WO2014000961A1

WO2014000961A1 - Fuel injector having a magnetic actuator

Info

Publication number: WO2014000961A1
Application number: PCT/EP2013/060109
Authority: WO
Inventors: Hans-Christoph Magel
Original assignee: Robert Bosch Gmbh
Priority date: 2012-06-29
Filing date: 2013-05-15
Publication date: 2014-01-03
Also published as: DE102012220856A1; DE102012220860A1

Abstract

The invention relates to a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine, comprising a nozzle needle (1) which is guided with a reciprocating movement in a high pressure bore (2) of a nozzle body (3) in order to open and close at least one injection opening (4) and is preferably loaded in the direction of a sealing seat (5) by the spring force of a spring (6), and a magnetic actuator (7) for the direct or indirect control of the reciprocating movement of the nozzle needle (1), wherein the magnetic actuator (7) comprises an annular solenoid (8) and an armature (9) which interacts with the solenoid (8) and is configured as a solenoid plunger. According to the invention, at least one section of the annular solenoid (8) surrounds an injector body (10) which has a section (11) with a reduced external diameter for receiving the solenoid (8). The injector body (10) is penetrated by an inlet bore (12) which widens towards the sealing seat (5) in the region of the section (11) and receives an internal pole body (13).

Description

description

title

Fuel! Neoprene with magnetic actuator

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

Accordingly, such a fuel! Njektor a nozzle needle, which is guided in a high-pressure bore of a nozzle body for releasing and closing at least one injection opening and preferably acted upon in the direction of a sealing seat of the spring force of a spring, and a magnetic actuator for direct or indirect control of the lifting movement of the nozzle needle. For this purpose, the magnet actuator comprises an annular magnet coil and an armature cooperating with the magnet coil and designed as a plunger armature.

State of the art

The use of magnetic actuators to control the lifting movement of the nozzle needle of a fuel! Njektors is well known. In this case, the magnetic actuator can be designed as a solenoid valve and control the lifting movement of the nozzle needle indirectly via a servo control chamber. In addition, the direct actuation of the nozzle needle via a magnetic actuator is possible. When operated directly, however, it must be ensured that sufficient force for opening the nozzle needle can be provided via the magnetic actuator. Because at the currently required system pressures of up to 3,000 bar, very high switching forces occur at fuel injectors on the nozzle needle. To increase the magnetic force of a magnetic actuator, it may be constructed according to the plunger-type armature principle, the injector body forming part of the magnetic circuit. The Inclusion of the injector body in the magnetic circuit of the magnetic actuator requires the use of a material having good magnetic properties. Disadvantage of these materials, however, is that they regularly do not have sufficient mechanical strength. In addition, to accommodate a magnetic coil of the magnetic actuator, the wall thickness of the injector body must be greatly reduced and thus the high pressure resistance of the injector body is further limited. It is therefore the high pressure resistance of

Injector body to improve.

In the published patent application DE 10 2010 002 646 A1, therefore, a fuel! njek- gate with a solenoid actuator for direct control of the lifting movement of a nozzle needle proposed, wherein the magnetic actuator comprises an at least partially received in the injector, annular magnetic coil and a trained as a plunger anchor annular armature. In order to increase the robustness of the injector, a sealing body is arranged between the armature and the coil, which prevents the injector body from being subjected to high pressure. This reduces the stress on the injector body, so that the walls can be made relatively thin-walled. For example, in the injector body another body may be used, which serves as an inner pole. In the present case, the additional body inserted into the injector body has an outer diameter which largely corresponds to the outer diameter of the armature, so that on the one hand the wall thickness of the injector body is greatly reduced, on the other hand, however, the additional body inserted into the injector body simultaneously serves as a separating body, which also acts as a high pressure prevents the injector body.

Based on the aforementioned prior art, the present invention seeks to provide a fuel injector whose high pressure resistance is further increased. In particular, the stated fuel injector should be usable for injection pressures of up to 3,000 bar. To solve the problem, a fuel injector with the features of claim 1 is proposed. Advantageous developments of the invention are specified in the subclaims. Disclosure of the invention

The proposed for injecting fuel into a combustion chamber of an internal combustion engine fuel! The injector includes a nozzle needle, which is guided in a high-pressure bore of a nozzle body for releasing and closing at least one injection opening and preferably acted upon in the direction of a sealing seat by the spring force of a spring, and a

Magnetic actuator for direct or indirect control of the lifting movement of the nozzle needle. For this purpose, the magnet actuator comprises an annular magnet coil and an armature cooperating with the magnet coil and designed as a plunger armature. According to the invention, at least a portion of the annular magnet coil surrounds an injector body which has a section with a reduced outside diameter for receiving the magnet coil. The injector body is also penetrated by an inlet bore, which expands in the direction of the sealing seat in the region of the reduced outer diameter section and receives an inner pole body.

The function of the inner pole is presently not of the

Injector body, but taken over by a used in the inlet bore of the injector body Innenpolkörper. This has the advantage that the respective material properties can be adapted to the respective functions of the body. Thus, for example, a material with high mechanical strength can be selected for the injector body, while the material of the inner pole body is chosen such that the inner pole body has good magnetic properties. The strength of the injector according to the invention is further increased by the fact that the additional hole passing through it is designed such that the inner pole body can be used here. The inlet bore thus forms at the same time a receiving space for the Innenpolkörper. In this case, the inner contour of the receiving space bounding the bore wall is selected such that the receiving space widens towards the armature. The receiving space can thus accommodate a Innenpolkörper, which has a large surface area or pole face to the armature, so that a sufficiently high magnetic force is ensured, whereas the cross-sectional area of the Innenpolkörpers decreases with distance to the armature to increase the

To allow wall thicknesses of the injector body. Through the areas with increased wall thickness, the mechanical strength of the injector body is increased, so that the injector is designed for higher system pressures.

According to a preferred embodiment of the invention, the inlet bore for expansion in the direction of the sealing seat is at least partially conical. The conical shape can be continuous or unsteady, so that the inlet bore in the area of the extension can also have curved wall surfaces. Alternatively or additionally, it is provided that the inflow bore is formed at least partially stepped for expansion in the direction of the sealing seat. For example, the inlet bore via a step in a conical

Pass section or be multi-stepped, i. have a plurality of successive stages in the axial direction. In addition, further embodiments of the inlet bore are possible, which comprise at least one conical section and / or one step. By widening the inlet bore to the outside, such embodiments of the inner contour can be produced in a simple manner by means of chip-removing processes. To ensure this, it is further preferred to dispense with an inner contour of the inlet bore, which has undercuts. Advantageously, the inner pole body accommodated in the inlet bore has an outer contour adapted to the inner contour of the inlet bore. This means that the inner pole body is also at least partially conical and / or stepped, so that the inner pole body can be inserted into the injector body as gap-free as possible. As a result, a seal is furthermore ensured via the inner pole body inserted into the injector body, which effectively prevents high pressure loading of the injector body in the region of the coil receptacle.

According to one embodiment of the invention, the Innenpolkörper has at least one cylindrical portion which is pressed into the inlet bore. That is, before assembly, the cylindrical portion of the Innenpolkörpers has at least a slight excess over the inner diameter of the inlet bore of the injector body. The interference fit can be realized in a simple manner and therefore the preferred connection. In addition, however, other connection methods can be used additionally or alternatively. In order to ensure the supply of fuel, it is further proposed that the inner pole body is penetrated by a bore, via which at least indirectly the inlet bore is connectable to the high-pressure bore of the nozzle body. Preferably, the bore of the inner pole body is formed concentrically to the inlet bore. Preferably, therefore, the inner pole body is penetrated centrally by a bore.

Further preferably, the armature has a bore, via which at least indirectly, the inlet bore with the high-pressure bore of the nozzle body is connectable. The bore of the armature is preferably guided obliquely through the armature. The inlet opening may, for example, be arranged centrally with respect to the anchor surface, which lies opposite the pole face of the inner pole body, while the outlet opening is further radially outward, for example to avoid a bolt or piston connected to the anchor. For example, a bolt inserted into the armature can act as a push pin and a piston connected to the armature as a coupler piston. The coupler piston can also limit a coupler volume and thus cause a force and / or stroke amplification of the magnetic actuator. Furthermore, mechanical coupling elements for force and / or lifting amplification may be connected to the armature, which also require a deflection of the fuel inlet.

Furthermore, it is proposed that the armature is received in a liftable manner in a high-pressure bore of a magnet body, wherein the high-pressure bore preferably also serves to guide the armature. The fuel inlet can be secured in this case via at least one bore and / or outer circumferential side arranged longitudinal groove. Further preferably, the armature receiving magnetic body is separated by an annular separator made of a non-magnetic material from the magnetic coil. To provide a fast-switching fuel injector, which also little

Requires installation space, it is also proposed that the magnetic actuator of the direct control of the lifting movement of the nozzle needle is used. For force and / or stroke amplification, the magnetic actuator preferably cooperates with hydraulic and / or mechanical means for increasing the force and / or stroke. The force and / or stroke amplification allows the use of small-volume actuators with at the same time low power. As a result, the space requirement can be further reduced.

According to a preferred embodiment of the invention, hydraulic means for force and / or stroke amplification are provided, which comprise a hydraulic coupler volume and a coupler piston delimiting the coupler volume. The coupler piston is connected to the armature and acted upon in the direction of the sealing seat by the spring force of a spring. Hydraulic power and / or Hubverstärkungsmittel have the advantage over mechanical advantage that wear-related tolerances have no effect on the functioning of the device. In this respect, a sufficient force and / or stroke amplification over the entire life of the fuel injector is ensured. The spring acting on the coupler piston preferably serves to return the coupler piston and the armature connected thereto.

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

1 shows a schematic longitudinal section through a first embodiment of a fuel according to the invention! njektors and

2 shows a schematic longitudinal section through a second embodiment of a fuel injector according to the invention.

Detailed description of the drawings

The fuel injectors illustrated in FIGS. 1 and 2 have the common feature that the lifting movement of a nozzle needle 1 received in a lift-capable manner in a high-pressure bore 2 of a nozzle body 3 is directly controlled in each case via a magnetic actuator 7. For this purpose, the magnetic actuator 7 has in each case a magnetic coil 8 and an armature 9 cooperating with the magnetic coil 8, which is designed as a plunger armature. When energizing the solenoid 8, the armature 9 is pulled in the direction of the coil 8, wherein it moves away from a sealing seat 5 of the nozzle needle 1. A connected to the armature 9 coupler piston 21 is carried against the spring force of a spring 22, wherein a hydraulic coupler volume 20 limited by the coupler piston 21 undergoes an increase in volume. The increase in volume has the consequence that the pressure in the hydraulic coupler volume 20 drops, so that a closing pressure acting on the nozzle needle 1 is reduced and the nozzle needle 1 lifts off from the sealing seat 5. Because next to the coupler piston 21 is the hydraulic

Coupler volume 20 of an end face of the nozzle needle 1 and a nozzle sleeve 1 surrounding sealing sleeve 23 limited. The hydraulic active surfaces on the nozzle needle 1 and the coupler piston 21 are chosen such that a force amplification is effected via the size ratio. Accordingly, with a comparatively small actuator force, the lifting of the nozzle needle 1 from the sealing seat 4 can be effected. The lifting movement of the nozzle needle 1 releases at least one injection opening 4, which is formed downstream of the sealing seat 5. Via the at least one injection opening 4 then fuel under high pressure is injected into the combustion chamber of the internal combustion engine (not shown).

To end the injection process, the energization of the solenoid actuator 7 and the solenoid 8 is stopped, so that the spring force of the spring 22 causes the return of the coupler piston 21 including the armature 9. The hydraulic coupler volume 20 experiences a reduction in volume, wherein, in addition, the pressure in the hydraulic coupler volume 20 increases and the nozzle needle 1 is acted upon in the direction of the sealing seat 5 by a closing force. The closing of the nozzle needle 1 is assisted by a spring 6, which is supported on the one hand on a collar of the nozzle needle 1 and on the other hand on the sealing sleeve 23. By way of the spring force of the spring 6, in particular the nozzle needle 1 is held in contact with the sealing seat 5.

The two fuel injectors shown in Figures 1 and 2 differ only with respect to the specific embodiment of a Innenpolkörpers 13, which is inserted into an inlet bore 12 of an injector body 10. Since in the region of the inserted Innenpolkörpers 13 of the injector body 10 has a portion having a reduced outer diameter 11 to form a receiving space for the solenoid 8, to increase the high pressure resistance of the injector body 10, the inlet bore 12 is designed such that it widens towards the armature 9 out. The same applies with respect to the inner pole body 13 inserted into the inlet bore 12, whose outer contour matches the inner contour of the inner Running bore 12 is adjusted. The cross-sectional area of the inner pole body 13 is therefore the largest towards the armature 9, so that the largest possible pole surface results, which lies opposite the armature 9. The end of the inner pole body 13 opposite the pole face is preferably designed as a cylindrical section 14, via which the inner pole body 13 into the inlet bore

12 is pressed. In order to continue to ensure the inflow of fuel, the Innenpolkörper 13 is penetrated by a central bore 15, which via an obliquely through the armature 9 extending bore 16 and at least one high-pressure bore 17 in the armature 9 receiving magnetic body 18 with the high-pressure bore 2 of the nozzle body 3 is connected. The oblique course of the bore 16 through the armature 9 allows the fuel to pass laterally past the coupler piston 21.

While the outer contour of Innenpolkörpers 13 in the inventive fuel shown in Figure 1! The injector is adapted to a conically widening inlet bore 12, the inner pole body 13 is designed in a stepped manner in accordance with the feed belt 12 of the fuel injector shown in FIG. The inner pole body 13 of the fuel injector shown in Figure 2 has three circumferential steps, so that a total of three sections are formed with different outer diameters. The section with the smallest outer diameter can serve as a cylindrical section 14, via which the inner pole body 13 is pressed into the inlet bore 12 of the injector body 10. At the same time, the inner pole body 13 of the injector of FIG. 2 is penetrated by a bore 15, which has the same diameter as the inlet bore 12. In the embodiment of Figure 1, however, the cylindrical portion 14 of the Innenpolkörpers 13 is so pressed into the inlet bore 12 that the cross section of the fuel inlet is reduced. However, a reduction of the cross section is not absolutely necessary, since in the embodiment of Figure 1 by forming a single stage, a receiving area for the cylindrical portion 14 of the Innenpolkörpers 13 can be created, which allows a diameter of the bore 15, the same size as the diameter of Inlet bore 12 is.

In this respect, the two exemplary embodiments illustrated in FIGS. 1 and 2 make it clear that further embodiments of a design according to the invention

Fuel! Njektors are possible by the outer contour of Innenpolkörpers 13 or the inner contour of the inlet bore 12 in the region of the portion 1 1 of the injector body 10 can be varied.

In order to separate the magnetic body 18, which accommodates the armature 9, from the magnetic coil 8, an annular separating body 19 is arranged between the coil 8 and the magnetic body 18, which consists of a non-magnetic material. The ring shape of the separating body 19 ensures that the movement space of the armature 9 is not restricted. Furthermore, the annular shape of the separating body 19 allows the formation of a working air gap 26 between the armature 9 and the inner pole body 13.

The injector body 10, the annular separating body 19, the magnetic body 18 and the nozzle body 3, are present concentrically arranged to each other and braced by means of a clamping nut 24 against each other in the axial direction. The electrical connection 25 takes place in each case via the end of the injector body 10 facing away from the nozzle body 3.

Claims

claims

1. Fuel! Injector for injecting fuel into a combustion chamber of an internal combustion engine comprising a nozzle needle (1), which in a high pressure bore (2) of a nozzle body (3) for releasing and closing at least one injection port (4) guided in a liftable manner and preferably in the direction of a sealing seat ( 5) of the spring force of a spring (6) is acted upon, and a magnetic actuator (7) for direct or indirect control of the lifting movement of the nozzle needle (1), wherein the magnetic actuator (7) an annular magnet coil (8) and one with the Magnetic coil (8) cooperating as

Plunger includes trained anchor (9),

characterized in that at least a portion of the annular magnetic coil (8) surrounds an injector body (10) having a portion (1 1) with a reduced outer diameter for receiving the magnetic coil (8), wherein the injector body (10) from an inlet bore (12 ) interspersed in the

Expands portion of the section (11) in the direction of the sealing seat (5) and a Innenpolkörper (13) receives.

2. Fuel! A nudger according to claim 1,

characterized in that for expansion in the direction of the sealing seat (5), the inlet bore (12) is at least partially conical and / or stepped.

3. Fuel! Ajector according to claim 1 or 2,

characterized in that in the inlet bore (12) received

Inner pole body (13) has a to the inner contour of the inlet bore (12) adapted outer contour.

4. Fuel injector according to one of the preceding claims, characterized in that the Innenpolkörper (13) has at least one cylindrical portion (14) which is pressed into the inlet bore (12).

5. Fuel! Ajector according to one of the preceding claims,

characterized in that the Innenpolkörper (13) of a bore (15) is interspersed, via which at least indirectly the inlet bore (12) with the high pressure bore (2) of the nozzle body (3) is connectable, wherein preferably the bore (15) concentric with Inlet bore (12) is formed.

6. Fuel! Ajector according to one of the preceding claims,

characterized in that the armature (9) has a bore (16) via which at least indirectly the inlet bore (12) with the high pressure bore (2) of the nozzle body (3) is connectable, preferably the bore (16) extending obliquely through the Anchor (9) is guided.

7. Fuel! Ajector according to one of the preceding claims,

characterized in that the armature (9) is received in a liftable manner in a high-pressure bore (17) of a magnetic body (18), wherein an annular separating body (19) of a non-magnetic material separates the magnetic body (18) from the magnetic coil (8).

8. Fuel! Ajector according to one of the preceding claims,

characterized in that the magnetic actuator (7) of the direct control of the lifting movement of the nozzle needle (1), wherein it cooperates with hydraulic and / or mechanical means for force and / or lifting amplification.

9. Fuel! A nudger according to claim 8,

characterized in that hydraulic means for force and / or stroke amplification are provided, which comprise a hydraulic coupler volume (20) and a coupler volume (20) defining the coupler piston (21), wherein the coupler piston (21) connected to the armature (9) is and is acted upon in the direction of the sealing seat (5) by the spring force of a spring (22).