EP1518050B1 - Injector for an injection system - Google Patents

Abstract

The invention relates to an injector (11) for an injection system which can be used for injecting fuel in the cylinder of an internal combustion engine. A similar injection system is known as an injection common rail system. A pressure drop which is produced at the level of injection holes (5) of the injector (11) during injection by reason of relatively long pipelines (32) between a high pressure accumulator (31) and the injector (11), generates undesirable pressure waves, in particular during a multiple injection. Said phenomenon adversely effects the homogeneity of an injection process. The aim of the invention is to design a high pressure hole (2) which is arranged in the injector casing in the form of a buffer accumulator (VI, V2, Vn). The aim is achieved, for example by embodying said high pressure hole (2) in the form of a multilevel hole.

Description

The invention is based on the preamble of the main claim • of an injector for an injection system, which is designed for the injection of fuel into an internal combustion engine. In such a system, the injector is connected by means of a high-pressure line to a high-pressure accumulator (rail) of the injection system, which provides the fuel required for injection into a cylinder of the internal combustion engine. The fuel is provided by a high pressure pump with a certain operating pressure in the high pressure accumulator. In an injection process, which is initiated by the lifting of the nozzle needle from its seat in a nozzle unit of the injector, however, there are pressure drops and pressure waves or vibrations in the injection system, since the connecting lines between the high-pressure accumulator and the more usually connected to the high-pressure accumulator Injectors are relatively long. These effects are particularly disadvantageous, especially in the case of multiple injections with short time intervals, since they can impair the intended course of injection.

So far, this problem has been solved by the fact that constructive measures, the connecting lines between the high-pressure accumulator and the injectors were chosen as short as possible. This was achieved, for example, by arranging the high-pressure accumulator as close as possible to the cylinder head of the internal combustion engine. The fuel is then fed via the shortened connecting lines and a high-pressure bore of constant bore diameter arranged in the injectors to the nozzle unit of the injector. While this arrangement provides some improvement, it does not provide satisfactory results, especially for fast multiple injections. From the Japanese Patent Abstract JP6088557 An injector for an injection system is known, which is designed for injection of fuel into an internal combustion engine. The injector can be connected via a pressurized fuel line to a high-pressure accumulator of the injection system. Furthermore, a high-pressure bore is provided, through which the fuel is guided by means of a controllable nozzle needle to injection holes of the injector. The high-pressure bore is in the form of stepped bores, the diameter of the individual stepped bores becoming narrower in the direction of the nozzle tip. In addition, a further bore is provided, which is likewise designed as a stepped bore, wherein the diameter of the individual stages of the further bore also decreases in the direction of the nozzle tip.

Out EP 1275841 A1 an injection valve with an integrated damping unit is known.

Out US 2002/0109022 A1 an injection valve is provided with a high-pressure bore for supplying fuel to injection holes of a nozzle needle. The high-pressure bore is formed as a stepped bore, wherein the diameter of the individual holes decrease in the direction of the nozzle tip. There is provided a further bore which is also formed as a stepped bore, wherein the diameter of the bore decreases in the direction of the nozzle tip.

Out GB 1487778 A Another injection valve is known which has a tapered bore for supplying fuel to a nozzle needle.

The invention has for its object to further form an injector for the fuel injection, that in particular the pressure drops, vibrations and their interactions occurring in the multiple injection of fuel can be reduced and a more uniform injection is possible. This object is achieved with the features of claim 1.

In the injector according to the invention is according to the features of the main claim, the high-pressure bore, which is mounted within the injector, designed such that it forms the largest possible buffer memory for the fuel. The high pressure bore is located in close proximity to the injection holes of the nozzle unit. As a result, the length of the connecting lines between the high-pressure accumulator and the connected injectors can advantageously be regarded as less critical, since the pressure drop occurring during the injection can be compensated in particular by the buffer volume which is made available by the high-pressure bore according to the invention within the injector. Furthermore, it is considered to be particularly advantageous that the unwanted reactions to the rail and the other injectors are largely suppressed by the inventive solution. The high-pressure bore in the injector is designed as a stepped bore. The stepped bore has two or more drill steps. According to the invention, the high-pressure bore has at least two bore diameters, with subsequent bore diameters being narrower towards the nozzle tip. It is provided a further step-shaped bore which is arranged parallel to the high-pressure bore. The bore diameter of the further bore expand in the direction of the nozzle tip.

As a result, the pressure waves propagating in the individual bore stages are reflected irregularly on the bore walls, so that they partially compensate each other or weaken. The damping of the pressure waves is the more pronounced, the more drilling stages can be attached to the high pressure bore.

According to the invention, the adjacent cross-sectional areas of the two holes are formed inversely proportional to each other. This ensures that the intermediate wall between the two holes always maintains the same strength. In this solution, the injector can be made overall slim, without compromising the necessary strength in the high pressure area.

The measures listed in the dependent claims advantageous refinements and improvements of the claim 1 injector are given.

A particularly advantageous solution is also seen, for example, make the individual drilling stages of the high-pressure bore in the flow direction of the fuel, for example, each narrower. Start at the top end of the injector with the widest hole and then drill the next hole with a smaller diameter so that the narrowest hole is formed near the nozzle tip. Such an arrangement of the individual drilling stages is particularly easy to carry out in terms of manufacturing technology. Furthermore, there is the fluidic advantage that the pressure waves are attenuated the more, the further they have moved away from their actual place of origin at the tip of the nozzle needle.

Due to the length of the individual drill stages in the high-pressure bore, the volume for the fuel to be stored can also be predetermined in a simple manner. It seems advantageous to make the volume smaller for the individual drilling stages in the flow direction of the fuel. In this way, one obtains in the upper part of the injector, a relatively large storage volume for the fuel, since there is usually enough space for the expansion of the high pressure bore available. In the lower drilling stages, however, the volume can be designed so that the damping effect of the pressure waves is particularly pronounced.

A further improvement of the damping effect for the pressure waves can also be achieved if the transition between two drilling stages is provided with a bevelled, in particular with a conical annular surface. At the ring surface, the pressure waves are also broken and partially absorbed.

In order to avoid that new vibrations can form at the transition between two adjacent drilling stages due to different flow velocities in the individual drilling stages, in an alternative embodiment of the invention it is proposed to design the transitions continuously. Such stepless transitions, which are formed, for example, arcuate, can be easily mounted manufacturing technology with a correspondingly shaped profile cutter.

It also seems favorable to influence the pressure waves or vibrations by drilling stages of different lengths.

Furthermore, it is advantageous that the two bores are drilled parallel to the longitudinal axis of the injector and have at the upper end of the injector housing an access opening. These access openings provide good access for the connection of electrical lines for the piezoelectric actuator and an external fuel line.

The injector according to the invention is particularly well suited for use in a common rail injection system. Especially When injecting diesel fuel is working with a very high fuel pressure, so here at Injection intensity of pressure waves and vibrations is especially high.

• Figur 1 zeigt in schematischer Darstellung einen Querschnitt durch einen erfindungsgemäßen Injektor,
• Figur 2 zeigt schematisch zwei Übergang zwischen jeweils zwei Bohrstufen und
• Figur 3 zeigt ein Common Rail Einspritzsystem mit einer Anordnung von vier erfindungsgemäße Injektoren.

An embodiment of the invention is illustrated in the drawing and will be explained in the description below.

• FIG. 1 shows a schematic representation of a cross section through an injector according to the invention,
• FIG. 2 schematically shows two transition between each two drill stages and
• FIG. 3 shows a common rail injection system with an array of four injectors according to the invention.

In FIG. 1 is shown in a schematic representation of an embodiment of an injector 10 according to the invention. In the cross-sectional drawing, first an injector housing 1 can be seen, in which an axially parallel, stepped longitudinal bore is introduced. The longitudinal bore is in the right part of FIG. 1 recognizable and is designed as a high-pressure bore 2. It has at its upper end an access opening 13 to which an external fuel line can be connected, for example with a screw thread.

In the left part of FIG. 1 is introduced a further stepped bore 10. Their drilling stages are preferably designed so that the drill diameters expand from top to bottom towards the nozzle tip. At the upper end of the injector housing 1, an access opening 13 is likewise provided, on which an electrical connection and control lines for the piezoelectric actuator 9 can be provided.

The adjacent two step-shaped holes 2,10 are preferably formed with their drill diameters such that at a Bohrquerschnitt the two adjacent Cross-sectional areas 14a, 14b behave inversely proportional to each other. In addition to a narrower bore, there is thus a larger bore, so that preferably the sum of the drill cross sections in different stages is preferably constant. This advantageously achieves that the wall thickness between the two holes is always made homogeneous and sufficiently strong to withstand the high fuel pressure.

The piezoelectric actuator 9 is fixedly arranged with its upper end on the injector 1. Its lower end is designed to be movable and acts on an axial length change to a nozzle needle 6, which is arranged in a nozzle unit 11. The nozzle needle 6 can open in response to control signals to the actuator with its lower conical portion injection holes 5 of the nozzle unit 11 or close fuel-tight.

To control the nozzle needle 6, a high-pressure chamber 7 and an inlet throttle 3 and an outlet throttle 8 are furthermore provided in the nozzle unit 11. The inlet throttle 3 is connected to a feed line 4, which is fed by the high pressure bore 2 and substantially promotes the high pressure fuel to the nozzle needle 6, so that the fuel exits when lifting the nozzle needle 6 via the injection holes 5 and into the combustion chamber of a Internal combustion engine can be injected.

The high-pressure bore 2 forms with its entire volume V1, V2, Vn a buffer for the fuel to be injected. In the upper part of the high pressure bore V1, a connection for an external connecting line is provided at the access opening 13, which can be firmly connected to the high-pressure bore 2, for example by means of a union nut. About the connecting line of the fuel to be injected, for example, gasoline or diesel to the injector 11th promoted. The black arrow above the high-pressure bore 2 should indicate the direction of flow of the fuel.

The high pressure bore 2 is formed in contrast to a conventional cylindrical bore as a multiple stepped bore. In FIG. 1 For example, three drill stages with the drill diameters d1, d2 and dn are shown. The uppermost drill step has the largest diameter d1, while the underlying drill stages are formed with a smaller diameter d2, dn. The number of drill steps is freely selectable and depends on the injector type or intended use. Alternatively, subsequent holes can also be formed further.

berechnen lassen (d= Bohrdurchmesser, L= Länge der Bohrung).Furthermore, it is provided that the length of the bores is preferably to be selected such that the largest possible buffer volume is formed but nevertheless sufficiently large wall thicknesses remain for the high-pressure bore. The uppermost drilling stage has a length L1 and the subsequent drilling stages have the lengths L2 and Ln, respectively. In this way, a specific volume V1, V2, Vn can be specified for the fuel to be stored with very simple means for each drilling stage, since the individual volumes V according to the trigonometric formula $$\mathrm{V}\mathrm{=}\mathrm{\pi }\mathrm{*}\mathrm{d}\mathrm{/}\mathrm{4}\mathrm{*}\mathrm{L}$$

let calculate (d = drill diameter, L = length of the bore).

It is desirable to make the storage volume of the entire buffer memory as large as possible, so that depending on the type of engine for which the injector 1 is to be used, the per se known high pressure accumulator (Rail) of a commercial common rail injection system can be saved. Furthermore, the injection system with the injector according to the invention can be made simpler and cheaper. In addition, the necessary installation space in the vehicle is reduced in an advantageous manner, so that the injection system, in particular in internal combustion engines Can be used with many cylinders and in tight spaces in the engine compartment.

In an alternative embodiment of the invention, it is provided to form the individual volumes V1, V2, Vn as a function of operating conditions of the internal combustion engine. For example, the uppermost volume V1 could be slightly smaller, the volume V2 larger, and the volume Vn again smaller or the same size. In this way, requirements of the internal combustion engine, for example, in terms of emissions, engine performance and fuel consumption can be optimized.

A significant further advantage of the invention is also seen in the fact that the pressure waves or vibrations occurring during the injection process are damped by the different bore diameters d1, d2, dn. As the pressure waves on the sidewalls of the individual drill stages are irregularly broken, reflected and absorbed, the attenuation results in a more uniform injection course. In particular, in the multiple injection, in which the fuel is injected in several individual injection pulses in the shortest time intervals, the exact control is particularly important. The high pressure bore 2 cache also supports this injection process.

FIG. 2 shows an enlarged view of a section of the in FIG. 1 explained high-pressure bore 2 of the injector 11. In FIG. 2 In particular, the transitions 20 are explained, which form between two adjacent drilling stages. According to the invention, the transitions 20 are formed, for example, with a beveled, in particular a conical annular surface. By this smooth transition, for example, from the diameter d1 to the diameter d2, the pressure waves are reflected even more diffusely and thereby absorbed, so that the damping properties are further improved.

By way of example, the edges of the annular surface 20, which each arise between a drilling step and the annular surface, were further rounded off with a corresponding tool between the two drilling stages d2 and dn, so that a stepless transition from the drilling step d2 to the drilling step dn arises. This prevents the edges from generating new pressure waves or vibrations that could affect the smooth flow of the injection.

FIG. 3 shows a schematic arrangement for a common rail injection system, as used for example in the diesel injection. It shows the previously described and per se known high-pressure accumulator (rail) 31 to which four injectors 11 are hydraulically connected via four connecting lines 32. The size of the high-pressure accumulator 31 and the number of connected injectors 11 depends essentially on the number and the volume of the combustion chambers (cylinder) of the engine type used. In this case, the four injectors 11 are provided for a four-cylinder engine.

The fuel is pumped by a high-pressure pump 33, which is connected to the high-pressure accumulator 31, at high pressure in the high pressure accumulator 31 and is then available in the individual buffer storage of the connected injectors 11 for injection. The high-pressure pump 33 is in turn supplied by a fuel pump 35. For this purpose, the fuel pump 35 from a reservoir (in FIG. 3 symbolized by the arrow) the fuel with a lower overpressure via lines 36 and one or more filter units 34 to the high-pressure pump 33. With the aid of an electronic control, the injection holes 5 (FIG. FIG. 1 ) are opened or closed again and thus the injection process can be controlled.

Claims (9)

1. Injector for an injection system designed for the injection of fuel into an internal combustion engine, wherein the injector (11) can be connected to a high-pressure accumulator (31) of the injection system via a pressurized fuel line (32), and having a high-pressure bore (2) through which the fuel can be conducted by means of a controllable nozzle needle (6) to injection holes (5) of the injector (11), wherein the high-pressure bore (2) of the injector (11) is designed as a buffer accumulator (V1, V2, Vn) for the pressurized fuel, wherein in the injector housing (1), a further stepped bore (10) is arranged parallel to at least one drilled stage of the high-pressure bore (2), wherein the drilled diameter of the further bore (10) widens from the top downwards, characterized in that, in at least two successive bores of the high-pressure bore (2) and of the stepped bore (10), a cross-sectional area (14a) of the high-pressure bore (2) is formed so as to be inversely proportional to a cross-sectional area (14b) of the further stepped bore (10).
2. Injector according to Claim 1, characterized in that the high-pressure bore (2) is formed as a stepped bore.
3. Injector according to Claim 1, characterized in that the first drilled diameter (d1) of the high-pressure bore (2) is larger than the second drilled diameter (d2), and the latter is larger than a third drilled diameter (dn) that may be provided.
4. Injector according to one of the preceding claims, characterized in that the volume (V1, V2, Vn), which accommodates the fuel, of the individual drilled stages is formed taking into consideration the spatial conditions in the injector (11) and/or operating conditions of an engine.
5. Injector according to one of the preceding claims, characterized in that the individual drilled stages have at their transitions (20) a beveled, in particular conical annular surface.
6. Injector according to one of the preceding claims, characterized in that the transition (20) between two adjacent drilled stages is designed to be continuous.
7. Injector according to one of the preceding claims, characterized in that the individual drilled stages have different lengths (L1, L2, Ln), wherein the lengths (L1, L2, Ln) decrease according to a predefined ratio in the direction of the nozzle tip.
8. Injector according to one of the preceding claims, characterized in that the high-pressure bore (2) and/or the further bore (10) are drilled parallel to the longitudinal axis of the injector housing (1) and have an access opening (13) at the top end of the injector housing (1).
9. Injector according to one of the preceding claims, characterized in that the injector (11) can be used for a common rail injection system, in particular for the injection of diesel fuel.

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