Fuel injector for a spark-ignition internal combustion engine with direct injection

Abstract

Injection valve (1) for directly injecting fuel into a combustion chamber (2) of a spark-ignition internal combustion engine, comprising a valve housing (3) with at least one valve seat (4) and at least one valve opening (5) formed on the valve seat (4) through which the fuel can be injected directly into the combustion chamber (2), and at least one first electrode (12) electrically insulated from the valve housing (3) and at least one second electrode (14) electrically insulated from the first electrode (12) and the valve housing (3), wherein end sections (12b, 12c, 14b, 14c) of the electrodes (12, 14), between which a spark gap for spark ignition is formed, are arranged relative to the valve housing (3) such that a fuel injection jet (6) exiting the valve opening (5) moves at least partially along or through the spark gap, characterized by at least one through the electrodes (12,14) and the fuel channel (16) running through the valve housing (3), which has an inlet opening (17) formed on the valve seat (4) and through which the fuel can be injected directly into the combustion chamber (2).

Description

The invention relates to an injection valve for the direct injection of fuel into a combustion chamber of a spark-ignition internal combustion engine, according to the preamble of claim 1 comprising a valve housing with at least one valve seat and at least one valve opening formed on the valve seat, through which the fuel can be injected directly into the combustion chamber, and at least one first electrode electrically insulated from the valve housing and at least one second electrode electrically insulated from the first electrode and the valve housing, wherein end sections of the electrodes, between which a spark gap for spark ignition is formed, are arranged relative to the valve housing in such a way that a fuel injection jet exiting the valve opening moves at least partially along or through the spark gap. Modern spark-ignition internal combustion engines, especially gasoline engines, are becoming increasingly compact and smaller. This is possible, among other things, due to the higher performance of modern internal combustion engines and is accompanied by a beneficial reduction in weight. However, the miniaturization of an internal combustion engine leads to a smaller cylinder head, which makes it increasingly difficult to fit an injector, a spark plug, and adequately sized intake and exhaust valves for each cylinder on the cylinder head. To solve this problem, DE 10 2006 029 210 A1 proposes an injection valve of the type mentioned above, in which components of an injection valve and components of a spark plug are combined into a single component. This integrated design of injection valve and spark plug provides more installation space for the charge exchange valves in a correspondingly equipped internal combustion engine. Furthermore, the injection valve according to DE 10 2006 029 210 A1 enables further miniaturization of internal combustion engines. Furthermore, JP H08-74703A describes an integrated injection valve in which a portion of the fuel is directed to the spark gap via a separate guide channel to stabilize ignition in lean mixtures. However, complete electrical insulation of the electrodes from the valve housing in the area of ​​the valve seat is not provided, and the guide channel only runs through one of the electrodes. US patent 2014 / 0090622A1 discloses a system in which the fuel is ignited directly upon entering the combustion chamber by a spark gap between different electrode configurations. While the patent shows electrodes insulated from the housing, it lacks a design for a fuel channel extending through both the electrodes and the valve housing to, for example, provide a cooling effect. Finally, US patent 2018 / 0363592 A1 discloses an injection valve for gaseous fuel in which components of the nozzle body itself function as the electrode assembly. This patent primarily addresses the spatial integration of the ignition system for optimizing installation space in gas engines, but does not propose targeted electrode cooling or mixture preparation via an internal fuel channel for liquid fuels running through the housing and electrodes. The invention is based on the objective of improving the spark ignition of an internal combustion engine equipped with at least one inlet valve of the type mentioned above, and the combustion within the internal combustion engine. According to the invention, the problem is solved by an injection valve with the features of claim 1, which has at least one fuel channel extending through the electrodes and the valve housing, which has an inlet opening formed on the valve seat and through which the fuel can be injected directly into the combustion chamber. It should be noted that the features and measures listed individually in the following description can be combined in any technically sensible way and demonstrate further embodiments of the invention. The description further characterizes and specifies the invention, particularly in conjunction with the figure. According to the invention, the fuel is injected both through the valve opening on the valve housing and directly into the combustion chamber via the fuel channel. The fuel injection jet injected through the valve opening reaches at least partially into the immediate vicinity of the electrode end sections, between which a spark is generated during spark ignition to ignite the fuel-air mixture in the combustion chamber. For this purpose, the timing of the fuel injection and the spark ignition are precisely coordinated. Thus, only a relatively small portion of the total amount of fuel injected into the combustion chamber during an injection process exits through the valve opening, preventing the spark from being extinguished by an excessive amount of fuel directed at it.This ensures reliable ignition of the fuel-air mixture in the combustion chamber, thereby improving the spark ignition of the internal combustion engine. The fuel injected into the combustion chamber through the fuel channel does not reach the electrode ends directly, but first mixes with the air drawn into the combustion chamber and is then reached and ignited by the flame generated in the spark plug area. The fuel flowing through the fuel channel also cools the electrodes, as it absorbs heat as it passes through them. This warms the fuel, allowing it to be more effectively atomized or vaporized upon exiting the fuel channel. This further improves combustion within the combustion chamber of the internal combustion engine. By injecting the fuel through the valve opening directly towards the end sections of the electrodes, lean and / or inhomogeneous fuel-air mixtures can be ignited, which improves combustion stability in certain conditions, for example during catalyst heating or stratified operation. The injection valve according to the invention additionally comprises a valve body which is slidably guided in the valve housing between a closed position, in which the valve body rests against the valve seat of the valve housing and closes the valve opening and the inlet opening of the fuel channel, and a release position, in which the valve body is arranged at a distance from the valve seat and releases the valve opening and the inlet opening. The valve body can be displaced along the longitudinal center axis of the valve housing. The valve opening formed on the valve seat of the valve housing, through which fuel can be injected directly into the combustion chamber, can, for example, be located on the longitudinal center axis of the valve housing or offset laterally from it. Accordingly, the axis of symmetry of a fuel injection jet exiting the valve opening, for example a conical jet, can be identical to the longitudinal center axis of the valve housing or run at an angle to this longitudinal center axis. The valve housing can also have two or more valve openings formed on the valve seat. The first electrode can be an anode electrode and the second electrode can be a cathode electrode. The first electrode is electrically insulated from the valve housing by at least one electrically insulating body. The second electrode is electrically insulated from the first electrode by at least one further electrically insulating body. During spark ignition of the internal combustion engine, ignition sparks are generated between the end sections of the electrodes in the spark gap between the end sections. The fuel injection jet exiting the valve opening travels at least partially along the spark gap, i.e., passes directly by the spark gap, or it travels directly through the spark gap without being deflected or deflected before reaching the spark gap.The fuel injection jet is therefore injected at least partially through the valve opening either into the immediate vicinity of the spark gap or directly into the spark gap. The fuel channel running through the electrodes and the valve body can be straight or at least partially curved. The fuel channel can, in particular, run through the end sections of the electrodes. Fuel flows into the fuel channel through the inlet opening formed on the valve seat when the valve body is lifted from the valve seat or is in its open position. The fuel flowing through the fuel channel passes through the electrodes, the valve body, and electrical insulation between the valve body and the first electrode, as well as between the electrodes, and is then injected directly into the combustion chamber. The outlet end of the fuel channel can be nozzle-shaped to atomize the fuel flowing through it.The injection valve according to the invention can also have two or more of these fuel channels, which are arranged, for example, circumferentially offset from one another with respect to the longitudinal center axis of the valve housing. By selecting the appropriate number of fuel channels, the amount of fuel injected into the combustion chamber via the valve opening can be varied. The spark-ignition internal combustion engine can be designed, in particular, as a spark-ignition engine. The internal combustion engine preferably comprises at least three cylinders, with an injection valve according to the invention arranged on a cylinder head of the internal combustion engine for each cylinder. Preferably, the injection valve of the respective cylinder is arranged on the cylinder head such that the longitudinal axis of the valve housing of the injection valve is identical to the longitudinal center axis of the cylinder. This provides the largest possible installation space for the arrangement of the charge exchange valves. According to an advantageous embodiment, the fuel channel is designed as a bore or as a pipe that is electrically insulated from the electrodes and the valve housing. Designing the fuel channel as a bore or through-bore is cost-effective and easy to manufacture. When the fuel channel is designed as a pipe made of a metallic material, electrical insulation of the pipe from the electrodes and the valve housing is necessary, particularly to prevent a short circuit between the electrodes. Another advantageous embodiment provides that the fuel channel runs transversely to the longitudinal center axis of the valve housing. In particular, the fuel channel can run radially to the longitudinal center axis of the valve housing. The angle between the longitudinal center axis of the valve housing and a longitudinal center axis of the fuel channel can be in a range of approximately 30° to approximately 85°, and in particular in a range of approximately 50° to approximately 75°. According to a further advantageous embodiment, the injection valve comprises at least one valve body which is slidably guided in the valve housing between a closed position, in which the valve body rests against the valve seat of the valve housing and closes the valve opening and the inlet opening of the fuel channel, and a release position, in which the valve body is spaced apart from the valve seat and opens the valve opening and the inlet opening. The valve body is spherical or segment-shaped, and a sealing surface of the valve seat rests on an imaginary spherical cap. Accordingly, the sealing surface of the valve seat has a curved profile, while the surface section of the valve body that can be brought into contact with the sealing surface has a shape complementary to the shape of the sealing surface.Alternatively, the valve body and valve seat can have complementary conical or frustoconical contact surfaces that are in contact with each other when the valve body is in its closed position. In particular, the valve body can form a section of a valve needle. The valve body can be biased towards its closed position. The valve body can be displaced or moved within the valve housing by means of an actuator of the injector. Furthermore, it is advantageous if the valve opening is located on the longitudinal center axis of the valve housing. This allows the fuel injection jet, injected into the combustion chamber via the valve opening, to be directed onto the piston crown of a working piston that is slidably guided within the combustion chamber. This also makes it possible, for example, to create a layered structure within the combustion chamber in order to influence the combustion process of the internal combustion engine. According to a further advantageous embodiment, the end sections of the electrodes are arc-shaped or angled, such that the free ends of the end sections point towards the longitudinal center axis of the valve housing. The end sections thus extend from a section of the electrodes located radially outside the valve housing towards the longitudinal center axis of the valve housing. The free ends of the end sections can be arranged at different or the same radial distance from the longitudinal center axis of the valve housing. Preferably, the two end sections are arranged such that the spark gap formed between the end sections essentially corresponds to the orientation of a portion of the conical fuel injection jet exiting the valve opening. Advantageously, at least one electrode comprises a sleeve-like section, at one axial end of which at least one end section of this electrode is formed and which radially surrounds at least one section of the valve housing. Preferably, two, three, or more end sections of the electrode are arranged circumferentially offset from one another at the axial end of the sleeve-like section. The end sections of such an electrode can be electrically contacted via the sleeve-like section, so that not each end section needs to be electrically contacted separately, which reduces wiring effort. In addition, the larger contact area between the electrode and the adjacent components of the injection valve ensures the precise positioning of the electrode relative to the other components of the injection valve.Preferably, each electrode comprises a sleeve-like section, at one axial end of which at least one end section of the respective electrode is formed. The sleeve-like section of the second electrode radially surrounds at least one section of the sleeve-like section of the first electrode. According to a further advantageous embodiment, the injection valve comprises at least one first insulating body arranged between the valve housing and the first electrode, and at least one second insulating body arranged between the first and second electrodes. The first electrode is electrically insulated from the valve housing and the second electrode from the first electrode by means of the insulating bodies, which are made, for example, of plastic or ceramic. A section of the second insulating body located between the end sections of the electrodes preferably has a shape that corresponds to the shape of the end sections, for example, a curved or angled shape. However, in such a case, the second insulating body arranged between the electrodes does not extend to the free ends of the end sections in the region of the electrode end sections, thus forming the spark gap between the end sections. Advantageously, at least one insulating body is designed in a sleeve-like form. This is particularly advantageous if at least one electrode has a sleeve-like section as described above, since the entire sleeve-like section of the electrode can be electrically insulated from an adjacent component of the injection valve via the sleeve-like insulating body. Preferably, both insulating bodies are designed in a sleeve-like form. Further advantageous embodiments of the invention are disclosed in the dependent claims and the following description of the figures. Figure 1 shows a schematic longitudinal section of a section of an exemplary embodiment of an injection valve according to the invention. Fig. 1 shows a schematic representation of a section of an embodiment of an injection valve 1 according to the invention for directly injecting fuel into a combustion chamber 2 of a spark-ignition internal combustion engine (not shown). The injection valve 1 is shown in longitudinal section. The injection valve 1 comprises a valve housing 3 with a valve seat 4 and a valve opening 5 formed centrally or in the middle of the valve seat 4, through which the fuel can be injected directly into the combustion chamber 2 in the form of a fuel injection jet 6. The valve opening 5 lies on the longitudinal center axis 7 of the valve housing 3. Furthermore, the injection valve 1 comprises a spherically shaped valve body 8, which is slidably guided in the valve housing 3 along the longitudinal axis 7 of the valve housing 3, as indicated by the double arrow 9. This spherical valve body is located between a closed position (shown in Fig. 1), in which the valve body 8 rests against the valve seat 4 of the valve housing 3 and closes the valve opening 5, and a release position (not shown), in which the valve body 8 is spaced apart from the valve seat 5 and releases the valve opening 5. A sealing surface 10 of the valve seat 4 rests on an imaginary spherical cap. Furthermore, the injection valve 1 comprises a first electrode 12 electrically insulated from the valve housing 3 by means of a sleeve-like insulating body 11, and a second electrode 14 electrically insulated from the first electrode 12 by means of a sleeve-like insulating body 13. For this purpose, the first insulating body 11 is arranged between the valve housing 3 and the first electrode 12, and the second insulating body 13 is arranged between the first electrode 12 and the second electrode 14. The first electrode 12 comprises a sleeve-shaped section 12a, at one axial end of which (in Fig. 1, the lower axial end) at least two end sections 12b and 12c of the first electrode 12 are formed. The first electrode 12 can also have more than two such end sections 12b and 12c, which is not shown in Fig. 1. The end sections 12b and 12c are arranged circumferentially offset from each other by 180°. The sleeve-shaped section 12a of the first electrode 12 surrounds at least one section of the valve housing 3 at a radial outer distance. The sleeve-shaped section 12a surrounds at least one section of the first insulating body 11 radially and is in contact with the first insulating body 11. The second electrode 14 comprises a sleeve-shaped section 14a, at one axial end of which (the lower axial end in Fig. 1) at least two end sections 14b and 14c of the second electrode 14 are formed. The second electrode 14 can also have more than two such end sections, which is not shown in Fig. 1. The end sections 14b and 14c are arranged circumferentially offset from each other by 180°. The sleeve-shaped section 14a of the second electrode 14 surrounds, radially spaced outwards, at least one section of the valve housing 3, at least one section of the first insulating body 11, and at least one section of the first electrode 12. The sleeve-shaped section 14a surrounds, radially outwards, at least one section of the second insulating body 13 and is in contact with the second insulating body 13. Between end sections 12b and 14b and between end sections 12c and 14c, a spark gap for external ignition is formed in each case, with Fig. 1 showing an ignition point at which a spark 15 is formed in each spark gap. The end sections 12b and 14b and the end sections 12c and 14c are arranged such that the spark gap formed between them essentially corresponds to the orientation of a portion of the conical fuel injection jet 6 exiting the valve opening 5. The end sections 12b and 14b, and 12c and 14c respectively, are each arranged relative to the valve housing 3 such that the fuel injection jet 6 exiting the valve opening 5 moves at least partially along or through the respective spark gap. For this purpose, the end sections 12b, 12c, 14b, and 14c of the electrodes 12 and 14 are arc-shaped, such that the free ends 12d and 14d of the end sections 12b, 12c, 14b, and 14c point in the direction of the longitudinal center axis 7 of the valve housing 3. The insulating bodies 11 and 13 each have a correspondingly arc-shaped end section 11a and 13a, respectively. The second insulating body 13, arranged between the electrodes 12 and 14, does not extend to the free ends 12d and 14d of the end sections 12b and 14b and 12c and 14c, respectively, in the region of the end sections 12b and 14b and 12c and 14c, respectively, thus forming the respective spark gap between the end sections 12b and 14b and 12c and 14c. The injection valve 1 also comprises at least one, ideally several, preferably two fuel channels 16 extending through the electrodes 12 and 14, the first insulating body 11, the second insulating body 13, and the valve housing 3. Each fuel channel 16 has an inlet opening 17 formed at the valve seat 5, through which the fuel can be injected directly into the combustion chamber 2 in the form of a fuel injection jet 18. In the closed position of the valve body 8, as shown, it also closes the inlet openings 17 of the fuel channels 16. In its open position, the valve body 8 also opens the inlet openings 17 of the fuel channels 16. The fuel channels 16 are arranged circumferentially offset from each other by 180°. The injection valve 1 can also have more than two fuel channels 16, which is not shown in Fig. 1. Each fuel channel 16 is designed as a bore and extends transversely to the longitudinal center axis 7 of the valve housing 3. An external thread (not shown) can be formed on the outer surface of the sleeve-like section 14a of the second electrode 14, through which the injection nozzle 1 can be screwed into a threaded bore on a cylinder head (not shown) of the internal combustion engine. Reference symbol list: 1 Injector 2 Combustion chamber 3 Valve body 4 Valve seat 5 Valve opening 6 Fuel injection jet 7 Longitudinal center axis of 3 8 Valve body 9 Double arrow (displacement of 8) 10 Sealing surface of 4 11 First insulating body 11a End section of 11 12 First electrode 12a Sleeve-shaped section of 12 12b End section of 12 12c End section of 12 12d Free end of 12b, 12c 13 Second insulating body 13a End section of 13 14 Second electrode 14a Sleeve-shaped section of 14 14b End section of 14 14c End section of 14 14d Free end of 14b, 14c 15 Spark plug 16 Fuel channel 17 Inlet of 16 18 Fuel injection jet

Claims

Injection valve (1) for directly injecting fuel into a combustion chamber (2) of a spark-ignition internal combustion engine, comprising a valve housing (3) with at least one valve seat (4) and at least one valve opening (5) formed on the valve seat (4) through which the fuel can be injected directly into the combustion chamber (2), and at least one first electrode (12) electrically insulated from the valve housing (3) and at least one second electrode (14) electrically insulated from the first electrode (12) and the valve housing (3), wherein end sections (12b, 12c, 14b, 14c) of the electrodes (12, 14), between which a spark gap for spark ignition is formed, are arranged relative to the valve housing (3) such that a fuel injection jet (6) exiting the valve opening (5) moves at least partially along or through the spark gap, characterized by at least one through the electrodes (12,14) and the fuel channel (16) running through the valve housing (3), which has an inlet opening (17) formed on the valve seat (4) and through which the fuel can be injected directly into the combustion chamber (2). Injection valve (1) according to claim 1, characterized in that the fuel channel is designed as a bore or as a pipe that is electrically insulated from the electrodes (12, 14) and the valve housing (3). Injection valve (1) according to claim 1 or 2, characterized in that the fuel channel (16) runs transversely to the longitudinal central axis (7) of the valve housing (3). Injection valve (1) according to one of the preceding claims, characterized by at least one valve body (8) which is slidably guided in the valve housing (3) between a closed position in which the valve body (8) rests against the valve seat (4) and closes the valve opening (5) and the inlet opening (17) of the fuel channel (16), and a release position in which the valve body (8) is arranged spaced apart from the valve seat (4) and releases the valve opening (5) and the inlet opening (17), wherein the valve body (8) is spherically or spherically segmented and a sealing surface (10) of the valve seat (4) lies on an imaginary spherical cap. Injection valve (1) according to one of the preceding claims, characterized in that the valve opening (5) is located on the longitudinal central axis (7) of the valve housing (3). Injection valve (1) according to one of the preceding claims, characterized in that the end sections (12b, 12c, 14b, 14c) of the electrodes (12, 14) are arcuate or angled, such that free ends (12d, 14d) of the end sections (12b, 12c, 14b, 14c) point in the direction of the longitudinal central axis (7) of the valve housing (3). Injection valve (1) according to one of the preceding claims, characterized in that at least one electrode (12, 14) has a sleeve-like section (12a, 14a) at an axial end of which at least one end section (12b, 12c, 14b, 14c) of this electrode (12, 14) is formed and which surrounds at least one section of the valve housing (3) radially outside. Injection valve (1) according to one of the preceding claims, characterized by at least one first insulating body (11) arranged between the valve housing (3) and the first electrode (12) and at least one second insulating body (13) arranged between the first electrode (12) and the second electrode (14). Injection valve (1) according to claim 8, characterized in that at least one insulating body (11, 13) is designed in a sleeve-like form.

Images