Injection valve for injecting fluid into a combustion chamber of an internal combustion engine

Abstract

Injection valve (1) for injecting fluid into a combustion chamber of an internal combustion engine, comprising - an injector body (2) with a fluid inlet (3) and a fluid outlet; - a nozzle body (4) with a recess (5) hydraulically coupled to the fluid inlet (3), in which recess a nozzle needle (6) is arranged to be axially movable, wherein the nozzle needle (6) in a closed position prevents a fluid flow through an injection opening (7) of the nozzle body (4) and otherwise releases it; - a control chamber (8) which is hydraulically coupled to the fluid inlet (3) and the nozzle needle (6); - a control valve (9) with a valve body (10) and a valve chamber (11) which is hydraulically coupled to the control chamber (8), wherein the valve chamber (11) can be hydraulically coupled to the fluid outlet depending on a closed position of the valve body (10); - an actuator (12) which can be coupled to the valve body (10) for actuating the control valve (9), wherein the valve body (10) is additionally directly coupled to the control chamber (8) in such a way that a force component which depends on a pressure prevailing in the control chamber (8) can be transmitted to the valve body (10);characterized in that a central bore is provided in the valve body (10), in which bore a coupling pin (31) is provided, wherein the coupling pin (31) defines a coupling volume (32) with the valve body (10) in the central bore, wherein two radial bores (33) are formed in the valve body (10), which connect the valve chamber (11) to the sealing gap between the coupling pin (31) and the valve body, and in that a mechanical coupling element (24) is provided for transmitting the force component, wherein an end (25) of the coupling element (24) assigned to the valve chamber (11) cooperates mechanically with the valve body (10) and an end (26) of the coupling element (24) facing away from the valve body (10) is hydraulically coupled to the control chamber (8);

Description

[0001] The invention relates to an injection valve for injecting fluid into a combustion chamber of an internal combustion engine. Furthermore, the invention relates to an internal combustion engine.

[0002] Due to increasingly strict legal regulations regarding permissible pollutant emissions from internal combustion engines installed in motor vehicles, it is necessary to implement various measures to reduce pollutant emissions. One possible approach here is to optimize the operation of internal combustion engine injection valves.

[0003] DE 102011090060 A1 discloses an injection valve for injecting fluid into a combustion chamber of an internal combustion engine. It comprises an injector body with a fluid inlet and a fluid outlet, a nozzle body with a recess hydraulically coupled to the fluid inlet, in which a nozzle needle is arranged for axial movement. In a closed position, the nozzle needle prevents fluid flow through an injection opening of the nozzle body and otherwise releases it. Furthermore, a control chamber is provided, which is hydraulically coupled to the fluid inlet and the nozzle needle, a control valve with a valve body and a valve chamber, which is hydraulically coupled to the control chamber. Depending on a closed position of the valve body, the valve chamber can be hydraulically coupled to the fluid outlet. An actuator, which can be coupled to the valve body for actuating the control valve, is provided.The valve body is additionally directly coupled to the control chamber in such a way that a force component, which depends on a pressure prevailing in the control chamber, can be transferred to the valve body.

[0004] DE 10140524 A1 and DE 102009000170 A1 show injection valves with a valve body of a control valve coupled to a control chamber. A force component is transmitted to the valve element by the control chamber pressure. These control valves have a coupling volume between the valve element and a coupling pin.

[0005] An object underlying the invention is to describe an injection valve which enables reliable and precise operation.

[0006] According to the invention, an injection valve for injecting fluid into a combustion chamber of an internal combustion engine is disclosed. The injection valve has an injector body with a fluid inlet and a fluid outlet. Furthermore, the injection valve has a nozzle body with a recess hydraulically coupled to the fluid inlet, in which a nozzle needle is arranged for axial movement. In a closed position, the nozzle needle prevents fluid flow through an injection opening of the nozzle body and otherwise releases it. The injection valve further has a control chamber hydraulically coupled to the fluid inlet and the nozzle needle. The injection valve also has a control valve with a valve body and a valve chamber. The valve chamber is hydraulically coupled to the control chamber. Depending on a closed position of the valve body, the valve chamber can be hydraulically coupled to the fluid outlet.Furthermore, an actuator is provided that can be coupled to the valve body to actuate the control valve. The valve body is additionally directly coupled to the control chamber in such a way that a force component, which depends on the pressure prevailing in the control chamber, can be transmitted to the valve body.

[0007] Typically, the control chamber is hydraulically coupled to the valve chamber via a throttle. This contributes to the fact that when the control valve is opened or closed, a significantly higher pressure prevails in the control chamber than in the valve chamber. The direct, additional coupling of the valve body to the control chamber enables precise closing of the control valve, for example, after the actuator has been discharged. Direct coupling means coupling without an intermediate throttle or the like. This means that the force component is transmitted to the valve body with almost no damping. Furthermore, the direct coupling of the valve body to the control chamber enables a high closing force to be achieved to close the valve. Furthermore, the direct coupling contributes to high injection accuracy and precise controllability of the injection valve.In particular, the fluid injection quantity, which depends on the movement of the nozzle needle, can be controlled particularly well. Furthermore, tolerances in the nozzle needle movement can be compensated for by directly coupling the control chamber to the valve body.

[0008] Furthermore, the injection valve according to the invention has a mechanical coupling element for transmitting the force component, wherein an end of the coupling element assigned to the valve chamber interacts mechanically with the valve body and an end of the coupling element facing away from the valve body is hydraulically coupled to the control chamber.

[0009] The mechanical coupling element is preferably designed as a bolt or pin. The mechanical coupling element allows the force component to be transmitted to the valve body, thereby achieving particularly high hydraulic rigidity.

[0010] According to one embodiment, the mechanical coupling element is arranged for axial movement in a bore connecting the control chamber and the valve chamber. This ensures reliable guidance of the coupling element when transferring the force component to the valve body.

[0011] According to a further embodiment, the coupling element is fitted into the bore in such a way that a sealing gap that forms between the bore and the coupling element essentially prevents any fluid exchange between the control chamber and the valve chamber during dynamic operation of the injection valve. The sealing gap is preferably approximately 1 µm. This results in a mating clearance between the coupling element and the bore, so that no jamming of the pin occurs. For highly dynamic movements, such as the movement of the actuator for actuating the control valve, the sealing gap is almost tight. As a result, the hydraulic coupling between the control chamber and valve chamber is defined, for example, only by an outlet throttle between the control chamber and valve chamber. In other words, during dynamic operation of the injection valve, any fluid exchange between the control chamber and the valve chamber is prevented, in particular essentially prevented.

[0012] According to a further embodiment, the sealing gap is approximately 0.5 µm to 5 µm. Preferably, the sealing gap is approximately 0.5 µm to 1.5 µm. Particularly preferably, the sealing gap is approximately 1.0 µm. This ensures the function described above.

[0013] According to a further embodiment, the transmittable force component depends on a surface of the coupling element facing the control chamber. In particular, the force depends on a cross-sectional area of ​​the coupling element. By selecting the appropriate area, the force component to be transmitted can thus be precisely adjusted.

[0014] According to a further embodiment, the injection valve has a spring element that exerts a force on the valve body in a closing direction of the control valve. The spring element is preferably a compression spring. The spring element contributes to the secure closing of the control valve. In particular, the spring element ensures that the control valve is securely closed even when the injection valve is depressurized.

[0015] According to a further embodiment, the actuator is designed to generate a measurement signal representative of the force component. From this measurement signal, information about the beginning of the opening and closing of the nozzle needle can be determined, since characteristic changes in the pressure prevailing in the control chamber occur at this time. Using this measurement signal, for example, the injection quantity accuracy can be determined particularly accurately.

[0016] According to a further embodiment, the actuator for actuating the valve body is hydraulically coupled to the valve body. In particular, a hydraulic clearance compensation device integrated into the valve body is provided. Despite the hydraulic coupling of the actuator to the valve body, the direct coupling of the control chamber to the valve body ensures sufficient closing force on the valve body to close the control valve.

[0017] Further advantages and functions are described in the following detailed description of an embodiment with the aid of the attached figures.

[0018] The figures show: Fig. 1 a schematic sectional view of an injection valve, Fig. 2 an enlarged sectional view of the injection valve and Fig. 3 a first diagram of three voltage curves of an actuator at the time of opening of a nozzle needle, Fig. 4 a second diagrammatic representation of a needle stroke curve at the time of opening of a nozzle needle, Fig. 5 a third diagram showing three voltage curves of the actuator at the time of closing a nozzle needle and Fig. 6 a fourth diagrammatic representation of three needle stroke curves at the time of closing of a nozzle needle.

[0019] Fig. 1 shows a schematic sectional view of an injection valve 1. The injection valve 1 has an injector body 2 in which a fluid inlet 3 is formed. The fluid inlet 3 is hydraulically coupled to a high-pressure accumulator, such as a so-called common rail, and is thus supplied with a pressurized fuel. The pressure is, for example, up to 2500 bar or higher. The term "fluid" can include a fuel, such as diesel or gasoline. However, the term can also include other substances, for example, organic compounds such as urea.

[0020] The injection valve 1 has a nozzle body 4 in which a recess 5 is formed. A nozzle needle 6 is arranged in the recess 5 and is axially movable with respect to a longitudinal axis of the nozzle needle 6. In a closed position, the nozzle needle 6 sits near a tip of the nozzle body 4 on an associated needle valve seat and prevents fluid flow through one or more injection openings 7. If the nozzle needle 6 lifts off the needle valve seat, fluid flow is permitted. The nozzle needle 6 is preloaded by a nozzle spring 20. The nozzle body 4 is mechanically coupled to the injector body 2 via a nozzle clamping nut 18. A combustion chamber seal 19 is also provided.

[0021] The recess 5 and the nozzle needle 6 are hydraulically coupled to the fluid inlet 3 via a nozzle orifice 22. The nozzle orifice 22 is incorporated into a throttle plate 17.

[0022] The injection valve 1 further has a control chamber 8, which is hydraulically coupled to the fluid inlet 3 via an inlet throttle 21 of the throttle plate 17. The control chamber 8 is further hydraulically coupled to the nozzle needle 6. The control chamber 8 is additionally hydraulically coupled to a valve chamber 11 of a control valve 9 via an outlet throttle 23 of the throttle plate 17. The control valve 9 is arranged in a valve plate 16 and is referred to as a servo valve. The control valve 9 has a valve body 10, which is arranged to be axially movable in the valve chamber 11. In a closed position of the control valve 9, the valve body 10 sits on an associated valve seat and prevents fluid flow from the valve chamber 11 to a fluid outlet (not shown). The fluid outlet is hydraulically coupled to a low-pressure region, such as a fuel tank.

[0023] The injection valve 1 has an actuator 12, which is designed as a piezo actuator. Alternatively, other materials, such as a magnetostrictive material, can be used for the actuator 12. The actuator 12 is integrated into the injector body 2 and has an actuator head plate 13 and an actuator base plate 14. The actuator 12 is mechanically coupled to the injector body 2 via the actuator head plate 13. The actuator 12 can be coupled to the control valve 9, in particular to the valve body 10, via the actuator base plate 14 for actuating the valve.

[0024] The actuator 12 is surrounded by a wave spring 15, which preloads it. The wave spring 15 seals the actuator 12 itself from the fluid.

[0025] At the beginning of an injection process, the injection valve 1 is closed. The recess 5, the control chamber 8, and the valve chamber 11 are completely filled with fluid under high pressure via the fluid inlet 3. Due to a force ratio acting on the valve body 10 of the control valve 9, the valve body 10 is in the closed position. Due to a further force ratio, the nozzle needle 6 is also in the closed position.

[0026] If voltage is applied to the actuator 12, the actuator 12 expands and actuates the control valve 9. This opens the control valve 9 and the pressure in the valve chamber 11 drops. For example, the pressure drops by 90% to, for example, 200 bar. Due to this pressure drop, fluid flows through the outlet throttle 23 into the valve chamber 11. At the same time, less fluid flows through the inlet throttle 21 into the control chamber 8, so that the pressure in the control chamber 8 drops, but less sharply than in the valve chamber 11. For example, the pressure drops to 1300 to 1400 bar. This ensures that the force ratio acting on the nozzle needle 6 is changed, so that the nozzle needle 6 lifts off its associated needle valve seat and fluid escapes through the injection openings 7.

[0027] When actuator 12 is discharged, control valve 9 closes again, pushing valve body 10 back into its valve seat. This causes pressure to build up again in valve chamber 11, control chamber 8, and recess 5. The force acting on nozzle needle 6 ensures that nozzle needle 6 is moved back into its closed position.

[0028] In order to ensure a sufficiently high closing force for closing the control valve 9, the valve body 10 is additionally directly coupled to the control chamber 8. This is achieved with the aid of the Fig. 2 described.

[0029] Fig. 2 shows a schematic, enlarged sectional view of the valve plate 16 with the control valve 9 and the throttle plate 17. The control chamber 8 is also partially shown. The valve body 10 is directly coupled to the control chamber 8 via a mechanical coupling element 24, which is designed as a pin. For this purpose, the coupling element 24 is fitted axially movably into a bore 29. The bore 29 connects the valve chamber 11 to the control chamber 8. With an end 25 facing the valve body 10, the valve body 10 can be mechanically coupled to the coupling element 24. An end 26 facing away from the valve body 10 faces the control chamber 8. The valve body 10 is separated from the coupling element 24. This enables the valve body 10 and the coupling element 24 to be aligned axially, in particular axially to one another.

[0030] Through the direct coupling by means of the coupling element 24, in particular, an additional closing force can be achieved on the valve body 10 for closing the control valve 9. When the nozzle needle 6 closes, the pressure in the control chamber 8 builds up more quickly than in the valve chamber 11. This is due to the fact that the control chamber 8 is hydraulically coupled to the valve chamber 11 via the outlet throttle 23. By means of the coupling element 24, a force component is now transmitted directly to the valve body 10. The force component depends on the pressure in the control chamber 8 and on a cross-section of the surface of the coupling element 24 facing the control chamber 8, in particular its cross-sectional area. The transmittable force component contributes to the reliable closing of the control valve 9. By means of the coupling element 24 and its cross-sectional area, the closing force for closing the control valve 9 can be precisely adjusted in a simple manner.

[0031] A sealing gap 30 of approximately 1 µm is provided between the bore 29 and the coupling element 24. This creates a mating clearance between the bore 29 and the coupling element 24, which ensures that almost no fuel can flow through the sealing gap 30 into the valve chamber 11 during dynamic operation of the injection valve 1. Thus, the sealing gap 30 is virtually sealed during dynamic operation.

[0032] Additionally, a spring element 28 is provided, which engages a spring plate 27 and exerts a force on the valve body 10 in the closing direction of the control valve 9. The spring element 28 serves to securely close the control valve 9 even when the injection valve 1 is depressurized.

[0033] How to proceed based on Fig. 2 is described below, instead of a mechanical coupling with an idle stroke between the actuator 12 and the valve body 10, a hydraulic coupling with a play compensation integrated in the valve body 10 is provided. The actuator 12 is hydraulically coupled to the valve body 10 via a coupling pin 31 for actuating the valve body 10. For this purpose, a central bore is made in the valve body 10, into which the coupling pin 31 is fitted. The coupling pin 31 delimits a coupling volume 32 in the central bore with the valve body 10. Between the coupling pin 31 and the valve body 10, a sealing gap is again formed, which, analogous to above, is approximately 1 µm.

[0034] In Fig. 2, at approximately half the height of the valve body 10, there are two radial bores 33 which connect the valve chamber 11 with the sealing gap between the coupling pin 31 and the valve body 10. When the injection valve 1 or the control valve 9 is closed, high pressure is present in the valve chamber 11, which is transferred into the coupling volume 32 via the radial bores 33 and the sealing gap. This pressure causes the coupling pin 31 to be constantly pressed towards the actuator base plate 14 of the actuator 12 and to rest against it. This ensures play-free contact between the actuator 12 and the valve body 10. Movements with very low dynamics, such as thermal expansion and wear, can be compensated for by changing the coupling volume 32. However, for highly dynamic movements, such as during the injection process, the sealing gap 30 is almost tight and thus the coupling between the valve body 10 and the coupling pin 31 is rigid.

[0035] With such a hydraulic coupling of the valve body 10 to the actuator 12, it is particularly advantageous that the valve body 10 is also directly coupled to the control chamber 8 via the coupling element 24. Due to the described force transmission to the valve body 10 by means of the coupling element 24, it is always ensured, despite the hydraulic clearance compensation, that the valve body 10 closes tightly and thus no fluid can flow through the valve seat.

[0036] From the force component transmitted by means of the coupling element 24, information about the beginning of the opening and closing of the nozzle needle 6 can be deduced. At these times, characteristic changes in the pressure prevailing in the control chamber 8 occur. By the corresponding coupling of the valve body 10 with the actuator 12, the force component proportional to the pressure in the control chamber 8 is fed back to the actuator 12. As a result, the actuator 12 generates a measurement signal which can be tapped. This is shown in the schematic diagrams of the Fig. 3 to 6 shown.

[0037] In the Fig. The diagram shown in Figure 3 plots a voltage U applied to actuator 12 in volts (V) against a time t in milliseconds (ms). Three voltage curves are shown when the nozzle needle 6 opens. Each voltage curve corresponds to a slightly varied injection valve 1, with nozzle parameters such as valve seat diameter or the like being altered. Regardless of the different nozzle parameters, a characteristic curve results in each case, from which the exact time of needle opening can be determined. Fig. 4 shows a Fig. 3 shows a correlating second schematic diagram, where a needle stroke n in millimeters (mm) is plotted against time t in milliseconds (ms). The needle stroke refers to an axial movement of the nozzle needle 6. Three needle stroke curves are shown at the time of opening of the nozzle needle 6, from which the voltage curves were determined and plotted against time.

[0038] Analogously, the Fig. 5 and Fig. 6 further diagrams with voltage curves and needle stroke curves at the time of closing of the nozzle needle 6.

[0039] Due to the coupling by means of the coupling element 24, sensor signals can be derived by feedback of the pressure prevailing in the control chamber 8 to the actuator 12, which serve to precisely regulate the injection quantity. Overall, this improves the injection quantity stability of the injection valve 1 during dynamic engine operation.

Claims

[1] Injection valve (1) for injecting fluid into a combustion chamber of an internal combustion engine, comprising - an injector body (2) with a fluid inlet (3) and a fluid outlet; - a nozzle body (4) with a recess (5) hydraulically coupled to the fluid inlet (3), in which recess a nozzle needle (6) is arranged to be axially movable, wherein the nozzle needle (6) in a closed position prevents a fluid flow through an injection opening (7) of the nozzle body (4) and otherwise releases it; - a control chamber (8) which is hydraulically coupled to the fluid inlet (3) and the nozzle needle (6); - a control valve (9) with a valve body (10) and a valve chamber (11) which is hydraulically coupled to the control chamber (8), wherein the valve chamber (11) can be hydraulically coupled to the fluid outlet depending on a closed position of the valve body (10); - an actuator (12) which can be coupled to the valve body (10) for actuating the control valve (9), wherein the valve body (10) is additionally directly coupled to the control chamber (8) in such a way that a force component which depends on a pressure prevailing in the control chamber (8) can be transmitted to the valve body (10); characterized byin that a central bore is provided in the valve body (10), in which bore a coupling pin (31) is provided, wherein the coupling pin (31) defines a coupling volume (32) with the valve body (10) in the central bore, wherein two radial bores (33) are formed in the valve body (10), which connect the valve chamber (11) to the sealing gap between the coupling pin (31) and the valve body, and in that a mechanical coupling element (24) is provided for transmitting the force component, wherein an end (25) of the coupling element (24) assigned to the valve chamber (11) interacts mechanically with the valve body (10) and an end (26) of the coupling element (24) facing away from the valve body (10) is hydraulically coupled to the control chamber (8). [2] Injection valve (1) according to claim 1, wherein the mechanical coupling element (24) is arranged to be axially movable in a bore (29) connecting the control chamber (8) and the valve chamber (11). [3] Injection valve (1) according to claim 2, wherein the coupling element (24) is fitted into the bore (29) in such a way that a sealing gap (30) formed between the bore (29) and the coupling element (24) essentially prevents fluid exchange between the control chamber (8) and the valve chamber (11) during dynamic operation of the injection valve (1). [4] Injection valve (1) according to claim 3, wherein the sealing gap (30) is approximately 0.5 µm to 5 µm. [5] Injection valve (1) according to one of claims 1 to 4, wherein the transmittable force component is dependent on a surface of the coupling element (24) facing the control chamber (8). [6] Injection valve (1) according to one of the preceding claims, comprising a spring element (28) which exerts a force on the valve body (10) in a closing direction of the control valve (9). [7] Injection valve (1) according to one of the preceding claims, wherein the actuator (12) is designed to generate a measurement signal which is representative of the force component. [8] Injection valve (1) according to one of the preceding claims, wherein the actuator (12) for actuating the valve body (10) is hydraulically coupled to the valve body (10).

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