Title: Fuel injector
Abstract: A fuel injector for fuel-injection systems of internal combustion engines includes a valve needle cooperating with a valve-seat surface to form a sealing seat, and an armature engaging with the valve needle, the armature being axially moveable at the valve needle and being damped, via a damping element, which is located in a recess in a downstream-side end face of the armature, with respect to a cup-shaped sleeve positioned downstream from the armature and joined to the valve needle in force-locking manner. Furthermore, the fuel injector includes a filter element, the filter element being positioned downstream from the armature in the cup-shaped sleeve.
Patent Number: 6,994,281 Issued on 02/07/2006 to Reiter
| Inventors:
|
Reiter; Ferdinand (Markgroeningen, DE)
|
| Assignee:
|
Robert Bosch GmbH (Stuttgart, DE)
|
| Appl. No.:
|
362399 |
| Filed:
|
May 25, 2002 |
| PCT Filed:
|
May 25, 2002
|
| PCT NO:
|
PCT/DE02/01927
|
| 371 Date:
|
July 25, 2003
|
| 102(e) Date:
|
July 25, 2003
|
| PCT PUB.NO.:
|
WO03/001051 |
| PCT PUB. Date:
|
January 3, 2003 |
Foreign Application Priority Data
| Jun 22, 2001[DE] | 101 30 205 |
| Current U.S. Class: |
239/533.2; 239/533.9; 239/575; 239/585.3; 239/585.5 |
| Current Intern'l Class: |
F02M 59/00 (20060101); F02M 39/00 (20060101); B05B 1/30 (20060101) |
| Field of Search: |
239/5332,533.3,533.9,584,575,88-93,5851-5855,533.11,533.13
251/129.21,129.15,127
|
References Cited [Referenced By]
U.S. Patent Documents
| 5190223 | Mar., 1993 | Mesenich.
| |
| 5238192 | Aug., 1993 | McNair.
| |
| 5325838 | Jul., 1994 | Bennett.
| |
| 5423489 | Jun., 1995 | Wood.
| |
| 6003791 | Dec., 1999 | Reiter.
| |
| 6363915 | Apr., 2002 | Cohen.
| |
| Foreign Patent Documents |
| 44 21 881 | Jan., 1996 | DE.
| |
| 42 00 710 | May., 1993 | JP.
| |
Primary Examiner: Hwu; Davis
Attorney, Agent or Firm: Kenyon & Kenyon
Claims
What is claimed is:
1. A fuel injector for a fuel injection system of an internal combustion engine, comprising:
a valve seat surface;
a valve needle which cooperates with the valve seat surface to form a sealing
seat;
an armature including a downstream-side end face having a recess, and axially
engaging the valve needle;
a damping element situated in the recess of the armature;
a cup-shaped sleeve situated downstream from the armature and joined to the valve
needle by force-locking using the damping element, wherein the armature is damped
with respect to the cup-shaped sleeve; and
a filter element positioned downstream from the armature in the cup-shaped sleeve.
2. The fuel injector of claim 1, wherein the filter element includes a flat filter.
3. The fuel injector of claim 2, wherein the filter element includes a screen mesh.
4. The fuel injector of claim 2, wherein the filter element includes a disk including orifices.
5. The fuel injector of claim 4, wherein the orifices of the filter element are
one of round and longitudinal.
6. The fuel injector of claim 4, wherein the orifices are produced by one of
stamping, eroding, etching and laser-drilling.
7. The fuel injector of claim 4, wherein the orifices of the filter element positioned
in the cup-shaped sleeve are smaller than the orifices of a filter element positioned
in a central fuel feed.
8. The fuel injector of claim 1, wherein the filter element is loosely inserted
in the cup-shaped sleeve.
9. The fuel injector of claim 1, wherein the filter element is radially compressed
in the cup-shaped sleeve.
10. The fuel injector of claim 1, wherein the filter element is fixed in place
inside the cup-shaped sleeve by a weld.
11. The fuel injector of claim 1, wherein the filter element is axially braceable
between the armature and the cup-shaped sleeve.
12. The fuel injector of claim 1, wherein the cup-shaped sleeve includes flow-through
orifices that are covered by the filter element.
Description
FIELD OF THE INVENTION
The present invention is directed to a fuel injector.
BACKGROUND INFORMATION
German Patent No. 44 21 881 (DE 44 21 881 A1) discusses a fuel injector having
a valve needle with a filter element mounted thereon or inside of it. The filter
element is used to keep any particles and impurities, upstream from the sealing
seat in the interior of the fuel injector, away from the sealing seat, thereby
avoiding clogging and/or leakages at the sealing seat. The filter element is designed
in the form of a screening sock which envelops the valve needle at least partially.
The fuel injector discussed in DE 44 21 881 A1 is such that the production and
installation of a sock-shaped filter element may be complex and, thus, cost-intensive.
Because of the large surface of the filter element, it is susceptible to twisting
and shifting during the operation of the fuel injector, due to considerable valve-needle movement.
SUMMARY OF THE INVENTION
In contrast, the fuel injector of the present invention has the advantage over
the related art that, in addition to a filter element positioned in the fuel feed,
an additional filter element is provided which is located downstream from the armature.
It allows either a second, finer filtering of the fuel flowing through in addition
to the filtering by the first filter element, or replacing the first filter element,
which has the advantage of allowing a shorter length for the fuel injector.
It is believed that it is advantageous in this context that the second filter
element is able to be produced in a simple manner from a screen mesh or by introducing
orifices into an annular sheet metal. The opening may be produced in a variety
of ways, such as laser drilling, etching, eroding or stamping.
It is believed that it is also advantageous that the filter element may either
be loosely placed into the sleeve positioned downstream from the armature, or be
braced against it or welded to it, thereby holding the filter element in place.
An advantageous, additional arrangement for fixation is offered by a concave,
convex or dish-like form of the filter element, since in this case a fixation is
possible by axial bracing between the armature and the sleeve, which may be biased
relative to one another for damping purposes, without requiring additional fixation
measures, yet providing excellent accuracy of fit.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic section of an exemplary embodiment of a fuel injector
configured according to the present invention in an overall view.
FIG. 2 is a schematic section through the exemplary embodiment, shown in FIG.
1, of a fuel injector designed according to the present invention, in region II
in FIG. 1.
DETAILED DESCRIPTION
A fuel injector
1, shown in FIG. 1, is designed in the form of a fuel
injector
for fuel-injection systems of mixture-compressing internal combustion engines having
externally supplied ignition. Fuel injector
1 is particularly suited for
the direct injection of fuel into a combustion chamber (not shown) of an internal
combustion engine.
Fuel injector
1 includes a nozzle body
2 in which a valve needle
3 is positioned. Valve needle
3 is in operative connection with a
valve-closure member
4, which cooperates with a valve-seat surface
6
situated on a valve-seat member
5 to form a sealing seat. In the exemplary
embodiment, fuel injector
1 is an inwardly opening fuel injector
1,
which has one spray-discharge orifice
7. Seal
8 seals nozzle body
2 from an outer pole
9 of a magnetic coil
10. Magnetic coil
10 is encapsulated in a coil housing
11 and wound on a coil brace
12, which rests against an inner pole
13 of magnetic coil
10.
Inner pole
13 and outer pole
9 are separated from each other by a
constriction
26 and joined to one another by a non-ferromagnetic connecting
part
29. Magnetic coil
10 is energized via a line
19 by an
electric current, which may be supplied via an electrical plug contact
17.
A plastic coating
18, which may be extruded onto inner pole
13, encloses
plug contact
17.
Valve needle
3 is guided in a valve-needle guide
14, which is
disk-shaped. A paired adjustment disk
15 adjusts the (valve) lift. On the
other side of adjustment disk
15 is an armature
20. It is connected
by force-locking to valve needle
3 via a flange
21, and valve needle
3 is connected to flange
21 by a welded seam
22. A restoring
spring
23, which, in the present design of fuel injector
1, is prestressed
by a sleeve
24, is braced against flange
21. Fuel channels
30a
through
30c run through valve needle guide
14, armature
20 and valve seat member
5, conducting the fuel, supplied via central
fuel supply
16 and filtered by a first filter element
25a;
to spray-discharge opening
7. Seal
28 seals fuel injector
1
from a fuel line (not shown further).
Positioned at a downstream side
34 of armature
20 in a recess
35 is a damping element
32 designed as an O-ring, which is made of
an elastomeric material. It rests against a shoulder-type broadened region
36
of a deep-drawn sleeve
31, which is joined to valve needle
3 in a
force-locking manner via a welding seam
33.
Positioned in deep-drawn sleeve
31 is a second filter element
25b,
which is designed as a flat filter
25 and may be made, for instance, from
screen mesh or have the form of a disk provided with many small orifices.
Formed in sleeve
31 are flow-through orifices
37 which are covered
by second filter element
25b, which, it is believed, protect the
valve seat from contamination by coarse particles in the fuel and preventing malfunctions
of fuel injector
1.
In the resting state of fuel injector
1, restoring spring
23 acts
upon armature
20, counter to its lift direction, in such a way that valve-closure
member
4 is sealingly held at valve seat
6. Upon excitation of magnetic
coil
10, it generates a magnetic field which moves armature
20 in
the lift direction, counter to the spring force of return spring
23, the
lift being predefined by a working gap
27 existing in the neutral position
between inner pole
12 and armature
20. Flange
21, which is
welded to valve needle
3, is moved by armature
20 in the lift direction
as well. Valve-closure member
4, which is connected to valve needle
3,
lifts off from valve seat surface
6, so that the fuel is spray-discharged
through spray-discharge orifice
7.
In response to the coil current being switched off, after sufficient decay of
the magnetic field, armature
20 falls away from inner pole
13 due
to the pressure of return spring
23, so that flange
21, being connected
to valve needle
3, moves in a direction counter to the lift. As a result,
valve needle
3 is moved in the same direction, causing valve-closure member
4 to set down upon valve seat surface
6 and fuel injector
1
to be closed.
FIG. 2 shows a part-sectional view of region II in FIG. 1 in an enlarged view.
As shown in FIG. 2, a segment of valve needle
3, flange
21 welded
thereto, sleeve
31 and second filter element
25b are configured
according to the present invention and inserted into recess
35 of armature
20.
When assembling the component made up of armature
20 and valve needle
3, flange
21 may be first welded to valve needle
3 via welding
seam
22. Damping element
32 is inserted into recess
35 formed
in discharge-side end face
34 of armature
20, and armature
20;
with damping element
32 inserted, is slipped over valve needle
3.
Then, second filter element
25b is inserted into sleeve
31
having a stepped design and which is may be produced by deep-drawing and provided
with stamped flow-through orifices
37 towards the fuel feed. Sleeve
31,
together with second filter element
25b, is then slipped over valve
needle
3 and joined to valve needle
3 via a welded seam
33
as well.
Second filter element
25b is positioned such that it covers
flow-through orifices
37 in cup-shaped sleeve
31. The form and fit
of armature
20 ensure that fuel is only able to flow through fuel channels
30a in the armature and flow-through orifices
37 in sleeve
31 in the direction of the sealing seat. In this way, using second filter
element
25b inserted in sleeve
31, in addition to first filter
element
25a positioned in central fuel feed
16, it is possible
to filter out coarse particles in the fuel, thereby protecting the sealing seat
from impurities which may lead to malfunctions of fuel injector
1.
Second filter element
25b may be configured in the form of a
flat filter
25b, which may be produced from screen mesh. Second filter
element
25b may also be produced as a disk from thin sheet metal
and be provided with round or longitudinal orifices through which the fuel flows.
The orifices may be produced by stamping, eroding, etching or laser-drilling. The
orifices may be smaller than the orifices of upstream first filter element
25a,
thereby increasing the effectiveness of the fuel filtering.
Second filter element
25b may be fixed in position inside sleeve
31 in different ways to avoid movement and subsequent entry of dirt particles
into the fuel flow.
If second filter element
25b is dimensioned such that its diameter
corresponds to the inside width of sleeve
31, it may be inserted into cup-shaped
sleeve
31 without being fixed in place. If second filter element
25b
has a slightly larger dimension, it may be pressed into sleeve
31 by
radial pressing.
However, a simpler installation is possible if second filter element
25b
is somewhat smaller than sleeve
31. In this case, second filter element
25b can be fixed in position on sleeve
31 by laser tack-welding
or spot welding using at least one spot.
In an alternate configuration, for instance, a configuration using a plate-shaped
or arched filter element
25b, an axial bracing of filter element
25b between armature
20 and sleeve
31 may be considered
as well. It is believed that this may be advantageous, in particular, because armature
20 is braced against sleeve
31 for damping purposes anyway.
The present invention is not limited to the exemplary embodiment shown, but is
also suited, for instance, for outwardly opening fuel injectors
1 and other
armature configurations, such as flat-type armatures.
*
