Information
-
Patent Grant
-
6168096
-
Patent Number
6,168,096
-
Date Filed
Friday, December 17, 199925 years ago
-
Date Issued
Tuesday, January 2, 200124 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Kashnikow; Andres
- Kim; Christopher S.
Agents
- Greigg; Ronald E.
- Greigg; Edwin E.
-
CPC
-
US Classifications
Field of Search
US
- 239 5333
- 239 5334
- 239 5335
- 239 5338
- 239 533
- 239 9
- 239 5332
- 239 1922
- 239 96
- 239 88
-
International Classifications
-
Abstract
A fuel injection device for internal combustion engines which under the control of a control unit supplies fuel injection valves with fuel from a high-pressure fuel source. The fuel injection valve has an injection valve member, whose opening and closing position is determined by a pressure acting upon the injection valve member set in a control chamber. To perform an injection, the pressure in the control chamber must be relieved, which is accomplished with a control valve that opens two different outflow cross sections of an outflow conduit of the control chamber in succession. It is thus possible to accomplish an adapted opening of a fuel injection valve member for a preinjection and a main injection.
Description
BACKGROUND OF THE INVENTION
The invention is based on a fuel injection device for internal combustion engines. In one such fuel injection device, known from German Patent Disclosure DE 196 24 001 A1, the valve chamber in a first version communicates with the control chamber without any reduction in cross section. Upon actuation by the piezoelectric actuator, the control valve makes the outflow cross section to the outflow conduit either fully open or the central valve closes the outflow cross section. In another version, the valve chamber communicates with the control chamber via a connecting conduit, and the connecting conduit is coaxial with the valve seat on the side of the outflow conduit. By actuation of the control valve member by the piezoelectric actuator, either the outflow cross section from the valve chamber to the outflow conduit is fully opened or closed, or to attain a preinjection, the control valve member is moved away from the valve seat toward the outflow conduit to the entrance of the connecting conduit and to the valve chamber; as a consequence of this motion, the control chamber is briefly opened to the outflow conduit via the valve chamber. For an ensuing main injection, the control valve member is moved into a middle position, in which both the cross section toward the outflow conduit and the cross section of the connecting conduit into the valve chamber are fully opened. This embodiment has the disadvantage that to relieve the pressure in the control chamber, only a single, geometrically defined outflow cross section to the outflow conduit exists. The preinjection quantity in the second version described is such that the speed of adjustment of the control valve member by the piezoelectric actuator and the geometrically defined travel of the control valve member are predetermined variables for the degree of relief of the pressure in the control chamber. In particular, the maximum relief cross section is the same for both the relief for the preinjection and for the relief for the main injection, which is disadvantageous in view of any fine adaptation of the opening speed of the injection valve in various operating conditions.
OBJECT AND SUMMARY OF THE INVENTION
The fuel injection device according to the invention has an advantage that two different outflow cross sections can be established in succession, by making two different connection cross sections to the control chamber as a function of the position of the control valve member. It is thus possible to graduate the outflow cross section as a function of the stroke. Particularly for a slight relief of the control pressure in the control chamber, a first, smaller outflow cross section can come into effect, with which the preinjection stroke of the injection valve member can be set with greater precision. For the main injection, a large outflow cross section is subsequently available, which allows a fast motion of the injection valve member.
Advantageously, a cross section that is additional to the first connection cross section is provided as the second connection cross section. This makes it possible to attain a large effective change in cross section. The first connection cross section is located in a space-saving way in the intermediate valve member, where sufficiently large flow cross section is furnished on the outer circumference. The second connection cross section can be defined by the flow cross section at the interstices between the longitudinal ribs, which is determined by the stroke of the intermediate valve member, which uncovers a certain flow cross section between the sealing seat shoulder and the sealing face.
In a further feature crosswise connections that are always open are furnished between the connecting conduit of the valve member and the valve chamber, so that this connecting conduit is ready as an always-open first connection cross section, to which a further, second connection cross section is added when the intermediate valve member is opened.
It is also advantageous to close the connecting conduit in the intermediate valve member when the control valve member contacts the intermediate valve member; thus the cross section of the connecting conduit is furnished not in the intermediate valve member, but along the outer circumference of the intermediate valve member.
The invention will be better understood and further objects and advantages thereof will become more apparent from the ensuing detailed description of preferred embodiments taken in conjunction with the drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a schematic illustration of a fuel injection device with fuel supply from a high-pressure fuel reservoir, and with a fuel injection valve of known design;
FIG. 2
shows a first exemplary embodiment of the invention, with a control valve member that actuates a first embodiment of an intermediate valve member;
FIGS.
3
a
through
3
c
show the stroke courses of the injection valve member, control valve member and intermediate valve member of the exemplary embodiment of
FIG. 2
;
FIG. 4
shows a modification of the exemplary embodiment of
FIG. 2
, with an intermediate valve member whose connecting conduit can be closed by the control valve member; and
FIGS.
5
a
through
5
b
show the stroke courses of the injection valve member, control valve member and intermediate valve member of the exemplary embodiment of FIG.
4
.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A fuel injection device with which a wide variation of the fuel injection with regard to the injection quantity and the instant of injection is possible at high injection pressures and at little expense is achieved by a so-called common rail system. This makes a different kind of high-pressure fuel source available than exists with the usual high-pressure fuel injection pumps. However, the invention is also applicable in principle to conventional fuel injection pumps. Nevertheless, its use in a common rail injection system is especially advantageous.
In the common rail injection system shown in
FIG. 1
, a high-pressure fuel reservoir
1
is provided as the high-pressure fuel source, and it is supplied with fuel by a high-pressure fuel feed pump
2
by a fuel supply container
4
. The pressure in the high-pressure fuel reservoir
1
is detected by a pressure sensor
6
and delivered in the form of a signal to an electric control unit
8
, which via a pressure control valve
5
controls the pressure in the high-pressure fuel reservoir. Alternatively, the supply quantity of the high-pressure fuel pump can be varied in this way. The control unit also controls the opening and closing of high-pressure fuel injection valves
9
, which are supplied for injection with fuel from the high-pressure fuel reservoir.
In a known version, the fuel injection valve
9
has a valve housing
11
, which on one end, that is, the end intended for mounting in the engine, has injection ports
12
, whose outlet from the interior of the fuel injection valve is controlled by an injection valve member
14
. This valve member is embodied in the example being described as an elongated valve needle, which on one end has a conical sealing face
15
that cooperates with an inner valve seat on the valve housing, and from there the injection ports
12
lead away. The injection ports can also begin at a bore that adjoins the valve seat. The valve needle is guided in a longitudinal bore
13
by its upper end, remote from the sealing face
15
, and is urged in the closing direction on the end remote from the sealing face
15
and emerging from the longitudinal bore
13
by a compression spring
18
. Between where it is guided in the longitudinal bore
13
and the valve seat, the valve needle
14
is surrounded by an annular chamber
19
, which discharges into a pressure chamber
16
that in turn communicates constantly, via a pressure line
17
, with the high-pressure fuel reservoir
1
. In the region of this pressure chamber, the valve needle
14
has a pressure shoulder
20
, by which it is acted upon by the pressure in the pressure chamber
16
, counter to the force of the spring
18
, in the direction of lifting of the sealing face
15
from the valve seat.
The valve needle is also actuated by a tappet
21
, whose face end
22
, remote from the valve needle
14
, defines a control chamber
24
in a tappet guide bore
23
. This control chamber communicates constantly with the pressure line
17
, or the high-pressure fuel reservoir
1
, via an inflow conduit
26
in which an inflow throttle
28
is provided. The inflow conduit discharges from the side into the control chamber
24
and cannot be closed. Coaxially with the tappet
21
, a connecting conduit
29
leads away from the control chamber
24
and discharges into a valve chamber
30
of a control valve
31
. In the connecting conduit, which at the same time is an outflow conduit, a diameter limitation is provided, preferably in the form of an outflow throttle
32
. The detailed structure of the control valve
31
is shown more specifically in the exemplary embodiments of
FIGS. 2 and 3
. A common feature of these exemplary embodiments is that the control valve
31
includes a control valve member
34
, which comprises a valve tappet
35
, the valve tappet
35
is guided in a tappet bore
36
, and a valve head
37
, is located on an end of the control valve member
34
that protrudes into the valve chamber
30
. On the end of the valve tappet
35
opposite the valve head, a spring plate
38
is provided, a compression spring
39
is supported on the spring plate
38
that seeks to urge the control valve member into the closing position. In the opposite direction, the control valve member
34
is acted upon by a piston
40
, which is part of a piezoelectric actuator
41
and upon excitation of the piezoelectric element the control valve member is positioned in different opening positions depending on the degree of excitation of the piezoelectric element. The piston can either be joined directly to the piezoelectric element of the piezoelectric actuator, or it can be moved by this element, by means of a hydraulic or mechanical intensification.
For a more-detailed illustration of the embodiment of the control valve
31
according to the invention, the control valve will be described in further detail in conjunction with FIG.
2
. Once again, the end of the tappet
21
is shown, which actuates the valve needle
14
. The tappet
21
, with a face end
22
acting as a movable wall, encloses the control chamber
24
in the tappet guide bore
23
. The upward adjustment of the tappet
21
, in the opening direction of the injection valve member
14
, is limited by a stop
42
that leaves an outer annular chamber
43
open, into which the inflow conduit
26
discharges. The connecting conduit
29
leads axially away in the region of the stop
42
and discharges into the valve chamber
30
. This valve chamber has a circular- cylindrical circumferential wall
45
, which changes over at a conical valve seat
46
into an annular chamber
48
surrounding the valve tappet
35
. From this annular chamber, an outflow conduit
49
leads to a fuel return or to a relief chamber.
The valve head
37
disposed on the end of the valve tappet
35
has a conical valve head sealing face
51
, remote from the entrance of the connecting conduit
29
into the valve chamber
30
, and this sealing face cooperates with the valve seat
46
and thus controls the communication between the valve chamber
30
and the annular chamber
48
or the adjoining outflow conduit
49
. The annular chamber
48
is formed by a recess on the circumference of the valve tappet
35
, adjacent to the sealing face
51
of the valve head
37
, and this recess communicates with the tappet bore
36
leading away from the valve chamber
30
.
The side of the valve head toward the connecting conduit
29
has a flat face end
53
, which upon actuation of the valve tappet
35
comes into contact with a face end
54
of an intermediate valve member
57
, which forms an intermediate valve
56
, and upon further actuation of the valve tappet
35
, the intermediate valve member
57
is moved out of its closing position.
The intermediate valve member
57
has ribs
59
on its outer circumference, between which flow cross sections are formed and which are guided by their face ends in a guide bore
60
. Toward the valve chamber
30
, the guide bore
60
narrows via a sealing seat shoulder
62
, to form a connecting bore
63
that discharges into the valve chamber
30
coaxially with the guide bore. The sealing seat shoulder
62
thus acts as the valve seat of the intermediate valve member.
The part of the intermediate valve member
57
that has the ribs
59
tapers, adjoining the ribs, via a conical sealing face
64
to form a cylindrical actuating portion
65
, which protrudes through the connecting bore with a clearance from the connecting bore into the valve chamber
30
. On the opposite side, the intermediate valve member
57
is loaded by a closing spring
68
, which puts the intermediate valve member with its sealing face
64
into contact with the sealing seat shoulder
62
. The closing spring
68
is supported at the transition between the guide bore
60
and the portion
29
leading onward of the outflow conduit, which discharges into the control chamber
24
coaxially with the guide bore
60
.
Extending through the intermediate valve member
57
is an axial connecting conduit
69
, which also connects the valve chamber
30
with the control chamber
24
via the portion
29
of the outflow conduit, when the intermediate valve member
57
is in its closing position. The connecting conduit can be embodied as a stepped bore, of which one stepped bore portion
70
, located toward the control chamber
24
and having a smaller diameter, determines a first connection cross section. On the side of the valve chamber
30
in the region of the actuating portion
65
, at least one recess
71
leads away from the connecting conduit
69
, extending crosswise to it, in such a way that upon contact of the flat face end
53
of the valve head
37
with the face end
54
of the intermediate valve member
57
, the communication between the control chamber
24
and the control chamber
30
is preserved, and the portion
70
of the connecting conduit
69
continues to determine the connection cross section.
The mode of operation of the embodiment of
FIG. 2
is such that to trip a fuel injection with the aid of the control valve
31
, the pressure in the control chamber
24
is lowered by opening the outflow conduit
29
,
70
,
69
,
30
,
48
,
49
. With decoupling by the throttle
28
in the inflow conduit
26
, the pressure in the control chamber
24
drops in such a way that the valve member opens under the influence of the opening forces in the pressure chamber
16
, counter to the force of the spring
18
. The degree of opening of the injection valve member
14
can be varied by means of the magnitude of the control chamber, or the quantity of the pressure fluid or fuel flowing out there. If the control valve member
34
executes only a partial stroke, such that the face end
53
does not come into contact with the intermediate valve member
57
, then this determines the maximum flow through the portion
70
of the connecting conduit
69
. The relief rate and thus the stroke of the injection valve member
14
are correspondingly slight. Hence only a slight fuel injection quantity, for instance for introducing a preinjection quantity into the combustion chamber, is pumped. However, if a larger fuel quantity is meant to gain injection, then the control valve member
34
opens fully and comes into contact with the intermediate valve member
57
and lifts the valve member
57
from the sealing seat shoulder
62
via the actuating portion
65
and thus in addition to the first connection cross section makes a second connection cross section available, the latter being determined by the portion
70
. The second connection cross section can be determined either by the flow cross section between the sealing seat shoulder
62
and the sealing face
64
, or by the remaining flow area between the ribs
59
. By means of the now-added second connection cross section, the relief of the control chamber
24
is faster and greater in extent, so that the injection valve member
14
can be opened to the intended extent, for instance with a stroke determined by the contact of its end face
22
with the stop
42
.
The partial relief of the control chamber
24
for performing the preinjection has the advantage that upon closure of the control valve member
34
, the pressure can build up again very rapidly, since the pressure has not been reduced as much as it would otherwise be reduced.
The functional sequence described can be understood better from FIGS.
3
a
through
3
c
. FIG.
3
a
shows the stroke of the injection valve member
14
over time. The stroke of the injection valve member for the preinjection V and the stroke of the injection valve member for performing the main injection H can be seen. These strokes are interrupted by an injection pause P. In FIG.
3
b
, the stroke of the control valve member
34
required for the purpose is shown, represented by a short stroke V
s
and a long stroke H
s
. In FIG.
3
c
, finally, the stroke Z of the intermediate valve member over time is plotted, with the association with the stroke H
s
of the control valve member
34
and the stroke H for the main injection of the injection valve member
14
.
In
FIG. 4
, a second exemplary embodiment of the invention is shown, in a modification of the version of FIG.
2
. With an otherwise identical construction, the difference here is that the valve head
134
instead of the flat face end
53
now has a conical face end
73
, embodied as a sealing face, which cooperates with a face end, embodied as a valve seat
74
, of the intermediate valve member
157
. The valve seat
74
surrounds the axial connecting conduit
69
, provided in the intermediate valve member
57
of
FIG. 2
, in the region of its outlet at the actuating portion
65
into the valve chamber
30
. Instead of a leaf spring
68
provided in the exemplary embodiment of
FIG. 2
, a spiral spring
168
is now provided, which loads the intermediate valve member
157
from the side of the control chamber
24
and keeps the intermediate valve
157
with its sealing face
64
in contact with the sealing seat shoulder
62
, as long as the intermediate valve member
157
has not been displaced by the control valve member
134
. In this version, the portion
70
of the connecting conduit
69
again forms the first connection cross section between the control chamber
24
and the valve seat
62
, but the connection is closed whenever the control valve member
134
comes into contact with the intermediate valve member
157
by seating the on the conical valve head
137
on the conical valve seat
74
. Now, however, by lifting of the intermediate valve member
157
, the second connection cross section between the ribs
59
, or between the sealing seat shoulder
62
and the sealing face
64
, is opened. The second connection cross section is designed such that the second connection is correspondingly larger than the first connection cross section
70
of the portion of the connecting conduit
69
, taking into account the fact that here the flow cross section of the second connection cross section takes the place of the flow cross section of the first connection cross section. This design can be more favorable in an individual instance, to make it possible to define the second connection cross section more exactly.
In FIG.
5
a
, analogously to FIG.
3
a
, the stroke of the injection valve member
14
is plotted over time, again with the stroke V for the preinjection and the stroke H for the main injection. From FIG.
5
b
, it can be seen that in the present case the further advantage of the feature of
FIG. 4
is that the control valve member, to interrupt the fuel injection between the preinjection V and main injection H, does not have to be returned to its original closing position. As indicated by the curve course S, the control valve member
134
executes a strokes hV in the process comes into contact with the conical valve seat
74
of the intermediate valve member. Over the travel distance between the closing position of the control valve member
134
at its conical valve seat
46
and its contact with the conical valve seat
74
, the relief of the control chamber
24
takes place, determined by the first connection cross section of the portion
70
of the connecting conduit
69
, which leads to the preinjection. After that, with the closure of the connecting conduit
69
, the pressure in the control chamber
24
can build up again and can close the injection valve member. For the main injection, the control valve member
134
is moved onward up to the stroke h
h
, and in the process it opens the intermediate valve member as indicated by the stroke curve Z. With this opening of the intermediate valve, the relief of the control chamber
24
takes place at a higher relief rate, and accordingly the opening stroke of the injection valve member that is required for the main injection is made possible.
The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.
Claims
- 1. A fuel injection device for internal combustion engines comprising:a high-pressure fuel source (1); and a fuel injection valve (9) supplied with fuel from the high-pressure fuel source, said fuel injection valve comprising: a housing; at least one injection port (12); an injection valve member (14) for controlling said at least one injection port (12); an inflow conduit (26) connected with the high-pressure fuel source (1); a movable wall (22) which communicates at least indirectly with the injection valve member (14), the movable wall (22) connected with the inflow conduit (26); a control chamber (24) defined by the movable wall (22); a valve control chamber (30); a piezoelectric actuator (41); a control valve (31) having a control valve member (34), the control valve member (34) further comprising a valve tappet (35) and a valve head (37), the control valve member (34) actuated by the piezoelectric actuator (41), the tappet (35) guided in the housing, the valve head (37) protruding into the valve control chamber (30), the valve head (37) provided with a valve head sealing face (51), the valve head sealing face (51) cooperating with a valve seat (46) to control an outflow of fuel, whereby when the control valve (31 ) is closed, the valve chamber (30) is exposed to a pressure of the high-pressure fuel source (1); an outflow conduit (29) which leads from the control chamber (24) to the valve control chamber (30), the control valve (31) controlling the outflow from the control chamber (24) through the outflow conduit (29); an intermediate valve (56) including an intermediate valve member (57) and a connecting conduit (70), the intermediate valve (56) disposed in a portion of the outflow conduit, the connecting conduit with a first connection cross section provided between the valve control chamber (30) and the control chamber (24), whereby the intermediate valve member (57) is moved by the valve head (37) of the control valve member (34) out of a closing position toward the control chamber (24) counter to a closing force and in this movement a second connection cross section between the valve chamber (30) and the control chamber (24) is opened up.
- 2. The fuel injection device according to claim 1, in which the second connection cross section is in addition to the first connection cross section.
- 3. The fuel injection device according to claim 1, in which the connecting conduit (69) leads through the intermediate valve member (57, 157) and is closed by the control valve member (34) when the intermediate valve member (57, 157) is lifted from its valve seat (62), and that the second connection cross section is larger than the first connection cross section (70).
- 4. The fuel injection device according to claim 2, in which the intermediate valve member (57, 157) is guided on an outer circumference in a guide bore (60), which originates at the control chamber (24) and narrows, via a sealing seat shoulder (62) acting as a valve seat, said sealing seat shoulder forms an adjoining connecting bore (63) that discharges into the valve chamber (30), and the intermediate valve member (57, 157) has a sealing face (64), at a transition from a guide portion guided in the guide bore (60) and an actuating valve portion (65) that protrudes with a clearance toward the wall of the connecting bore (63) into the valve chamber (30) and can be brought with the sealing face into contact with the sealing seat shoulder (62) by a force of a closing spring (68).
- 5. The fuel injection device according to claim 3, in which the intermediate valve member (57, 157) is guided on an outer circumference in a guide bore (60), which originates at the control chamber (24) and narrows, via a sealing seat shoulder (62) acting as a valve seat, said sealing seat shoulder forms an adjoining connecting bore (63) that discharges into the valve chamber (30), and the intermediate valve member (57, 157) has a sealing face (64), at a transition from a guide portion guided in the guide bore (60) and an actuating valve portion (65) that protrudes with a clearance toward the wall of the connecting bore (63) into the valve chamber (30) and can be brought with the sealing face into contact with the sealing seat shoulder (62) by a force of a closing spring (68).
- 6. The fuel injection device according to claim 4, in which the intermediate valve member (57, 157) has longitudinal ribs (59) for guidance, which slide along the wall of the guide bore (60).
- 7. The fuel injection device according to claim 5, in which the intermediate valve member (57, 157) has longitudinal ribs (59) for guidance, which slide along the wall of the guide bore (60).
- 8. The fuel injection device according to claim 6, in which the second connection cross section is formed between the longitudinal ribs (59) and the wall of the guide bore (60).
- 9. The fuel injection device according to claim 7, in which the second connection cross section is formed between the longitudinal ribs (59) and the wall of the guide bore (60).
- 10. The fuel injection device according to claim 6, in which the second connection cross section is adjusted between the sealing seat shoulder (62) and the sealing face (64) while the intermediate valve member (57, 157) is lifted.
- 11. The fuel injection device according to claim 7, in which the second connection cross section is adjusted between the sealing seat shoulder (62) and the sealing face (64) while the intermediate valve member (57, 157) is lifted.
- 12. The fuel injection device according to claim 6, in which the connecting conduit (69) leads axially through the intermediate valve member (57, 157) and has crosswise connections (71) on the end of the actuating portion (65) toward the valve chamber, which crosswise connections, when the valve head (37) is resting on its face end on the actuating portion (65), maintains the communication between the valve chamber (30) and the connecting conduit (69).
- 13. The fuel injection device according to claim 8, in which the connecting conduit (69) leads axially through the intermediate valve member (57, 157) and has crosswise connections (71) on the end of the actuating portion (65) toward the valve chamber, which crosswise connections, when the valve head (37) is resting on its face end on the actuating portion (65), maintains the communication between the valve chamber (30) and the connecting conduit (69).
- 14. The fuel injection device according to claim 10, in which the connecting conduit (69) leads axially through the intermediate valve member (57, 157) and has crosswise connections (71) on the end of the actuating portion (65) toward the valve chamber, which crosswise connections, when the valve head (37) is resting on its face end on the actuating portion (65), maintains the communication between the valve chamber (30) and the connecting conduit (69).
- 15. The fuel injection device according to claim 6, in which the connecting conduit (69) leads axially through the intermediate valve member (57, 157) and on the end of the actuating portion (65) toward the valve chamber ends in a valve seat (74), on which the valve head (37) comes to rest before the intermediate valve member (57, 157) is lifted from the valve seat (62) by the valve head (37), and the communication between the valve chamber (30) and the connecting conduit (69) is thus closed.
- 16. The fuel injection device according to claim 8, in which the connecting conduit (69) leads axially through the intermediate valve member (57, 157) and on the end of the actuating portion (65) toward the valve chamber ends in a valve seat (74), on which the valve head (37) comes to rest before the intermediate valve member (57, 157) is lifted from the valve seat (62) by the valve head (37), and the communication between the valve chamber (30) and the connecting conduit (69) is thus closed.
- 17. The fuel injection device according to claim 10, in which the connecting conduit (69) leads axially through the intermediate valve member (57, 157) and on the end of the actuating portion (65) toward the valve chamber ends in a valve seat (74), on which the valve head (37) comes to rest before the intermediate valve member (57, 157) is lifted from the valve seat (62) by the valve head (37), and the communication between the valve chamber (30) and the connecting conduit (69) is thus closed.
- 18. The fuel injection device according to claim 4, in which the closing spring is a leaf spring (68).
- 19. The fuel injection device according to claim 5, in which the closing spring is a leaf spring (68).
- 20. The fuel injection device according to claim 4, in which the closing spring is a spiral spring (168).
Priority Claims (1)
Number |
Date |
Country |
Kind |
198 60 397 |
Dec 1998 |
DE |
|
US Referenced Citations (10)