Injectors for gaseous or liquid fuels

Abstract

The injector for discharging gaseous or liquid fuel includes a housing (1) having a fuel chamber (5) that can be filled with fuel, and a piston-shaped valve element (6) that cooperates with a valve seat (7) to open and close a metering opening (9) in the fuel chamber (5), the valve element (6) being movable in the 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) that defines a lubricant chamber (10) containing a lubricant (24) for lubricating the valve element (6). A compensation chamber (23) connected to the lubricant chamber (10) is formed in the housing (1), and the compensation chamber (23) is partially filled with the lubricant (24) and partially filled with a gas (25).

Description

[Technical Field]

[0001] The present invention relates to an injector used for metering liquid or gaseous fuel, in particular for discharging fuel directly into the combustion chamber or intake tract of an internal combustion engine. [Background technology]

[0002] Gaseous or liquid fuel required for the operation of an internal combustion engine is metered into the intake duct or directly into the combustion chamber of the engine. When metering fuel directly into the combustion chamber, the fuel must be released by the injector at a precise time and in a precise amount. To achieve this, the injector has a movable valve element that can be actuated via an electromagnet or other electrical actuator. The movement of the valve element opens or closes a metering opening. Such an injector is known, for example, from U.S. Pat. No. 5,623,399 and has a piston-shaped valve element that is longitudinally displaceable within the injector housing. The valve element is surrounded by a lubricant chamber that is sealed against the fuel chamber by a corrugated bellows, and fuel flows through the fuel chamber to the metering opening. The lubricant ensures friction-free movement of the valve element and, therefore, precise metering of fuel over its service life.

[0003] In injectors with an outward-opening valve element, the valve element moves outward from the housing during the opening stroke, expanding the lubricant chamber defined by the corrugated bellows. The subsequent closing stroke causes the lubricant chamber to shrink accordingly. This change in size is made possible by the corrugated bellows, which is longitudinally flexible and fixedly connected to the valve element at one end. However, because the lubricant is liquid and therefore incompressible, a compensation chamber is required to accommodate the lubricant expelled from the lubricant chamber and subsequently release it again. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] German Patent Application Publication No. 102021200689 Summary of the Invention

[0005] The injector for discharging gaseous or liquid fuel according to the present invention has the advantage that a compensation chamber can be easily formed, thereby ensuring the function of the injector over its entire service life. To this end, the injector has a housing in which a fuel chamber capable of being filled with fuel is formed, and a piston-shaped valve element is arranged in the housing, cooperating with a valve seat for opening and closing a metering opening in the fuel chamber. The valve element is movable in an opening direction by an actuator against the force of a closing spring and is at least partially surrounded by a corrugated bellows, which defines a lubricant chamber containing a lubricant for lubricating the valve element. Furthermore, a compensation chamber connected to the lubricant chamber is formed in the housing, and the compensation chamber is partially filled with lubricant and partially filled with gas.

[0006] Because only one end of the corrugated bellows is connected to the valve element, when the valve element moves longitudinally to open, the corrugated bellows expands, allowing the valve element to move and simultaneously ensuring a tight seal on the lubricant chamber. In this case, the volume of the lubricant chamber changes in the area of ​​the corrugated bellows. Because the lubricant is liquid and therefore nearly incompressible, it must flow out of the compensation chamber. Conversely, during the closing movement, the volume shrinks, and the difference must be able to flow from this part of the lubricant chamber into the compensation chamber. That is, the compensation chamber must accommodate and release a specific amount of lubricant during the opening and closing movements of the valve element. The necessary elasticity is provided by the gas in the lubricant chamber. This is because the lubricant flowing into the lubricant chamber compresses the gas, which then expands accordingly when the lubricant flows out. The pressure generated by the gas compression is also applied to the lubricant. The connection to the compensation chamber also compensates for changes in the volume of the lubricant due to temperature changes.

[0007] In a preferred embodiment of the invention, the connection between the lubricant chamber and the compensation chamber includes a connecting pipe that protrudes into the compensation chamber. The compensation chamber is preferably filled with lubricant in such a manner that the opening of the connecting pipe is always covered with lubricant. Because gas rises due to gravity, if the lubricant chamber is sufficiently filled, it is guaranteed that gas will not reach the connecting pipe and thus the region of the lubricant chamber of the nozzle body, regardless of the orientation of the injector. Otherwise, lubrication of the valve element may be hindered, which could result in the valve element malfunctioning.

[0008] In another advantageous embodiment, a membrane is arranged in the compensation chamber, dividing the compensation chamber into two mutually sealed regions, one connected to the lubricant chamber and the other containing gas. Its function is the same as in the embodiment without a membrane, but the membrane already prevents the lubricant and gas from mixing, thereby preventing the gas from entering the lubricant chamber. In this case, the membrane can advantageously be biased toward the gas by the pressure in the lubricant chamber, i.e., the membrane protrudes convexly into the gas volume, biasing it toward the lubricant and creating a certain pressure that ensures reliable filling of the lubricant chamber.

[0009] In another advantageous embodiment, the compensation chamber contains only the lubricant and the gas, i.e. no other medium is required to separate these two media.

[0010] The lubricant is advantageously in liquid form, and in particular a lubricating oil can be used as lubricant, which has the necessary lubricating properties to produce a friction-free movement of the valve element. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a longitudinal cross-sectional view of an injector according to the present invention; [Figure 2] 1 , showing only the area of ​​the compensation chamber of the injector; FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Two exemplary embodiments of the invention are shown in the drawings.

[0013] FIG. 1 shows a longitudinal cross-sectional view of an injector according to the present invention, which can be used to meter liquid or gaseous fuel. The injector includes a housing 1 containing a multi-piece valve body 2, a mantle tube 3, and a nozzle body 4. Similarly, the valve body 2 is a multi-piece structure, with the individual parts connected gas-tight and liquid-tight to each other and extending to the nozzle body 4, which forms the combustion chamber end of the injector. A fuel chamber 5 is defined between the valve body 2 and the surrounding mantle tube 3, and the fuel chamber 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 longitudinally displaceable. The valve element protrudes from the nozzle body 4 and has a valve plate 106 including 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 opened by longitudinal movement of the valve element 6 between the valve seat 7 and the sealing surface 8.

[0014] The end of the valve element 6 opposite the valve seat 7 is accommodated in a guide sleeve 15, with a closing spring 16 clamped under compression between the guide sleeve and a support member 14. The closing spring 16 applies a closing force to the valve element 6 in the direction of the closed position, in which the sealing surface 8 abuts the valve seat 7. A bolt 17 abuts the guide sleeve 15 on the side opposite the valve element 6. The bolt is connected to a magnetic armature 21 and, together with a damping element 18, damps the contact of the sealing surface 8 with the valve seat 7, thereby reducing the mechanical load in this area and also noise emissions. An actuator in the form of an electromagnet 20 is arranged in the valve body 2 at the level of the bolt 17. When energized, the valve body applies a longitudinal force to the magnetic armature 21 and, therefore, via the bolt 17, to the valve element 6. This pushes the valve element out of the nozzle body 4 in the opening direction against the force of the closing spring 16, thereby opening the metering opening 9. In that case, an electrical connection 19 supplies the electromagnet 20 with the required voltage from a power supply (not shown).

[0015] The valve element 6 is surrounded by a corrugated bellows 11 in the nozzle body 4, which is connected fluid-tight at its seat end to the valve element 6 by a weld 12 and at its other end to the valve body 2. The corrugated bellows 11 defines a lubricant chamber 10 surrounding the valve element 6, which extends within the valve body 2 past the guide sleeve 15 and bolt 17 to the compensation chamber 23. The connection from the lubricant chamber 10 to the compensation chamber 23 is made by a connecting tube 26, which protrudes into the compensation chamber 23 and, in this exemplary embodiment, extends approximately to the center of the compensation chamber 23. To ensure that the guide of the valve element 6 in the guide sleeve 15 and other points on the valve element 6 where friction occurs are virtually friction-free, the lubricant chamber 10 is filled with a lubricant. The lubricant can be, for example, a lubricating oil, such as a relatively low-viscosity mineral lubricant. The lubricant chamber 10 and the associated compensation chamber 23 are filled with lubricant 24 in such an amount that the lubricant chamber 10 is mostly, but not completely, filled with lubricant and that gas is also present in the compensation chamber 23 in addition to the lubricant. In the assembled injector, the lubricant chamber 10 and the compensation chamber 23 are sealed against the outside, so that the lubricant does not mix with the fuel.

[0016] The injector operates as follows: The fuel chamber 5 is filled with gaseous or liquid fuel and is under injection pressure. At the start of the injection process, the electromagnet 20 is de-energized, causing the closing spring 16 to press the valve element 6 against the valve seat 7 via the valve disc 106, closing the fuel chamber 5. When fuel is to be released, the electromagnet 20 is energized, and its magnetic force pulls the magnetic armature 21 toward the valve seat 7 against the force of the closing spring 16, pushing the valve element 6 outward to its open position. This opens the metering opening 9 between the valve seat 7 and the valve disc 106, allowing fuel to flow out of the fuel chamber 5 and into, for example, the combustion chamber of an internal combustion engine. During the opening movement of the valve element 6, the corrugated bellows 11 expands, expanding the lubricant chamber 10. For compensation, 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 injection, the electromagnet 20 is de-energized and the closing spring 16 pushes the valve element 6 back into its closed position. The corrugated bellows 11 then contracts again, which reduces the lubricant chamber 10, which pushes a corresponding amount of lubricant back into the compensation chamber 23, where the gas is compressed and compensates for the additional amount of lubricant.

[0017] The central location of the connecting tube in the compensation chamber 23 ensures that, when properly filled with lubricant 24, the gas 25 does not reach the connecting tube 26 and therefore the lubricant chamber 10, regardless of the position of the injector relative to gravity. In Figure 1, the gas 25 is shown on the left side, where it would collect if the injector were rotated 90° to the side.

[0018] FIG. 2 shows another exemplary embodiment of an injector according to the present invention. This injector differs from the previous exemplary embodiment only in the configuration of the compensation chamber 23, so only this region of the injector, designated II in FIG. 1, is shown in longitudinal section. In this exemplary embodiment, the gas 25 and lubricant 24 in the compensation chamber 23 are separated by a membrane 30 made of a flexible, fuel-resistant material. The function is the same as in the injector shown in FIG. 1, but the lubricant flowing into the compensation chamber 23 now pushes the membrane 30 into the gas 25, causing it to deform convexly. Because the membrane 30 is flexible, it can exert a certain pressure on the lubricant, in addition to the pressure of the gas 25, to keep the lubricant always within the lubricant chamber 10. When using the membrane 30, the gas and lubricant are prevented from mixing regardless of the position of the injector, regardless of the amount of lubricant in the compensation chamber 23, so the connecting pipe 26 can be omitted.

[0019] In addition to compensating for the lubricant volume during the opening and closing movements of the valve element 6, the compensation chamber 23 is also used to compensate for volume changes of the lubricant or the defining components due to thermal expansion of the lubricant. [Explanation of symbols]

[0020] 1. Housing 2 Valve body 3 Mantle tube 4 Nozzle body 5 Fuel chamber 6 Valve elements 7 Valve seat 8 Sealing Surface 9 Metering opening 10 Lubricant chamber 11 Bellows 12 Welded Connections 13 Fuel inlet 14 Support member 15 Guide sleeve 16 Closing spring 17 volts 18 Damping Elements 19 terminals 20 Electromagnet 21 Magnetic Armature 23 Compensation Room 24 Lubricants 25 Gas 26 Connecting pipe 30 membrane 106 Bento Plate

Claims

1. 1. An injector for discharging a gaseous or liquid fuel, comprising: a housing (1) in which a fuel chamber (5) capable of being filled with fuel is formed; a piston-shaped valve element (6) cooperating with a valve seat (7) for opening and closing a metering opening (9) of said fuel chamber (5), said valve element (6) being movable in the opening direction by an actuator (20) against the force of a closing spring (16); and a corrugated bellows (11) at least partially surrounding said valve element (6) and defining a lubricant chamber (10) containing a lubricant (24) for lubricating said valve element (6), 1. The injector according to claim 1, wherein a compensation chamber (23) connected to the lubricant chamber (10) is formed in the housing (1), and the compensation chamber (23) is partially filled with the lubricant (24) and partially filled with gas (25).

2. 2. The 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) projecting into the compensation chamber (23).

3. 3. The injector according to claim 2, wherein the compensation chamber contains a lubricant (24) in an amount such that the pipe opening (27) of the connecting pipe (26) is always covered with the lubricant.

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

5. 5. The injector according to claim 1, wherein the corrugated bellows (11) is fixedly connected at one end to the valve element (6), whereby the corrugated bellows is compressed when the valve element (6) moves longitudinally.

6. 6. The injector according to claim 1, wherein a flexible membrane (30) is arranged in the compensation chamber (23), separating the gas (25) from the lubricant (24).

7. 7. Injector according to claim 6, characterized in that the flexible membrane (30) is biased into the gas (25) by the lubricant (24).

8. 8. Injector according to any one of claims 1 to 7, characterized in that the compensation chamber (10) contains only lubricant (24) and gas (25).

Images