WO2012038115A1

WO2012038115A1 - Fuel injector

Info

Publication number: WO2012038115A1
Application number: PCT/EP2011/062549
Authority: WO
Inventors: Walter Fuchs
Original assignee: Robert Bosch Gmbh
Priority date: 2010-09-20
Filing date: 2011-07-21
Publication date: 2012-03-29
Also published as: DE102010041013A1; EP2619440A1; RU2013118102A; CN103109072B; CN103109072A

Abstract

The invention relates to a fuel injector for injecting fuel into the combustion chamber of an internal combustion engine having a nozzle needle (3) which is guided in a hole (1) of a housing part (2) such that it can move in a reciprocating motion for opening and closing at least one injection opening (4) and a magnet assembly (5) for the direct or indirect actuation of the nozzle needle (3), wherein the magnet assembly (5) comprises an armature component (6) which is of single-piece or multiple-piece configuration and can move in a reciprocating motion. According to the invention, the magnet assembly (5) comprises, furthermore, a sleeve-shaped component (7) in order to enlarge the magnetic circuit, which sleeve-shaped component (7) can be used as a clamping sleeve (8) and/or to connect the housing part (2) to at least one further housing part (9, 15), with the result that the sleeve-shaped component (7) defines the maximum external diameter D of the fuel injector in the region which is critical for installation space.

Description

description

title

Fuel injector Field of the invention

The invention relates to a fuel injector for injecting fuel into the combustion chamber of an internal combustion engine having the features of the preamble of claim 1.

A generic fuel injector comprises a magnet assembly for direct or indirect actuation of a nozzle needle guided in a bore of a housing part of the fuel injector in a lift-movable manner, which releases or closes at least one injection opening when actuated. In particular, a direct actuation of the nozzle needle proves to be advantageous since the direct actuation takes place without return flow.

This means that no Absteuermenge must be supplied to a return to effect a reduction of the nozzle needle acting on the control pressure and thus opening of the nozzle needle. The direct operation thus allows a simplified structure of the fuel injector. In addition, the efficiency of an injection system is increased, in which the fuel injector is used. The return flow-free operation reduces the flow rate. Consequently, the power of a delivery unit used in the injection system can be reduced.

However, direct needle control places high demands on the actuators used. For one thing, there is a sufficiently high force to open the nozzle needle, on the other hand provide a sufficiently large stroke for Sitzentdrosselung the nozzle needle. It is not always possible to use a larger and thus more powerful actuator, since the dimensions of the fuel injector are generally predetermined and thus the available installation space for accommodating the actuator is given. is limited. There are therefore other measures to be taken by which it is ensured that the actuator force for actuating the nozzle needle, in particular for direct actuation of the nozzle needle, is sufficiently large.

State of the art

The published patent application DE 10 2007 034 610 A1 discloses a magnet assembly which can be used, for example, in a generic fuel injector. The magnet assembly comprises an annular magnetic circuit with an annular recess, in which a magnetic coil is accommodated. When energized, the magnetic coil actuates an armature which is designed in one or more parts. Furthermore, the magnet assembly comprises a magnetic sleeve which is mounted on the magnetic core. The magnet sleeve has an inner pole surface which extends radially and expands the outer pole surface of the magnetic core in the radial direction. Thereby, a better magnetic flux guide is to be achieved, which can be fully used for power generation.

Based on the above-mentioned prior art, the invention is based on the object to provide a fuel injector with a magnetic assembly as the actuating means, which designed particularly strong and so in the

Fuel injector is integrated, that the usual dimensions of the injector can be maintained.

The object is achieved by a fuel injector with the features of claim 1. Advantageous developments of the invention are specified in the subclaims.

Disclosure of the invention

The proposed fuel injector has for direct or indirect actuation of a nozzle needle, which is guided in a bore of a housing part of the fuel injector for exposing and closing at least one injection opening in a liftable manner, a magnetic assembly with a one or more parts, liftable anchor member. According to the invention, the magnet assembly comprises for magnification tion of the magnetic circuit further comprises a sleeve-shaped component, which is used as a clamping sleeve and / or for connecting the housing part with at least one further housing part, so that the sleeve-shaped component defines the maximum outer diameter D of the fuel injector in the space critical area. The sleeve-shaped component can thus be used on the one hand for inference of the magnetic circuit, on the other hand as a clamping sleeve. Preferably, the sleeve-shaped component allows a high pressure-tight connection and positional fixing of at least two housing parts of the fuel injector, for example by means of bracing. Furthermore, a magnetic circuit is realized, which uses the entire injector diameter. The magnetic circuit, which is enlarged by the sleeve-shaped component, causes an increase in the magnetic force, which proves to be advantageous, in particular, in injector concepts with direct needle control. In addition, the dimensions of the fuel injector remain unchanged since the sleeve-shaped component replaces the clamping sleeve and / or union nut usually used for connecting a plurality of housing parts.

According to a preferred embodiment of the invention, the sleeve-shaped component to increase the magnetic circuit is air-gaplessly connected to at least one housing part of the fuel injector. Preferably, for this purpose, the sleeve-shaped component is pressed or shrunk onto the housing part. An air gapless connection has the additional benefit that the sleeve-shaped component participates in the support of the pressure applied to the internal components compressive forces. The support by the sleeve-shaped component causes the maximum tensile stress on the inner fiber of the inner components is reduced. Due to the lower load or stress, therefore, the wall thicknesses of the inner components can be reduced and / or without overload the pressure forces applied to the inner components can be increased by increasing the system pressure. The fuel injector according to the invention is accordingly particularly suitable for injection systems which have system pressures of 2,000 bar and more. For applications which are not critical to stress, it is sufficient if the sleeve-shaped component is only pushed on.

According to a further preferred embodiment of the invention, the magnet assembly is provided for direct actuation of the nozzle needle and the fuel injector operated return-free amount. The high actuator force required for direct needle control can be achieved by the design of the magnet proposed in accordance with the invention. be achieved, since the sleeve-shaped component outside the coil takes over the inference of the field lines as part of the magnetic assembly, which leads to an enlargement of the magnetic circuit and thus to an increase in the actuator force.

According to one embodiment of the invention, the magnet assembly is subjected to high pressure during operation of the fuel injector, at least in some areas. Thus, a separate arrangement of the magnet assembly in a low-pressure region that is sealed from the high-pressure region is not required. Accordingly, at least parts of the magnet assembly are circulated in the operation of the fuel injector of fuel under high pressure.

Further preferably, the high pressure guide is at least in a partial region rotationally symmetrical and / or formed between two opposite inner wall surfaces. Accordingly, a laterally arranged additional high-pressure bore can be dispensed with, so that no housing part is additionally weakened by the formation of an additional lateral high-pressure bore. In this way, the high pressure resistance of the fuel injector is further increased.

Alternatively or additionally, it may be provided that the high-pressure guide comprises at least one bore or groove guided through a component of the magnet assembly. Such a bore or groove proves to be particularly useful if no sufficient air gap between two components to form the high pressure guide is available. The bore or groove can be guided axially and / or radially through a component of the magnet assembly and, for example, hydraulically connect a first pressure chamber to a second pressure chamber. The component separating the pressure chambers can be, for example, a magnetic disk or an anchor plate in which the bore or groove is then formed. In addition, such a bore or groove can also be guided obliquely and, for example, create a hydraulic connection between a centrally located high-pressure bore and a radially outer, annular pressure chamber.

According to a further preferred embodiment of the invention, the single-part or multi-part, liftable armature component comprises a magnetic needle. The magic Needle needle is preferably also guided axially movable in a central bore of the anchor member. Alternatively, an anchor bolt and / or a pin-shaped pressure compensation element can be accommodated in the armature component. The anchor component can also be designed as a plunger anchor, step armature or flat armature.

It proves to be advantageous to have a one-part or multi-part design, liftable armature component, which is designed as a plunger armature with a radial expansion in the region of an air gap. Advantages result from this, in particular, if the armature also consists of a magnetically nobler material than a component surrounding the armature, since the actuator force is less strongly throttled due to saturation effects on the less noble component. This results in an advantageous additional effect.

Preferred embodiments of the invention are explained below with reference to the accompanying drawings. These show:

1 shows a longitudinal section through a known from the prior art

fuel injector,

FIG. 2 shows a longitudinal section through a fuel injector according to the invention in the region of the magnet assembly, comprising a plunger armature,

3 shows a longitudinal section through a further fuel injector according to the invention in the region of the magnet assembly, comprising a stepped armature and

4 shows a longitudinal section through a further fuel injector according to the invention in the region of the magnet assembly, comprising a flat armature.

Detailed description of the drawings

The known fuel injector shown in Figure 1 comprises a nozzle body as a housing part 2, with a central bore 1, in which a nozzle needle 3 is guided in a liftable manner. By the lifting movement of the nozzle needle 3 is at least one Injection opening 4 of the fuel injector released or closed. The bore 1 serves in a subsection at the same time the high pressure guide, by means of which the injection port 4 is supplied under high pressure fuel. The formed as a high-pressure guide region of the bore 1 extends from an annular space formed in the housing part 2 pressure chamber 17 to the injection port 4. In the pressure chamber 17 of the fuel under high pressure passes through a laterally guided high-pressure channel 18th

The housing part 2 or the nozzle body is adjoined by a magnet assembly 5 which comprises a valve body 15 as a further housing part and a coil 14 inserted therein. Within the valve body 15, a multipart lifting armature component 6 is also accommodated, which in the present case consists of a plunger armature 19 and a magnetic needle 12. The magnetic needle 12 is acted upon by the pressure force of a spring element 16 in the closing direction of the nozzle needle 3. The spring element 16 thus serves to restore the magnetic needle 12 and the nozzle needle 3, which is returned via the magnetic needle 12 in its sealing seat. The magnet assembly 5 and a further housing part 9 are clamped together high-pressure-tight manner via a clamping sleeve 8, wherein the clamping sleeve 8 indicates the maximum outer diameter D of the fuel injector in the critical space critical area. The fuel injector shown in FIG. 1 further has a booster piston 20 surrounding the magnetic needle 12, which is coupled to the nozzle needle 3 via a hydraulic coupler volume 21. In a first phase of the opening stroke of the nozzle needle 3, the booster piston 20 bears against the housing part 2, while the magnetic needle 12 pulls the nozzle needle 3 out of its sealing seat via the hydraulic coupler volume 21. In this case, the significantly smaller effective hydraulic area on the magnetic needle 12 with respect to the nozzle needle 3 causes a force increase, so that the force acting on the nozzle needle 3 initially high clamping force is overcome. Only in a second phase of the opening stroke of the nozzle needle 3, the booster piston 20 lifts off from the housing part 2, wherein due to the now existing area ratios of a power gain is switched to a 1/1 translation.

In a fuel injector according to the invention, as shown for example in Figures 2-4, a force amplification is effected by the fact that the magnetic circuit to the maximum outer diameter D of the fuel injector in the space critical Area is expanded. For the magnet assembly 5 of a fuel injector according to the invention comprises, in addition to the coil 14 and the valve body 15, further a sleeve-shaped member 7, which also serves as a clamping sleeve 8 and defines the outer diameter D of the fuel injector in the space critical area. Thus, the full injector diameter is available for forming the magnetic circuit. The outer dimensions of the fuel injector remain unchanged. At the same time, the sleeve-shaped component serves to support the inner walls against pressure-induced forces. Because the sleeve-shaped member 7 is connected to the housing parts 2, 9 and the valve body 15 as a further housing part air gap. The support can also be reinforced by the fact that the sleeve-shaped member 7 is pressed onto the housing parts 2, 9 and the valve body 15. In addition, the strength of the housing parts 2, 9 or of the magnet assembly 5 is increased by a substantially rotationally symmetrical high-pressure guide 10. The supply of the fuel takes place essentially via annular air gaps between opposite inner wall surfaces, wherein the annular air gaps can extend mainly both in the axial direction, as well as in the radial direction. In addition, holes 11 can serve as high pressure channels or as a high pressure guide.

In the exemplary embodiment of a fuel injector according to the invention shown in FIG. 2, the magnet assembly 5 comprises an armature component 6, which is designed as a plunger armature. The plunger armature has a radial widening 13, by means of which the working air gap between the plunger armature and the coil 14 is reduced. Advantages from this arise in particular when the armature is made of a magnetically nobler material than the adjoining the working air gap component, since then the force acting on the plunger armature magnetic force is less throttled. However, the radial expansion 13 is not absolutely necessary.

The trained as a plunger anchor armature 6 of the embodiment of Figure 2 is received in a bore of the valve body 15. An annular air gap remaining between the plunger armature and the valve body 15 serves as a high-pressure guide 10. Thus, during operation of the fuel injector, the plunger armature flows around high-pressure fuel. For high-pressure guide 10, the fuel passes in the illustrated embodiment via an obliquely extending bore 11, which connects the annular space with a central bore in the housing part 9. The high pressure Guide 10 including the bore 11 may also be rotationally symmetrical, so that the internal components undergo no weakening by a laterally disposed high-pressure channel. By a corresponding high-pressure guide, the strength of the fuel injector can be further increased.

Of the embodiment of Figure 2, that of Figure 3 differs essentially in that the anchor member 6 is formed as a step armature and the magnet assembly 5 further includes a magnetic disc 22, which can also serve as a stroke stop for the step armature. The magnetic disk 22 has at least one bore 11 for the hydraulic connection of two ring-shaped pressure chambers. Alternatively or additionally, an air gap remaining between the step armature and the magnetic disk 22 and / or between the step armature and the housing part 9 can also be used for the high-pressure guidance. The housing part 9 preferably also has a bore 11, via which the fuel passes into the region of the coil receptacle.

A third embodiment of the fuel injector according to the invention is shown in FIG. This differs from the preceding essentially in that the armature component 6 is designed as a flat armature and has at least one bore 11 for the hydraulic connection of two annularly formed pressure chambers. In addition, air gaps between the armature component 6 designed as a flat armature and the housing part 9 can serve as a high-pressure guide 10.

In addition to the embodiments illustrated in FIGS. 2-4, further embodiments are conceivable which may vary, for example, with regard to the specific design of the armature component 6 and / or the magnet assembly 5. Thus, it is clear that the illustrated embodiments are chosen only by way of example. Common to all embodiments, however, is the external arrangement of a sleeve-shaped component 7, which is part of the magnet assembly 5 and extends the magnetic circuit to the entire injector diameter. The correspondingly enlarged magnetic circuit allows a reinforcement of the actuator force while maintaining the usual external dimensions of the fuel injector. The supporting-acting sleeve-shaped component 7 also contributes to an increase in the strength of the fuel injector. An inventive The corresponding fuel injector can therefore also be used in injection systems whose temdruck is well above 2,000 bar.

Claims

claims

1. A fuel injector for injecting fuel into the combustion chamber of an internal combustion engine with a in a bore (1) of a housing part (2) liftably guided nozzle needle (3) for releasing and closing at least one injection port (4) and a magnetic assembly (5) for direct or indirect actuation of the nozzle needle (3), wherein the magnet assembly (5) comprises a one-part or multi-part designed, liftable armature component (6),

characterized in that the magnetic assembly (5) for enlarging the magnetic circuit further comprises a sleeve-shaped component (7), which is used as a clamping sleeve (8) and / or for connecting the housing part (2) with at least one further housing part (9, 15) , so that the sleeve-shaped component (7) defines the maximum outer diameter D of the fuel injector in the space critical area.

2. Fuel injector according to claim 1,

characterized in that the sleeve-shaped component (7) to increase the magnetic circuit is air-gaplessly connected to at least one housing part (2, 9, 15), wherein the connection is preferably effected by means of pressing.

3. Fuel injector according to claim 1 or 2,

characterized in that the magnet assembly (5) is provided for direct actuation of the nozzle needle (3) and the fuel injector is operable without backflow.

4. Fuel injector according to one of the preceding claims,

characterized in that the magnet assembly (5) is subjected to high pressure during operation of the fuel injector, at least in some areas.

5. Fuel injector according to one of the preceding claims, characterized in that the high pressure guide (10) is formed at least in a partial region rotationally symmetrical and / or between two opposite inner wall surfaces.

6. Fuel injector according to one of the preceding claims,

characterized in that the high-pressure guide (10) comprises at least one bore (11) guided through a component of the magnet assembly (5).

7. Fuel injector according to one of the preceding claims,

characterized in that the one or more parts designed, liftable armature component (6) comprises a magnetic needle (12) and / or is designed as a plunger armature, step armature or flat armature.

8. Fuel injector according to one of the preceding claims,

characterized in that the monobloc or multi-part, liftable armature component (6) is designed as a plunger armature with a radial expansion (13) in the region of a working air gap.