Injector for gaseous or liquid fuel

Abstract

The invention relates to an injector for dispensing gaseous or liquid fuel, comprising: a housing (1) in which a fuel chamber (5) that can be filled with fuel is formed; a piston-shaped valve element (6) which interacts with a valve seat (7) in order to open and close a metering opening (9) of the fuel chamber (5), the valve element (6) being movable in an opening direction by means of an actuator (20) against the force of a closing spring (16). The valve element (6) is surrounded at least in sections by a bellows (11) which delimits a lubricant chamber (10) in which a lubricant (24) for lubricating the valve element (6) is present. A compensation chamber (23) connected to the lubricant chamber (10) is formed in the housing (1), the compensation chamber (23) being partially filled with the lubricant (24) and partially filled with a gas (25).

Description

Field of the Invention

[0001] The present invention relates to an injector, such as for metering the output of liquid or gaseous fuel, in particular for directly outputting fuel into the combustion chamber or the intake mechanism of an internal combustion engine. Background Art

[0002] For operating an internal combustion engine, the required gaseous or liquid fuel is either metered and supplied to the intake mechanism of the internal combustion engine or metered and directly supplied to the combustion chamber. In the case of direct metered supply to the combustion chamber, the fuel must be output by an injector at the desired time point and in the correct quantity. For this purpose, the injector has a movable valve element, which can be moved by an electromagnet or other electric actuator, wherein the metering opening is controlled to be opened or closed by the movement of the valve element. Such an injector is known, for example, from DE102021200689A1, which has a piston-shaped valve element that is arranged longitudinally displaceably in the housing of the injector. The valve element is surrounded by a lubricant chamber, which is sealed relative to the fuel chamber by a bellows, and the fuel flows through the fuel chamber to the metering opening. The lubricant ensures low-friction movement of the valve element and thus precise metering of the fuel over the service life.

[0003] In an injector with an outward-opening valve element, the valve element projects from the housing during the opening stroke movement, wherein the lubricant chamber bounded by the bellows is enlarged. During the subsequent closing movement, the lubricant chamber is correspondingly reduced again. This volume change can be achieved by the bellows, which is flexible in the longitudinal direction and is fixedly connected to the valve element at one end. However, since the lubricant is liquid and thus incompressible, a compensation chamber must be present to receive the lubricant discharged from the lubricant chamber and then output again. Summary of the Invention

[0004] The advantage of the injector according to the invention for outputting gaseous or liquid fuel is that the compensation chamber is configured in a simple manner and thus ensures the function of the injector over the service life. For this purpose, the injector has a housing in which a fuel chamber that can be filled with fuel is constructed, and a piston-shaped valve element is arranged in the housing, which cooperates with a valve seat to open and close the metering opening of the fuel chamber. Here, the valve element can be moved in the opening direction by an actuator against the force of a closing spring and is at least partially surrounded by a bellows that bounds a lubricant chamber in which there is a lubricant for lubricating the valve element. In addition, a compensation chamber connected to the lubricant chamber is constructed in the housing, wherein the compensation chamber is partially filled with lubricant and partially filled with gas.

[0005] During the opening movement of the valve element in the longitudinal direction, the bellows elongates because only one end of the bellows is connected to the valve element to enable the mobility of the valve element and at the same time ensure the sealing of the lubricant chamber. Here, the volume in the region of the bellows of the lubricant chamber changes. Since the lubricant is liquid and thus largely incompressible, the lubricant must flow in (nachflieβen) from the compensation chamber. Conversely, during the closing movement, this volume becomes smaller, and the volume difference must flow out from this smaller part of the lubricant chamber into the compensation chamber. Therefore, the compensation chamber must receive or output a certain volume of lubricant during the opening and closing movements of the valve element. The required elasticity is established by the gas in the compensation chamber because the lubricant flowing into the lubricant chamber compresses the gas, and the gas expands correspondingly again when the lubricant flows out, where the pressure depending on the gas compression also acts on the lubricant. The volume change of the lubricant caused by temperature changes can also be compensated by the connection to the compensation chamber.

[0006] In an advantageous configuration of the invention, the connection between the lubricant chamber and the compensation chamber includes a connecting pipe extending into the compensation chamber. Here, advantageously, there is always so much lubricant in the compensation chamber that the pipe opening of the connecting pipe is covered by the lubricant. Since the gas is lifted upwards by the action of gravity, it is ensured that, regardless of the orientation of the injector, no gas enters the connecting pipe and thus into the region of the lubricant chamber in the nozzle body when the lubricant chamber is sufficiently filled. Otherwise, the lubrication of the valve element may be affected, which may in turn lead to impaired functionality.

[0007] In another advantageous configuration, a diaphragm is arranged in the compensation chamber, which divides the compensation chamber into two hermetically sealed regions. Here, there is lubricant in the region connected to the lubricant chamber, and gas in the other region. The function is the same as in the configuration without a diaphragm, but the diaphragm prevents the mixing of the lubricant and the gas and thus prevents the gas from entering the lubricant chamber. Advantageously, the diaphragm can be pre-tensioned into the gas by the pressure in the lubricant chamber here, i.e., the diaphragm protrudes convexly into the gas volume, to generate a pre-tensioning force and thus generate a certain pressure in the lubricant and ensure the reliable filling of the lubricant chamber.

[0008] In another advantageous configuration, only lubricant and gas are present in the compensation chamber. Other media for separating these two media, for example, are not required.

[0009] Advantageously, the lubricant is liquid. In particular, lubricating oil with the required lubricating properties can be used as the lubricant to achieve low-friction movement of the valve element. Description of the Drawings

[0010] Two embodiments of the invention are shown in the drawings. The drawings show:

[0011] Figure 1Shows a longitudinal sectional view of an injector according to the present invention;

[0012] Figure 2 Shows another embodiment, in which, in accordance with Figure 1 Local II in shows the injector only in the region of the compensation chamber. Detailed description

[0013] In Figure 1 a longitudinal sectional view shows an injector according to the present invention, such as can be used to meter out liquid or gaseous fuel. The injector has a housing 1, which includes a multi-component valve body 2, a sleeve 3 and a nozzle body 4. The valve body 2 is also constructed as multi-component, where the individual partial bodies are connected to one another in an airtight and liquid-tight manner and extend up to the nozzle body 4, which forms the combustion chamber-side end of the injector. Between the sleeve 3 surrounding the valve body 2 and the valve body 2, a fuel chamber 5 is constructed, which can be filled with fuel through a fuel inlet 13 constructed 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 movably in the longitudinal direction, which projects from the nozzle body 4 and has a valve disk 106 with a sealing surface 8. The sealing surface 8 co-operates with a valve seat 7 constructed on the nozzle body 4 for opening and closing an annular metering opening 9, which is controlled to open between the valve seat 7 and the sealing surface 8 by the longitudinal movement of the valve element 6.

[0014] The end of the valve element 6 facing away from the valve seat 7 is received in a guide sleeve 15, in which a closing spring 16 is pressed under a pressure pre-tension between the guide sleeve and a support member 14. By means of the closing spring 16, a closing force is applied to the valve element 6 in the direction of the closed state, in which the sealing surface 8 is in contact with the valve seat 7. A stud 17 bears against the guide sleeve 15 facing away from the valve element 6, which is connected to an electromagnetic armature 21 and co-operates with a damping element 18 for cushioning the placement of the sealing surface 8 on the valve seat 7, thereby reducing the mechanical load and noise generation in this region. At the height of the stud 17, an actuator in the form of an electromagnet 20 is arranged in the valve body 2, which, when energized, exerts a longitudinal force on the electromagnetic armature 21 and thus also on the valve element 6 via the stud 17 in order to press it out of the nozzle body 4 against the force of the closing spring 16 in the opening direction and to control the opening of the metering opening 9. Here, the electromagnet 20 is supplied with the required voltage of an unshown current source via an electrical interface 19.

[0015] The valve element 6 is surrounded in the nozzle body 4 by a bellows 11 which is liquid-tightly connected to the valve element 6 at its valve seat side end by a welded connection 12 and is liquid-tightly connected to the valve body 2 at the other end. The bellows 11 delimits a lubricant chamber 10 surrounding the valve element 6, which lubricant chamber extends through a guide sleeve 15 and a stud 17 into a compensation chamber 23 in the valve body 2. Here, 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 and, in the present embodiment, projects approximately up to the middle of the compensation chamber 23. In order to keep the guiding of the valve element 6 in the guide sleeve 15 and the parts of the valve element 6 where there is friction between the components as frictionless as possible, the lubricant chamber 10 is filled with a lubricant. The lubricant can be, for example, a lubricating oil, such as a mineral oil with a low viscosity. The lubricant chamber 10 and the compensation chamber 23 connected thereto are filled with so much lubricant 24 that the lubricant chamber 10 is mostly, but not completely, filled with the lubricant, and there is also gas in the compensation chamber 23 in addition to the lubricant. When the injector is assembled, the lubricant chamber 10 and the compensation chamber 23 are sealed to the outside, so that the lubricant does not mix with the fuel.

[0016] The function of the injector is as follows: In the injector, the fuel chamber 5 is filled with gaseous or liquid fuel under injection pressure. At the start of the injection process, the electromagnet 20 is de-energized, so that the closing spring 16 presses the valve element 6 together with the valve disk 106 against the valve seat 7 and closes the fuel chamber 5. If fuel is to be discharged, the electromagnet 20 is energized, and its magnetic force overcomes the force of the closing spring 16 and pulls the armature 21 in the direction of the valve seat 7, whereby the valve element 6 is pressed outwards into its open position. Here, the metering opening 9 between the valve seat 7 and the valve disk 106 is controlled to open, and fuel flows out of the fuel chamber 5, for example, into the combustion chamber of an internal combustion engine. During the opening movement of the valve element 6, the bellows 11 elongates, which enlarges the lubricant chamber 10. For compensation, lubricant flows from the compensation chamber 23 into the lubricant chamber 10, and the gas 25 in the compensation chamber expands accordingly. To end the injection, the energization of the electromagnet 20 is interrupted, and the closing spring 16 presses the valve element 6 back into its closed position again. Here, the bellows 11 shortens again, and the lubricant chamber 10 thus becomes smaller, which presses the corresponding amount of lubricant back into the compensation chamber 23, where the gas is compressed in the compensation chamber to compensate for the additional amount of lubricant.

[0017] By the position of the connecting pipe in the middle of the compensation chamber 23, it is ensured that, regardless of the orientation of the injector with respect to gravity, the gas 25 does not enter the connecting pipe 26 and thus does not enter the lubricant chamber 10. In Figure 1 , for illustration, the gas 25 is shown on the left, where it would accumulate if the injector were rotated 90° laterally.

[0018] Figure 2 Another embodiment of an injector according to the invention is shown, which injector differs from the previous embodiment only in the configuration of the compensation chamber 23. Therefore, only this region of the injector is shown in a longitudinal sectional view, and this region is marked II in Figure 1 . In this embodiment, the gas 25 and the lubricant 24 in the compensation chamber 23 are separated by a diaphragm 30, which is made of a flexible fuel-resistant material. This function is the same as that of the injector shown in Figure 1 , but the lubricant flowing into the compensation chamber 23 presses the diaphragm 30 into the gas 25 here, and the diaphragm 30 is deformed convexly. Since the diaphragm 30 is flexible, in addition to the pressure of the gas 25, the diaphragm can also apply a certain pressure to the lubricant to always keep the lubricant in the lubricant chamber 10. When using the diaphragm 30, the connecting pipe 26 can be omitted because the mixing of gas and lubricant is prevented in any orientation of the injector regardless of the amount of lubricant in the compensation chamber 23.

[0019] In addition to compensating for the lubricant volume during the opening and closing movement of the valve element 6, the compensation chamber 23 is also used to compensate for the change in lubricant volume caused by the thermal expansion of the lubricant or the limiting member.

Claims

1. An injector for outputting gaseous or liquid fuel, having: a housing (1) in which a fuel chamber (5) that can be filled with fuel is constructed; a piston-shaped valve element (6) that cooperates with a valve seat (7) to open and close a metering opening (9) of the fuel chamber (5), wherein, The valve element (6) can be moved in the opening direction by the actuator (20) against the force of the closing spring (16); and a bellows (11) that at least sectionally surrounds the valve element (6), and the bellows delimits a lubricant chamber (10) in which there is a lubricant (24) for lubricating the valve element (6). It is characterized in that a compensation chamber (23) connected to the lubricant chamber (10) is constructed in the housing (1), wherein the compensation chamber (23) is partially filled with the lubricant (24) and partially filled with a gas (25).

2. The injector according to claim 1, characterized in that, The connection between the lubricant chamber (10) and the compensation chamber (23) includes a connecting pipe (26) extending into the compensation chamber (23).

3. The injector according to claim 2, characterized in that, The amount of lubricant (24) present in the compensation chamber is such that the pipe opening (27) of the connecting pipe (26) is always covered by the lubricant.

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

5. The injector according to any one of claims 1 to 4, characterized in that, One end of the bellows (11) is fixedly connected to the valve element (6) such that the bellows elongates during the longitudinal movement of the valve element (6).

6. The injector according to any one of claims 1 to 5, characterized in that, A flexible diaphragm (30) is arranged in the compensation chamber (23), and the diaphragm separates the gas (25) from the lubricant (24).

7. The injector according to claim 6, characterized in that, The flexible diaphragm (30) is pre-tensioned into the gas (25) by the lubricant (24).

8. The injector according to any one of claims 1 to 7, characterized in that, Only the lubricant (24) and the gas (25) are present in the compensation chamber (10).

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