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

Abstract

The injector (1) for metering the discharge of gaseous or liquid fuel comprises a housing (2) having a fuel chamber (11) that can be filled with fuel under injection pressure and a valve body (3) surrounded by a mantle tube (7), an intermediate space that is part of the fuel chamber (11) is formed between the valve body (3) and the mantle tube (7), and one end of the mantle tube (7) forms a seal point (40) together with the valve body (3) for sealing the fuel chamber (11) from the outside. A return chamber (45) is formed within the housing (2), and the return chamber is connected to a return line (46) and is separated from the fuel chamber (11) by the seal point (40).

Description

[Technical Field]

[0001] The invention takes as its starting point an injector for metering liquid or gaseous fuel, which is preferably used to introduce fuel into the combustion chamber or intake tract of an internal combustion engine. [Background technology]

[0002] In internal combustion engines operating on gaseous or liquid fuel, fuel is metered into the intake duct or directly into the combustion chamber of the engine. Compressed fuel, and therefore under injection pressure, is supplied, and an electrically controlled injector is used to release the required amount of fuel at the desired time. For this purpose, the injector has a movable valve element that can be actuated via an electromagnet or other electrical actuator. The movement of this valve element opens or closes a metering opening. Such an injector is known, for example, from U.S. Pat. No. 5,623,399, and includes a piston-shaped nozzle needle as the valve element, which is longitudinally displaceable within the injector housing. The fuel is guided through a fuel chamber in the injector, from one end with a fuel inlet to the outlet end with an injection opening. A lubricant chamber surrounds the valve element for friction-free support. The injector chambers are sealed to prevent mixing of the fuel and lubricant.

[0003] An injector consists of several parts that are connected together during assembly. Where the parts meet, a seal must be formed to ensure that, on the one hand, fuel does not leak out of the injector, and, on the other hand, lubricant does not mix with the fuel. This is particularly challenging when using hydrogen as fuel, as hydrogen can diffuse very easily into even the smallest gaps.

[0004] Injectors for large internal combustion engines are designed for long operating times and are correspondingly expensive. Therefore, such injectors are repeatedly repaired to ensure continued use when wear reduces the injector's functionality. This requires disassembly of the injector to replace individual parts or, in some cases, to clean and then continue use. Sealing the parts together and from the outside by welded joints is usually not considered, since welded joints cannot be broken without destruction, thus making disassembly difficult or impossible. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] German Patent Application Publication No. 102021200689 Summary of the Invention

[0006] The injector according to the present invention has the advantage that it can be disassembled into individual components without destruction while at the same time ensuring reliable sealing of the fuel passage of the injector. To this end, the injector has a housing with a valve body including a fuel inlet through which fuel can be filled into a fuel chamber formed in the housing. The valve body is surrounded by a mantle tube, and an intermediate space that is part of the fuel chamber is formed between the mantle tube and the valve body, and one end of the mantle tube forms a sealing point together with the valve body for sealing the fuel chamber from the outside. A return chamber is formed in the housing, and the return chamber is connected to a return line and separated from the fuel chamber by the sealing point.

[0007] The return chamber is used to contain fuel that passes through the seal due to leaks or micro-leaks in the seal, which can occur especially when using hydrogen as fuel.

[0008] The fuel that reaches the return chamber is then led out of the injector via a return line, which allows the return chamber to be kept at a constant low pressure. This allows for a certain amount of leakage in the seal, making it possible to repair the injector by replacing or repairing individual components. This function is maintained even after disassembly and reassembly of the components.

[0009] In a first advantageous embodiment of the present invention, the sealing point includes first and second sealing rings arranged parallel to each other and clamped between the outer casing and the valve body, with the annular space defined by the sealing rings connected to the return chamber. When fuel passes through the first sealing ring and leaves the fuel chamber, it is directed into the return chamber and discharged via the return line. The second sealing ring ensures that all escaping fuel is thus contained by the return chamber. Advantageously, such a seal can also be formed between the nozzle body and the outer casing, which forms the end of the injector facing the combustion chamber and where the injection openings are formed.

[0010] In another advantageous development of the invention, the sealing ring surrounds the valve body. The rotationally symmetrical sealing formed in this way allows for great freedom in design and therefore easy adaptation of the injector to various installation situations. Preferably, the sealing ring is made of an elastic material, in particular an elastomer.

[0011] In a further development of the invention, a seal is formed between the nozzle body and the magnet body, which can enclose the electromagnet, so that the inner region of the injector can be sealed against the fuel and the components therein are protected against the fuel.

[0012] In another advantageous embodiment, the valve element is at least partially surrounded by a first corrugated bellows defining a lubricant chamber that can be filled with lubricant. The seal according to the invention allows the lubricant chamber to be sealed against fuel, thereby maintaining lubrication of the valve element over its service life.

[0013] In the proposed method of operating the injector according to the invention, the pressure in the return chamber is kept lower than the pressure in the fuel chamber, which prevents gas or liquid from reaching the fuel chamber from the return chamber and being contaminated or spoiled there, the pressure in the return chamber being preferably ambient pressure. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a longitudinal sectional view showing only the main parts of an injector according to the present invention; [Figure 2] FIG. 2 is an enlarged view of a portion indicated by II in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] An exemplary embodiment of an injector according to the invention is shown in the drawings.

[0016] FIG. 1 shows a longitudinal cross-section of an injector 1 for metering liquid or gaseous fuel according to the present invention. The injector 1 is specifically designed to deliver fuel into the combustion chamber or intake duct of an internal combustion engine. The injector 1 includes a housing 2, which includes a valve body 3 including a connecting element 6, a magnet element 4, and a nozzle element 5, which are adjacent to each other and longitudinally fixed to each other by a clamping device (not shown in detail) or connected by a screw connection. The valve body 3 is surrounded by a hollow, cylindrical outer casing 7, which defines an annular space between the valve body 3 and the outer casing 7. This annular space is part of a fuel chamber 11, which can be filled with gaseous or liquid fuel under injection pressure via a connecting element 6 threaded onto the valve body 3 and a fuel inlet 10 formed therein. The injection pressure depends on the fuel used and the type and operating conditions of the internal combustion engine. For example, when using a gaseous fuel such as hydrogen or natural gas, the injection pressure is between 30 and 300 bar (3 and 30 MPa).

[0017] The fuel inlet 10 is connected via a connecting hole 17 to a portion of the fuel chamber 11 defined by the outer casing 7, allowing fuel to flow through the fuel chamber 11 and via a further connecting hole 18 to the nozzle body 5. A piston-shaped valve element 12 is longitudinally displaceably arranged in the nozzle body 5. The valve element has a valve seat 112 at its outlet end that protrudes through an injection opening 15 formed in the nozzle body 5. The valve seat 112 has a sealing surface 14 that cooperates with a valve seat 13 surrounding the injection opening 15 to open and close the injection opening 15. When 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 can flow out of the fuel chamber 11. When the valve element 12 abuts against the valve seat 13, the injection opening 15 is closed.

[0018] The valve element 12 is housed in a guide sleeve 20 at its end opposite the valve retainer 112. A closing spring 21 is housed under compression between the guide sleeve 20 and a step in the housing 2, and the closing spring exerts a closing force on the valve element 12 toward the nozzle body 5. The guide sleeve 20 rests on a bolt 22, which is supported and movable in the longitudinal direction, on the side opposite the valve element 12, and the bolt is connected to a magnetic armature 24. A damping piston 25 is arranged in the valve body 3 in the extension of the bolt 22, which damps the closing movement of the valve element 12, causing the valve retainer 112 to come into contact with the valve seat 13 and thereby reducing the mechanical load.

[0019] An electromagnet 26 is arranged in the magnet body 4 at the height of the bolt 22 and surrounds a magnetic armature 24 in an annular shape, the magnetic field of which is strengthened and deflected by an inner magnetic pole 27. When the electromagnet 26 is energized, a force acts on the magnetic armature 24, which pulls the magnetic armature towards the outlet opening 15 against the force of the closing spring 21, thereby opening the injection opening 15 and allowing fuel to flow out of the fuel chamber 11. When the energization of the electromagnet 26 is terminated, the closing spring 21 returns the valve element 12 to its closed position and the outlet opening 15 is closed again.

[0020] The valve element 12 is surrounded by a valve sleeve 31, which in turn is surrounded by a first corrugated bellows 30. The corrugated bellows 30 is sealingly connected to the valve sleeve 31, which in turn is sealingly connected to the valve element 12 by a welded joint 32, allowing the valve sleeve 31 to move longitudinally along with the valve element 12. The other end of the corrugated bellows 30 is sealingly connected to the disk 28. The first corrugated bellows 30 encloses a lubricant chamber 35 that extends through the closing spring 21, the magnet armature 24, and the damping piston 25 to the region of the valve body 3 opposite the valve element. The lubricant chamber 35 is then bounded by a second corrugated bellows 36, which forms a compensation chamber. As 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 corrugated bellows 36. A plurality of longitudinal holes 124 are formed in the magnet armature 24 to allow the lubricant to flow unimpeded through the area of ​​the magnet armature 24. The lubricant chamber 35 is filled with a liquid lubricant, such as a suitable mineral oil, to lubricate the guide area of ​​the valve element 12 and thereby allow for frictionless movement of the valve element 12.

[0021] A seal 40, consisting of a first seal ring 41 and a second seal ring 42, is formed between the outer tube 7 and the valve body 3, sealingly connecting the upper end of the outer tube 7 to the valve body 3 (see FIG. 1). The seal 40 prevents fuel from leaking out of the fuel chamber 11, which must be ensured at all times, especially with gaseous fuels. The seal rings 41 and 42 are made of an elastic material, such as an elastomer. Between the two seal rings 41 and 42, an annular space 43 is formed between the outer tube 7 and the valve body 3, which is connected to a return chamber 45 via a connecting hole 47. Because it is very difficult to completely prevent even small leaks from the seal, any fuel that does leak out 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 form of multiple interconnected holes in the housing 2, extending from the valve body 3 through the magnet body 4 to the nozzle body 5. In that case, a low pressure lower than the pressure in the fuel chamber 11, preferably ambient pressure, is always present in the return chamber 45.

[0022] The opposite second end of the outer casing 7 forms a second seal 50 with the nozzle body 5, which also consists of two parallel sealing rings 51, 52 defining an annular space 53. Again, the annular space 53 is connected to the return chamber 45 via a connecting hole 48, so that fuel that may have overflowed the first sealing ring 51 is discharged via the return chamber 45. Figure 2 shows this region of the injector 1, with the portion indicated by II in Figure 1 further enlarged for clarity.

[0023] The connection between the magnet body 4 and the nozzle body 5 is formed by a seal 60, which includes a first seal ring 61 clamped between the magnet body 4 and the nozzle body 5. If fuel from the fuel chamber 11 passes through the seal ring 61, it also enters the return chamber 45. A second seal ring 62 is arranged inside the nozzle body 5, which seals the return chamber 45 against the fuel entering the interior of the nozzle body 5. Further seals are arranged at the level of the damping piston 25 between the magnet body 4 and the valve body 3 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; the two seals 70, 80 are formed by seal rings.

[0024] The seals 40, 50, 60, 70, 80 are arranged so that fuel leaving the fuel chamber 11 is collected in the return chamber 45 and led out via the return line. Therefore, for repair purposes, the injector 1 can be disassembled without destruction and reassembled after repair or replacement of individual parts without compromising the sealing of the fuel chamber 11.

[0025] The fuel leaking out through the return line 46 is an indication of a non-sealing injector 1 and can be used to identify this. A corresponding sensor is fitted to the return line 46, which reports a fault if the fuel in the return line 46 exceeds a predetermined concentration, so that the injector 1 can be replaced or repaired. [Explanation of symbols]

[0026] 1 injector 2. Housing 3 Valve body 4. Magnet body 5 Nozzle body 6 Connectors 7 Mantle tube 10 Fuel inlet 11 Fuel chamber 12 Valve element 112 Valve holder 13 Valve seat 14 Sealing surface 15 Injection opening, outlet opening 17 Connection hole 18 Connection hole 20 Guide sleeve 21 Closing spring 22 volts 24 magnetic armature 25 Damping piston 26 Electromagnet 27 Inner magnetic pole 28 discs 30 Corrugated Bellows 31 Valve sleeve 32 Welded joints 35 Lubricant chamber 36 Corrugated bellows 124 Longitudinal hole 40 stickers 41 First seal ring 42 Second seal ring 43 Annular Space 45 Return Room 46 Return line 47 Connection hole 48 Connection hole 50 stickers 51, 52 Seal ring 53 Annular Space 60 stickers 61 First seal ring 62 Second seal ring 70 stickers 80 stickers

Claims

1. An injector (1) for metering the discharge of gaseous or liquid fuel, comprising a housing (2) having a fuel chamber (11) that can be filled with fuel under injection pressure, and a valve body (3) surrounded by a mantle tube (7), wherein an intermediate space that is part of the fuel chamber (11) is formed between the valve body (3) and the mantle tube (7), and one end of the mantle tube (7) forms a sealing point (40) together with the valve body (3) for sealing the fuel chamber (11) from the outside.

1. An injector comprising: a return chamber (45) formed in the housing (2), the return chamber being connected to a return line (46) and separated from the fuel chamber (11) by the sealing point (40).

2. 2. The injector (1) according to claim 1, wherein the sealing point (40) comprises a first sealing ring (41) and a second sealing ring (42) arranged parallel to each other and clamped between the outer casing (7) and the valve body (3), whereby an annular space (43) is defined between the first sealing ring (41) and the second sealing ring (42), and the annular space (43) is connected to the return chamber (45).

3. 3. The injector according to claim 1, wherein the housing (2) includes a nozzle body (5), which forms the combustion chamber side end of the injector (1), and in which a valve element (12) for controlling an injection orifice (15) is arranged, and the nozzle body (5) forms a second sealing point (50) together with the outer casing (7), the sealing point including two parallel sealing rings (51; 52) clamped between the outer casing (7) and the valve body (3), and an annular space (53) between the two sealing rings (51; 52) is connected to the return chamber (45) formed in the valve body (3).

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

5. Injector according to any one of claims 2 to 4, characterized in that the sealing ring (41; 42; 51; 52) is made from a resilient material, preferably an elastomer.

6. 6. The injector according to claim 1, wherein the nozzle body (5) forms another sealing point (60) together with a magnet body (4), the magnet body (4) surrounding an electromagnet (26).

7. 7. The injector according to claim 1, wherein the valve element (12) is at least partially surrounded by a first corrugated bellows (30) defining a lubricant chamber (35) that can be filled with lubricant.

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

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

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

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