Injector for gaseous or liquid fuel

Abstract

The invention relates to an injector for dispensing gaseous or liquid fuel, having a housing (1), in which a fuel chamber (5) which can be filled with the fuel is formed, and having a piston-like valve element (6), which interacts with a valve seat (7) to open and close a dispensing opening (9) of the fuel chamber (5), wherein the valve element (6) can be moved in an opening direction by an actuator (20), against the force of a closing spring (16). The valve element (6) is at least partially surrounded by a corrugated bellows (11), which delimits a lubricant chamber (10), in which a lubricant (24) is present for lubricating the valve element (6). A compensating chamber (23) connected to the lubricant chamber (10) is formed in the housing (1), wherein the compensating chamber (23) is filled partly with the lubricant (24) and partly with a gas (25).

Description

[0001] title Fuels

[0002] The invention relates to an injector as used for the metered delivery of liquid or gaseous fuel, in particular for delivering fuel directly into a combustion chamber or the intake tract of an internal combustion engine.

[0003] State of the art

[0004] To operate internal combustion engines, the required gaseous or liquid fuel is metered either into the intake tract of the internal combustion engine or directly into the combustion chamber of the internal combustion engine. When metered directly into the combustion chamber, the fuel must be delivered by an injector very precisely at the desired time and in the correct quantity. For this purpose, the injector has a movable valve element that can be moved via an electromagnet or other electrical actuator, whereby the movement of the valve element opens or closes a metering opening. Such an injector is known, for example, from DE 10 2021 200 689 A1 and has a piston-shaped valve element that is arranged so as to be longitudinally displaceable in the housing of the injector. The valve element is surrounded by a lubricant chamber that is sealed off from a fuel chamber by a corrugated bellows, through which the fuel flows to the metering opening.The lubricant ensures low-friction movement of the valve element and thus precise fuel dosing over its service life.

[0005] In injectors with an outward-opening valve element, the valve element moves out of the housing during the opening stroke, expanding the lubricant chamber defined by the bellows. During the subsequent closing movement, the lubricant chamber shrinks again accordingly. This change in size is made possible by the bellows, which is flexible in its length and firmly connected to the valve element at one end. However, since the lubricant is liquid and therefore incompressible, a compensation chamber must be present to absorb the lubricant displaced from the lubricant chamber and then release it again.

[0006] Advantages of the invention

[0007] The injector according to the invention for dispensing gaseous or liquid fuel has the advantage that a compensation chamber is designed in a simple manner, thus ensuring the function of the injector over its service life. For this purpose, the injector has a housing in which a fuel chamber that can be filled with the fuel is formed and in which a piston-shaped valve element is arranged, which cooperates with a valve seat for opening and closing a metering opening of the fuel chamber. The valve element is movable by an actuator against the force of a closing spring in an opening direction and is surrounded at least in sections by a corrugated bellows that delimits a lubricant chamber in which a lubricant for lubricating the valve element is present. Furthermore, a compensation chamber connected to the lubricant chamber is formed in the housing, wherein the compensation chamber is partially filled with the lubricant and partially with a gas.

[0008] During the longitudinal opening movement of the valve element, the bellows is extended, as only one end of the bellows is connected to the valve element. This allows the valve element to move while simultaneously ensuring the sealing of the lubricant chamber. The volume of the lubricant chamber in the area of ​​the bellows changes. Since the lubricant is liquid and therefore largely incompressible, lubricant must flow from a compensation chamber. Conversely, the volume decreases during the closing movement, and the differential volume must be able to flow from this part of the lubricant chamber into the compensation chamber. The compensation chamber must therefore absorb and release a certain volume of lubricant during the opening and closing movement of the valve element.The gas in the lubricant chamber provides the necessary elasticity, as the lubricant flowing into the lubricant chamber compresses the gas, and the gas expands accordingly as the lubricant flows out. The compression of the gas also exerts pressure on the lubricant. Changes in the lubricant's volume due to temperature changes can also be compensated for by the connection to the compensation chamber.

[0009] In an advantageous embodiment of the invention, the connection between the lubricant chamber and the compensation chamber comprises a connecting pipe that extends into the compensation chamber. Advantageously, there is always enough lubricant in the compensation chamber to cover the opening of the connecting pipe. Since the gas rises due to gravity, a sufficiently filled lubricant chamber ensures that no gas enters the connecting pipe and thus the area of ​​the lubricant chamber in the nozzle body, regardless of the orientation of the injector. Otherwise, the lubrication of the valve element could be compromised, resulting in functional impairments.

[0010] In a further advantageous embodiment, a membrane is arranged in the compensation chamber, which divides the compensation chamber into two mutually sealed areas, with lubricant in the area connected to the lubricant chamber and gas in the other area. The function is identical to the embodiment without a membrane, but the membrane itself prevents mixing of lubricant and gas and thus penetration of gas into the lubricant chamber. Advantageously, the membrane can be pre-tensioned into the gas by the pressure in the lubricant chamber, i.e. the membrane protrudes convexly into the gas volume in order to create a pre-tension and thus a certain pressure in the lubricant and to ensure reliable filling of the lubricant chamber.

[0011] In a further advantageous embodiment, only lubricant and gas are present in the compensation chamber. Additional media, such as separating these two media, are not necessary.

[0012] The lubricant is advantageously liquid. In particular, a lubricating oil can be used as the lubricant, which has the necessary lubricating properties to ensure low-friction movement of the valve element. Drawing

[0013] The drawing shows two embodiments of the invention.

[0014] Fig. 1 shows a longitudinal section through an injector according to the invention and Fig. 2 shows a further embodiment, wherein the injector is shown only in the region of the compensation chamber according to section II in Fig. 1 .

[0015] Description of the embodiments

[0016] Fig. 1 shows a longitudinal section through an injector according to the invention, which can be used for the metered delivery of liquid or gaseous fuel. The injector has a housing 1 comprising a multi-part valve body 2, a jacket tube 3, and a nozzle body 4. The valve body 2 is also constructed in several parts, with the individual parts being connected to one another in a gas-tight and liquid-tight manner, and extends into the nozzle body 4, which forms the combustion chamber end of the injector. Between the jacket tube 3, which surrounds the valve body 2, a fuel chamber 5 is formed, which can be filled with fuel via a fuel inlet 13 formed in the valve body 2. The fuel chamber 5 extends into the nozzle body 4, in which a piston-shaped valve element 6 is arranged for longitudinal displacement. This valve element protrudes from the nozzle body 4 and has a valve plate 106 with a sealing surface 8.The sealing surface 8 cooperates with a valve seat 7 formed on the nozzle body 4 to open and close an annular metering opening 9, which is controlled by the longitudinal movement of the valve element 6 between the valve seat 7 and the sealing surface 8.

[0017] The end of the valve element 6 facing away from the valve seat 7 is accommodated in a guide sleeve 15, between which and a support part 14 a closing spring 16 is clamped under compressive preload. The closing spring 16 exerts a closing force on the valve element 6 in the direction of the closed position in which the sealing surface 8 is in contact with the valve seat 7. A bolt 17 is located on the guide sleeve 15 facing away from the valve element 6. The bolt 17 is connected to a magnet armature 21 and interacts with a damping element 18 to slow down the contact of the sealing surface 8 on the valve seat 7 and thus reduce the mechanical stress in this area and also the noise generation.At the level of the bolt 17, an actuator in the form of an electromagnet 20 is arranged in the valve body 2. When energized, this actuator exerts a longitudinal force on the magnet armature 21 and thus, via the bolt 17, also on the valve element 6, in order to push the latter out of the nozzle body 4 in the opening direction against the force of the closing spring 16 and to open the metering opening 9. The electromagnet 20 is supplied with the necessary electrical voltage from a power source (not shown) via an electrical connection 19.

[0018] The valve element 6 is surrounded within the nozzle body 4 by a corrugated bellows 11, which is connected at its valve seat end by a welded joint 12 in a liquid-tight manner to the valve element 6 and at the other end to the valve body 2. The corrugated bellows 11 delimits a lubricant chamber 10 surrounding the valve element 6, which extends past the guide sleeve 15 and the bolt 17 into a compensation chamber 23 in the valve body 2. The connection from the lubricant chamber 10 to the compensation chamber 23 is formed by a connecting pipe 26, which projects into the compensation chamber 23, in this embodiment approximately to the middle of the compensation chamber 23. In order to keep the guidance of the valve element 6 in the guide sleeve 15 and also the other points on the valve element 6, where friction occurs between components, largely friction-free, the lubricant chamber 10 is filled with a lubricant.The lubricant can be a lubricating oil, for example, a mineral lubricating oil with a relatively low viscosity. Sufficient lubricant 24 is filled into the lubricant chamber 10 and the connected compensation chamber 23 so that the lubricant chamber 10 is largely—but not completely—filled with lubricant, and gas is present in the compensation chamber 23 in addition to the lubricant. In the fully assembled injector, the lubricant chamber 10 and compensation chamber 23 are sealed to the outside so that the lubricant does not mix with the fuel.

[0019] The injector functions as follows: In the injector, the fuel chamber 5 is filled with gaseous or liquid fuel, which is applied there under injection pressure. At the start of an injection process, the electromagnet 20 is de-energized, so that the closing spring 16 presses the valve element 6 with the valve plate 106 against the valve seat 7 and closes the fuel chamber 5. If fuel is to be released, the electromagnet 20 is energized and its magnetic force pulls the magnet armature 21 against the force of the closing spring 16 towards the valve seat 7, whereby the valve element 6 is pushed outwards into its opening position. The metering opening 9 between the valve seat 7 and the valve plate 106 is opened and fuel escapes from the fuel chamber 5, for example into a combustion chamber of an internal combustion engine. During the opening movement of the valve element 6, the bellows 11 is lengthened, which enlarges the lubricant chamber 10.To compensate, lubricant flows from the compensation chamber 23 into the lubricant chamber 10, causing the gas 25 in the compensation chamber 23 to expand accordingly. To end the injection, the current supply to the electromagnet 20 is interrupted, and the closing spring 16 pushes the valve element 6 back into its closed position. The bellows 11 shortens again, thus reducing the size of the lubricant chamber 10, which pushes the corresponding amount of lubricant back into the compensation chamber 23, where the gas is compressed to compensate for the additional amount of lubricant.

[0020] The position of the connecting pipe in the center of the compensation chamber 23 ensures, when filled with lubricant 24, that the gas 25 does not enter the connecting pipe 26 and thus the lubricant chamber 10, regardless of the injector's position relative to gravity. In Fig. 1, the gas 25 is shown on the left side for illustrative purposes, where it would collect if the injector were rotated 90° laterally.

[0021] Fig. 2 shows a further embodiment of the injector according to the invention, which differs from the previous embodiment only in the design of the compensation chamber 23, which is why only this area of ​​the injector is shown in longitudinal section, designated II in Fig. 1. In this embodiment, gas 25 and lubricant 24 are separated in the compensation chamber 23 by a diaphragm 30 made of a flexible, fuel-resistant material. The function is identical to the injector shown in Fig. 1, but here the lubricant flowing into the compensation chamber 23 presses the diaphragm 30 into the gas 25, causing the diaphragm 30 to deform convexly. Since the diaphragm 30 is flexible, it can exert a certain pressure on the lubricant in addition to the pressure of the gas 25 in order to always keep it in the lubricant chamber 10.When using the membrane 30, the connecting pipe 26 can be omitted, since this prevents mixing of gas and lubricant in any position of the injector, regardless of the amount of lubricant in the compensation chamber 23.

[0022] In addition to compensating the lubricant volume during the opening and closing movement of the valve element 6, the compensation chamber 23 also serves to compensate for volume changes of the lubricant due to thermal expansion of the lubricant or the limiting components.

Claims

Claims 1. Injector for dispensing gaseous or liquid fuel, comprising a housing (1) in which a fuel chamber (5) is formed which can be filled with the fuel, and comprising a piston-shaped valve element (6) which cooperates with a valve seat (7) for opening and closing a metering opening (9) of the fuel chamber (5), wherein the valve element (6) is movable in an opening direction by an actuator (20) against the force of a closing spring (16), and comprising a corrugated bellows (11) which surrounds the valve element (6) at least in sections and which delimits a lubricant chamber (10) in which a lubricant (24) for lubricating the valve element (6) is present, characterized in that a compensation chamber (23) connected to the lubricant chamber (10) is formed in the housing (1), wherein the compensation chamber (23) is partially filled with the lubricant (24) and partially with a gas (25).

2. Injector according to claim 1, characterized in that the connection between the lubricant chamber (10) and the compensation chamber (23) comprises a connecting pipe (26) which projects into the compensation chamber (23).

3. Injector according to claim 2, characterized in that there is so much lubricant (24) in the compensation chamber that the pipe opening (27) of the connecting pipe (26) is always covered with lubricant.

4. Injector according to one of claims 1 to 3, characterized in that the lubricant (24) is liquid.

5. Injector according to one of claims 1 to 4, characterized in that the corrugated bellows (11) is firmly connected to the valve element (6) at one end, so that it is compressed during the longitudinal movement of the valve element (6).

6. Injector according to one of claims 1 to 5, characterized in that a flexible membrane (30) is arranged in the compensation chamber (23) which separates the gas (25) from the lubricant (24).

7. Injector according to claim 6, characterized in that the flexible membrane (30) is prestressed into the gas (25) by the lubricant (24) 8. Injector according to one of claims 1 to 7, characterized in that only lubricant (24) and gas (25) are present in the compensation chamber (10).

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