed for long mileage and are accordingly expensive. Therefore, when such injectors are impaired due to wear, they are often repaired to ensure continued use. This requires disassembling the injector so that the individual components can either be replaced or, if necessary, cleaned, reused. Sealing the components between each other and from the outside with welded joints is therefore generally not an option, as welded joints cannot be removed without damaging the components, making disassembly difficult or impossible.

[0007] Advantages of the invention

[0008] The injector according to the invention has the advantage that it is possible to disassemble the injector into its individual components without causing any damage, while at the same time ensuring that the fuel-carrying parts of the injector are securely sealed. For this purpose, the injector has a housing that includes a valve body with a fuel inlet, via which a fuel chamber formed in the housing can be filled with fuel. The valve body is surrounded by a jacket tube, with an intermediate space being formed between the jacket tube and the valve body, which space is part of the fuel chamber, with one end of the jacket tube forming a sealing point with the valve body in order to seal the fuel chamber from the outside. A return chamber is formed in the housing, which is connected to a return line and is separated from the fuel chamber by the sealing point.

[0009] The return chamber serves to collect fuel that passes through the seal due to leaks at the seal or micro-leakage, which can occur particularly when hydrogen is used as a fuel. The fuel that enters the return chamber is drained from the injector via a return line, so that the return chamber can always be maintained at a low pressure. Since a certain amount of leakage is therefore tolerable at the seals, the injector can be repaired by replacing or reconditioning individual components. This function is retained even after the components have been disassembled and reassembled.

[0010] In a first advantageous embodiment of the invention, the sealing point comprises a first sealing ring and a second sealing ring, which are arranged parallel to one another and clamped between the jacket tube and the valve body, wherein the annular space delimited by the sealing rings is connected to the return chamber. If fuel escapes from the fuel chamber past the first sealing ring, this fuel is guided into the return chamber and discharged via the return line. The second sealing ring ensures that all of the escaping fuel is thus absorbed by the return chamber. Such a seal can advantageously also be formed between a nozzle body and the jacket tube, wherein the nozzle body forms the combustion chamber-side end of the injector, in which an injection opening is formed.

[0011] In a further advantageous development of the invention, the sealing rings surround the valve body. The resulting rotationally symmetrical seal allows for considerable design freedom and thus easy adaptation of the injector to various installation situations. The sealing rings are preferably made of an elastic material, in particular an elastomer.

[0012] In a further development of the invention, a sealing point can be formed between the nozzle body and a magnetic body, with the magnetic body surrounding an electromagnet. This allows the interior of the injector to be sealed against the fuel in order to protect the components located there from the fuel.

[0013] In a further advantageous embodiment, the valve element is surrounded at least in sections by a first corrugated bellows, which defines a lubricant chamber that can be filled with a lubricant. This chamber can be sealed against the fuel by the seals according to the invention, so that the lubrication of the valve element is maintained throughout its service life.

[0014] In a method according to the invention for operating the proposed injector, the pressure in the return chamber is maintained at a pressure that is below the pressure in the fuel chamber. This prevents gas or liquid from the return chamber from entering the fuel chamber and causing contamination or damage there. The pressure in the return chamber is preferably ambient pressure.

[0015] drawing

[0016] The drawing shows an embodiment of the injector according to the invention.

[0017] Fig. 1 is a longitudinal section through an injector according to the invention, showing only the essential parts of the injector,

[0018] Fig. 2 is an enlarged view of the section marked II in Fig. 1.

[0019] Description of the embodiments

[0020] Fig. 1 shows a longitudinal section of an injector according to the invention for the metered delivery of liquid or gaseous fuel, wherein the injector 1 is designed in particular to deliver fuel into a combustion chamber or an intake tract of an internal combustion engine. The injector 1 has a housing 2 comprising a valve body 3 with a connecting body 6, a magnet body 4 and a nozzle body 5, which adjoin one another and are clamped against one another in the longitudinal direction by a clamping device (not shown in detail) or are connected by screw connections. The valve body 3 is surrounded by a hollow cylindrical jacket tube 7, so that an annular space is formed between the valve body 3 and the jacket tube 7.This annular space is part of a fuel chamber 11, which can be filled with gaseous or liquid fuel at an injection pressure via the connecting body 6 screwed into the valve body 3 and a fuel inlet 10 formed therein. The injection pressure depends on the fuel used and the type and operating condition of the internal combustion engine and is, for example, 30 to 300 bar (3 to 30 MPa) when using gaseous fuel, such as hydrogen or natural gas.

[0021] The fuel inlet 10 is connected via connecting bores 17 to the part of the fuel chamber 11 delimited by the jacket tube 7, so that the fuel can flow through the fuel chamber 11 and via further connecting bores 18 into the nozzle body 5. A piston-shaped valve element 12 is arranged in the nozzle body 5 for longitudinal displacement. At its outlet end, the valve element has a valve disk 112 which projects through an injection opening 15 formed in the nozzle body 5. A sealing surface 14 is formed on the valve disk 112, which interacts with a valve seat 13 surrounding the injection opening 15 to open and close the injection opening 15. If the valve element 12 moves out of the nozzle body 5, an annular gap is opened between the sealing surface 14 and the valve seat 13, through which fuel flows out of the fuel chamber 11. If the valve element 12 rests against the valve seat 13, the injection opening 15 is closed.

[0022] The valve element 12 is received at its end facing away from the valve plate 112 in a guide sleeve 20. Between the guide sleeve 20 and a shoulder in the housing 2, a closing spring 21 is received under compressive preload, which exerts a closing force on the valve element 12 into the nozzle body 5. The guide sleeve 20 rests, facing away from the valve element 12, on a longitudinally movable bolt 22 which is connected to a magnet armature 24. Arranged in the valve body 3 as an extension of the bolt 22, this damping piston 25 effects damping during the closing movement of the valve element 12, so that the valve plate 112 rests on the valve seat 13 in a braked manner, thereby reducing the mechanical load.

[0023] An electromagnet 26 is arranged in the magnet body 4 at the level of the bolt 22. The electromagnet 26 surrounds the magnet armature 24 in a ring-like manner and its magnetic field is amplified and directed by an internal pole 27. When the electromagnet 26 is energized, a force acts on the magnet armature 24, pulling it toward the outlet opening 15 against the force of the closing spring 21, so that the injection opening 15 is opened and fuel exits the fuel chamber 11. When the energization of the electromagnet 26 is discontinued, the closing spring 21 pushes the valve element 12 back into its closed position, and the outlet opening 15 is closed again.

[0024] The valve element 12 is surrounded by a valve sleeve 31, which in turn is surrounded by a first corrugated bellows 30. A welded connection 32 seals the corrugated bellows 30 into the valve sleeve 31, and the valve sleeve 31 into the valve element 12, so that the valve sleeve 31 moves longitudinally together with the valve element 12. The other end of the corrugated bellows 30 is seals the disk 28. The first corrugated bellows 30 encloses a lubricant chamber 35, which extends past the closing spring 21, the magnet armature 24, and the damping piston 25 into the region of the valve body 3 facing away from the valve element. There, the lubricant chamber 35 is delimited by a second corrugated bellows 36, which forms a compensation chamber. When the valve element 12 moves in the opening and closing direction, the volume of the lubricant chamber in the nozzle body 5 changes, which is compensated by the second bellows 36.To enable unhindered flow of the lubricant in the area of ​​the magnet armature 24, several longitudinal bores 124 are formed in the magnet armature 24. The lubricant chamber 35 is filled with a liquid lubricant, such as a suitable mineral oil, to lubricate the guide areas of the valve element 12 and thus enable low-friction movement of the valve element 12.

[0025] The jacket tube 7 is sealingly connected to the valve body 3 at its upper end in Fig. 1 by a seal 40 consisting of a first sealing ring 41 and a second sealing ring 42 being formed between the jacket tube 7 and the valve body 3. The seal 40 prevents fuel from escaping from the fuel chamber 11 to the outside, which must always be ensured, especially with gaseous fuels. The sealing rings 41, 42 are made of an elastic material, for example an elastomer. An annular chamber 43 is formed between the two sealing rings 41, 42, between the jacket tube 7 and the valve body 3, which is connected to a return chamber 45 via a connecting bore 47. Since slight micro-leakage is difficult to completely prevent at seals, any escaping fuel is absorbed in the return chamber 45 and discharged from the injector 1 via a return line 46.The return flow chamber 45 is designed in the form of several interconnected bores in the housing 2 and extends from the valve body 3 via the magnet body 4 into the nozzle body 5. In the return flow chamber 45 there is always a low pressure which is lower than the pressure in the fuel chamber 11, preferably ambient pressure.

[0026] The opposite, second end of the jacket tube 7 forms a second seal 50 with the nozzle body 5, which also consists of two parallel sealing rings 51, 52 that define an annular space 53. Here, too, the annular space 53 is connected to the return chamber 45 via a connecting bore 48, so that any fuel that may overcome the first sealing ring 51 is discharged via the return chamber 45. For clarity, Fig. 2 shows this area of ​​the injector 1 again in an enlarged view of the section designated II in Fig. 1.

[0027] The connection between the magnetic body 4 and the nozzle body 5 is formed by a seal 60, which comprises a first sealing ring 61 that is clamped between the magnetic body 4 and the nozzle body 5. If fuel from the fuel chamber 11 passes the sealing ring 61, it also reaches the return chamber 45. A second sealing ring 62 is arranged on the inside of the nozzle body 5 and seals the return chamber 45 against the fuel present inside the nozzle body 5. Further seals are arranged between the magnetic body 4 and the valve body 3 at the level of the damping piston 25 in the form of a seal 70 and between the interior of the valve body 3 and the connecting body 6 in the form of a seal 80, whereby both seals 70, 80 are formed by sealing rings.

[0028] The seals 40, 50, 60, 70, 80 are arranged so that fuel escaping from the fuel chamber 11 is collected in the return chamber 45 and drained via the return line. The injector 1 can therefore be disassembled non-destructively for repair purposes and reassembled after reconditioning or replacing the individual parts without compromising the tightness of the fuel chamber 11.

[0029] Since fuel flowing through the return line 46 is an indication of a leak in the injector 1, this can be used to detect leaks. A corresponding sensor is installed in the return line 46. If a predefined fuel concentration in the return line 46 is exceeded, it signals a malfunction, allowing the affected injector 1 to be replaced or repaired.

Claims

Claims 1 . Injector (1) for the metered delivery of a gaseous or liquid fuel, with a housing (2) which has a fuel chamber (11) which can be filled with fuel under an injection pressure and a valve body (3) which is surrounded by a jacket tube (7), wherein an intermediate space is formed between the valve body (3) and the jacket tube (7), which intermediate space is part of the fuel chamber (11), wherein one end of the jacket tube (7) forms a sealing point (40) with the valve body (3) in order to seal the fuel chamber (11) to the outside, characterized in that a return chamber (45) is formed in the housing (2), which is connected to a return line (46) and which is separated from the fuel chamber (11) by the sealing point (40).

2. Injector (1) according to claim 1, characterized in that the sealing point (40) comprises a first sealing ring (41) and a second sealing ring (42) which are arranged parallel to one another and which are clamped between the casing tube (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) being connected to the return space (45).

3. Injector (1) according to claim 1 or 2, characterized in that the housing (2) comprises a nozzle body (5) which forms the combustion chamber-side end of the injector (1) and in which a valve element (12) controlling an injection opening (15) is arranged, wherein the nozzle body (5) forms a second sealing point (50) with the jacket tube (7) and the sealing point comprises two parallel sealing rings (51; 52) which are clamped between the jacket tube (7) and the valve body (3), wherein the annular space (53) between the two sealing rings (51; 52) is connected to the return space (45) formed in the valve body (3).

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

5. Injector 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. Injector according to one of claims 1 to 5, characterized in that the nozzle body (5) forms a further sealing point (60) with a magnetic body (4), wherein the magnetic body (4) surrounds an electromagnet (26).

7. Injector according to one of claims 1 to 6, characterized in that the valve element (12) is surrounded at least in sections by a first corrugated bellows (30) which delimits a lubricant chamber (35) which can be filled with a lubricant.

8. Injector according to one of claims 1 to 7, characterized in that a fuel sensor for determining the fuel concentration is arranged in the return line (46).

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

10. Method according to claim 9, characterized in that ambient pressure prevails in the return chamber (45) (0.1 MPa absolute).

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