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Patent Abstract
A solenoid valve is proposed for controlling an injection valve
of an internal combustion engine, including a housing part, an electromagnet
having a magnetic coil and a magnetic core, an armature acted upon
by a valve spring and axially movable between the electromagnet
and a valve seat, and a control valve member moved by the armature
and cooperating with the valve seat for opening and closing a fuel
passage, in which the armature is situated in the housing part movable
in the radial direction free from mechanical guiding means. A further
development provides that, when a current is applied to the electromagnet,
the armature may be aligned in the radial direction, by magnetic
reluctance forces then acting upon the armature, into a centrical
position with reference to the centerline of the electromagnet.
Patent Claims
What is claimed is:
1. A solenoid valve for controlling an injection valve of an internal
combustion engine, comprising: a housing part; a valve seat; a valve
spring; an electromagnet including a magnetic coil and a magnetic
core; an armature acted upon by the valve spring and axially movable
between the electromagnet and the valve seat; and a control valve
member moveable by the armature and able to cooperate with the valve
seat for opening and closing a fuel passage; wherein the armature
is situated in the housing part and is movable in a radial direction
without an arrangement for mechanical guiding.
2. The solenoid valve as recited in claim 1, wherein the armature
includes a disk-shaped armature plate able to act directly upon
the control valve member using a side of the disk-shaped armature
plate facing away from the electromagnet.
3. The solenoid valve as recited in claim 2, wherein: the disk-shaped
armature plate and the control valve member are produced as separate
parts; and the disk-shaped armature plate is shiftable in the radial
direction relative to the control valve member.
4. The solenoid valve as recited in claim 1, wherein the armature
aligns in the radial direction into a centrical position with reference
to a first centerline of the electromagnet by a magnetic reluctance
force when a current is applied to the electromagnet.
5. The solenoid valve as recited in claim 4, wherein: the magnetic
core includes a first plurality of geometric structures situated
concentrically about the first centerline at a first pole face;
the armature includes a second plurality of geometric structures
situated concentrically about a second centerline of the armature
at a second pole face, the first pole face and the second pole face
mutually facing each other; and the first plurality of geometric
structures and the second plurality of geometric structures cooperate
to align the armature into the centrical position when the current
is applied to the electromagnet.
6. The solenoid valve as recited in claim 4, wherein a second centerline
of the armature is situated concentrically with the fuel passage
when the armature is in the centrical position.
7. The solenoid valve as recited in claim 5, wherein: the first
plurality of geometric structures and the second plurality of geometric
structure are formed by respective recesses in the first pole face
and the second pole face of the magnetic core and of the armature
facing each other; and the first plurality of geometric structures
and the second plurality of geometric structures are situated one
over another in a covering manner when the armature is in the centrical
position.
8. The solenoid valve as recited in claim 7, wherein: the first
pole face includes a first annular recess, the magnetic coil being
situated in the first annular recess; and the second pole face of
the armature facing the electromagnet includes one of a second annular
recess and a partially annular recess, the one of the second annular
recess and the partially annular recess being allocated to the first
annular recess and being situated concentrically about the second
centerline.
9. The solenoid valve as recited in claim 5, wherein: the first
plurality of geometric structures are formed by a first annular
pole face section of the magnetic core surrounding the magnetic
coil; and the second plurality of geometric structures are formed
by one of a second circular pole face of the armature and a second
annular pole face of the armature, an external diameter of the one
of the second circular pole face and the second annular pole face
being slightly larger than an internal diameter of the first annular
pole face section.
10. The solenoid valve as recited in claim 9, wherein the external
diameter is less than about one millimeter larger than the internal
diameter.
11. The solenoid valve as recited in claim 1, wherein: the valve
seat is centrically situated in a truncated cone-shaped area of
a valve piece including the fuel passage, the truncated cone-shaped
area projecting towards the armature; and a space surrounding the
truncated cone-shaped area forms an accommodation for an adjusting
nut by which the valve piece is fixed in the injection valve.
Patent Description
FIELD OF THE INVENTION
[0001] The present invention relates to a solenoid valve for controlling
an injection valve of an internal combustion engine.
BACKGROUND INFORMATION
[0002] German Published Patent No. 196 50 865 discusses a solenoid
valve used for controlling the fuel pressure in the control pressure
chamber of an injection valve, such as an injector of a common rail
injection system. In such injection valves, the fuel pressure in
the control pressure chamber controls the movement of a valve plunger
with which the injection opening of the injection valve is opened
or closed. The known solenoid valve has an electromagnet situated
in a housing part, an axially movable armature guided in a sliding
piece and acted upon by a closing spring, and a control valve member
moved by the armature which cooperates with the valve seat of the
solenoid valve and thereby controls the fuel discharge from the
control pressure chamber. The armature has an armature plate, and
an armature bolt which is supported in a slidingly movable manner
in the mechanical guideway formed as a bore in the sliding piece.
[0003] In the known solenoid valves the sliding piece has to be
manufactured with great precision in order to guarantee optimal
functionality of the solenoid valve. The mechanical armature guideway
through the sliding piece gives rise to frictional losses, which
have to be considered when designing the overall system. In addition
to that, fitting the sliding piece into the housing part of the
solenoid valve requires a mechanically costly overall construction.
SUMMARY OF THE INVENTION
[0004] The advantages of the present invention arise by saving
the sliding piece which has been used up to the present time, and
discontinuing of the production and work steps connected with the
sliding piece. Because of the discontinuation of the sliding piece
guiding the armature, frictional losses caused by the mechanical
armature guideway during opening and closing the solenoid valve
are avoided. Because of the discontinuation of the sliding piece,
the construction of the armature can advantageously be greatly simplified
and optimized from a functional point of view. On account of the
simplified construction, the deviation of the dynamic behavior of
the solenoid valve is further advantageously reduced, so that the
reliability of the overall system is increased. Beyond that, a substantial
advantage comes about from the considerable cost reduction during
production of the solenoid valve. Thus, not only is the sliding
piece omitted, but the armature can also be designed to be less
costly, and can be made, for example, as a simple stamped part.
[0005] A particularly flat construction method of the armature
is achieved by designing the armature as a disk-shaped armature
plate, which acts directly upon the control valve member with its
side facing away from the electromagnet. Advantageously, in the
closed position of the solenoid valve, tilting moments transmitted
by the closing spring to the armature are greatly reduced.
[0006] Advantageously, armature plate and control valve member
are produced as separate components, so that the radially movable
armature plate can shift relatively to the control valve member,
without the control valve member necessarily being shifted from
its centrical position relative to the valve seat. A lateral impact
of the control valve member next to the valve seat and a sliding
into the valve seat connected with frictional losses are hereby
largely avoided.
[0007] Especially advantageous is an exemplary embodiment in which,
when a current is applied to the electromagnet, the armature may
be aligned in the radial direction, by magnetic reluctance forces
acting upon the armature, into a centrical position with reference
to the centerline of the electromagnet. This can advantageously
be achieved if the armature and the magnetic core have geometrical
structures situated concentrically about their respective centerline
at their mutually facing pole faces, which structures cooperate,
when current is applied to the electromagnet, in such a way that
the armature is aligned in the centrical position.
[0008] Because in the centrical position of the armature its center
axis is situated concentrically with the fuel passage, tilting moments
acting upon the armature may be further reduced. During the closing
of the solenoid valve, the armature meets the control valve member
centrically from its centrical position, so that in the closed state
of the solenoid valve the control valve member lies centrically
on the valve seat for fuel passage, and tilting moments are reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 shows a section of the upper part of a fuel injector
in an exemplary embodiment of the solenoid valve according to the
present invention.
[0010] FIG. 2 shows a section from the upper part of a fuel injector
in another exemplary embodiment of the solenoid valve according
to the present invention.
[0011] FIG. 3 shows an enlarged detailed view as in another exemplary
embodiment having the geometrical structures centering the armature.
[0012] FIG. 4 shows an enlarged detailed view of another exemplary
embodiment.
DETAILED DESCRIPTION
[0013] FIG. 1 shows the upper part of a fuel injector which is
intended for use in a fuel injection system, particularly a common
rail system for diesel fuel, which is equipped with a fuel high-pressure
reservoir that is continually supplied with high-pressure fuel by
a high-pressure fuel booster pump. The fuel injector has a valve
housing 4 having a longitudinal bore 5, in which a valve plunger
6 is positioned, which acts with its one end upon a valve needle
positioned in a nozzle body. The valve needle is situated in a pressure
chamber which is supplied with fuel under high pressure via a pressure
bore. When there is an opening lift movement of valve plunger 6,
the valve needle is lifted by the high fuel pressure, applied steadily
to a pressure shoulder of the valve needle, in the pressure chamber
counter to the closing force of a spring. The injection of the fuel
into the combustion chamber of the internal combustion engine takes
place through an injection orifice then connected to the pressure
chamber. By lowering of valve plunger 6, the valve needle is pressed
in the closing direction into the valve seat of the injection valve,
and the injection process is ended. Valve plunger 6 is guided in
a cylindrical bore 11, at its end facing away from the valve needle,
which has been inserted into valve piece 12 which is set into valve
housing 4. In cylindrical bore 11, the end face of valve plunger
6 closes in a control-pressure chamber 14, which is connected to
a fuel high-pressure connection via a supply channel. The supply
channel is essentially designed in three parts. A bore going radially
through the wall of valve piece 12, whose inner walls form a supply
throttle 15 along part of their length, is constantly connected
to an annular space 16 surrounding valve piece 12 on its outer circumference,
which annular space, in turn, is in constant connection to the fuel
high-pressure connection. Control pressure chamber 14 is subjected
via supply throttle 15 to the high fuel pressure prevailing in the
high-pressure reservoir. A bore running through valve piece 12 branches
out from control pressure chamber 14 coaxially with valve plunger
6, and it forms a fuel discharge channel 17, furnished with a discharge
throttle 18, which opens out into a discharge chamber 19, which
is connected to a fuel low-pressure connection. The outlet of fuel
discharge channel 17 from valve piece 12 lies in the region of a
cone-shaped, countersunk part 21 of the end face of valve piece
12. In the exemplary embodiment shown here, valve piece 12 is held
in valve housing 4, with the aid of a clamping element 23 having
two alternate clamping shoulders, together with housing part 39
of the solenoid valve via a screw member 7. For this purpose, valve
piece 12 has a circumferential flange 13 which lies on an annular
shoulder 47 of valve housing 4. Flange 13 is clamped between clamping
element 23 and valve housing 4. An adjustment disk 48 lies against
the other shoulder of clamping element 23, facing away from valve
housing 4. The circumferential edge section of housing part 39 of
the solenoid valve lies up against adjustment disk 48. The clamping
shoulder of screw member 7 lies against solenoid valve housing 39,
and is screwed to valve housing 4. In this exemplary embodiment,
using only one screw member 7, solenoid valve housing 39 is fixed
to valve housing 4 and valve piece 12 is clamped at the same time.
[0014] In conical part 21 a valve seat 24 is formed, with which
a control valve member 22, 25 of a solenoid valve controlling the
injection valve cooperates. Control valve member 22, 25 is formed
in two parts, having one valve ball 25 and a socket part 22 accommodating
valve ball 25 and coupled to an armature 27 which acts together
with an electromagnet 29 of the solenoid valve. Although it is conceivable
to form the armature and control valve member 22, 25 in one piece,
it is provided in the exemplary embodiment shown here that armature
27 and control valve member 22, 25 shall be formed as separate parts.
The side of socket part 22 facing away from valve ball 25 is formed
as a flat contact surface for armature 27. Armature 27 is made in
one piece, and is formed essentially as a circular disk-shaped armature
plate. The armature plate has a pole face 37 facing electromagnet
29 and a flat surface 36 facing away from it which acts directly
upon socket 22 of the control valve member. A peg 35 projects perpendicularly
from pole face 37 of armature 27, which penetrates a recess 10 of
electromagnet 29, in which a closing spring 31 is also situated
which is supported on peg 35. Armature 27 and control valve member
22, 25 coupled to the armature are constantly acted upon by a housing-mounted
supported closing spring 31 in the closing direction, so that control
valve member 22, 25 normally lies adjacent to valve seat 24 in the
closing position. When the electromagnet is activated, armature
27 is drawn away from valve seat 24 in the axial direction, and
discharge channel 17 is opened towards discharge chamber 19.
[0015] As can also be seen in FIG. 1, electromagnet 20 includes
a solenoid coil 32 and a magnetic core 33. Magnetic core 33 at its
pole face 38 has an annular recess 41, in which solenoid coil 32
is situated. Connections 34 of the solenoid coil run to the outside
through magnetic core 33. Recess 41 subdivides pole face 38 of the
magnetic core into an inner annular pole face section 45 and an
outer annular pole face section 44, which both face pole face 37
of the armature plate, as can be seen best in FIG. 3. When a current
acts upon the electromagnet, a closed magnetic circuit forms over
the gap between pole face section 44 and pole face 37 of the armature
and the gap between pole face 37 of the armature and pole face section
45 of the magnetic core. Between the pole face of magnetic core
33 and pole face 38 of the armature plate a minimum distance may
be allowed, in order to prevent a so-called magnetic adhesion of
the armature to magnetic core 33. As shown in FIG. 3, this can be
achieved, for example, by a layer 26 made of a magnetic, non-conductive
material on pole face 37 of the armature plate. Layer 26 can be
made, for instance, of chromium or teflon. The layer may be connected
to the armature by soldering, welding, adhesion, or in another suitable
way. It is also possible to insert one or more distance washers
between pole face 38 of armature 27 and magnetic core 33. A further
possibility for seeing that the minimum distance between the armature
plate and the magnetic core is kept, is to provide the armature
with structures proceeding from pole face 37 (such as studs), which
are supported on the electromagnet or on a sleeve mounted in the
electromagnet. Furthermore, for example, the armature plate may
be made to lie against a sleeve mounted in the electromagnet and
proceeding from pole face 38 of magnetic core 33.
[0016] The opening and closing of the injection valve is controlled
by solenoid valve 30, as described below. As described before, armature
bolt 27 is constantly acted upon by closing spring 31 in the closing
direction, so that control valve member 25 lies against valve seat
24 in the closing position when the electromagnet is not activated,
and control pressure chamber 14 is closed towards discharge side
19, so that high pressure very rapidly builds up there, via the
supply channel, which is also present in the fuel high-pressure
reservoir. The pressure in control pressure chamber 14 generates
a closing force on valve plunger 6, and thus on the valve needle
connected with it, which is greater than the forces acting, on the
other hand, in the opening direction as a result of the high pressure
present. If control pressure chamber 14 is opened toward discharge
side 19 by opening the solenoid valve, the pressure in the low volume
of control pressure chamber 14 goes down very fast, since it is
decoupled from the high-pressure side via supply throttle 15. As
a result, the force acting on the valve needle in the opening direction
outbalances the high fuel pressure present at the valve needle,
so that the latter moves upwards, and with that the at least one
injection orifice is opened for injection. However, if solenoid
valve 30 closes fuel discharge channel 17, the pressure in control
pressure chamber 14 may be built up again by fuel that continues
to flow via supply channel 15, so that the original closing force
is present, and the valve needle of the fuel injector closes.
[0017] As shown in FIG. 1, armature 27 of the solenoid valve according
to an exemplary embodiment of the present invention may be moved
in housing part 39 of the solenoid valve in the radial direction
without interference by a mechanical guideway. During a radial movement
of armature 27, surface 36 of the armature plate may glide along
on socket part 22. During closing of the solenoid valve, closing
spring 31 presses armature 27 and control valve member 22, 25 against
valve seat 24, it being possible that the mechanically unguided
armature plate may tilt a little if it hits socket part 22 in an
off-center fashion. However, even in the case of a slight deflection
of the armature plate in the radial direction, control valve member
25 is always reliably pressed into valve seat 24. Because of the
flat design of armature 27 as a disk-shaped armature plate, the
tilting moments are greatly reduced in comparison with the case
of a T-shaped armature having armature bolts proceeding from the
armature plate.
[0018] FIG. 2 shows a further exemplary embodiment of the present
invention. The basic design of the solenoid valve shown in FIG.
2 is similar to that in FIG. 1. The same parts have the same reference
numerals. As may be seen, in contrast to FIG. 1, plate-shaped armature
27 here has a centrical recess 40 on its side facing the electromagnet,
into which closing spring 31 penetrates. Here the point of contact
of closing spring 31 lies particularly close to ball 25 of the control
valve member, so that tilting moments acting upon the armature when
the solenoid valve is closed are even further reduced. Furthermore,
valve piece 12 is clamped into valve housing 4 using a separate,
screwable clamping member 23. Solenoid valve housing 39 is fastened
by screw member 7 directly to valve housing 4 via adjustment disk
48. In order to have sufficient room for clamping member 23, in
spite of the flat armature, end face 12 of the valve piece which
faces the electromagnet is provided with a truncated-cone-shaped
section 20, which is surrounded by a flange 13. Valve seat 24 is
mounted centrically into truncated-cone-shaped section 20. As may
be seen, the space surrounding truncated-cone-shaped section 20
forms an accommodation for adjusting nut 23, which lies adjacent
to flange 13 of valve piece 12. The minimum distance between armature
27 and electromagnet 29 is attained by putting a coating of nonmagnetic
material on the armature.
[0019] A further exemplary embodiment of the present invention
is especially advantageous, in which the armature plate is centered
using magnetic reluctance forces, in order to avoid off-centering
of the armature plate and the resulting tilting of the armature
plate when it hits the control valve member. This may be attained
by providing armature 27 and magnetic core 33 of electromagnet 29
with geometrical structures which cooperate, when a current is applied
to electromagnet 29, in such a way that armature 27 is aligned to
a centrical position, in which its centerline 45 runs coaxially
with centerline 30 of the electromagnet (centerline 45 and centerline
30 lie on a straight line). This has the advantage that the armature
plate is constantly centered when the solenoid valve is opened,
and, at switching off of the electromagnet when the solenoid valve
is closed, it hits the control valve member from this centrical
position. The geometrical structures may be provided both for the
solenoid valve shown in FIG. 1 and the one shown in FIG. 2. In FIG.
2 the geometrical structures are indicated by reference numerals
41 and 42. An enlarged detailed view is found in FIG. 3.
[0020] As may be seen in FIG. 3, electromagnet 29 has a magnetic
core 33 and a coil 32. Magnetic core 33 is furnished with groove-shaped
recess 41 running concentrically with its centerline 30, in which
coil 32 is mounted. Pole face 38 of magnetic core 33 is subdivided
into an outer annular pole face section 44 and an inner pole face
section 45 by recess 41. The special feature of this exemplary embodiment
is the recess 42, which is inserted in pole face 37 of armature
27 concentrically with centerline 45 of the armature, and facing
magnetic core 33. This likewise annular recess 42 in the form of
a circumferential groove has approximately the same outer diameter
and inner diameter, and thus it has the same width d as recess 41
of magnetic core 33. Recesses 41 and 42, allocated to each other,
cooperate magnetically in such a way that, when a current is applied
to the electromagnet, centerline 45 of armature 27 runs coaxially
with centerline 30 of the electromagnet. The magnetically centering
effect is explained by magnetic reluctance forces which appear when
there is a radial deflection of the armature plate. If recesses
41 and 42 are not situated over one another in a covering manner,
the magnetic field lines at the edges of the two recesses 41, 42
are distorted. The reluctance forces resulting from this pull the
armature plate back again until recesses 41, 42 lie above one another
in a covering manner, and centerline 45 of the armature runs coaxially
with centerline 30 of electromagnet 29. For this, recess 42 does
not necessarily have to be mounted circumferentially in armature
27. It is also possible to use segments situated concentrically
with centerline 45 or other suitable designs.
[0021] An additional exemplary embodiment is represented in FIG.
4. In this exemplary embodiment pole face 37 of armature 27 is designed
without a recess, but it has an external diameter which is a little
greater than the internal diameter of outer pole face section 44
of the magnetic core. Preferably, the external diameter of pole
face 37 of the armature is designed to be about one millimeter larger
than the internal diameter of outer pole face section 44 of magnetic
core 33. When a current is applied to the electromagnet, the magnetic
field in the overlapping region e of pole face 37 and of outer pole
face section 44 is strengthened, since there the magnetic field
lines have to run more densely. The strengthening is the greater,
the smaller the overlapping region e. In the case of a radial deflection
of the armature plate, strong reluctance forces act in this region,
which drive the armature plate back into the centrical position,
in which centerlines 30, 45 lie coaxially (i.e. lie on a straight
line).
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