Fuel injector

Abstract

A fuel injector for direct injection of fuel into a combustion chamber includes: a housing having at least one combustion chamber-side injection aperture; a linearly movable valve needle for opening and closing the injection aperture; a solenoid; an armature which is linearly movable by the solenoid; and a first sleeve attached to the armature. A first stop surface facing away from the combustion chamber is formed on the first sleeve, and a second stop surface facing the combustion chamber is formed on the valve needle, the first and second stop surfaces striking one another when the valve needle and/or the armature is/are moved linearly.

Claims

1. A fuel injector for direct injection of fuel into a combustion chamber, comprising: a housing having at least one combustion-chamber side injection aperture; a linearly movable valve needle for opening and closing the injection aperture; a solenoid; an armature which is linearly movable by the solenoid; and a first sleeve, the first sleeve being formed as a hollow, tubular component having a constant inside and outside diameter; wherein the first sleeve is a separate component and the first sleeve is attached to the armature; wherein a first stop surface facing away from the combustion chamber is formed on the first sleeve, and a second stop surface facing the combustion chamber is formed on the valve needle, the first and second stop surfaces striking one another when at least one of the valve needle and the armature is moved linearly; and wherein the armature has a continuous recess and the first sleeve is situated on a wall of the recess; wherein a groove is formed in the wall of the recess, and wherein the first sleeve is situated in the groove and further comprising a second sleeve attached to a base body of the valve needle, wherein the second stop surface is formed on the second sleeve; wherein a total length of the first sleeve and the second sleeve, measured parallel to a longitudinal axis of the fuel injector, has a same value as a length of the recess.

2. The fuel injector as recited in claim 1, wherein the recess has a uniform diameter over the entire length of the recess.

3. The fuel injector as recited in claim 1, wherein the first sleeve protrudes beyond the wall of the recess.

4. The fuel injector as recited in claim 1, wherein the groove is open on a side of the armature facing away from the combustion chamber.

5. The fuel injector as recited in claim 1, wherein at least one of: the first sleeve is made from a more solid material than the armature; and the second sleeve is made from a more solid material than the remaining components of the valve needle.

6. The fuel injector as recited in claim 1, wherein at least one of: the first sleeve is attached to the armature in at least one of a form-locked manner, a friction-fit manner, and an integrally joined manner; and the second sleeve is attached to the valve needle in at least one of a form-locked manner, a friction-fit manner, and an integrally joined manner.

7. The fuel injector as recited in claim 1, wherein the first sleeve and the wall of a recess are in contact along the linear axis of the fuel injector.

8. A fuel injector for direct injection of fuel into a combustion chamber, comprising: a housing having at least one combustion-chamber side injection aperture; a linearly movable valve needle for opening and closing the injection aperture; a solenoid; an armature which is linearly movable by the solenoid; and a first sleeve, the first sleeve is formed as a hollow, tubular component having a constant inside and outside diameter; wherein the first sleeve is a separate component and the first sleeve is attached to the armature; wherein a first stop surface facing away from the combustion chamber is formed on the first sleeve, and a second stop surface facing the combustion chamber is formed on the valve needle, the first and second stop surfaces striking one another when at least one of the valve needle and the armature is moved linearly; and wherein the armature has a continuous recess and the first sleeve is situated on a wall of the recess, wherein the first sleeve is a harder material than the armature; wherein a groove is formed in the wall of the recess, and wherein the first sleeve is situated in the groove and further comprising a second sleeve attached to a base body of the valve needle, wherein the second stop surface is formed on the second sleeve; wherein a total length of the first sleeve and the second sleeve, measured parallel to a longitudinal axis of the fuel injector, has a same value as a length of the recess.

9. The fuel injector as recited in claim 1, wherein the first sleeve is situated in the recess of the armature, wherein the first stop surface of the first sleeve and the second stop surface of the valve needle lie in an interior of the recess.

10. The fuel injector for direct injection of fuel into a combustion chamber as recited in claim 8, wherein the first sleeve is situated in the recess of the armature, wherein the first stop surface of the first sleeve and the second stop surface of the valve needle lie in an interior of the recess.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a fuel injector according to the present invention according to a first through a fourth exemplary embodiment.

(2) FIG. 2 shows a detail of the fuel injector according to the present invention according to the first exemplary embodiment.

(3) FIG. 3 shows a detail of the fuel injector according to the present invention according to the second exemplary embodiment.

(4) FIG. 4 shows a detail of the fuel injector according to the present invention according to the third exemplary embodiment.

(5) FIG. 5 shows a detail of the fuel injector according to the present invention according to the fourth exemplary embodiment.

DETAILED DESCRIPTION OF THE INVENTION

(6) Referring to FIG. 1, the basic structure of fuel injector 1 will be explained for the four exemplary embodiments described below.

(7) FIG. 1 shows fuel injector 1 in a section parallel to longitudinal axis 6. Fuel injector 1 includes a housing 2, which on a side 3 facing the combustion chamber includes at least one injection aperture 5. Via this injection aperture 5, fuel is injected into a combustion chamber. A side 4 facing away from the combustion chamber is diametrically opposed to side 3 facing the combustion chamber

(8) In housing 2, a valve needle 7 is guided coaxially to longitudinal axis 6 in a linearly movable manner. This valve needle 7 has a base body 8. This base body 8 is internally hollow and has apertures 9. With the aid of valve needle 7, a spherical closing body 10 is pressed onto injection aperture 5. For opening the fuel injector, valve needle 7 is moved in the direction of side 4 facing away from the combustion chamber. Closing body 10 then lifts off from injection aperture 5, making it possible for fuel to be injected.

(9) Furthermore, a solenoid 11 and an annular internal pole 12 are situated in housing 2. An armature 13 is attached to base body 8 of valve needle 7. Internal pole 12 is magnetized via solenoid 11 and thus moves armature 13 linearly to longitudinal axis 6. Moreover, a plug connector 14 of the fuel injector is represented in FIG. 1.

(10) Four exemplary embodiments of fuel injector 1 are shown based on FIGS. 2 through 5. FIGS. 2 through 5 each show the detail from FIG. 1 labeled II-V. Identical or functionally identical components are provided with the same reference numerals in all exemplary embodiments.

(11) FIG. 2 shows a detail of fuel injector 1 according to the first exemplary embodiment. Armature 13 is shown having an inner, continuous recess 20. A first sleeve 15 is attached to the wall of recess 20. This first sleeve 15 is fixedly connected to armature 13. Furthermore, valve needle 7 is situated within recess 20. A thickening 19 is formed on the end of base body 8 of valve needle 7 facing away from the combustion chamber.

(12) On its side facing away from the combustion chamber, first sleeve 15 has a first stop surface 16. A second stop surface 18 facing the combustion chamber is formed on thickening 19. In the case of a movement of armature 13 and/or of valve needle 7, the two stop surfaces 16, 18 strike one another. First sleeve 15 is manufactured from a harder material than armature 13. This largely avoids wear on first stop surface 16.

(13) Furthermore, FIG. 2 shows a length 21 of recess 20, measured parallel to longitudinal axis 6, and a diameter 22 of recess 20. The external diameter of first sleeve 15 corresponds to diameter 22 of recess 20. The length of first sleeve 15 is shorter than length 21 of recess 20. A total length of first sleeve 15 and thickening 19, measured parallel to longitudinal axis 6, corresponds to length 21 of recess 20.

(14) FIG. 3 shows a detail of fuel injector 1 according to the second exemplary embodiment. In the second exemplary embodiment, armature 13 has a circumferential groove 23. First sleeve 15 is inserted into this circumferential groove 23. In this connection, first sleeve 15 has in particular a square cross-section. The diameter of recess 20 on the combustion chamber side of groove 23 is smaller than the diameter of recess 20 on the side of groove 23 facing away from the combustion chamber. As a result, first sleeve 15 protrudes beyond the wall of recess 20 and at least one portion of first sleeve 15 may be used as first stop surface 16.

(15) FIG. 4 shows a detail of fuel injector 1 according to the third exemplary embodiment. In this case, groove 23 is formed on an end of armature 13 facing away from the combustion chamber. As a result, groove 23 is open both to side 4 facing away from the combustion chamber and to longitudinal axis 6. This groove 23 makes it possible to mount first sleeve 15 relatively simply and simultaneously makes it possible for the entire side of first sleeve 15 facing away from the combustion chamber to be available as first stop surface 16.

(16) FIG. 5 shows a detail of fuel injector 1 according to the fourth exemplary embodiment. First sleeve 15 and armature 13 are formed just as in the first exemplary embodiment. Instead of thickening 19 on base body 8 of valve needle 7, a second sleeve 17 is in this case fixedly connected to base body 8 of valve needle 7. This second sleeve 17 is preferably made from a hardened material or includes a hardened surface, so that the wear on second stop surface 18 is also reduced. As shown in FIG. 5, a total length of first sleeve 15 and second sleeve 17, measured parallel to longitudinal axis 6, has the same value as length 21 of recess 20.