EP4399404A1

EP4399404A1 - Fuel injector

Info

Publication number: EP4399404A1
Application number: EP22802657.1A
Authority: EP
Inventors: Martin Seidl; Florian Schiller; Johannes SEIDL
Original assignee: Liebherr Components Deggendorf GmbH
Current assignee: Liebherr Components Deggendorf GmbH
Priority date: 2021-11-08
Filing date: 2022-11-08
Publication date: 2024-07-17
Also published as: CN118202143A; WO2023079163A1; DE102021129011A1

Abstract

The present invention relates to a fuel injector for injecting a fuel into a combustion chamber of an internal combustion engine, in particular a diesel engine, which comprises a feed opening for feeding in fuel, at least one outlet opening for outputting the fuel, a nozzle needle which is movable between a closed position, in which the at least one outlet opening is closed, and an open position, in which the at least one outlet opening is opened, and a primary valve which is arranged downstream of the feed opening and upstream of the nozzle needle and is designed to establish a fluid connection between the feed opening and the nozzle needle only when a positive pressure is exceeded by a region upstream of the primary valve with respect to a region downstream of the primary valve. The fuel injector is characterized by a safety valve which is arranged downstream of the feed opening and upstream of the nozzle needle and is designed to establish a fluid connection between the feed opening and the nozzle needle only when a positive pressure is exceeded by a region downstream of the safety valve with respect to a region upstream of the safety valve.

Description

fuel injector

The present invention relates to an injector for injecting fuel.

In internal combustion engines such as diesel engines or gasoline engines, fuel is usually injected into a combustion chamber via an injector in a specific quantity and for a specific period of time. Due to the very short injection durations, which are in the micro to millisecond range, it is necessary to open or close the outlet opening of the injector at a very high frequency.

An injector typically has a nozzle needle (also: injector needle), which allows fuel that has been subjected to high pressure to exit when an outlet hole of the injector is released. In interaction with this outlet opening or the injector housing, this nozzle needle acts like a closure which allows the fuel to escape when it is lifted. Accordingly, it is therefore necessary to raise this needle at relatively short time intervals and, after a short time, to let it slide back into its closed position again. Hydraulic servo valves can be used to trigger this movement. Such valves, in turn, are typically controlled with the aid of an electromagnet or a piezo element. In addition, it is advantageous if an injector connected to a high-pressure line has an overpressure valve or is connected to one that prevents fuel from flowing into the injector up to a certain overpressure.

This prevents, for example, fuel from penetrating into the injector in standby mode (maintenance mode), during which the fuel lines leading to the injector, to which the injector is connected, are cleaned by flushing. In addition, the overpressure valve function prevents unwanted and uncontrolled injection into the combustion chamber or even flooding of the combustion chamber in the event of a permanently open, blocked nozzle needle, which could lead to serious damage when the engine is started. This sealing function can be implemented using an overpressure valve (ÜDV), whereby the overpressure valve only opens when there is a certain overpressure from the rail (or the fuel line leading to the injector) to the injector and is otherwise closed.

One or more injectors are typically installed in an engine or on a test bench. These are either connected to a common high-pressure volume and thus indirectly connected to one another (see FIG. 1a) or, in the case of several injectors, can be connected directly to one another via fuel lines (see FIG. 1b). In this case, the injectors themselves usually contain a high-pressure storage volume (pressure reservoir), which they share with the other injectors via the connection through the fuel lines (see FIG. 1b). The accumulator volume serves to dampen pressure fluctuations and to maintain system pressure during injection.

To relieve the pressure on the test bench or the engine, a pressure relief valve is attached to the common high-pressure volume (e.g. rail), which can be actively controlled and allows the fuel to flow from the high-pressure volume into the tank. The pressure relief valve can, for example, be activated after the engine or test stand has been switched off in order to ensure a safe, depressurized condition reached, so that maintenance work can be carried out on the depressurized system, for example.

The problem here, however, is that when a pressure relief valve is actuated (e.g. arranged on the rail) due to the pressure relief valve (which is designed to block in the direction from the injector to the feeding fuel line), an extremely large pressure difference arises across components in the injector, which can lead to component damage in the injector and is considered to be disadvantageous from a safety point of view. Finally, due to the high level of tightness of the injector components, it takes a very long time before the high pressure difference has dissipated via an actually undesired leakage. Only then is it possible for the maintenance personnel to work safely on the injector.

It is the object of the present invention to provide a fuel injector which overcomes or mitigates the disadvantages listed above. This is achieved with a fuel injector that has all the features of claim 1. Advantageous configurations can be found in the dependent claims.

Accordingly, it is provided that a fuel injector according to the invention for injecting fuel into a combustion chamber of an internal combustion engine, in particular a diesel engine, has a supply opening for supplying fuel, at least one outlet opening for dispensing the fuel, a nozzle needle, which is positioned between a closed position in which the at least one outlet opening is closed, as well as an open position in which the at least one outlet opening is released, and comprises a primary valve, which is arranged downstream of the supply opening and upstream of the nozzle needle and is designed to establish a fluid connection between the supply opening and the nozzle needle only at a Exceeding an overpressure from an area upstream of the primary valve to generate an area downstream of the primary valve. The fuel injector is characterized by a safety valve which is arranged downstream of the supply opening and upstream of the nozzle needle and is designed to establish a fluid connection between the Supply opening and the nozzle needle to generate upstream of the safety valve only when an overpressure is exceeded from an area downstream of the safety valve compared to an area.

The primary valve is therefore open or moves into its open position when the pressure in the area of the supply opening is greater than the pressure in the area of the nozzle needle by a predetermined threshold value. The situation is exactly the opposite for the safety valve, since it moves into its open position when the pressure in the area of the supply opening is lower by a predetermined threshold value than the pressure in the area of the nozzle needle.

In addition to the primary valve acting as a pressure relief valve, which only allows fuel to flow from a fuel supply line into the injector if a certain overpressure prevails, a safety valve is also provided, which acts in the opposite direction to the pressure relief valve (primary valve).

As a result, when the pressure relief valve arranged on the rail is actuated, the state inside the injector in which a very high pressure difference occurs can be avoided. Specifically, if the pressure inside the injector exceeds a certain threshold value compared to the pressure at the supply opening of the injector, which is fluidically connected to the fuel supply line, the safety valve ensures that the pressure difference is reduced in a controlled manner. Finally, the safety valve is then opened so that the pressure can escape in the direction of the feed opening. The provision of the safety valve makes it possible to work safely with the injector immediately after actuating the pressure relief valve arranged, for example, on the rail, since the injector then no longer has any chambers that are under high pressure.

According to a further optional modification of the present invention, it can be provided that the primary valve has a movable primary valve body, a primary valve seat that can be sealed by the primary valve body, and an elastic tensioning element for urging the primary valve body in the direction of the primary valve seat comprises, and/or the safety valve comprises a movable safety valve body, a safety valve seat which can be sealed by the safety valve body and an elastic clamping element for urging the safety valve body in the direction of the safety valve seat.

The sealing effect that can be generated by a valve arises in that the valve body interacts with the valve seat and thus closes a passage, so that a fluid connection running through the closed passage is interrupted by the valve. The valve body is typically movably arranged in the injector and is urged by an elastic clamping element in the direction of the valve seat. Depending on the prevailing pressure conditions upstream or downstream of the valve body, this results in the valve being released or closed. If the pressure conditions upstream and downstream of the valve body are identical, the elastic clamping element ensures that the valve body moves in the direction of the valve seat, which leads to the valve being closed. If the pressure conditions change in such a way that the force exerted by the elastic clamping element is increased, the valve remains in its closed position. If the pressure conditions are reversed thereto, the valve body is forced out of its sealing position with the valve seat when the force exerted by the elastic tensioning element has been overcome.

According to an advantageous modification of the present invention, it can be provided that the primary valve seat is arranged on a stop part, which has at least one passage that can be closed or opened by the primary valve body, and wherein the stop part has at least a second passage that cannot be closed by the primary valve body and has only can be closed or released by means of the safety valve.

The stop part can be rigidly connected to an injector housing.

According to a further development, the stop part, which has the primary valve seat, also has another one that cannot be closed by the primary valve body Carrying out, which can be closed or released by the safety valve. The effective directions of the primary valve and the safety valve are aligned in opposite directions, so that the desired functions are implemented. This further passage is exclusively sealed by the safety valve. The primary valve cannot act on this.

According to a further optional development of the present invention, it can be provided that the safety valve is integrated into the stop part, interacts with it and/or forms it in connection with an elastic tensioning element.

For example, the safety valve can be integrated into the stop part, in that the path of movement of the safety valve body is fixed in a recess in the stop part. Furthermore, it can also be provided that the safety valve seat, which can be closed or released by the safety valve body, is arranged in the interior of the stop part.

Alternatively or additionally, however, it is also possible that the safety valve body is not arranged in the interior of the stop part, but interacts with an outside of the stop part.

Furthermore, it can be provided that the safety valve body has a passage that can be released or closed by the primary valve body. In addition, the safety valve body can have at least one further passage which can be closed or opened by a flange-like element rigidly connected to the injector housing when the safety valve body is positioned appropriately in the injector. In such a configuration in particular, it is advantageous if the force of the elastic tensioning element, which acts on the safety valve body, is greater than the force that is exerted on the primary valve body by the other elastic tensioning element. According to an optional modification of the present invention, it can be provided that the safety valve produces a sealing effect through a safety valve body in the form of a sphere and a safety valve seat designed as a spherical seat or conical seat, and/or the safety valve generates a sealing effect through a safety valve body in the form of a cone and a constructed as a cone seat safety valve seat produced. The combination of the safety valve body in the form of a ball together with a conical seat is also possible.

The coordinated shape of the valve body and valve seat of the safety valve in the form of a ball or cone enable a simple and particularly effective seal that can be implemented with little maintenance.

According to a further development of the present invention, it can be provided that the safety valve body is designed in one, two or more parts.

For example, the safety valve body can be formed only by a sphere or by a sphere and an urging element that interacts with the sphere and on which the elastic tensioning element attaches. The urging element can be firmly connected to the ball or a cone, although this is not mandatory. Especially for the design with a ball, it is not absolutely necessary for the connection to the urging element to be fixed.

According to a further advantageous embodiment of the present invention, it can be provided that the primary valve body and/or the safety valve body is/are formed in one piece. In order to allow corresponding pressure differences for a movement of the valve body in the injector, the valve body has at least one passage.

According to an advantageous modification of the present invention, it can be provided that the tensioning element of the primary valve urges the primary valve body in a direction that opposes the direction in which the tensioning element of the Safety valve urges the safety valve body, wherein preferably the two directions are aligned antiparallel to each other.

Furthermore, it can be provided according to the present invention that the safety valve is arranged upstream of the primary valve.

According to a further optional modification of the present invention, it can be provided that the secondary valve is arranged in the primary valve, preferably in that the primary valve body has a passage (e.g. at least one bore) which can be fluidically blocked by the secondary valve. The passage is capable of bypassing the primary valve in an unblocked state, while bypassing is not possible in a blocked state. For this purpose, the passage arranged in the primary valve body is designed in an unblocked state to create a fluid connection to the supply opening of the injector with an area downstream of the primary valve.

According to an optional development of the present invention, it can be provided that the primary valve body is in a closed position, in which it is urged by its associated elastic tensioning element, in contact with the safety valve body and seals a passage of the safety valve body, with preferably the tensioning element of the primary valve and the tensioning element of the safety valve in each case exert a force in order to press the primary valve body and the safety valve body together, the force emanating from the clamping element of the safety valve preferably being greater than that of the clamping element of the primary valve.

Furthermore, according to the invention it can be provided that the primary valve is also designed to limit a flow of fuel introduced from the supply opening to the at least one outlet opening, preferably with the outflow of fuel downstream of the primary valve causing a pressure drop to be created To move a primary valve body in an opposite direction from its valve seat, so that this with a second downstream valve seat comes into contact and stops the flow from the supply port to the at least one outlet port or the nozzle needle.

Accordingly, the primary valve body is thus arranged between two different primary valve seats, it being possible for it to be in contact with only one of them at any given time. The time that the primary valve body needs under the appropriate pressure conditions to move from its closing starting position, into which the elastic tensioning element forces it, into the second primary valve seat, is decisive for limiting the flow. The number and the diameter of the passages going through the primary valve body, through which the fuel is guided, must also be taken into account for the flow rate.

According to an optional modification of the present invention, it can be provided that the injector has a pressure reservoir in which the primary valve is arranged. It can preferably be provided that the primary valve is arranged in the downstream half, preferably in the downstream third of the pressure reservoir. At its end opposite to the fuel supply, the pressure reservoir is connected via a high-pressure connection to an area in which the switching valve including the nozzle needle is arranged.

According to an optional development of the present invention, it is provided that the primary valve body and/or the safety valve body has at least one passage for conducting fuel from an upstream section to a downstream section or vice versa.

Furthermore, it can be provided that the at least one passage for the passage of fuel of the primary valve body is offset to the associated elastic clamping element, preferably so that a through the Passage flowing fluid flow is not passed through turns of the elastic clamping element.

This brings with it the advantage that there is no undesired turbulence in the fluid flow, which would otherwise arise if the fluid flow were to cross the windings of the elastic tensioning element.

The present invention also relates to an internal combustion engine, in particular for diesel and/or gasoline, having at least one fuel injector according to one of the preceding claims.

It can be provided in particular that several fuel injectors are connected to a common high-pressure volume and are thus indirectly connected to one another.

Furthermore, it can be provided that several fuel injectors are connected directly to one another via fuel lines and each have a high-pressure accumulator volume which they share with the other injectors via the connection through the fuel lines.

Further features, details and advantages of the invention can be seen from the following description of the figures. show:

Fig. 1 a/b: Principle sketches of a connection of fuel injectors to a fuel accumulator,

2: a schematic diagram of a fuel injector according to the invention,

Fig. 3a-f: Principle sketches of different embodiments of the fuel injector according to the invention, Fig. 4a/b: Principle sketches of the fuel injector with designations of the coordinate systems and the different pressure ranges,

Fig. 5: an explanatory view when performing normal full load

fuel injector injection,

Fig. 6: An explanatory diagram when an injection of the

fuel injector in the event of a jammed needle,

Fig. 7: an explanatory representation for the embodiment of the fuel injector without a safety valve according to the invention,

Fig. 8: an explanatory representation of the embodiment of the fuel injector with a safety valve according to the invention,

9: a schematic diagram of a fuel injector according to the invention, in which a flow limitation is not provided,

Fig. 10a-d: Principle sketches with different arrangement positions of pressure relief valve and flow control valve in the fuel injector, and

Figure 11: Diagram illustrating the differences in the various

Arrangement positions of pressure relief valve in the fuel injector.

1a shows a schematic diagram for connecting fuel injectors to a fuel supply.

One or more injectors 1 are installed on a test bench or in an engine. These are connected to a common high-pressure volume 10 (for example a rail) and are thus indirectly connected to one another. A pressure relief valve 13 is attached to the common high-pressure volume 10 to relieve the pressure on the engine or the test bench, which can be actively controlled and allows the fuel to flow out of the high-pressure volume 10 or out of the injectors into a tank 14 . The pressure relief valve can be activated, for example, after the test bench or engine has been switched off, in order to be able to carry out maintenance work on the depressurized system.

FIG. 1b, on the other hand, shows a different configuration for the fuel supply, in which the injectors 1 are connected directly to one another via fuel lines 11. FIG. In this case, the injectors 1 themselves usually contain a high-pressure accumulator volume 12 (for example a pressure reservoir), which they share with the other injectors 1 via the connection through the fuel lines 11 . The pressure accumulator volume 12 serves to dampen pressure fluctuations and to maintain the system pressure during injection. As shown in FIG. 1b, in addition to the high-pressure storage volume 12 that is present in each injector 1, there can also be a common storage volume 15 that can be connected to the tank 14 via a pressure relief valve 13. Here, too, the high pressure in storage volume 12 or storage volume 15 can be brought to the normal level by opening pressure relief valve 13 , since the fuel that has been taken up and is under high pressure can flow back into tank 14 .

Fig. 2 shows a sectional view of an injector 1 according to the invention.

Injector 1 comprises a housing and contains an actively controlled switching valve (not shown, indirectly driven hydraulic valve or directly driven piezo valve), which closes or closes at least one connection between the injector volume and combustion chamber 16 via a nozzle needle seat 17 via a nozzle needle 4 that can move in translation . The fuel is supplied to the injector 1 via a high-pressure connection 2 and conducted within the injector 1 via a high-pressure connection to the nozzle needle seat 17 of the switching valve.

In addition, the injector includes a primary valve 5 for implementing the flow limitation and enabling safe flushing of the fuel lines or storage volumes 10, 15 leading to the injector 1, which in the embodiment shown is capable of limiting the flow of fuel flowing through the injector 1 and at the same time allow fuel to flow into the injector 1 only when there is a certain excess pressure in the supplying fuel line compared to the primary valve 5 downstream areas.

In order to also fulfill the function, according to which no very high pressure drop remains inside the injector when the fuel supply line is reset to a pressureless state, a safety valve 6 is also provided, which acts in the opposite direction to the overpressure valve function of the primary valve 5.

Both the primary valve body 51 and the safety valve body 61 can be moved in a translatory manner and close or open a passage 71 , 72 .

In a starting position, in which the pressure in the injector 1 is the same everywhere, respective elastic tensioning elements 53, 63 ensure that the primary valve body 51 and the safety valve body 61 are pushed in the direction of their respective valve seat 52, 62. If there is a sudden drop in pressure due to the nozzle needle 4 being raised, the pressure downstream of the primary valve body 51 is reduced, so that the primary valve body 51 is lifted out of the valve seat 52 . The passages 55 provided in the primary valve body 51 allow a certain amount of fuel to flow in, but cannot withstand the prevailing pressure conditions when the injector is open equalize In a regular injection cycle, the needle 4 is returned to its sealing position before the primary valve body 51 touches the second stop 18 located downstream of the first stop 7 . Contact between the primary valve body 51 and the second valve seat 54 at the second stop 18 occurs only in the event of a fault, i.e. if the nozzle needle 4 remains in the open position for an unexpectedly long time Damage in the combustion chamber 16 could cause.

If, on the other hand, in the starting position shown in FIG. 2, in which fuel is present at high pressure everywhere in the injector, the pressure in the fuel supply line is reduced (for example by actuating a pressure relief valve 13 as can be seen in FIG. 1 a or FIG. 1 b), pressure is equalized in the area downstream of the primary valve body 51 via the safety valve 6. The high-pressure fuel can escape in the direction of the fuel supply line via the passage 72 by means of the safety valve seat, so that there are no longer any areas in the injector 1 where fuel is stored under very high pressure.

In the embodiment of the injector 1 shown in FIG. 2 , the flow limitation function and the functionality of the overpressure valve are implemented as a combined functionality in the primary valve 5 . However, the invention also encompasses the fact that these two functionalities are embodied in different valves which are arranged at different positions in the flow path of the injector 1 .

the figs 3a-d each show different embodiments of the injector 1 according to the invention. To improve clarity, not all of the reference numbers known from FIG. 2 have been included in the representations of FIGS. 3a-d inserted. 3a shows an implementation of the injector 1 in which the safety valve body is designed in two parts. In the present case, the safety valve body 61 comprises a ball which can be moved in translation together with a (cylindrical) element inside the stop part 7 . The elastic clamping element 63 is in contact with the (cylindrical) element, which in turn urges the ball in the desired direction. The safety valve seat 62 is adapted to the spherical shape of the safety valve body 61 and can accordingly also be implemented as a spherical seat.

FIG. 3b shows an implementation of the safety valve body 61 using a conical shape, with the safety valve 6 being arranged inside the stop part 7 . The corresponding safety valve seat 62 can be a conical seat.

3c shows a further embodiment of the injector 1 according to the invention. In contrast to the implementations of the injector 1 discussed above, the safety valve body 61 is now no longer arranged inside the stop part 7. FIG. The stop part 7 is now arranged between the primary valve body 51 and the safety valve body 61 . The safety valve 6 is provided upstream and the primary valve 5 is provided downstream. Both the primary valve body 51 and the safety valve body 61 have at least one passage that cannot be closed independently of an actuation and an arrangement position of the associated valve body 51 , 61 . In addition, the stop part has at least two passages, a first of which can be closed by the primary valve 5 and a second by the safety valve 6 . The embodiment shown in FIG. 3c allows for larger components, in particular with regard to the safety valve body 61, which simplifies assembly and also manufacture.

FIG. 3d is a further development of the embodiments considered above, which is optimized in terms of its structural height and nevertheless avoids the use of small components inside the stop part 7 . As can be seen in FIG. 3d, there is no longer a stop part 7 which is rigidly connected to the housing and whose passage through the primary valve 5 can be closed. In the present case, its function is taken over by the translatory movable safety valve body 61 . The safety valve body 61 has a passage that can be sealed by the primary valve body 51 when the safety valve body 61 is in a corresponding position, in that the primary valve body 51 comes into direct contact with the safety valve body 61 . Accordingly, the primary valve seat 52 is arranged on the safety valve body 61 . In addition, the safety valve body 61 has at least one further passage that can be sealed with a modified stop part 19 , the stop part 19 having no passage, in particular no passage that can be sealed by the primary valve body 51 . It is advantageous that the force of the elastic tensioning element 53 which acts on the primary valve body 51 is less than the force of the elastic tensioning element 63 which acts on the safety valve body 61 .

FIG. 3e shows an embodiment in which the safety valve 6 is integrated in the primary valve 7. FIG. The primary valve body 51 has a passage that can be closed by the secondary valve. The state in which the secondary valve 6 closes the passage running through the primary valve body 51 is shown in FIG. 3e. A spring 63 urges the secondary valve body 61 into a closed position, so that the passage running through the primary valve body 51 is fluidically blocked.

In contrast, FIG. 3f shows a state in which the passage running through the primary valve body 51 is not fluidically blocked by the secondary valve body 61 . It is therefore possible for a pressure equalization to take place downstream of the primary valve 5 to an area upstream of the primary valve 5, although the primary valve body 51 is in its closed position. The functional behavior of the injector 1 is described below for different scenarios. The initial situation is the same in all cases and is based on Fig. 2. The switching valve (not shown) with the nozzle needle 4 is closed, i.e. the nozzle needle 4 closes the connection between the injector 1 and the combustion chamber 16 by sealing in the nozzle needle seat 17. In the entire high-pressure area of the Injector 1 and in rail 10 is the rail pressure p _rail . The primary valve body 51 is preloaded by the spring 53 and is located at its upper stop 52 and thus seals the injector 1 against the rail 10 in the simultaneous function as a pressure relief valve. The safety valve body 61 is prestressed by the associated spring 63 and is in its stop on the safety valve seat 62. It also seals the injector 1 against the rail 10.

4a and 4b show the coordinate systems of the moving parts and the reference spaces for the listed pressures, as they are described in the diagrams of the following FIGS. 5-8.

Figure 5 shows a diagram and the corresponding movement of the components in the injector for normal full load injection.

Phase A: primary valve body in the upper stop

At time t ₀ a control signal is sent to injector 1 so that nozzle needle 4 begins to move out of seat 17 and the connection between injector 1 and combustion chamber 16 is released. The injection starts. The pressure downstream from the primary valve body 51 decreases and the primary valve body 51 begins (with a slight delay, not shown here) to move downwards.

Phase B: Primary valve body moves down

At time t ₂ the control signal of the switching valve (not shown) is terminated and the nozzle needle 4 then returns to its original position in the sealing seat 17 (t ₃ -t ₄ ). The injection thus ends at time t ₄ . The primary valve body 51 moves as a result of the pressure difference prevailing over the primary valve 5, which is determined by the size and number of the throttle bores 55 in the primary valve body 51 can be adjusted downwards throughout the injection.

Phase C: Primary valve body moves up

After the injection, the injector 1 fills up with fuel again. As a result, the primary valve 5 is pressure-balanced, so that the primary valve body 51 is returned upwards again by the elastic tensioning element 53 to its upper stop 52 (t ₄ -t ₆ ). (In reality, the reversal point of the primary valve body 51 occurs slightly offset in time between about t ₄ and t ₅ due to the mass inertia, which is not shown here.) The primary valve body 51 always maintains a safety distance from the lower stop 18 to avoid an unintentional To prevent closing of the primary valve 5 during normal injection.

Phase D: The initial state at the beginning of phase A has been reached again

The primary valve body 51 reaches the upper stop at time t ₆ . All mechanical components and pressures have returned to their original state (t ₆ - 1 ₇ ).

Fig. 6 shows a diagram and the corresponding movement of the components in the injector in the event of a jammed nozzle needle 4.

Phase A: primary valve body in the upper stop

Phase A is identical to the “normal injection (full load)” case, which is shown in FIG. At time t ₀ a control signal is sent to the injector, so that at time t _± the nozzle needle 4 begins to move out of the seat 17 and the connection between the injector 1 and the combustion chamber 16 is released. The injection starts. The pressure downstream from the primary valve body 51 decreases and the primary valve body 51 begins (with a slight delay, not shown here) to move downwards.

Phase B: Primary valve body moves down Phase B initially begins identically to the “normal injection (full load)” case, which is shown in FIG. At time t ₂ the control signal of the switching valve (not shown) is terminated. However, due to an error, the nozzle needle 4 now remains fixed in its open position. This can occur, for example, due to direct jamming of the nozzle needle or due to a malfunction of an upstream hydraulic valve (t ₃ - t ₆ ). The result is continuous injection with a quantity entering the combustion chamber that exceeds the full-load quantity, which can result in very serious damage to the combustion chamber. Thus, without a flow restriction, the continuous introduction of fuel would result in engine damage.

In contrast to the "normal injection (full load)" case (cf. Fig. 5), the primary valve body 51 now moves downwards until it hits the seat 54 at the lower stop 18 at time t ₄ and then (possibly after brief bouncing) blocked the flow of fuel.

Phase C: Primary valve body remains in the lower stop

As soon as the primary valve body 51 closes the lower sealing seat, the remaining amount of fuel located downstream of the primary valve body 51 is introduced into the combustion chamber 16 until the pressure in the injector 1 downstream of the primary valve body 51 has equalized the pressure in the combustion chamber 16 (t ₄ - t ₅ ). The pressure upstream of the second stop 18 equalizes the fuel pressure again.

Phase D: Final state is reached

The primary valve body 51 remains in the lower stop due to the applied pressure difference and continues to prevent the fuel from flowing further from the fuel supply into the injector (t ₅ -1 ₆ ).

Fig. 7 shows a diagram and the corresponding movement of the components in the injector, which is designed without a safety valve 6. Phase A: initial state before/after normal injection

At time t _{0 ,} all components and pressures are in their initial state before or after a normal injection.

Phase B: Pressure relief of the rail

The rail 10 or the common high-pressure reservoir 12, 15 of the injectors is relieved of high pressure by switching on a pressure relief valve 13 connected to the rail 10, for example, at time t ₀ , via which the fuel is returned from the rail 10 to the tank 14. As a rule, the pressure in the rail 10 drops within a very short time (a few milliseconds) down to the tank pressure (ambient pressure) at the point in time t _t .

In the case of no safety valve 6, the primary valve 5 (here simultaneously the overpressure valve and the flow-limiting valve) blocks the outflow of fuel from the injector 1 into the rail 10 back to the tank 14 in the upper stop 52. This creates an extremely high pressure difference in the amount of the previously prevailing Fuel pressure built over the upper stop part of the primary valve 5.

Phase C: Final state reached

The high pressure difference does not decrease or only decreases extremely slowly (t » t^. On the one hand, this can lead to damage to components within the injector 1. On the other hand, this poses a considerable danger to people when the injector 1 is dismantled.

FIG. 8 shows a diagram and the corresponding movement of the components in an injector 1 according to the invention, which has a safety valve 6 .

Phase A: initial state before/after normal injection

This phase is analogous to the case illustrated in FIG. 7 without a safety valve.

At time t _{0 ,} all components and pressures are in their initial state before or after a normal injection. Phase B: Pressure relief of the rail

The rail 10 or the common high-pressure reservoir 12, 15 of the injectors 1 is relieved of high pressure by switching a pressure control valve 13 connected to the rail 10 at time t ₀ , via which the fuel is returned from the rail 10 to the tank 14. The pressure in the rail 10 thus drops down to the tank pressure (ambient pressure) at the point in time t _t . This is analogous to the case without a safety valve (illustrated Fig. 7).

In the case of an injector 1 with a safety valve 6 , however, the safety valve body 61 now moves upward due to the prevailing pressure difference between the rail and the injector, and fuel can flow out of the injector 1 into the rail 10 . As a result, only a very small pressure difference acts across the safety valve seat 62. Mechanical damage and danger to people are thus safely and reliably avoided by a purely mechanical valve.

Phase C: Final state reached

The entire system including injector 1 is pressureless after a relatively short time (t > ti). The injector can thus be safely dismantled without endangering people. The injector remains undamaged.

9 shows an embodiment of the injector according to the invention without the function of a flow limitation. In contrast to the representation in FIG. 2 , there is at least one passage 20 in the lower stop 18 which cannot be sealed by placing the primary valve body 51 in place.

FIGS. 10a-d show different approaches for arranging these two valves in a configuration in which the overpressure valve 21 is designed separately from the valve for flow limitation 22. 10a shows several identically constructed injectors 1, in whose pressure reservoir 25 the pressure limiting valve 22 is arranged at the bottom and the pressure relief valve 21 at the top. The space for the switching valve that includes the nozzle needle 4 is identified by reference number 24 . The pressure reservoir 25 and the area for the switching valve 24 are connected via a high-pressure connection 23 .

10b shows an embodiment in which the overpressure valve 21 is arranged in the center of the pressure reservoir 25 and the pressure-limiting valve 22 is still located in the lower area.

10c shows an embodiment in which both the overpressure valve 21 and the pressure-limiting valve 22 are arranged in the lower region of the pressure reservoir 25, with the overpressure valve 21 being arranged upstream of the pressure-limiting valve 22.

10d shows a further embodiment in which both the pressure relief valve 21 and the pressure relief valve 22 are arranged in the lower region of the pressure reservoir 25, with the pressure relief valve 22 being arranged upstream of the pressure relief valve 21.

11 shows that the positioning of the overpressure valve 21 has an influence on the functional behavior of an injector 1.

If the pressure relief valve 21 is positioned at the top in the pressure reservoir 25 (see Fig. 10a), the injector currently injecting cannot access the high-pressure volume of the injectors 1 connected via the fuel line 11, but only its own or a connected rail 10, if present. This can lead to a sharp drop in the pressure in injector 1 during injection and thus to a drop in the injection rate (undesirable loss of performance). This can be seen in the diagram shown in FIG. 11 using the dot-dash line. When positioned at the bottom (see Fig. 10c), during the injection in the opening phase of the injector 1 - after an initially normal injection process - the rate may drop in the meantime compared to the normal injection process, since the pressure relief valve 21 (ÜDV) initially restricts the fuel post-flow blocked and only opens when a pressure difference of p _rail - p _injector APÜDV is reached. The opening takes place - due to the mass inertia and the hydraulic balance of forces - in a short but not negligible time. During this time, in which the pressure-limiting valve insert is still throttling the fuel flow at the upper stop, the pressure in the injector volume (switching valve volume + pressure-limiting valve volume) collapses, and the rate collapses as a result. As soon as the pressure relief valve is opened wide enough, the injection rate is adjusted to the normal one.

Positioning at the bottom of the pressure reservoir allows a combined design of pressure relief valve and pressure relief valve and is also considered advantageous in terms of performance. This is also the variant shown and preferred in this patent. When positioned in the middle of the pressure reservoir, the advantages of the two previous positions can be combined or their disadvantages eliminated or reduced.

An influence on the rate curve can be largely avoided.

The disadvantage here is that the pressure relief valve usually has to be designed as a separate assembly. In addition, a combined design would lead to an undesirable reduction in the pressure reservoir (displacement of the fluid volume by the component volume).

Claims

24

Expectations

1 . Fuel injector (1) for injecting fuel into a combustion chamber of an internal combustion engine, in particular a diesel engine, comprising: a supply opening (2) for supplying fuel, at least one outlet opening (3) for dispensing the fuel, a nozzle needle (4) between a A closed position, in which the at least one outlet opening (3) is closed, and an open position, in which the at least one outlet opening (3) is uncovered, can be moved, and a primary valve (5), which is located downstream of the supply opening (2) and upstream of the nozzle needle (4) and is designed to release a fluid connection between the supply opening (2) and the nozzle needle (4) only when an excess pressure is exceeded in an area upstream of the primary valve (5) compared to an area downstream of the primary valve (5), characterized by a safety valve (6) which is arranged downstream of the supply opening (2) and upstream of the nozzle needle (4) and is designed to establish a fluid connection between the supply opening (2) and the nozzle needle (4) only when an overpressure of one Release area downstream of the safety valve (6) to an area upstream of the safety valve (6). 2. The fuel injector (1) according to the preceding claim 1, wherein the primary valve (5) has a movable primary valve body (51), a primary valve seat (52) that can be sealed by the primary valve body (51), and an elastic clamping element (53) for urging the primary valve body (51 ) in the direction of the primary valve seat (52), and/or the safety valve (6) comprises a movable safety valve body (61), a safety valve seat (62) that can be sealed by the safety valve body (61) and an elastic tensioning element (63) for urging the safety valve body (61) in the direction of the safety valve seat (62).

3. Fuel injector (1) according to claim 2, wherein the primary valve seat (52) is arranged on a stop part (7) which has at least one passage (71) which can be closed or opened by the primary valve body (51), and wherein the stop part ( 7) has at least one second passage (72) which cannot be closed by the primary valve body (51) and which can only be closed or opened by means of the safety valve (6).

4. Fuel injector (1) according to claim 3, wherein the safety valve (6) is integrated into the stop part (7), interacts with it and/or forms it in connection with an elastic clamping element (63).

5. Fuel injector (1) according to one of the preceding claims, wherein the safety valve (6) produces a sealing effect by means of a safety valve body (61) in the form of a sphere and a safety valve seat (62) designed as a spherical seat or conical seat, or the safety valve (6) produces a Sealing effect by a safety valve body

(61) in the form of a cone and a safety valve seat designed as a cone seat

(62) generated.

6. Fuel injector (1) according to one of the preceding claims, wherein the safety valve body (61) is designed in one, two or more parts. 7. The fuel injector (1) according to any one of the preceding claims, wherein the tensioning element (53) of the primary valve (5) urges the primary valve body (51) in a direction that opposes the direction in which the tensioning element (63) of the safety valve (6) pushes the safety valve body (61) urges, the two directions preferably being aligned antiparallel to one another.

8. Fuel injector (1) according to any one of the preceding claims, wherein the safety valve (6) is arranged upstream of the primary valve (5).

9. Fuel injector (1) according to one of the preceding claims, wherein the primary valve body (51) in a closed position, in which it is urged by its associated elastic clamping element (53), with the safety valve body (61) in contact and a passage of the safety valve body ( 61 ), whereby preferably the clamping element (53) of the primary valve (5) and the clamping element (63) of the safety valve (6) each exert a force in order to press the primary valve body (51 ) and the safety valve body (61 ) together, with the preferred Clamping element (63) of the safety valve (6) outgoing force is greater than that of the clamping element (53) of the primary valve (5).

10. Fuel injector (1) according to any one of the preceding claims, wherein the primary valve (5) is further designed to limit a flow rate of a fuel introduced from the supply opening (2) towards the at least one outlet opening (3), preferably wherein the outflow of fuel downstream of the primary valve (5) results in a pressure differential being created to move a primary valve body (51) in a direction opposite to its primary valve seat (52) so that it comes into contact with a second downstream primary valve seat (54) and stops the flow from the feed opening (2) to the at least one outlet opening (3). 27

11. Fuel injector (1) according to one of the preceding claims, wherein the primary valve body (51) and / or the safety valve body (61) at least one passage (55; 65) for conducting fuel from an upstream section to a downstream section or vice versa having.

12. Fuel injector (1) according to the preceding claim 11, wherein the at least one passage (55) for conducting fuel of the primary valve body (51) offset to the associated elastic clamping element (53) is arranged, preferably such that a passage ( 55) flowing fluid flow is not passed through windings of the elastic tensioning element (53).

13. Internal combustion engine, in particular for diesel and / or gasoline, with at least one fuel injector (1) according to any one of the preceding claims.

14. Internal combustion engine according to claim 13, wherein a plurality of fuel injectors (1) connected to a common high-pressure volume (10) and are thus indirectly connected to each other.

15. Internal combustion engine according to any one of the preceding claims 13 or 14, wherein a plurality of fuel injectors (1) are connected directly to one another via fuel lines (11) and each have a high-pressure storage volume (12) which they communicate with the other fuel injectors (1) via the connection divided by the fuel lines.