fuel injector

Abstract

Fuel injector nozzle (10; 10'; 10") for a high-pressure fuel injection system, comprising a nozzle housing (20) and a nozzle needle (30) axially movable in the nozzle housing (20), with which an outlet opening in a valve seat (21) of the fuel injector nozzle (10; 10'; 10") can be closed and opened, wherein at least one pulsation reducer (40; 41) is arranged between the nozzle needle (30) and the inside (22) of the nozzle housing (20), which is sleeve-shaped and extends coaxially to the nozzle needle (30), characterized in that the pulsation reducer (40; 41) has at least one wave-breaking element (43) which locally reduces the cross-section through which fuel flows within the nozzle housing (20), wherein the at least one wave-breaking element (43) is connected to the valve seat (21) of the fuel injector nozzle (10; A blade or lamella pointing towards 10'; 10") is formed.

Description

The invention relates to a fuel injector having the features of the preamble of claim 1.DE 10 2011 120 945 A1 discloses a fuel injection nozzle with a sleeve-shaped pulsation reducer which is arranged coaxially with respect to a nozzle needle within a nozzle housing. The pulsation reducer is formed by a stack of a plurality of perforated plates and / or mesh layers or woven fabric layers through which the fuel flows.DE 199 42 855 A1 discloses a high-pressure fuel accumulator with an accumulator chamber for the fuel, to which fuel injectors can be connected. A vibration damping device is introduced into this storage chamber. EP 2 110 542 A1 likewise describes a high-pressure fuel accumulator having an accumulator chamber for the fuel, into which an orifice element is introduced. The same applies to JP 2002-89402 A, which discloses a high pressure fuel accumulator having a pulsation reducer in a fuel supply line.DE 102 47 775 A1 describes an accumulator injection system having a damping device which is preferably mounted at the location at which pressure waves are generated, which includes in particular also the region inside the injector between the actuator and the injection nozzle.In contrast, DE 10 2013 213 621 A1 describes a fluid delivery system having a low-pressure delivery system and a high-pressure delivery system, each of which has a low-pressure pump and a high-pressure pump. A pressure damper is arranged in the low-pressure delivery system, wherein the pressure damper can be arranged in particular in an inlet line or a return line.Many modern motor vehicles employ injection engines that require a high pressure fuel injection system to deliver high pressure fuel to the engine via a plurality of such injectors. The injection nozzles are, for example, electromagnetically actuated injectors which supply fuel to the engine in metered cycles. This is controlled by an electronic motor controller.The operation of such injection nozzles and the associated fuel pump causes pressure pulsations and thus vibrations in the fuel supply line, which can be transmitted to the vehicle body, in particular in the case of rigid fuel supply lines. This can lead to undesirable noise generation, so that various measures are known for attenuating such pressure pulsations or preventing their transmission to other vehicle parts. Damping elements are used at different positions within the fuel supply system, for example, or components of the fuel supply system are designed such that they have a damping effect.For example, U.S. Pat. No. 6,948,479 B1 discloses a flexible hose element which can be used within a fuel supply system to mitigate pressure pulsations in fuel lines. For this purpose, the hose element has in its interior a flexible damping element which is designed in the manner of a corrugated jacket. This damping element is preferably embedded in an elastic foam which fills the hose element.Furthermore, U.S. Pat. No. 6,148,798 A discloses a fuel feed system which has a fuel distributor pipe with a fuel feed line and a return line for excess fuel. In this case, the fuel return line is guided within the fuel feed line and is surrounded by a tubular damping element in such a way that pressure pulsations are intended to be attenuated. For this purpose, the damping element has a cross section which is not circular, but rather, for example, oval or rectangular. As a result, the side walls of the damping tube should be flexible enough that they can damp pressure pulsations. EP 0 886 066 A1 also proposes a damping element within a fuel feed system.However, pressure pulsations due to opening and closing of an injection nozzle and fuel supply by a pump may not only generate undesirable noises but also cause problems in the injection operation. During the injection process, pressure pulsations of + / - 20 bar can occur, in particular in the seat of the injection nozzle, which can influence the injected fuel quantity. This type of injection error cannot be compensated for by a fuel control system.In view of the state of the art presented, the area of reduction of pressure pulsations in high-pressure fuel injection systems thus still offers room for improvements.The object of the invention is to provide a fuel injection nozzle in which pressure pulsations are reduced, in particular in the region of the seat of the nozzle.According to the invention, the object is achieved by a fuel injection nozzle having the features of claim 1.The present invention provides a fuel injection nozzle for a high-pressure fuel injection system, having a nozzle housing and a nozzle needle which is axially movable in the nozzle housing and by means of which an outflow opening in a valve seat of the fuel injection nozzle can be closed and released, at least one pulsation reducer being arranged between the nozzle needle and the inner side of the nozzle housing, said pulsation reducer being of sleeve-shaped design and extending coaxially with the nozzle needle. According to the invention, the pulsation reducer has at least one wave-breaking element which locally reduces the cross section through which fuel flows within the nozzle housing, wherein the at least one wave-breaking element is formed by a blade or lamella pointing towards the valve seat of the fuel injection nozzle.Advantageous embodiments of this fuel injection nozzle are evident from dependent claims 2-8.It should be noted that the features and measures individually listed in the following description can be combined with one another in any technically meaningful manner and reveal further configurations of the invention. The description additionally characterizes and specifies the invention, in particular in conjunction with the figures.The fuel injection nozzle according to the present invention is suitable for a high-pressure fuel injection system. It has a nozzle housing and a nozzle needle which is axially movable in the nozzle housing and by means of which an outflow opening in a valve seat of the fuel injection nozzle can be closed and released. Between the inside of the nozzle housing and the nozzle needle, a certain gap is usually present. It is provided to arrange at least one pulsation reducer in this region. The pulsation reducer is sleeve-shaped and extends coaxially with the nozzle needle. Furthermore, according to the invention, the pulsation reducer has at least one element which is designed as a type of wavebreaker and is referred to below as a wavebreaker element.This pulsation reducer is characterized in that it attenuates pressure pulsations of the fuel inside the nozzle. This in turn allows pressure fluctuations in the valve seat to be reduced. In this case, the at least one pulsation reducer locally reduces the cross section through which fuel flows within the nozzle housing at one or more points.The pulsation reducer used can be designed and arranged in various ways. For example, it can be designed as an element which is firmly connected to the nozzle housing. This element can be formed integrally with the nozzle housing or it is fixedly attached to the inner side of the nozzle housing as a separate component. In another possible embodiment, however, the pulsation reducer according to the invention can also be fixedly connected to the nozzle needle, so that it moves with the nozzle needle.It can thus be a permanently installed or movable pulsation reducer, but a combination of both embodiments is also possible. If a first pulsation reducer is fixedly attached to the nozzle housing, a second pulsation reducer can be attached to the nozzle needle such that both elements together bring about a weakening of pressure pulsations in the nozzle.Different geometries can be selected for the respective pulsation reducer in order to influence the fuel flow between the nozzle housing and the nozzle needle in terms of flow in such a way that the pressure pulsations are attenuated.The at least one wave-breaking element of the pulsation reducer is formed in such a way that it locally reduces the cross section through which fuel flows within the nozzle housing. The wave break element is formed as a blade or lamella, which is arranged accordingly in the fuel flow. According to the invention, such a wave-breaking element is formed by a blade or lamella pointing towards the valve seat of the fuel injection nozzle. Of course, the shaft breaking element can also be arranged directly on the nozzle housing and / or the nozzle needle without the sleeve. The shaft breaking elements could be manufactured in one piece with the nozzle needle and / or the nozzle housing.A pulsation reducer comprises in particular a plurality of such wave-breaking elements. These are spaced apart from one another, for example, in the axial direction. In one embodiment of the invention, at least one pulsation reducer is formed, for example, by a hollow cylindrical base body, on which at least one wave-breaking element, preferably a plurality of wave-breaking elements, are attached. The base body thus forms a sleeve from which one or more wave breaking elements project. This sleeve-shaped base body can abut the inner side of the nozzle housing, wherein the wave breaking elements project inwardly from the sleeve in the direction of the nozzle needle. In the case of a pulsation reducer on the nozzle needle, the latter can be surrounded by a sleeve from which one or more shaft breaking elements project outwards in the direction of the nozzle housing. In a combination of both embodiments, the shaft breaking elements of the two pulsation reducers are expediently arranged in such a way that they do not touch one another during the movement of the nozzle needle. However, they can engage one another in a comb-like manner, wherein the movable shaft breaking elements of the nozzle needle move within the free spaces between the stationary shaft breaking elements on the nozzle housing.In one embodiment of the invention, at least one pulsation reducer is flexible at least in regions, so that it can at least partially absorb energy from pressure waves in the fuel. This can be achieved by a corresponding material selection and / or a suitable geometry of the wave break elements. For example, a pulsation reducer may be made of metal or an elastic material such as rubber, so that rubber elements or very thin metal plates can be used as the wave-breaking elements. The base body can also be formed from metal or from elastic material. It is of course also possible to use different materials for the sleeve and / or for the shaft breaking elements.Further advantageous embodiments of the invention are disclosed in the dependent claims and the following description of the figures. The following are shown: FIG. 1 shows a schematic illustration of a first embodiment of a fuel injection nozzle having a pulsation reducer on the nozzle needle, which pulsation reducer can be moved together with the nozzle needle, FIG. 2 shows a schematic illustration of a second embodiment of a fuel injection nozzle with a fixed pulsation reducer on the inside of the nozzle housing, and FIG. 3 is a schematic illustration of a third embodiment of a fuel injector illustrating a combination of the pulsation reducers of FIGS. 1 and 2.In the different figures, identical parts are always provided with the same reference numerals, which is why they are generally also described only once. The fuel injection nozzles 10, 10', 10" shown in FIGS. 1 to 3 are embodied in a known manner, wherein, to explain the embodiment according to the invention, only that end of the fuel injection nozzles 10, 10', 10" is shown at which the outflow opening for injecting fuel is located in an engine. The electromagnetic actuation of the fuel injection nozzles, for example, which are also referred to below as injection nozzles, and the supply of fuel to these are not shown.The injection nozzles 10, 10', 10'' each have a nozzle housing 20 and a nozzle needle 30 movably guided therein. The nozzle needle 30 can have, for example, a needle tip 31 in the form of a ball, which closes the outflow opening of the respective injection nozzle in a funnel-shaped valve seat 21. The nozzle needle 30 is axially movable within the nozzle housing 20 so that it can alternately close and open the outflow opening in order to supply fuel to an engine, not shown, in a clocked manner. The fuel is in turn supplied to the respective injection nozzle 10, 10', 10'' under high pressure by a fuel pump, likewise not shown.In typical fuel injection nozzles, a distance, i.e. a radial gap, is provided between the nozzle needle 30 and the nozzle housing 20, so that a pulsation reducer 40, 41 according to the invention can be arranged in the space between the nozzle needle 30 and the inner side of the nozzle housing 20.In the embodiment of FIG. 1, the fuel injector 10 includes a movable pulsation reducer 40 formed as a sleeve 42 having a plurality of shaft break elements 43 attached thereto. This sleeve-shaped pulsation reducer 40 surrounds the nozzle needle 30 and moves together with it within the nozzle housing 20. They preferably project at an angle different from 90°, wherein they are inclined with their free end in particular in the direction of the valve seat 21. These blades can be designed as straight or curved plates.The size and the pattern of the wave-breaking elements 43 on the base body 42 are selected such that the fuel can still be moved without impairment to the outflow opening in the valve seat 21, but disadvantageous pressure pulsations in the fuel are reduced by the shape and arrangement of the wave-breaking elements 43. In this case, the movement of the nozzle needle 30 is not impaired by the pulsation reducer 40.In the embodiment of the fuel injection nozzle 10' according to FIG. 2, the pulsation reducer 41 is not attached to the nozzle needle 30, but to the inner side 22 of the nozzle housing 20.In the embodiment of the fuel injection nozzle 10'' according to FIG. 3, both variants are combined, so that a first pulsation reducer 40 is attached to the nozzle needle 30 and a second pulsation reducer 41 is attached to the nozzle housing 20. The dimensions of these two elements 40, 41 are selected such that their wave breaking elements 43 do not touch during the movement of the nozzle needle 30 and thus of the pulsation reducer 40, but rather the nozzle needle 30 can still move freely within the nozzle housing 20.As in the embodiment of FIG. 3, the shaft breaking elements 43 of the two pulsation reducers 40, 41 can be arranged in particular such that the shaft breaking elements 43 on the nozzle needle 30 can move within the free spaces between the shaft breaking elements 43 of the stationary pulsation reducer 41. The two pulsation reducers 40, 41, i.e. their shaft breaking elements 43, thus engage one in the other in a comb-like manner, without touching one another during a movement of the nozzle needle 30, however. However, the dimensions can also be selected such that the two pulsation reducers 40, 41 do not engage in one another, but can move freely next to one another.Furthermore, a pulsation reducer also does not have to have a plurality of wave-breaking elements, as are shown by way of example in the embodiments of the figures. Rather, it can also have only individual elements which are arranged at specific positions within the nozzle housing 20.The shaft breaking elements 43 can also be referred to as lamellae and are spaced apart from one another in the axial direction and, viewed in the circumferential direction of the sleeve 42, preferably configured continuously, wherein, of course, a configuration interrupted viewed in the circumferential direction could also be provided. The wave-breaking elements 43 preferably have an equal distance as viewed in the axial direction, wherein the distance between respectively adjacent wave-breaking elements 43 can of course also be different. An offset arrangement is also possible if the shaft breaking elements 43 are provided interrupted when viewed in the circumferential direction.The aim is to provide for the axial spacing of the shaft breaking elements 43 following one another in the axial direction to correspond to the stroke of the fuel injection nozzle, that is to say to the stroke of the nozzle needle, wherein this can also apply to the offset arrangement of the shaft breaking elements 43 and also to the configuration according to FIG. 3. In a possible embodiment, the shaft breaking elements 43 can have an axial distance with an amount of 1 mm to 5 mm or even a distance smaller than 1 mm from one another. It is conceivable for the shaft breaking elements 43 to have an axial distance of 0.3 to 0.5 mm, possibly even 0.1 mm.List of reference numbers:10, 10', 10" fuel injection nozzle 20 nozzle housing 21 valve seat 22 inside of nozzle housing 30 nozzle needle 31 needle tip 40, 41 pulsation reducer 42 main body, sleeve 43 shaft breaking element, blade, lamella

Claims

Fuel injection nozzle (10; 10'; 10") for a high-pressure fuel injection system, having a nozzle housing (20) and a nozzle needle (30) which is axially movable in the nozzle housing (20) and by means of which an outflow opening in a valve seat (21) of the fuel injection nozzle (10; 10'; 10") can be closed and released, wherein at least one pulsation reducer (40; 41) is arranged between the nozzle needle (30) and the inner side (22) of the nozzle housing (20), said pulsation reducer being of sleeve-shaped design and extending coaxially with the nozzle needle (30), characterized in that the pulsation reducer (40; 41) has at least one wave-breaking element (43) which locally reduces the cross section through which fuel flows within the nozzle housing (20), wherein the at least one wave-breaking element (43) is formed by a pulse width which is greater than the valve seat (21) of the fuel injection nozzle (10; 10'; 10") is formed in a blade or lamella pointing towards it.Fuel injection nozzle according to Claim 1, characterized in that the pulsation reducer (41) is fixedly connected to the nozzle housing (20).Fuel injection nozzle according to Claim 1 or 2, characterized in that the pulsation reducer (40) is fixedly connected to the nozzle needle (30).Fuel injection nozzle according to one of the preceding claims, characterized in that the at least one pulsation reducer (40; 41) has a sleeve (42), on which at least one wave-breaking element (43) is mounted.Fuel injection nozzle according to one of the preceding claims, characterized in that the at least one pulsation reducer (40; 41) has a plurality of shaft breaking elements (43) which are spaced apart from one another in the axial direction.Fuel injection nozzle according to one of the preceding claims, characterized in that the at least one pulsation reducer (40; 41) is flexible at least in regions.Fuel injection nozzle according to one of the preceding claims, characterized in that the at least one pulsation reducer (40; 41) is made of metal, its sleeve (42) and / or its at least one shaft-breaking element (43) being made of the same and / or a different material.Fuel injection nozzle according to one of the preceding claims, characterized in that the at least one pulsation reducer (40; 41) is made of an elastic material, its sleeve (42) and / or its at least one wave-breaking element (43) being made of the same and / or a different material.

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