Information
-
Patent Grant
-
6499669
-
Patent Number
6,499,669
-
Date Filed
Friday, January 19, 200123 years ago
-
Date Issued
Tuesday, December 31, 200221 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
-
CPC
-
US Classifications
Field of Search
-
International Classifications
-
Abstract
An injection valve member for the closing and opening of injection orifices of a valve seat element is installed longitudinally adjustably in a central housing bore of a fuel injection valve. The opening and closing movement sequence of the injection valve member is controlled by a control device. A control piston operatively connected to the injection valve member is loaded, on the one hand, by the fuel system pressure prevailing in a high-pressure zone and, on the other hand, by the fuel control pressure in a control space. The high-pressure zone includes the central housing bore which is closed off sealingly by a control body fixed to the housing. The control space is arranged between the control body and a piston end face and is at least temporarily delimited radially by a control sleeve which is moveable transversely to the longitudinal axis of the housing. A narrow sliding guide between a control piston part and the control sleeve, said sliding guide separating the control space from the high-pressure zone, forms an accurate longitudinal guide for the control sleeve. The fuel injection valve is simple in terms of manufacture and assembly.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a fuel injection valve for the intermittent injection of fuel into the combustion space of an internal combustion engine.
2. Discussion of the Background
EP-B-0 228 578 describes a fuel injection valve with an injection valve member which is guided longitudinally displaceably in a housing in a bore extending in the direction of the longitudinal axis of the housing. This bore, which is connected via a throttle to a fuel high-pressure connection and is designed as an accumulator space, is closed off, at one end, by a seat for the injection valve member, said seat being provided with injection orifices, and, at the other end, by a cylindrical end piece which is guided in the housing by means of a narrow guide performing a sealing function. The end piece serves as a narrow sliding guide for a piston which forms part of the one-piece injection valve member. The injection valve member is narrowly guided in a further guide in the vicinity of the seat. The movement of opening and closing the injection valve member is controlled by controlling the pressure in a control space above the piston of the injection valve member.
As mentioned, the two guides for the one-piece injection valve member a produced in the form of narrow sliding fits, which means that these guides have to be accurately oriented axially, so that no lateral forces are exerted on the injection valve member, which could cause distortion of the latter, severe friction or even jamming and would impair the functioning of the fuel injection valve. The fuel injection valve is consequently complicated to manufacture and assemble. Moreover, the housing has a relatively large cross section, because, as mentioned, the central bore is designed as an accumulator space, this being a disadvantage for installation in internal combustion engines.
A generic fuel injection valve of the type initially mentioned is known, for example, from EP-B-0 686 763. In this fuel injection valve, the opening and closing movement sequence of an injection valve member installed longitudinally adjustably in a housing is controlled by means of a control device comprising a control piston which is a component separate from the injection valve member and operatively connected to the latter. Between the end face of the control piston and a control body fixed to the housing is located a control space which is delimited radially by a control sleeve. The control sleeve is arranged displaceably and with a narrow sliding fit in a housing bore receiving the control device. The control piston is likewise guided with a narrow sliding fit in the control sleeve. High-pressure supply lines are arranged parallel to the housing bore, in which the control device is accommodated, in the housing and are connected to a fuel high-pressure connection. One high-pressure supply line leads to the control device, the control space being connected to this high-pressure supply line via an inlet throttle connection. By an outlet orifice in the control body being opened or closed (by means of a controllable pilot valve), the fuel control pressure in the control space, which acts on the control piston, is capable of being controlled. The other high-pressure supply line leads to an annular space and to injection orifices of a valve seat element arranged at the lower end of the fuel injection valve. The injection valve member is accurately guided in a bore of the valve seat element by means of a component which is arranged above the annular space and on which the fuel system pressure acts from below.
So that the high-pressure supply lines can be accommodated in the housing, the latter must have a relatively large cross section, and this proves to be a disadvantage for installation in internal combustion engines on grounds of space.
The housing bore, in which the multi-piece injection valve member runs, is connected in this middle part to a fuel return line. This means that a low fuel pressure prevails in this region of the housing bore. This leads to leakages out of the adjoining regions, in which the fuel high pressure prevails, into this low-pressure region of the housing bore.
SUMMARY OF THE INVENTION
The object on which the present invention is based is to provide a fuel injection valve which is simple and cost-effective in terms of manufacture and assembly, in which at most insignificant leakages occur and which, even in its external shape, is advantageous for installation in internal combustion engines.
This object is achieved, according to the invention, by means of a fuel injection valve having the features of the independent claims set forth herein.
The fuel injection valve according to the invention not only has a simple and cost-effective makeup. Its special advantages are also that functional identity can be achieved in a simple way in all the valves of an internal combustion engine, since, in all components, the tolerances as regards both manufacture and assembly can be adhered to without difficulty. Dispensing with lateral high-pressure supply lines in the housing makes it possible to have a slender configuration of the fuel injection valve, this being advantageous for installation in internal combustion engines. The central bore which is located in the housing and in which the fuel high pressure prevails forms a completely leaktight region, so that leakages into spaces with lower pressure are virtually eliminated.
Preferred developments of the fuel injection valve according to the invention form the subject-matter of the dependent claims.
A fuel injection valve of the type initially mentioned, with a particularly preferred embodiment of the control device, forms the subject-matter of the independent claim
20
.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is explained in more detail below by means of the drawings in which:
FIG. 1
shows a first exemplary embodiment of a fuel injection valve in longitudinal section;
FIG. 2
shows, on an enlarged scale and in longitudinal section, part of the fuel injection valve shown in
FIG. 1
, with the first embodiment of a control device;
FIG. 3
shows part of the control device according to
FIG. 2
on a further-enlarged scale;
FIG. 4
shows, in longitudinal section, a second exemplary embodiment of a fuel injection valve with a second embodiment of the control device;
FIG. 5
shows the control device according to
FIG. 4
on an enlarged scale and in longitudinal section;
FIG. 6
shows an illustration, corresponding to that of
FIG. 2
or
5
, of a third embodiment of a control device for a fuel injection valve; and
FIG. 7
shows an illustration, corresponding to that of
FIG. 2
or
5
, of a fourth embodiment of a control device for a fuel injection valve.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
According to
FIG. 1
, a fuel injection valve
1
is connected via a fuel high-pressure connection
10
to a high-pressure feed device, not illustrated in the drawing, which delivers fuel at a pressure of 100 to 2000 bar and above. The fuel injection valve
1
is connected, furthermore, to an electronic control, likewise not shown, via electric connections
12
.
The fuel injection valve
1
has a housing
14
which comprises a lower housing part
14
a
and an upper housing part
14
b
. The lower housing part
14
a
has a tubular configuration, is long, is narrow in diameter and has a central bore
40
coaxial to the longitudinal axis A of the fuel injection valve
1
. The central bore
40
is widened in the region of the upper housing part
14
b
. This bore of larger diameter is designated by
42
in
FIG. 1. A
passage bore
44
connecting the fuel high-pressure connection
10
to the widened part
42
of the central bore is arranged radially to the longitudinal axis A.
The lower housing part
14
a
is connected at its lower end to a screwed-on holding part
16
produced in the form of a union nut. The holding part
16
presses a nozzle body
18
sealingly onto a lower surface
20
of the housing part
14
a
. The radial position of the nozzle body
18
relative to the housing part
14
a
is fixed by means of one or more pins
24
which also prevent twisting. A nozzle tip
22
of the nozzle body
18
, said nozzle tip forming a valve seat element, projects out of the holding part
16
. The nozzle tip
22
is provided with a nozzle needle seat
26
and with a plurality of injection orifices
28
. The injection orifices
28
are capable of being closed off by means of a lower end
34
of an axially adjustable nozzle needle
30
forming an injection valve member. The nozzle needle
30
extends upward from the lower nozzle needle seat
26
through an annular space
38
and a bore
32
of the nozzle body
18
and also through the central bore
40
of the housing part
14
a
and in the upper end part has a collar
35
and two piston parts
31
,
33
. These piston parts
31
,
33
form part of a control device S
1
for controlling the adjustment movement of the injection valve member, that is to say of the nozzle needle
30
. The control device S
1
is described in detail further below by means of
FIGS. 2 and 3
. In the region of the nozzle body bore
32
, the nozzle needle
30
is provided with axially running ground-down surfaces
36
which connect to the annular space
38
hydraulically to the central bore
40
of the housing part
14
a.
In the exemplary embodiment illustrated in
FIG. 1
, the nozzle needle
30
is produced in one piece. However, the nozzle needle could also consist of a plurality of elements operatively connected to one another.
A holding nut
17
is screwed onto the upper housing part
14
b
. Inside the holding nut
17
is accommodated an electromagnetically actuable pilot valve
46
which comprises an armature
58
fixably connected to a pilot valve stem
54
. When an electromagnet
50
is in a currentless state, the pilot valve stem
54
is pressed downward by the force of a compression spring
60
. The magnitude of this force is capable of being set by means of a spring tensioning element
62
. For actuating the pilot valve
46
or for raising the pilot valve stem
54
connected to the armature
58
, control pulses are supplied by the electronic control, via the electric connections
12
, to an exciting coil
52
of the electromagnet
50
, said exciting coil being assigned to the armature
58
.
The spring tensioning element
62
is accommodated in a closing-off part
64
which sealingly closes off the fuel injection valve
1
at its upper end. Installed, together with the electromagnet
50
, in the holding nut
17
is a fuel return connection
66
connected to a space
67
which surrounds the pilot valve
46
and is a so-called low-pressure zone in which fuel of low pressure flows.
The control device S
1
, then, is described with reference to
FIGS. 2 and 3
.
Pressed sealingly into the widened bore
42
in the upper housing part
14
b
is a control body
74
which lies with a flange
78
on a housing step surface
80
and which is fixed axially by means of a retaining nut
76
(FIG.
2
). Sealing off between the bore
42
and the control body
74
could, of course, also be implemented differently, and, instead of a press fit, for example, suitable sealing rings could assume the sealing-off function. The control body
74
has an outlet bore
75
tapering at the top into an outlet orifice
77
. The lower end face of the control body
74
is designated by
88
. A sleeve-shaped spacer part
70
is pressed with its upper annular end face
71
onto this lower end face
88
by means of a closing spring or nozzle needle spring
68
. The nozzle needle spring
68
is prestressed between a lower step surface
82
of the spacer part
70
(or a spacer disk
90
bearing on said step surface) and an upper step surface
84
of the nozzle needle collar
35
. The prestressing force of the nozzle needle spring
68
, which is to hold securely the nozzle needle
30
downwardly in the closing direction of the fuel injection valve
1
counter to the fuel high pressure exerted on the nozzle needle
30
, must be relatively high and may amount, for example, to 100 to 300 N. The prestressing force of a plurality of fuel injection valves of an internal combustion engine must coincide exactly, in order to ensure functional identity. The respective manufacturing tolerances can be compensated by means of the spacer disk or spacer disks
90
.
The injection valve member or the nozzle needle
30
has a first piston part
31
adjoining the collar
35
and a second piston part
33
stepped in diameter relative to said first piston part. The second piston part
33
has an upper end face
39
. The annular step surface between these two piston parts
31
,
33
is designated by
37
. As is evident, in particular, from
FIG. 3
, the first piston part
31
projects with some radial play R
1
into a lower part
70
a
of the spacer part
70
. The inner cylindrical guide surface of this part
70
a
for the piston part
31
is designated by
94
. The spacer part
70
has, furthermore, an upper part
70
b
of widened diameter. The step surface
82
already mentioned is present between the two parts
70
a
and
70
b
of the spacer part
70
. Arranged inside the spacer part
70
, at a distance from the step surface
82
, is an inner step surface
98
which connects the cylindrical guide surface
94
to a further cylindrical guide surface
95
of larger diameter. This step surface
98
is located above the step surface
37
present between the two piston parts
31
,
33
. The second piston part
33
is surrounded by a control sleeve
72
, the cylindrical outer surface
72
a
of which is assigned with some radial play R
2
to the guide surface
95
of the spacer part
70
(cf. FIG.
3
). This radial play R
2
may (in a similar way to the radial play R
1
between the first piston part
31
and the guide surface
94
) amount to approximately between 6 and 50 μm (micrometers). By contrast, a narrow sliding fit, that is to say a radial play R
0
of only 1 to 8 μm, is provided between the inner surface
72
i
of the control sleeve
72
and the outer surface of the second piston part
33
. Since the pressure is the same everywhere (both on the inside and on the outside of the control sleeve
72
and of the spacer part
70
), no pressure-induced deformations of the control sleeve
72
and of the spacer part
70
occur and the radial plays R
0
, R
1
, R
2
and also the gap S remain the same, irrespective of the pressure level.
In an alternative embodiment, not shown, of the control device S
1
, the radial plays R
1
and R
2
, which extend over the respective length of the parts, are replaced by one or more ribs with some radial play. These ribs could be attached either to the respective insides of the spacer part
70
or to the outer cylindrical surface
72
a
of the control sleeve
72
and to the outer cylindrical surface of the first piston part
31
. The flow caused by the ribs is independent of the fuel viscosity (that is to say, of its temperature), which is not the case where elongated radial plays are concerned. The independence of the flow from the viscosity may signify a functional benefit. (The radial plays R
1
and R
2
could also be implemented in the same way in the control devices S
2
and S
3
described further below.)
The axial length of the control sleeve
72
is smaller by a small amount S, which amounts, for example, to 5 to 40 μm, than the distance between the inner step surface
98
of the spacer part
70
and its upper annular end face
71
.
FIG. 3
shows the control sleeve
72
in a position in which the lower end face
72
u
of the control sleeve
72
lies on the inner step surface
98
and a gap S is thereby formed between the upper end face
72
o
of the control sleeve and the lower end face
88
of the control body
74
(in
FIG. 3
, the gap S is illustrated as exaggeratedly large; in reality, this gap S is about ten times smaller than the nozzle needle stroke). At the same time, the lower end face
72
u
closes off from above a space
106
which is radially delimited by the second piston part
33
, on the one hand, and by the guide surface
94
of the spacer part
70
, on the other hand, and which is axially delimited downwardly by the step surface
37
between the two piston parts
31
,
33
.
The spacer part
70
has a passage
100
at its upper end. As is clear from
FIG. 3
, the upper end face
72
o
of the control sleeve
72
is provided with a radial depression
102
(or a plurality of radial depressions). The passage
100
and the depression
102
connect the space enclosed by the housing bore
42
, that is to say the high-pressure zone connected to the fuel high-pressure connection
10
via the passage bore
44
, to a control space
110
arranged above the second piston part
33
. This control space
110
, radially delimited in the lower region by the guide surface
95
of the spacer part
70
and in the upper region by the outlet bore
75
and the outlet orifice
77
, can be kept closed or opened at the top by means of the pilot valve stem
54
. The flat seat part of the pilot valve stem
54
, by means of which the outlet orifice
77
can be closed, is designated by
56
in
FIGS. 1
to
3
.
FIGS. 1
to
3
show the fuel injection valve
1
in a position prior to the injection operation. The same high pressure prevails in the control space
110
, closed by the flat seat part
56
of the pilot valve stem
54
, as in the high-pressure zone, that is to say as in the space which is enclosed by the housing bores
42
,
40
and by the bore
32
and which extends via the annular space
38
as far as the nozzle needle seat
26
and surrounds the nozzle needle
30
and, in the upper region, the spacer part
70
. The space
106
delimited by the step surface
37
, on the one hand, and by the lower end face
72
u
of the control sleeve
72
is also connected to the high-pressure zone via the radial gap R
1
between the first piston part
31
and the guide surface
94
. The control sleeve
72
is in neutral equilibrium, in which all the hydraulic forces are compensated. The control space
110
is connected to the high-pressure zone via the gap S between the lower end face
88
of the control body
74
and the upper end face
72
o
of the control sleeve
72
and via the depression
102
. In this position, it is the nozzle needle spring
68
which holds the nozzle needle
30
in its lower closing position, while the pressure force, which, with the nozzle needle
30
open, acts below the nozzle needle seat
26
in the opening direction of the nozzle needle
30
, is absent.
As soon as a pulse of selected duration is imparted to the electromagnet
50
via the electronic control, the armature
58
is pulled up counter to the force of the compression spring
60
and consequently the pilot valve stem
54
of the pilot valve
46
is raised. The flat seat part
56
of the pilot valve stem
54
releases the outlet orifice
77
of the control body
74
. The pressure in the control space
110
falls somewhat. The hydraulic equilibrium with regard to the control sleeve
72
is thereby disturbed, and a hydraulic force acts on the control sleeve
72
in the direction of the control body
74
, so that said control sleeve is moved toward the lower end face
88
of the latter. At the same time, the lower end face
72
u
of the control sleeve
72
is lifted away from the step surface
98
and the gap S is formed at this point, a small fuel quantity being supplied, via the gaps R
1
and R
2
, to the space
106
which is slightly enlarged because of the control sleeve
72
being moved upward. The control space
110
is still connected to the high-pressure zone only via the depression
102
, with the result that the pressure in the control space
110
falls more sharply. The injection operation commences. While the nozzle needle
30
is executing the opening movement, fuel is displaced continuously in the control space
110
via the outlet orifice
77
and in the space
106
via the gaps R
1
and R
2
. A particular overpressure with respect to the high-pressure zone prevails in the space
106
and, via the surface
72
u
, presses the control sleeve
72
onto the lower end face
88
of the control body
74
.
In order to terminate the injection operation, the pilot valve
46
is moved into its closing position via the electromagnet
50
, once again by electronic control. Since the outlet orifice
77
is then closed again, fuel replenishment via the depression
102
acting as an inlet throttle causes the pressure in the control space
110
to rise quickly, said pressure acting on the upper end face
39
of the second piston part
33
. The nozzle needle spring
68
moves the nozzle needle
30
downward in a closing direction, with the result that an underpressure, as compared with the remaining high-pressure zone, is then generated in the space
106
becoming larger, the consequence of this being that the control sleeve
72
undergoes a hydraulic force away from the lower end face
88
of the control body
74
and releases the gap S again at the top. This produces a rapid pressure rise in the control space
110
due to the fuel which flows via the passage
100
and the gap S, present once again, and also the depression
102
into the control space
110
and which allows a substantially quicker termination of the injection operation than if the filling of the control space
110
were to take place solely via the depression
102
.
Since, even before the commencement of the injection operation, the control sleeve
72
closes the direct connection of the control space
110
to the high-pressure zone via the gap S, the fuel control stream flowing out through the outlet orifice
77
into the low-pressure space
67
and into the fuel return connection
66
is appreciably reduced in an advantageous way. This takes place merely via the depression
102
, which may almost be as small as desired, since its function is merely, during the closing of the outlet orifice
77
, to bring about the initial pressure buildup in the control space
110
so as to restore the gap S at the top on the control-body side. In principle, instead of a precision-manufactured upper end face
72
o
provided with a depression
102
, an end face which is less precise (or relatively approximate and therefore less complicated to manufacture) and has some leakages could be used, in which case the leakages would assume the inlet throttle function of the depression
102
.
The gap S can be manufactured accurately by simple means. As already mentioned, the gap S is defined by the difference in length of the control sleeve
72
and of the distance between the step surface
98
of the spacer part
70
and its end face
71
. That is to say, this gap S is set prior to assembly and, in the assembled fuel injection valve
1
, is maintained exactly, and independently of the high-pressure level, since the planar lower end face
88
of the control body
74
is common to the spacer part
70
and to the control sleeve
72
and the pressure conditions before and after the injection are compensated, with the result that no pressure-induced deformations, dependent on the high-pressure level, of these control elements occur. In other words, the gap S is preserved, even after assembly, without any readjustment.
It would also be possible, however, for the lower end face
88
of the control body
74
, on which end face the spacer part
70
bears with its end face
71
, to be provided with a depression, and for the travel S for the longitudinal adjustment of the control sleeve
72
to be defined by the difference between the control sleeve length and the distance between the step surface
98
and the base surface of the depression. In such a variant, not illustrated in the drawing, for example, the control sleeve
72
could then be of exactly the same length as the distance between the step surface
98
and the end face
71
of the spacer part
70
.
In the control device S
1
according to the invention, the control sleeve
72
and the spacer element
70
are not axially centered exactly, that is to say not fixed radially in the central housing bore
42
, but, instead, are movable transversely to the longitudinal axis A of the housing
14
. Some radial offset of the control piston
31
,
33
relative to the nozzle needle seat
26
for the injection valve member or the nozzle needle
30
is thereby possible, without at the same time lateral forces being exerted on the nozzle needle
30
, which could lead to the distortion of the latter, to the generation of severe frictional forces or to jamming and could impair the functioning of the fuel injection valve. The nozzle needle
30
can be adapted to the radial offset and is free of lateral forces.
Moreover, only a single accurate fit is necessary: that between the outer surface of the second piston part
33
and the inner surface
72
i
of the control sleeve
72
(designated by R
0
in FIG.
3
). However, even this accurate fit needs to be less exact than those according to EP-B-0 686 763, since, as already mentioned, no pressure-induced deformations, dependent on the pressure level, of the elements of the control device S
1
occur. All other fits may even be wider, thus entailing an additional advantage in manufacturing terms. The housing
14
of the fuel injection valve
1
according to the invention does not have to b e provided anywhere with an exact guide, at which friction and consequently wear would also occur, that is to say the housing
14
does not have to be hardened.
A further essential advantage of the fuel injection valve
1
according to the invention is that the high-pressure zone, that is to say the space and the passage bore
44
concentrically surrounding the nozzle needle
30
from the nozzle needle seat
26
via the annular space
38
and the housing bores
40
,
42
, and the control space
110
as far as the outlet orifice
77
, also forms a completely leaktight region without any leakage points.
The housing
14
of the fuel injection valve according to the invention can have a very slender design, this being advantageous for the installation of the fuel injection valve into the cylinder head of the internal combustion engine.
FIG. 4
shows a second exemplary embodiment of a fuel injection valve
2
. The parts which are already known from
FIGS. 1
to
3
and remain the same are designated by the same reference numerals in FIG.
4
. In contrast to the fuel injection valve
1
according to
FIGS. 1
to
3
, t he housing
120
of the fuel injection valve
2
consists of two mutually assembled parts
122
,
124
. The first part
122
, out of which, at its lower end, a nozzle tip
121
provided with the nozzle needle seat
26
and with a plurality of injection orifices
28
projects once again, is designed as a long slender tubular piece which projects with its upper part into the second housing part
124
and is connected to the latter, as described in more detail further below. The nozzle tip
121
is pressed from below, with a press fit
123
, into the housing bore
126
of the housing part
122
and is positioned axially by means of a step surface
125
. In comparison with the fuel injection valve
1
, the union nut
16
, the centering pin or centering pins
24
and the sealing surface
20
are dispensed with.
Screwed into the second housing part
124
is the fuel high-pressure connection
10
which is connected to the housing bore
126
via a bore
127
of an annular intermediate piece
128
and a short radial bore
129
in the first housing part
122
. The intermediate piece
128
is provided on each of its end faces with a spherical sealing surface
131
. Other embodiments of the intermediate piece
128
would also be perfectly conceivable, for example with conical sealing surfaces. The intermediate piece
128
could also be omitted per se and, in this case, a prolonged fuel high-pressure connection
10
be sealingly connected directly to the tubular housing part
122
.
Both in the embodiment illustrated and in the possible embodiments mentioned above, the upper second housing part
124
does not undergo any stresses caused by the fuel high pressure. This means that the upper second housing part
124
may consist of lower-grade material than the tubular first part
122
enclosing the high-pressure zone. This affords several possibilities for material combination and for the type of connection of the two housing parts
122
,
124
. For example, the second housing part
124
, consisting of a more cost-effective metal, may be shrunk onto the first housing part
122
. However, the second housing part
124
may also consist, for example, of aluminum and be connected to the first housing part
122
in an injection molding method. A second housing part
124
consisting of plastic may also be connected to the first housing part
122
by means of injection molding.
The second housing part
124
is provided in its lower region with two surfaces
130
running parallel and in the axial direction and with two step surfaces
132
, via which the fuel injection valve
2
is fastened by means of a clamping fork into the cylinder head of the internal combustion engine in a way known per se.
In the fuel injection valve
2
, the electromagnetic
50
for actuating the pilot valve
46
is not connected to the valve housing by means of a holding nut, as in the fuel injection valve
1
, but is firmly embedded in a magnetic body
136
and, together with the latter, is screwed by means of screws
138
to the second housing part
124
having corresponding threaded holes
139
. The magnetic body
136
may, again, be made, for example, from plastic and be connected to the electromagnet
50
by the injection molding method. In the exemplary embodiment illustrated, three threaded holes
139
arranged in a triangle are provided for screws
138
, one of which can be seen in FIG.
4
and is located on the side of the valve longitudinal axis A other than the fuel high-pressure connection
10
. The latter is arranged between the other two threaded holes
139
which cannot be seen in FIG.
4
. In this embodiment, the second housing part
124
and the magnetic body
136
, in its external shape, may taper triangularly in the direction of the threaded hole
139
evident from FIG.
4
and lying in the sectional plane of FIG.
4
. Such an external shape is particularly favorable for installation into the internal combustion engine. However, for example, four threaded holes and connecting screws arranged in a square could also be provided.
A control device S
2
is arranged in the upper region of the tubular first housing part
122
. This control device S
2
corresponds in functioning to the control device S
1
described with reference to
FIGS. 1
to
3
. Above all, the deviations of this control device S
2
in terms of configuration are therefore described below with reference to FIG.
5
. The parts remaining the same are designated by the same reference numerals as in
FIGS. 1
to
3
.
Once again, sleeve-shaped spacer part
140
is arranged in the housing bore
126
with radial play and is pressed continuously with its upper end face
141
onto the lower end face
88
of the control body
74
by the relatively strong nozzle needle spring
68
. In contrast to the control device Si, the nozzle needle spring
68
is prestressed between an inner step surface
143
of the spacer part
140
and a spring holding piece
146
placed onto a conical part
144
of the nozzle needle
30
. The step surface of the holding piece
146
, provided to support the nozzle needle spring
68
, is designated by
145
. The spring holding piece
146
has a conical inner surface
147
. Between the conical inner surface
147
and the conical part
144
of the nozzle needle
30
is arranged a conical ring
148
which, in order to be placed onto the nozzle needle part
144
, is either slotted or consists of two separate half rings. The conicity of the nozzle needle part
144
, of the ring
148
and of the inner surface
147
of the spring holding piece
146
is preferably selected such that, after assembly, these parts remain clamped together.
The spacer part
140
is, again, provided with the guide surface
94
for the first piston part
31
and the guide surface
95
of widened diameter for a control sleeve
142
, said guide surfaces being connected to one another by the step surface
98
. In the exemplary embodiment illustrated in
FIG. 5
, the entire upper end face
142
o
of the control sleeve
142
is of planar configuration (in exactly the same way as the end face
72
o
of the control sleeve
72
according to FIGS.
2
and
3
). In exactly the same way as the control device S
1
, the control sleeve
142
is shorter by the amount S than the distance between the step surface
98
and the upper end face
141
of the spacer part
140
.
The spacer part
140
is additionally provided with an inner recess
155
adjoining the step surface
98
. Prestressed between a step surface
156
of the recess
155
and the lower end face
142
u
of the control sleeve
142
is a compression spring
158
which, in comparison with the nozzle needle spring
68
, is substantially weaker and the pressure action of which is also negligible, as compared with the fuel pressure forces. The recess
155
delimits a space
160
corresponding to the space
106
according to previous variants.
In contrast to the control device variant S
1
described above, in this version the control sleeve
142
is pressed onto the lower end face
88
of the control body
74
as early as in the initial position, that is to say prior to the injection operation. This means that, from the outset, the control space
110
is connected to the high-pressure zone via the small throttle bore
150
only, thus resulting in an immediate rapid fall of the pressure in the control space
110
during the rising of the flat seat part
56
of the pilot valve stem. During the operation of closing the fuel injection valve
2
, during which the flat seat part
56
of the pilot valve stem is again moved into its closing position and the pressure in the control space
110
rises again, the control sleeve
142
, assisted at the same time by the compression spring
158
, remains initially pressed onto the control body
74
. The nozzle needle
30
is moved downward by the force acting on the second piston part
33
from above, the fuel pressure falling instantaneously in the space
160
becoming larger. During the defined fall of this pressure, the control sleeve
142
follows the piston movement. As soon as the control sleeve
142
is lifted off from the lower end face
88
of the control body
74
, fuel abruptly passes from the passage
100
into the control space
110
via this new connection, and the piston part
33
is accelerated downward and also the control sleeve
142
is moved downward, until it lies on the step surface
98
and the initial gap S is canceled there. In this variant, the gap S may be larger than in the control device S
1
according to
FIGS. 2 and 3
.
The second piston part
33
, again guided with an accurate sliding fit (radial play R
0
of 1 to 8 μm) in the control sleeve
142
, has a conically tapering part
33
a
at its upper end. In a region surrounding this piston part
33
a
, the control sleeve
142
is equipped with a small radial throttle bore
150
which connects an annular space
149
in the spacer part
140
to the control space
110
. The annular space
149
is connected via a radially arranged large throttle bore
151
to the high-pressure zone surrounding the spacer part
140
. In this exemplary embodiment, the small throttle bore
150
assumes the function of the end-face depression
102
according to
FIGS. 2 and 3
, and the large throttle bore
151
assumes the function of the passage
100
. Too rapid a closing of the injection orifices
28
can be prevented by means of the large throttle bore
151
. The acceleration of the control piston during the closing operation is slightly damped, and the impact of the nozzle needle
30
on the nozzle needle seat
26
at the end of the closing operation is thereby reduced.
FIG. 6
shows a variant, designated by S
3
, of the control device S
2
according to
FIG. 5
or of the control device S
1
according to
FIGS. 1
to
3
, in which the control sleeve
142
known from
FIG. 5
, and having the small throttle bore
150
, is combined with a spacer part
154
which again has the passage
100
known from
FIGS. 2 and 3
. in this variant, the injection valve member or the nozzle needle
30
has an extremely simple shape with a uniform diameter as far as and together with the piston part
33
. The nozzle needle
30
is again slidably guided in the control sleeve
142
narrowly with the radial play R
0
and in the spacer part
154
with the greater radial play R
1
.
The spacer part
154
is again pressed continuously onto the lower end face
88
of the control body
74
by the nozzle needle spring
68
prestressed between the step surfaces
143
,
145
of the spacer part
154
and of a spring holding piece
157
. A slotted spring ring
162
engaging into an annular groove
159
of the nozzle needle
30
is inserted from below into the spring holding piece
157
.
In contrast to the version according to
FIGS. 2
,
3
and
5
, in this exemplary embodiment the end face of the control sleeve
142
is provided with an inner and with an outer bevel, so that only a narrow annular sealing surface
142
d
is located opposite the lower control body end face
88
. This design is conducive to the closing operation and takes account of the fact that, in this variant, there is no stepping of the control piston and no space
106
, as in the control devices S
1
or S
2
. Here, too, during the closing of the outlet orifice
77
the control sleeve
142
undergoes a hydraulic force away from the lower end face
88
of the control body
74
and releases the gap S at the top, with the result that a rapid pressure rise in the control space
110
and a quick termination of the injection operation take place.
The control sleeve
142
could also be configured in an identical or similar way to the valve body
26
a
according to
FIG. 3
of EP-B-0 675 281 for the same purpose (assisting the closing operation).
A further embodiment of a control device S
4
is illustrated in FIG.
7
. In this variant, a control sleeve
164
is pressed directly and continuously onto the lower end face
88
of the control body
74
by the nozzle needle spring
68
. In other words, the control sleeve
164
remains stationary under the action of the nozzle needle spring
68
. There is no spacer part, as in the control devices S
1
, S
2
and S
3
described above. The control sleeve
164
has a radially arranged throttle bore
165
which connects the control space
110
to the high-pressure zone surrounding the control sleeve
164
. In this variant, which is extremely simple in configuration terms, it is the pressure in the control space
110
alone which controls the nozzle needle movement. This control space is defined exactly by the throttle bore
165
and the outlet orifice
77
. The throttle bore
165
is of larger dimensioning, as compared with the throttle bore
150
according to
FIGS. 5 and 6
. Here, of course, instead of the throttle bore
165
, an end-face depression (or plurality of depressions) could also form the inlet throttle connection of the high-pressure zone to the control space
110
.
In this embodiment, too, the nozzle needle
30
has an extremely simple shape (no stepping of the control piston). Advantageously, here too, the spring holding piece
157
known from
FIG. 6
, together with the spring ring
162
engaging into an annular groove
159
of the nozzle needle
30
, is used for supporting or prestressing the nozzle needle spring
68
. A spacer disk
90
, similar to that in
FIG. 2
, could also be used here to achieve the same prestressing force of a plurality of fuel injection valves.
The lower housing part
122
of the fuel injection valve
2
according to
FIG. 4
has a constant diameter virtually of the entire length and can be manufactured cost-effectively from a long tubular pressure piece withstanding the high fuel high-pressure stresses.
In the two embodiments of the fuel injection valve
1
,
2
, the injection valve member or the nozzle needle
30
can be installed from above into the tubular housing
14
or
120
. Instead of a one-piece design of injection valve member/control piston, the two parts could be connected to one another nonpositively or positively.
Fuel injection valves equipped with control devices S
2
, S
3
or S
4
according to
FIGS. 5
,
6
or
7
have the same advantages, already mentioned, as the fuel injection valve
1
according to
FIGS. 1
to
3
provided with the control device S
1
(simple and cost-effective configuration, possibility of an advantageous slender external shape, reduction in the fuel control stream flowing out into the fuel return connection
66
, high-pressure zone without leakages, but, above all, elimination of disadvantages or risks present in the case of previous fuel injection valves and resulting from a possible radial offset of the control piston relative to the seat for the injection valve member). Of course, one of the control devices S
2
to S
4
could be used in the fuel injection valve
1
or else, conversely, the fuel injection valve
2
could be equipped with the control device S
1
. In all the versions, tolerances for individual parts in terms of both manufacture and assembly can be adhered to without difficulty, with the result that not only satisfactory functioning, but also functional identity in all the valves of an internal combustion engine are ensured.
In all the exemplary embodiments described above, the respective control device S
1
, S
2
, S
3
or S
4
was accommodated on that end of the fuel injection valve
1
,
2
which faces away from the nozzle body provided with a nozzle tip
22
,
121
. There is, however, also the possibility of integrating the control device S
1
, S
2
, S
3
or S
4
very near to the nozzle body or even in the latter, with the result that the injection valve member can have a very short configuration. A small actuator for the flat seat part
56
of the pilot valve stem is necessary for this embodiment which is not illustrated in the drawing. A suitable actuator is a small electromagnet or a piezoelectric element which may be accommodated within the slender housing part
14
a
or
120
. This dispenses with the thicker housing part
14
b
or
124
. However, the region in which the actuator is located must lie outside the high-pressure zone. Furthermore, the hydraulic force from the outlet orifice
77
onto the flat seat part
56
must be kept as low as possible, so that a small low-power actuator can be used. This condition is fulfilled particularly effectively in the control devices S
1
, S
2
and S
3
.
Claims
- 1. A fuel injection valve for intermittent injection of fuel into a combustion space of an internal combustion engine, said fuel injection valve comprising a housing, a valve seat element provided with injection orifices, an injection valve member for closing or opening the injection orifices, said injection valve member being installed longitudinally adjustably in the housing, and a control device for controlling an adjustment movement of the injection valve member, said control device comprising a control piston which is operatively connected to the injection valve member and which is loaded, on the one hand, by a fuel system pressure prevailing in a high-pressure zone connected to a fuel high-pressure connection and, on the other hand, by a fuel control pressure in a control space which is arranged in a longitudinal direction of the fuel injection valve between an end face of the control piston and a control body fixed to the housing and which is at least temporarily delimited radially, at least from commencement of an injection operation until commencement of a closing movement of the injection valve member, by a control sleeve having an inner guide surface which forms with the control piston a narrow sliding fit, the control pressure in the control space being capable of being controlled by an opening or closing of at least one outlet orifice in the control body by a controllable pilot valve, wherein the high-pressure zone includes a central bore which runs in a direction of a longitudinal axis of the housing and in which the injection valve member runs and which is connected, on the one hand, to the fuel high-pressure connection and, on the other hand, to a seat for the injection valve member, said seat being provided with the injection orifices, and which is closed off sealingly by the control body fixed to the housing, wherein the control piston and the injection valve member are in takeup connection to one another and wherein the control sleeve is capable of being moved transversely to the longitudinal axis of the housing and allows a radial offset of the control piston relative to the seat for the injection valve member, wherein the control sleeve is guided displaceably in a coaxial spacer part, which bears on the control body and through which passes a passage issuing into the high-pressure zone, and, in order to make a direct connection of the control body to the high-pressure zone, is longitudinally adjustable relative to said control space by the amount of a travel, the injection valve member being urged into a closing position by a closing spring which, at one end, is supported fixedly relative to the housing and, at the other end, engages on the injection valve member.
- 2. The fuel injection valve as claimed in claim 1, wherein a radial bore in the housing connects the central bore of the housing to the fuel high-pressure connection and forms a high-pressure supply line.
- 3. The fuel injection valve as claimed in claim 1, wherein the control space is connected to the high-pressure zone via a throttle connection.
- 4. The fuel injection valve as claimed in claim 3, defined by a stationary control sleeve which is pressed continuously onto the control body by a closing spring and which encloses the control space and is provided with a passage which forms a throttle connection and which connects the control space to the space formed between the circumference of the control sleeve and the wall of the central housing bore and belonging to the high-pressure zone, the closing spring, at one end, being supported on the control sleeve and, at the other end, engaging on the injection valve member, preferably on a step surface assigned to the injection valve member.
- 5. The fuel injection valve as claimed in claim 1, wherein the closing spring is supported, at one end, on the spacer part and thereby presses the spacer part onto the control body fixed to the housing.
- 6. The fuel injection valve as claimed in claim 1, wherein the control sleeve is capable of being adjusted longitudinally between an inner step surface of the spacer part and a lower end face of the control body, on which end face the spacer part bears with an upper end face thereof, the travel for the longitudinal adjustment of the control sleeve being defined by the difference between the length of the control sleeve and the distance between the step surface and the end face of the spacer part and is about 10 times smaller than the opening or closing stroke of the injection valve member.
- 7. The fuel injection valve as claimed in claim 1, wherein the control sleeve is capable of being adjusted longitudinally between an inner step surface of the spacer part and a depression in the lower end face of the control body, on which end face the spacer part bears with an upper end face, the travel for the longitudinal adjustment of the control sleeve being defined by a difference between a length of the control sleeve and a distance between the step surface and a base surface of the depression.
- 8. The fuel injection valve as claimed in claim 1, wherein, with the injection valve member in the closing position between two injection operations, the control sleeve is in a state of equilibrium, in which hydraulic forces acting from the fuel system pressure on the control sleeve are compensated and no further forces act on the control sleeve.
- 9. The fuel injection valve as claimed in claim 1, wherein there is formed, between a side of the control sleeve which faces away from the control body and an annular step surface of the control piston, a space which is delimited radially by the wall of the spacer part and the control piston and a volume of which is varied, at least shortly before and during the operation of opening and closing the injection valve member, as a result of the longitudinal adjustment of the control sleeve relative to the control body, said adjustment being caused during the opening of the at least one outlet orifice, with the result that the pressure in the space is likewise varied in relation to the remaining high-pressure zone, so that the control sleeve is assisted in a function of closing the travel shortly before and during the opening operation and of opening said travel again during the closing operation.
- 10. The fuel injection valve as claimed in claim 9, wherein the control piston has two piston parts of different diameter, between which the annular step surface is arranged, the control sleeve being guided with a narrow sliding fit on the piston part having the smaller diameter, and the spacer part being guided with an inner surface thereof on the piston part having a larger diameter, with a first radial play, and, with a part thereof of widened diameter, surrounding the control sleeve with a second radial play, the space between the piston part of smaller diameter and the inner surface being formed for the other piston part.
- 11. The fuel injection valve as claimed in claim 1, wherein the control piston has an essentially constant diameter, and the control sleeve is controlled by hydraulic forces alone which act on an annular surface facing the control body.
- 12. The fuel injection valve as claimed in claim 1, wherein the control sleeve radially delimits the control space in each case only from commencement of each injection operation until commencement of the movement of closing the injection valve member.
- 13. The fuel injection valve as claimed in claim 1, defined by a compression spring pressing the control sleeve onto the control body before and during the injection operation and at commencement of the closing operation.
- 14. The fuel injection valve as claimed in claim 1, wherein the injection valve member and the control piston are produced in one piece or are connected nonpositively or positively to one another.
- 15. The fuel injection valve as claimed in claim 14, defined by a stationary control sleeve which is pressed continuously onto the control body by a closing spring and which encloses the control space and is provided with a passage which forms a throttle connection and which connects the control space to the space formed between the circumference of the control sleeve and the wall of the central housing bore and belonging to the high-pressure zone, the closing spring, at one end, being supported on the control sleeve and, at the other end, engaging on the injection valve member, preferably on a step surface assigned to the injection valve member.
- 16. The fuel injection valve as claimed in claim 1, wherein a radial play of the narrow sliding fit between the inner guide surface of the control sleeve and the control piston part guided therein is 1 to 8 mm.
- 17. A fuel injection valve for intermittent injection of fuel into a combustion space of an internal combustion engine, said fuel injection valve comprising a housing, a valve seat element provided with injection orifices, an injection valve member for closing or opening the injection orifices, said injection valve member being installed longitudinally adjustably in the housing, and a control device for controlling an adjustment movement of the injection valve member, said control device comprising a control piston which is operatively connected to the injection valve member and which is loaded, on the one hand, by a fuel system pressure prevailing in a high-pressure zone connected to a fuel high-pressure connection and, on the other hand, by a fuel control pressure in a control space which is arranged in a longitudinal direction of the fuel injection valve between an end face of the control piston and a control body fixed to the housing and which is at least temporarily delimited radially, at least from commencement of an injection operation until commencement of a closing movement of the injection valve member, by a control sleeve having an inner guide surface which forms with the control piston a narrow sliding fit, the control pressure in the control space being capable of being controlled by an opening or closing of at least one outlet orifice in the control body by a controllable pilot valve, wherein the high-pressure zone includes a central bore which runs in a direction of a longitudinal axis of the housing and in which the injection valve member runs and which is connected, on the one hand, to the fuel high-pressure connection and, on the other hand, to a seat for the injection valve member, said seat being provided with the injection orifices, and which is closed off sealingly by the control body fixed to the housing, wherein the control piston and the injection valve member are in takeup connection to one another and wherein the control sleeve is capable of being moved transversely to the longitudinal axis of the housing and allows a radial offset of the control piston relative to the seat for the injection valve member,wherein the control space is connected to the high-pressure zone via a throttle connection, and wherein a passage provided in the spacer part, together with a throttle connection provided in the control sleeve, connect the control space to a space present between the circumference of the spacer part and the central housing bore and belonging to the high-pressure zone.
- 18. A fuel injection valve for intermittent injection of fuel into a combustion space of an internal combustion engine, said fuel injection valve comprising a housing, a valve seat element provided with injection orifices, an injection valve member for closing or opening the injection orifices, said injection valve member being installed longitudinally adjustably in the housing, and a control device for controlling an adjustment movement of the injection valve member, said control device comprising a control piston which is operatively connected to the injection valve member and which is loaded, on the one hand, by a fuel system pressure prevailing in a high-pressure zone connected to a fuel high-pressure connection and, on the other hand, by a fuel control pressure in a control space which is arranged in a longitudinal direction of the fuel injection valve between an end face of the control piston and a control body fixed to the housing and which is at least temporarily delimited radially, at least from commencement of an injection operation until commencement of a closing movement of the injection valve member, by a control sleeve having an inner guide surface which forms with the control piston a narrow sliding fit, the control pressure in the control space being capable of being controlled by an opening or closing of at least one outlet orifice in the control body by a controllable pilot valve, wherein the high-pressure zone includes a central bore which runs in a direction of a longitudinal axis of the housing and in which the injection valve member runs and which is connected, on the one hand, to the fuel high-pressure connection and, on the other hand, to a seat for the injection valve member, said seat being provided with the injection orifices, and which is closed off sealingly by the control body fixed to the housing, wherein the control piston and the injection valve member are in takeup connection to one another and wherein the control sleeve is capable of being moved transversely to the longitudinal axis of the housing and allows a radial offset of the control piston relative to the seat for the injection valve member,wherein a radial bore in the housing connects the central bore of the housing to the fuel high-pressure connection and forms a high-pressure supply line, and wherein the valve housing is produced in two pieces and has a first tubular housing part which projects into a second upper housing part and is connected to the second upper housing part, a radial bore which issues into the central bore being arranged in the tubular housing part and being connected to the fuel high-pressure connection.
- 19. A fuel injection valve for the intermittent injection of fuel into the combustion space of an internal combustion engine, said fuel injection valve comprising a housing, a valve seat element provided with injection orifices, an injection valve member for closing or opening the injection orifices, said injection valve member being installed longitudinally adjustably in the housing, and a control device for controlling adjustment movement of the injection valve member, said control device comprising a control piston which is operatively connected to the injection valve member and which is loaded, on the one hand, by the fuel system pressure prevailing in a high-pressure zone connected to a fuel high-pressure connection and, on the other hand, by the fuel control pressure in a control space which is arranged in the longitudinal direction of the fuel injection valve between an end face of the control piston and a control body fixed to the housing and is at least temporarily delimited radially, at least from commencement of the injection operation until commencement of the closing movement of the injection valve member, by a control sleeve, the inner guide surface of which forms with the control piston a narrow sliding fit, the control pressure in the control space being capable of being controlled by the opening or closing of at least one outlet orifice in the control body by a controllable pilot valve, wherein the control sleeve is guided displaceably in a coaxial spacer part, which bears on the control body and through which passes a passage issuing into the high-pressure zone, and, in order to make a direct connection of the control space to the high-pressure zone, is capable of being adjusted longitudinally relative to said control body by the amount of a travel, the injection valve member being urged into a closing position by a closing spring which, at one end, is supported fixedly relative to the housing and, at the other end, engages on the injection valve member.
- 20. The fuel injection valve as claimed in claim 19, wherein the control device is arranged in the high-pressure zone, which is located around the longitudinal axis of the fuel injection valve, wherein in the high pressure zone fuel is guided to the control device as well as to the injection orifices, and wherein fuel is guided to the injection orifices coaxially around the longitudinal axis of the fuel injection valve.
- 21. A fuel injection valve for intermittent injection of fuel into a combustion space of an internal combustion engine, said fuel injection valve comprising a housing, a valve seat element provided with injection orifices, an injection valve member for closing or opening the injection orifices, said injection valve member being installed longitudinally adjustably in the housing, and a control device for controlling an adjustment movement of the injection valve member, said control device comprising a control piston which is operatively connected to the injection valve member and which is loaded, on the one hand, by a fuel system pressure prevailing in a high-pressure zone connected to a fuel high-pressure connection and, on the other hand, by a fuel control pressure in a control space which is arranged in a longitudinal direction of the fuel injection valve following an end face of the control piston turned towards a control body fixed to the housing and comprising an end face, a sleeve shaped spacer part pressed with an annular end face onto the end face of the control body by a closing spring urging the injection valve member into a closing position, the spacer part comprising an inner cylindrical guide surface for the control piston and a passage or large throttle bore issuing into the high-pressure zone, the passage or large throttle bore being large relative to a small throttle bore or depression connecting the control space and the high-pressure zone, the control pressure in the control space being capable of being controlled by an opening or closing of a least one outlet orifice in the control body by a controllable pilot valve, wherein the high pressure-zone includes a central bore which runs in a direction of longitudinal axis of the housing and in which the injection valve member runs and which is connected, on the one hand, to the fuel high-pressure connection and, on the other hand, to a seat for the injection valve member, said seat being provided with the injection orifices, and which is closed off sealingly by the control body.
- 22. The fuel injection valve as claimed in claim 21, further comprising a control sleeve which is guided displaceably in the spacer part, and, in order to make a direct connection of the control space to the high-pressure zone, is longitudinally adjustable relative to said control body by an amount of travel.
- 23. The fuel injection valve as claimed in claim 22, wherein the control sleeve is capable of being moved transversely to the longitudinal axis of the housing.
Priority Claims (1)
Number |
Date |
Country |
Kind |
0092/00 |
Jan 2000 |
CH |
|
US Referenced Citations (5)