Fuel injection valve for large diesel engine and large diesel engine

Abstract

The present invention relates to a fuel injection valve for a large diesel engine and a large diesel engine. The fuel injection valve comprises a nozzle head, a fuel pipe, a nozzle needle, an actuating piston with a movable first valve seat, and a control chamber. An intermediate chamber is provided that can be connected to the control chamber via a closable flow connection. The end of the actuating piston is designed as a closing body, and when the actuating piston is in a first position, the closing body closes the flow connection between the control chamber and the intermediate chamber. A closable open throttle orifice is provided, and the intermediate chamber can be connected to an outlet for fuel via the open throttle orifice. A first orifice is provided that connects the control chamber to the fuel pipe. A second orifice is provided that connects the intermediate chamber to the fuel pipe, and the diameter of the second orifice is smaller than the diameter of the first orifice.

Description

Technical Field

[0001] The present invention relates to a fuel injection valve for a large diesel engine and the large diesel engine. Background Art

[0002] Large diesel engines (such as longitudinally scavenged two-stroke large diesel engines) are often used as drive units for ships or even for stationary operation, for example, to drive large generators for generating electrical energy. The engines are usually operated in continuous operation for a considerable period of time, which places high demands on operational safety and availability. Therefore, particularly long maintenance intervals, low wear and economical handling of operating materials are core criteria for operators. Large diesel engines usually have a cylinder with an internal diameter (bore) of at least 200 mm. Today, large diesel engines with a bore of up to 960 mm or even larger are used.

[0003] Over the years, exhaust gas quality has also become an increasingly important aspect. Thus, in particular, the combustion of classic heavy fuel oils (heavy fuel oils with pollutants) as well as diesel or other fuels in large two-stroke diesel engines has become increasingly problematic, as compliance with emission limits has become increasingly difficult, technically more complex and therefore more expensive, or simply no longer possible at a meaningful level.

[0004] Therefore, in practice, there has long been a need for engines that can operate with at least two different fuels. For example, these can be two different liquid fuels, or also a liquid fuel and a gaseous fuel. These engines are generally referred to as multi-fuel engines and can switch from one fuel to another during operation. In addition to heavy fuel oil, marine diesel and diesel, known liquid or gaseous fuels that can alternatively be burned in multi-fuel large diesel engines also include alcohols such as methanol or ethanol, natural gas (liquid or gaseous state) or emulsions or suspensions.

[0005] For example, we can mention here the emulsions known as MSAR (Multiphase Superfine Atomized Residue). These emulsions are essentially emulsions of heavy hydrocarbons (e.g., bitumen, heavy oil, etc.) and water, produced using a special process. Another example is the suspension (e.g., made from coal dust and water), which is also used as fuel for large diesel engines.

[0006] A special type of multi-fuel engine is an engine that can operate with two different fuels, commonly referred to as a "dual-fuel engine." In gas mode, a gas (e.g., natural gas such as LNG (liquefied natural gas)) is burned, while in liquid mode, a suitable liquid fuel such as diesel or heavy fuel oil can be burned in the same engine.

[0007] Within the framework of the present application, the term "large diesel engine" also refers to multi-fuel large engines, dual-fuel engines, and large engines that can be operated not only in diesel operation, which is characterized by autoignition of the fuel, but also in Otto operation, or in a mixture of the two. The term "large diesel engine" also includes those large engines that can alternatively be operated with at least two different fuels, at least one of these different fuels being suitable for operating the diesel engine in diesel operation.

[0008] Modern large diesel engines are typically fully electronically controlled and typically include a common rail system for fuel injection with a fuel accumulator for supplying fuel, such as heavy fuel oil or diesel, to the cylinders. Each cylinder is equipped with at least one fuel injection valve to inject fuel into the corresponding cylinder's combustion chamber. Multiple fuel injection valves, for example, two or three, are typically provided for each cylinder. Each fuel valve is connected to the accumulator and comprises a nozzle body and a nozzle tip, which typically extends into the cylinder's combustion chamber. The nozzle tip, also known as an atomizer, typically includes multiple nozzle holes through which fuel is injected into the combustion chamber. To initiate or terminate injection, a movable valve needle is provided in the fuel injection valve, engaging a valve seat to open or close access to the nozzle holes. To initiate injection, the nozzle needle is lifted off the valve seat against a spring force, allowing fuel at injection pressure to flow into the nozzle holes. To terminate injection, the nozzle needle is brought into sealing contact with the valve seat, closing access to the nozzle holes.

[0009] The injection process is electronically controlled, for example by applying current to a solenoid control valve, which in turn causes the nozzle needle of the fuel injection valve to perform a corresponding stroke movement. When the injection is complete, the force of the spring and the force of the actuating piston push the nozzle needle back into sealing contact with the valve seat.

[0010] Figure 1 A known fuel injection valve is shown in cross section, with which liquid and autoignitable fuels, ie for example heavy oil or diesel, can be introduced into the combustion chamber of a cylinder of a large diesel engine.

[0011] Within the framework of the present application, relative position indications such as “lower”, “upper”, “below”, “above” etc. are to be understood as referring in each case to the normal position of use.

[0012] Figure 1 A known fuel injection valve 1' for a large diesel engine is shown in a schematic longitudinal section. In particular, the fuel injection valve 1' is suitable for a longitudinally scavenged two-stroke large diesel engine. Of course, the fuel injection valve 1' is also suitable for other large engines that can operate with different liquid fuels, for example, a four-stroke large diesel engine or a large engine.

[0013] Figure 1 The fuel injection valve 1 ′ is shown in its normal position of use.

[0014] In a manner known per se, a large diesel engine comprises a plurality of cylinders, for example, six to twelve cylinders or even more. A piston is disposed in each cylinder and is arranged to move back and forth along the cylinder's running surface between top dead center and bottom dead center. The upper side of the piston, together with the cylinder head, delimits a combustion chamber 50'. Fuel (for example, heavy oil) is injected into the combustion chamber 50' by means of a fuel injection valve 1'.

[0015] The fuel injection valve 1' is part of an injection system designed, for example, as a common rail injection system. The injection system comprises at least one, but often a plurality (for example, two or three) fuel injection valves 1' per cylinder for injecting fuel into a combustion chamber 50' which is often arranged in a cylinder head.

[0016] The construction and individual components of a large diesel engine (such as the injection system, the gas exchange system, the exhaust system or the turbocharger system for providing scavenging or boost air, as well as the details of the monitoring and control system of the large diesel engine) are well known to those skilled in the art and therefore no further explanation is required here.

[0017] Today, modern large diesel engines are fully electronically controlled and monitored. An engine control unit (not shown) controls and monitors all functions of a large diesel engine, such as the actuation of outlet valves for gas exchange or fuel injection. These various functions are controlled or regulated using electrical or electronic signals, which actuate the corresponding engine components. The engine control unit also receives information from various detectors, sensors, or measuring devices.

[0018] Common rail injection systems that supply the combustion chamber 50' of each cylinder with fuel (e.g., heavy fuel oil) typically include a pressure accumulator (not shown), also known as an accumulator. The pressure accumulator contains fuel at a high pressure that substantially corresponds to the injection pressure when the fuel is injected into the corresponding combustion chamber 50'. The pressure accumulator is typically designed as a tubular container extending along all cylinders of a large diesel engine. One or more fuel pumps supply the pressure accumulator with fuel at a high pressure. For example, the fuel pressure in the pressure accumulator can be 700-900 bar, but it can also be higher or lower. A boost pump connected to the fuel tank delivers the fuel to the high-pressure fuel pump.

[0019] Each fuel injection valve 1' is connected to a pressure accumulator via a pressure pipe, so that fuel at injection pressure can be transferred from the pressure accumulator to the fuel injection valve 1'. In addition, a flow limiting valve may be provided between each fuel injection valve 1' and the pressure accumulator to prevent unintended continuous injection, for example, due to a malfunction.

[0020] Below, we will explain in more detail Figure 1 Schematically shown in FIG and known from the prior art is a fuel injection valve 1 ′ and its operation.

[0021] The fuel injection valve 1' extends in an axial direction A' defined by the longitudinal axis of the fuel injection valve 1' and includes a nozzle body 30' and a nozzle head 31', which is arranged at the lower end of the fuel injection valve 1' and connected to the nozzle body 30'. The nozzle head 31' can be designed as a separate component connected to the nozzle body 30'. As an alternative, the nozzle head 31' can also be an integral part of the nozzle body 30'. The nozzle head 31' has at least one nozzle hole 32' (typically a plurality of nozzle holes 32'), through which the fuel can be introduced into the combustion chamber 50' of the cylinder. The fuel injection valve 1' is mounted on the cylinder head of the cylinder, for example, in such a way that the nozzle head 31' extends into the combustion chamber 50' of the cylinder.

[0022] Fuel injection valve 1' further comprises a fuel line 10', which is preferably designed as a bore in nozzle body 30'. Fuel line 10' can be connected to a pressure line (not shown), by means of which fuel injection valve 1' is connected to a fuel pressure accumulator (not shown), so that fuel at injection pressure can enter fuel line 10'.

[0023] The fuel pipe 10' extends to a pressure chamber 33' in the nozzle body 30', so that fuel under pressure can be introduced into the pressure chamber 33' through the fuel pipe 10'. The pressure chamber 33' is designed to be substantially annular in shape.

[0024] The fuel injection valve 1' further comprises a nozzle needle 3'. The nozzle needle 3' extends into the pressure chamber 33' in the axial direction A' and is arranged to be movable back and forth relative to the axial direction A'.

[0025] The lower end of the nozzle needle 3' is designed to cooperate with a first valve seat 35'. The first valve seat 35' is arranged below the pressure chamber 33' and is adjacent to the pressure chamber 33' or forms the lower end of the pressure chamber 33'. Preferably, the lower end of the nozzle needle 3' is designed to be conical or frustoconical, and the first valve seat 35' is also designed to be conical or frustoconical so that the nozzle needle 3' and the valve seat 35' can cooperate in a sealing manner.

[0026] In the closed state, the nozzle needle 3' engages in a sealing manner with the first valve seat 35', thereby closing the flow connection between the pressure chamber 33' and the nozzle head 31'. No fuel can enter the nozzle head 31' from the pressure chamber 33'. In the open state, the flow connection between the pressure chamber 33' and the nozzle head 31' is opened due to the stroke of the nozzle needle 3' in the axial direction A' (upward, as shown), allowing fuel to flow from the pressure chamber 33' between the nozzle needle 3' and the first valve seat 35' into the nozzle head 31' and toward the nozzle opening 32'. The nozzle needle 3' is spring-loaded by means of a spring 34'. The spring 34' is arranged such that its spring force is directed in the direction of the first valve seat 35', i.e., it attempts to press the nozzle needle 3' into the first valve seat 35'.

[0027] An actuating piston 2' is provided for actuating the nozzle valve needle 3', i.e. changing between an open and a closed state. The actuating piston 2' extends in the direction of the longitudinal axis A' and acts with its lower end (as presented) on the nozzle valve needle 3', more precisely, on that end of the nozzle valve needle 3' which faces away from the first valve seat 35'. Of course, the nozzle valve needle 3' and the actuating piston 2' can be designed as a one-piece. The end of the actuating piston 2' which faces away from the nozzle valve needle 3' is received in a control chamber 4', which serves to move the actuating piston 2'. With the aid of a control fluid provided in the control chamber 4', which is often fuel under pressure, the actuating piston 2' can be moved from a first position to a second position, and vice versa. If the actuating piston 2' is in the first position, the nozzle valve needle 3' is in the open state, and if the actuating piston 2' is in the second position (as Figure 1 ), the nozzle valve needle 3' is in a closed state.

[0028] The control chamber 4' is connected to an annular space 91' via an orifice 7'. The annular space 91' is connected to an outlet 9', through which the control fluid can flow to the low-pressure side, for example, to a tank for the control fluid or fuel. For example, the low-pressure side may be at ambient pressure or a return line pressure slightly above ambient pressure.

[0029] The control chamber 4' is also fluidically connected to a fuel line 10' via an orifice 8', so that fuel under high pressure can flow from the fuel line 10' into the control chamber 4'. The orifice 8' has a diameter d' that is smaller than the diameter D' of the orifice 7'.

[0030] Furthermore, an electromagnetic actuating member 40' is provided, with which the passage through the throttle opening 7' can be opened and closed. The electromagnetic actuating member 40' can preferably be actuated by a motor control unit. Figure 1In the embodiment shown in FIG, the electromagnetic actuating member 40' comprises a coil 41' and an armature 42'. The armature 42' is designed as a valve needle 44' having a generally rod-shaped structure and is arranged so that the valve needle 44' can release or close the passage through the orifice 7' with its axial end. The armature 42' is preloaded against the orifice 7' by an armature spring 43'. When the coil 41' is de-energized, the armature 42' is pressed into the annular space 91' when the valve needle 44' abuts the mouth of the orifice 7', thereby sealingly closing the passage through the orifice 7'.

[0031] The fuel injection valve 1' operates as follows. As long as no injection is being carried out into the combustion chamber 50' of the cylinder, the coil 41' of the electromagnetic actuating member 40' is not energized. Consequently, the armature spring 43' presses the armature 42' so that the valve needle 44' comes into sealing contact with the open throttle hole 7', preventing the control fluid (in this case, fuel under pressure) from flowing out of the control chamber 4' through the open throttle hole 7'. Since the control chamber 4' is fluidically connected to the fuel pipe 10' via the joint throttle hole 8', a high pressure prevails in the control chamber 4'. The value of this high pressure depends in particular on the fuel pressure in the fuel pipe 10'. In particular, the actuating piston 2' is dimensioned so that the high pressure in the control chamber 4', together with the force exerted by the spring 34', is sufficient to press the nozzle valve needle 3' into the first valve seat 35' in a sealed manner, so that no fuel can flow from the pressure chamber 33' into the combustion chamber 50'. The open orifice 7 ′ and the orifice 8 ′ are dimensioned such that they optimally control the movement of the nozzle needle 3 ′ in both directions and substantially define the opening and closing speed of the nozzle needle 3 ′.

[0032] To initiate the injection process, current is applied to the coil 41' of the electromagnetic actuating member 40', causing the armature 42' to move in an upward stroke against the spring force of the armature spring 43', as shown. As a result, the passage through the orifice 7' is opened, allowing the control fluid (in this case, fuel) to flow from the control chamber 4' through the orifice 7' into the annular space 91' and from there to the low-pressure side through the outlet 9'. Although pressurized fuel can flow from the fuel line 10' into the control chamber 4' through the orifice 8', the larger diameter D' of the orifice 7' causes the pressure in the control chamber 4' to drop to a lower pressure. The orifice 7' is designed such that the lower pressure value in the control chamber 4' and, therefore, the force of the actuating piston, together with the spring force of the spring 34', is no longer sufficient to maintain the nozzle needle 3' in the closed state. Due to the pressure prevailing in the pressure chamber 33', the nozzle needle 3' is lifted off the first valve seat 35' and is in the open state, so that fuel can now flow from the pressure chamber 35' into the nozzle head 31' and from there through the nozzle hole 32' into the combustion chamber 50'. Thus, injection begins.

[0033] To terminate injection, the power supply to coil 41' of electromagnetic actuating member 40' is terminated. Consequently, armature 42' moves downward due to the spring force of armature spring 43', and valve needle 44' thereby closes the passage through open orifice 7', preventing further fuel from flowing through orifice 7' to outlet 9'. Since orifice 8' remains open, high-pressure fuel continues to flow from fuel line 10' through orifice 8' into control chamber 4', causing the pressure there to rise again to a high-pressure value. Consequently, the hydraulic pressure on actuating piston 2' and the force of spring 34' seal the nozzle needle 3' against the first valve seat 35', terminating the injection process.

[0034] Although this fuel injection valve 1 ′ for large diesel engines has proven itself in practice, there is still room for improvement.

[0035] One problem is high wear on the components of the fuel injection valve 1'. During the injection process, the orifice 8' is permanently open, and the open orifice 7' is also open, so that the entire pressure drop from the high pressure in the fuel line 10' to the low pressure at the outlet 9' occurs via the orifice 8' and the open orifice 7'. The open orifice 7' and the orifice 8' are in an optimal ratio for the function of the fuel injection valve 1'. This results in extremely high flow rates, particularly through the orifice 8' and the open orifice 7'. Because the diameter d' of the orifice 8', which is optimally proportioned for the opening and closing behavior of the fuel injection valve 1', is relatively large, the fuel flow rate through the open orifice 7' is very high, resulting in increased wear. This is particularly noticeable in the area between the outlet of the open orifice 8' and the tip of the valve needle 44' of the armature 42' of the electromagnetic actuator 40'. This is particularly critical because this area represents the sealing area.

[0036] The wear on the components of the fuel injection valve 1 ′ through which the fuel flows depends in particular on the flow rate and flow time (i.e., the duration of the injection) of the fuel through these components, the mass of the fuel flowing through, and the particles present in the fuel, to name a few. This wear is caused in particular by abrasion or erosion.

[0037] In particular, wear on and within the throttled orifice 7' and on the end of the valve needle 44' of the armature 42' that cooperates with the throttled orifice 7' can also cause the start, duration, and end of injection to vary, thereby jeopardizing at least the economical and thermodynamically efficient operation of large engines, since the start and end times of injection and the duration of injection predetermined by the engine control unit no longer correspond to the actual values due to wear. Furthermore, it is possible that the throttled orifice 7' can no longer be sealed. This can lead to undesirable leakage when no injection is taking place. Summary of the Invention

[0038] The present invention is directed to solving this problem.

[0039] Therefore, the object of the present invention is to propose a fuel injection valve for a large diesel engine with significantly reduced wear based on this prior art. In addition, the object of the present invention is to propose a corresponding large diesel engine.

[0040] 20. The fuel injection valve according to claim 19, wherein the fuel injection valve comprises: a nozzle head having at least one nozzle hole, through which fuel can be introduced into a combustion chamber; a fuel pipe, through which fuel can be introduced into a pressure chamber under high pressure; a nozzle valve needle loaded with a spring; a first valve seat, which is designed to cooperate with the nozzle valve needle in the following manner: in the open state of the nozzle valve needle, the flow connection between the pressure chamber and the nozzle head is opened, and in the closed state, the nozzle valve needle cooperates with the first valve seat in a sealing manner, so that the flow connection between the pressure chamber and the nozzle head is closed; a movable actuating piston, which is designed to move the nozzle valve needle from the open state to the closed state by a stroke movement; and a control chamber, which is used to move the actuating piston from the open state to the closed state. The nozzle needle moves from a first position in the open state to a second position in the closed state, wherein the control chamber receives one end of the actuating piston, wherein an intermediate chamber is provided which can be connected to the control chamber via a closable flow connection, wherein the end of the actuating position is designed as a closing body, and when the actuating piston is in the first position, the closing body closes the flow connection between the control chamber and the intermediate chamber, wherein a closable open throttle hole is provided, and the intermediate chamber can be connected to an outlet for fuel by means of the open throttle hole, wherein a first joint flow hole is provided for connecting the control chamber to the fuel pipe, wherein a second joint flow hole is provided for connecting the intermediate chamber to the fuel pipe, and wherein the diameter of the second joint flow hole is smaller than the diameter of the first joint flow hole.

[0041] The embodiment according to the invention with two orifice holes of different diameters results in a significant reduction in wear and therefore a significantly longer operating life, with optimal, unaltered functionality of the fuel injection valve. During the injection process, the first orifice hole (i.e., the orifice with the larger diameter) can be closed, so that the high-pressure control liquid (e.g., fuel) can only escape via the second orifice hole and the intermediate chamber.

[0042] Because the second orifice has a smaller diameter than the first, the pressure drop across it is significantly greater, resulting in two positive effects. On the one hand, the smaller diameter of the second orifice significantly reduces the flow rate of the control fluid downstream of the second orifice compared to the rate downstream of an orifice with a larger diameter. Consequently, the control fluid flows through the intermediate chamber at a much lower rate, significantly reducing wear on components flowing through or around it (such as the valve needle of the orifice and the armature of the electromagnetic actuator). Reducing the flow rate of the fuel or control fluid generally results in less wear. On the other hand, the amount of fuel flowing out through the outlet during the injection process is also significantly reduced due to the smaller diameter of the second orifice, significantly improving the energy efficiency of the diesel engine. The less unused high-pressure fuel flows to the low-pressure side, the better the energy balance.

[0043] With known fuel injection valves, in particular during partial load operation or at low loads, the proportion of unused fuel released from high pressure to low pressure can be 30%-40% of the injection volume, which is of course unsatisfactory for energy reasons. Here, the fuel injection valve according to the invention offers very important advantages.

[0044] Due to the embodiment according to the invention having a first and a second orifice, wherein the second orifice has a smaller diameter than the first orifice, both the amount and the rate of fuel flowing out through the outlet can be significantly reduced during the injection process. This results in a significant reduction in wear and a significantly longer stability of the injection process over time, thus resulting in a longer operating life.

[0045] According to a preferred embodiment, when the actuating piston is in the first position, the actuating piston completely closes the first orifice. In this way, fuel can only flow to the outlet via the second orifice.

[0046] Furthermore, an embodiment is preferred in which the sum of the flow cross-sectional area having the diameter of the first orifice and the flow cross-sectional area having the diameter of the second orifice is smaller than the flow cross-sectional area having the diameter of the open orifice.

[0047] Preferably, the diameter of the second orifice is at most half, preferably at most a quarter, of the diameter of the first orifice. The diameter of an orifice is a dimension that determines the flow cross section or flow cross-sectional area of the orifice through which fluid can flow.

[0048] Particularly preferably, the diameter of the second orifice is at most one tenth of the diameter of the first orifice.

[0049] In a preferred embodiment, the closable flow connection between the control chamber and the intermediate chamber comprises a second valve seat, wherein the end of the actuating piston is designed for sealing engagement with the second valve seat.

[0050] According to a preferred embodiment, the throttled opening is designed such that a flow can pass through it in the direction of the longitudinal axis of the fuel injection valve.

[0051] According to a further preferred embodiment, the throttle opening is designed such that a flow can flow through it in a direction perpendicular to the longitudinal axis of the fuel injection valve.

[0052] Preferably, an electromagnetic actuating member is provided for opening and closing the throttle orifice.

[0053] The electromagnetic actuating member preferably comprises a coil and an armature with a valve needle, wherein the valve needle, which is integrated into the armature or is also loose, closes the passage through the throttled orifice as long as the coil is not energized.

[0054] In a preferred embodiment, the coil is arranged coaxially with respect to the longitudinal axis of the fuel injection valve.

[0055] In another preferred embodiment, the coil is arranged parallel to the longitudinal axis of the fuel injection valve.

[0056] Of course, embodiments are also possible in which the coil has a different orientation relative to the longitudinal axis of the fuel injection valve. For example, the axis of the coil may form an acute or obtuse angle with the longitudinal axis, or may have any other arbitrary orientation.

[0057] Furthermore, the present invention proposes a large diesel engine comprising a fuel injection valve designed according to the present invention.

[0058] Preferably, the large diesel engine is designed as a longitudinally scavenged two-stroke large diesel engine.

[0059] In particular, large diesel engines can also be designed as multi-fuel engines which can be operated with at least two different fuels.

[0060] In particular, the large diesel engine may be designed as a dual-fuel large diesel engine capable of operating in a liquid mode in which liquid fuel is introduced into the combustion chamber for combustion, and in a gas mode in which gas is introduced into the combustion chamber as fuel.

[0061] Large diesel engines can switch from liquid to gas mode and vice versa during operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The present invention will be described in more detail below based on embodiments and the accompanying drawings.

[0063] Figure 1 is a schematic longitudinal sectional view of a fuel injection valve known in the prior art;

[0064] Figure 2 is a schematic longitudinal sectional view of a first embodiment of a fuel injection valve according to the present invention; and

[0065] Figure 3 2 is a schematic longitudinal sectional view of a second embodiment of a fuel injection valve according to the present invention. DETAILED DESCRIPTION

[0066] Figure 1 A known fuel injection valve 1 ′ is shown in a schematic cross-sectional view, with which a liquid and autoignitable fuel, ie for example heavy oil or diesel, can be introduced into a combustion chamber 50 ′ of a cylinder of a large diesel engine.

[0067] because Figure 1 has been described in detail as prior art and therefore does not require further description. Figure 1 In order to better distinguish the prior art from the embodiments of the present invention, reference symbols with single quotes are used for components belonging to the prior art. Some components according to the embodiments of the present invention may be designed in the same manner or in a manner similar to that of the prior art. Figure 1 In the following description of the embodiment according to the invention, only the differences with the prior art will be discussed in more detail. Figure 1 The other explanations also apply to the embodiments according to the present invention in the same manner or approximately the same manner.

[0068] Figure 2 A schematic longitudinal section through a first embodiment of a fuel injection valve according to the present invention is shown, which is designated overall by the reference symbol 1. The longitudinal axis of the fuel injection valve 1 is designated by the reference symbol A.

[0069] In a manner known per se, the fuel injection valve 1 comprises a nozzle head 31 ( Figure 1 ), the nozzle head 31 has at least one nozzle hole 32, but preferably a plurality of nozzle holes 32, through which liquid fuel can be introduced into the combustion chamber 50 of the cylinder of a large diesel engine not shown in greater detail. The fuel is, for example, heavy oil or diesel.

[0070] The fuel injection valve 1 includes a fuel pipe 10, through which fuel can be introduced into a pressure chamber 33 under high pressure. The fuel pipe 10 is preferably connected to a pressure accumulator of a common rail system, in which the fuel under high pressure is provided. The fuel injection valve 1 also includes a nozzle needle 3 extending in the direction of the longitudinal axis and arranged in a nozzle body 30. As shown, the lower end of the nozzle needle 3 is designed to engage with a first valve seat 35 ( Figure 1 ) match. The nozzle needle 3 is spring loaded by a spring 34, which exerts a downward force on the nozzle needle 3, as shown ( Figure 2 ), so that the spring force attempts to press the nozzle needle 3 into the first valve seat 35. In the open state of the nozzle needle 3, the nozzle needle 3 is lifted off the valve seat 35, so that the flow connection between the pressure chamber 33 and the nozzle head 31 is open. In the closed state, the nozzle needle 3 is pressed into the first valve seat 35 and cooperates with the first valve seat 35 in a sealing manner, so that the flow connection between the pressure chamber 33 and the nozzle head 31 is closed.

[0071] An actuating piston 2 is provided to actuate the nozzle needle 3. As shown, the actuating piston 2 is arranged on the upper end face of the nozzle body 3 and extends in the direction of the longitudinal axis A to an end 21. The actuating piston 2 can be designed as a single piece with the nozzle needle 3 or as a separate component. The actuating piston 2 is designed to move the nozzle needle 3 from an open state to a closed state, or vice versa, by a stroke movement in the direction of the longitudinal axis A. To effect movement of the actuating piston 2, a cylindrical control chamber 4 is provided that receives the end 21 of the actuating piston 2. The inner diameter of the control chamber is dimensioned so that it substantially corresponds to the outer diameter K of the actuating piston 2 or is slightly larger than this outer diameter K. The end 21 of the actuating piston 2 received by the control chamber 4 is preferably designed as a closing body 21 and has a smaller diameter than the rest of the actuating piston 2. The end of the actuating piston 2 designed as the closing body 21 includes a conical, frustoconical, or spherical portion designed for sealing engagement with the second valve seat 61.

[0072] With the aid of the control chamber 4, the actuating piston 2 can be moved from a first position in which the nozzle needle 3 is open to a second position in which the nozzle needle 3 is closed. With the aid of the control chamber 4, the actuating piston 2 can also be moved from the second position to the first position.

[0073] As shown, the intermediate chamber 5 is arranged above the control chamber 4 and can be connected to the control chamber 4 via a closable flow connection 6. The flow connection 6 comprises a second valve seat 61 designed to cooperate sealingly with the end of the actuating piston 2 designed as the closure body 21. When the actuating piston 2 is in a first position, the closure body 21 is seated in a sealing manner in the second valve seat 61, and the flow connection 6 between the control chamber 4 and the intermediate chamber 5 is closed. When the actuating piston 2 is in a second position, the closure body 21 is lifted off the second valve seat 61, and the flow connection 6 between the intermediate chamber 5 and the control chamber 4 is opened. Figure 2 The actuating piston 2 is shown in a second position.

[0074] The intermediate chamber 5 is connected to the annular space 91 via a closable open orifice 7. An outlet 9 leads from the annular space 91 to the low-pressure side. The low-pressure side may include, for example, a tank or a collecting vessel in which ambient pressure or return line pressure prevails, the return line pressure being greater than ambient pressure. In a first embodiment, the open orifice 7 extends in the direction of the longitudinal axis A, allowing flow through it in the direction of the longitudinal axis A. The open orifice has a diameter D.

[0075] Whenever a diameter is mentioned in connection with a throttle bore, within the framework of the present application this refers to the size of the respective throttle bore which determines the flow cross section or flow cross-sectional area of the throttle bore which is available for a fluid to flow through the throttle bore.

[0076] Fuel injection valve 1 further includes two orifices 81 and 82, namely, a first orifice 81 connecting control chamber 4 to fuel pipe 10 and a second orifice 82 connecting intermediate chamber 5 to fuel pipe 10. The diameter of first orifice 81 is indicated by d1, and the diameter of second orifice 82 is indicated by d2. The diameter d2 of second orifice 82 is smaller than the diameter of first orifice 81. Orifices 81 and 82 each open into the housing surface of control chamber 4 and intermediate chamber 5, respectively.

[0077] To open and close the throttle opening 7, an electromagnetic actuating member 40 is provided. The electromagnetic actuating member 40 comprises a coil 41 and an armature 42 having a generally rod-shaped valve needle 44. Both the armature 42 and the valve needle 44 can be formed as one piece or consist of separate loose parts. The valve needle 44 extends in the direction of the longitudinal axis A. Here, the coil 41 is arranged coaxially with the longitudinal axis A. The valve needle 44 of the armature 42 extends into the annular space 91 and is designed so that, when the coil 41 is not energized, the valve needle 44 closes the passage from the intermediate chamber 5 through the throttle opening 7 into the annular space 91. The armature 42 is spring-loaded by an armature spring 43. As long as no current is applied to the coil 41, the armature spring 43 presses the armature 42, causing the valve needle 44 to enter the annular space 91 and rest against the mouth of the throttle opening 7.

[0078] According to the present invention, the diameter d2 of the second orifice 82 is smaller than the diameter d1 of the first orifice 81. Preferably, the diameter d2 of the second orifice 82 is much smaller than the diameter d1 of the first orifice 81, for example, at most one-fifth or at most one-tenth.

[0079] Furthermore, it is preferred that both the diameter d1 of the first orifice 81 and the diameter d2 of the second orifice 82 are smaller than the diameter D of the open orifice 7. Particularly preferably, the diameters d1 and d2 are dimensioned so that the sum of the flow cross-sectional area having the diameter d1 of the first orifice 81 and the flow cross-sectional area having the diameter d2 of the second orifice 82 is smaller than the flow cross-sectional area having the diameter D of the open orifice 7. Then, d1 2 +d2 2 <D 2 .

[0080] Figure 2 The actuating piston 2 is shown in its second position, i.e., in the position in which the nozzle needle 3 is in the closed state. If the injection process is to be started, current is applied to the coil 41, whereby the armature 42 is attracted to the coil 41 against the force of the armature spring 43. As a result, the passage through the open throttle bore 7 is opened, and the fuel under high pressure flows out through the open throttle bore 7 and the annular space 91 into the outlet 9. Since the pressure in the intermediate chamber 5 and the control chamber 4 connected thereto is reduced in this state, the fuel in the pressure chamber 33 ( Figure 1 ) is greater than the sum of the spring force of the spring 34 and the liquid pressure, so that the nozzle valve needle 3 is lifted off the first valve seat 35 and starts to spray into the combustion chamber.

[0081] Due to this upward movement, the actuating piston 2 is also moved upward, as shown, into its second position in which the closing body 21 of the actuating piston 2 cooperates in a sealing manner with the second valve seat 61, so that the flow connection between the control chamber 4 and the intermediate chamber 5 is closed. Consequently, no more fuel can flow through the first orifice 81.

[0082] In the open state of nozzle needle 3, i.e., during the injection process, fuel under high pressure can flow to outlet 9 only via second orifice 82 and no longer via first orifice 81. Since diameter d2 of second orifice 82 is significantly smaller than diameter d1 of first orifice 81, the rate of fuel flow to outlet 9 and the amount of fuel flowing thereto are significantly reduced compared to known fuel injection valves.

[0083] To terminate the injection process, the current through coil 41 is cut off, whereby armature 42 is compressed by armature spring 43, causing valve needle 44 to be pressed into annular space 91 and against the mouth of orifice 7, thereby closing the passage through orifice 7. As a result, due to the open second orifice 82, a higher pressure initially builds up in intermediate chamber 5, thereby causing actuating piston 2 and, consequently, nozzle needle 3 to move downward, as shown. Once this movement has begun, the passage through first orifice 81 also opens, allowing flow through both orifices 81, 82 to terminate the injection process, resulting in a rapid and precise closing process. This is achieved when actuating piston 2 returns to its second position.

[0084] Figure 3 Similar to Figure 2 The illustration shows a second embodiment of a fuel injection valve 1 according to the present invention. In the following description of the second embodiment, only the differences from the first embodiment will be discussed in more detail. Otherwise, the explanations regarding the example of the first embodiment also apply in the same or approximately the same manner to the example of the second embodiment. In the second embodiment, identical or functionally equivalent parts are designated by the same reference symbols as in the first embodiment.

[0085] In the second embodiment, the annular space 91 is arranged transversely adjacent to the intermediate chamber 5 and preferably at the same height as the intermediate chamber 5. Therefore, in the second embodiment, the throttled opening 7 arranged between the intermediate chamber 5 and the annular space 91 extends in the direction of the longitudinal axis A, so that the flow passes through the throttled opening 7 perpendicular to the longitudinal axis A.

[0086] In the second embodiment, an electromagnetic actuating member 40 is also provided, comprising a coil 41 and an armature 42 with a valve needle 44. The coil 41 is arranged parallel to the longitudinal axis A. The armature 42 extends so that the valve needle 44 enters the annular space 91 and is designed so that the valve needle 44 closes the passage from the intermediate chamber 5 through the throttle opening 7 into the annular space 91 as long as the coil 41 is not energized.

[0087] It will be understood that an embodiment of the fuel injection valve according to the present invention is also possible in approximately the same manner in which more than two orifice holes 81 , 82 are provided.

Claims

1. A fuel injection valve for a large diesel engine, the fuel injection valve comprising: a nozzle head (31) having at least one nozzle hole (32) through which fuel can be introduced into the combustion chamber (50); a fuel pipe (10) through which fuel can be introduced into the pressure chamber (33) under high pressure; a nozzle valve needle (3) which is loaded with a spring (34); a first valve seat (35) designed to cooperate with the nozzle valve needle (3) in such a way that, in the open state of the nozzle valve needle (3), the flow connection between the pressure chamber (33) and the nozzle head (31) is opened, and in the closed state, the nozzle valve needle (3) cooperates with the first valve seat (35) in a sealing manner, so that the flow connection between the pressure chamber (33) and the nozzle head (31) is closed; a movable actuating piston (2) designed to move the nozzle valve needle (3) from the open state to the closed state through a stroke movement; as well as a control chamber (4) for moving the actuating piston (2) from a first position in which the nozzle valve needle (3) is in the open state to a second position in which the nozzle valve needle (3) is in the closed state, wherein the control chamber (4) receives one end (21) of the actuating piston (2), It is characterized by: An intermediate chamber (5) is provided which can be connected to the control chamber (4) via a closable flow connection (6), wherein the end of the actuating piston is designed as a closing body, which closes the flow connection (6) between the control chamber (4) and the intermediate chamber (5) when the actuating piston (2) is in the first position. Therein, a closable open throttle hole (7) is provided, by means of which the intermediate chamber (5) can be connected to an outlet (9) for fuel, A first joint orifice (81) is provided for connecting the control chamber (4) to the fuel pipe (10). wherein a second joint orifice (82) is provided for connecting the intermediate chamber (5) to the fuel pipe (10), and The diameter (d2) of the second joint flow hole (82) is smaller than the diameter (d1) of the first joint flow hole (81).

2. The fuel injection valve according to claim 1, wherein When the actuating piston (2) is in the first position, the actuating piston (2) completely closes the first orifice (81).

3. The fuel injection valve according to claim 1 or 2, wherein: The sum of the flow cross-sectional area of the first orifice (81) having the diameter (d1) and the flow cross-sectional area of the second orifice (82) having the diameter (d2) is smaller than the flow cross-sectional area of the open orifice (7) having the diameter (D).

4. The fuel injection valve according to claim 1 or 2, wherein: The diameter (d2) of the second orifice (82) is at most half the diameter (d1) of the first orifice (81).

5. The fuel injection valve according to claim 1 or 2, wherein: The diameter (d2) of the second orifice (82) is at most one quarter of the diameter (d1) of the first orifice (81).

6. The fuel injection valve according to claim 1 or 2, wherein: The diameter (d2) of the second orifice (82) is at most one tenth of the diameter (d1) of the first orifice.

7. The fuel injection valve according to claim 1 or 2, wherein: The closable flow connection (6) between the control chamber (4) and the intermediate chamber (5) comprises a second valve seat (61), wherein the end (21) of the actuating piston (2) is designed for sealing engagement with the second valve seat (61).

8. The fuel injection valve according to claim 1 or 2, wherein: The throttled bore (7) is designed such that a flow can flow through it in the direction of the longitudinal axis (A) of the fuel injection valve.

9. The fuel injection valve according to claim 1 or 2, wherein: The throttle opening (7) is designed such that a flow can flow through it in a direction perpendicular to the longitudinal axis (A) of the fuel injection valve.

10. The fuel injection valve according to claim 1 or 2, wherein: An electromagnetic actuating member (40) is provided for opening and closing the throttle hole (7).

11. The fuel injection valve according to claim 10, wherein: The electromagnetic actuating member (40) comprises a coil (41) and an armature (42) having a valve needle (44), wherein the valve needle (44) closes the passage through the throttled orifice (7) as long as the coil (41) is not energized.

12. The fuel injection valve according to claim 11, wherein The coil (41) is arranged coaxially with the longitudinal axis (A) of the fuel injection valve.

13. The fuel injection valve according to claim 11, wherein The coil (41) is arranged parallel to the longitudinal axis (A) of the fuel injection valve.

14. A large diesel engine, characterized in that: The large diesel engine comprises a fuel injection valve (1) designed according to any one of claims 1 to 13.

15. The large diesel engine according to claim 14, wherein the large diesel engine is designed as a longitudinally scavenged two-stroke large diesel engine.

16. The large diesel engine according to claim 14 or 15, being designed as a dual-fuel large diesel engine, capable of operating in a liquid mode in which liquid fuel is introduced into the combustion chamber for combustion, and also capable of operating in a gas mode in which gas is introduced into the combustion chamber as fuel.

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