Information
-
Patent Grant
-
6808124
-
Patent Number
6,808,124
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Date Filed
Tuesday, November 26, 200221 years ago
-
Date Issued
Tuesday, October 26, 200419 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 239 96
- 239 124
- 239 5332
- 239 5333
- 239 5339
- 123 446
- 123 467
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International Classifications
-
Abstract
The fuel injection system has one high-pressure fuel pump and one fuel injection valve for each cylinder of the engine. A pump work chamber can be made to communicate with a pressure chamber of the injection valve which has a valve member movable in an opening direction by the pressure in the pressure chamber, counter to a closing force. A first control valve, controls a communication of the work chamber with a relief chamber, and a second control valve, controls the pressure prevailing in a control pressure chamber urging the injection valve closed. In a first switching position of the first control valve the work chamber is made to communicate with the relief chamber, while the pressure chamber and the control pressure chamber are disconnected from the work chamber, and for a second switching position, the work chamber is disconnected from the relief chamber by the first control valve, while the pressure chamber and the control pressure chamber communicate with the work chamber.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to an improved fuel injection system for an internal combustion engine.
2. Description of the Prior Art
One fuel injection system of the type with which this invention is concerned, known from European Patent Disclosure EP 0 957 261 A1, has one high-pressure fuel pump and one fuel injection valve, communicating with it, for each cylinder of the engine. The high-pressure fuel pump has a pump piston, driven in a reciprocating motion by the engine, and this piston defines a pump work chamber that can be made to communicate with a pressure chamber of the fuel injection valve, which valve has an injection valve member by which at least one injection opening is controlled and which is movable by the pressure prevailing in the pressure chamber, counter to a closing force, in an opening direction to uncover the at least one injection opening. A first electrically actuated control valve is provided, which can be switched back and forth between two switching positions and by which a communication of the pump work chamber with a relief chamber is controlled. A second electrically actuated control valve is also provided, by which the pressure prevailing in a control pressure chamber is controlled, by which pressure the injection valve member is urged in the closing direction. The control pressure chamber has a communication with the pump work chamber, and by means of the second control valve, a communication of the control pressure chamber with a relief chamber is controlled. A disadvantage of this known fuel injection system is that the course of the fuel injection, or in other words the injected fuel quantity and the pressure at which the fuel injection is effected, can vary to only a limited extent during an injection cycle. In particular, in an injection cycle with a preinjection and a subsequent main injection, the pressure at which the main injection begins, and the spacing between the main injection and the preinjection are coupled with one another and are not freely variable. If the main injection is meant to begin at a slight pressure, then the spacing from the preinjection is only slight, and if the main injection is meant to begin at a high pressure, then the spacing from the preinjection is long.
OBJECT AND SUMMARY OF THE INVENTION
The fuel injection system of the invention has the advantage over the prior art that by means of the first control valve, in its first switching position, an elevated pressure can be maintained in the pressure chamber and in the control pressure chamber, even when the pump work chamber is in communication with the relief chamber, so that regardless of a relief of the pump work chamber by means of the second control valve, a fuel injection can be controlled, particularly for a preinjection and/or a postinjection. The pressure buildup for a main injection can be controlled by the first control valve, and the instant at which the main injection begins can be controlled by the second control valve. This makes a decoupling possible between the pressure at which the main injection begins and the spacing from a preceding preinjection.
Other advantageous features and refinements of the fuel injection system of the invention are disclosed. One embodiment enables a simultaneous relief of the pump work chamber, the pressure chamber and the control pressure chamber. Another embodiment makes a control of the pressure in the control pressure chamber possible in a simple way, while another enables adjusting the fuel inflow into the control pressure chamber and the fuel outflow from the control pressure chamber. A further embodiment makes it possible to operate the engine with low noise and pollutant emissions while another, in a simple way, enables adjusting the fuel quantity for the preinjection by means of the length of time for which the first control valve is closed. Further embodiments make it possible in a simple and purely mechanical way to adjust the fuel quantity for the preinjection, enables a postinjection, without fuel having to be pumped by the pump piston during the postinjection, makes it possible in a simple way to perform a preinjection, and enables a relief of the pressure chamber and of the control pressure chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
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 drawings, in which:
FIG. 1
schematically shows a fuel injection system for an internal combustion engine in terms of a first exemplary embodiment;
FIG. 2
shows the fuel injection system in detail, in a second exemplary embodiment;
FIG. 3
shows a course of a pressure at injection openings of a fuel injection valve of the fuel injection system during one injection cycle; and
FIG. 4
shows the course of the speed of a pump piston in the fuel injection system during one injection cycle.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In
FIGS. 1 and 2
, a fuel injection system for an internal combustion engine of a motor vehicle is shown. The engine is preferably a self-igniting internal combustion engine. The fuel injection system is preferably embodied as a so-called unit fuel injector system, and for each cylinder of the engine has one high-pressure fuel pump
10
and one fuel injection valve
12
, communicating with the pump and combined into a structural unit. Alternatively, the fuel injection system can also be embodied as a so-called pump-line-nozzle system, in which once again the high-pressure fuel pump
10
and the fuel injection valve
12
are provided for each cylinder of the engine, but are disposed spaced apart from one another and communicate with one another via a line. The high-pressure fuel pump
10
has a pump piston
18
, guided tightly in a cylinder bore
16
of a pump body
14
, and this pump piston is driven in a reciprocating motion by a cam
20
of an engine camshaft, either directly or via a transmission element, such as a tilt lever, counter to the force of a restoring spring
19
. In the cylinder bore
16
, the pump piston
18
defines a pump work chamber
22
, in which fuel at high pressure is compressed in the pumping stroke of the pump piston
18
. Fuel from a fuel tank
9
of the motor vehicle is delivered to the pump work chamber
22
by means of the feed pressure of a feed pump
21
.
The fuel injection valve
12
has a valve body
26
, connected to the pump body
14
, which can be embodied in multiple parts and in which an injection valve member
28
is guided longitudinally displaceably in a bore
30
. On its end region toward the combustion chamber of the cylinder of the engine, the valve body
26
has at least one and preferably a plurality of injection openings
32
. The injection valve member
28
, in its end region toward the combustion chamber, has a sealing face
34
, which for instance is approximately conical, and which cooperates with a valve seat
36
, embodied in the valve body
26
in its end region toward the combustion chamber, from which seat, or downstream of which, the injection openings
32
lead away. There is an annular chamber
38
in the valve body
26
, between the injection valve member
28
and the bore
30
, toward the valve seat
36
, and this chamber, in its end region remote from the valve seat
36
, merges through a radial widening of the bore
30
with a pressure chamber
40
surrounding the injection valve member
28
. At the level of the pressure chamber
40
, as a result of a cross-sectional reduction, the injection valve member
28
has a pressure shoulder
42
. A prestressed closing spring
44
engages the end of the injection valve member
28
remote from the combustion chamber, and by means of this spring the injection valve member
28
is pressed toward the valve seat
36
. The closing spring
44
is disposed in a spring chamber
46
of the valve body
26
that adjoins the bore
30
.
Adjoining the spring chamber
46
, on its end in the valve body
26
remote from the bore
30
, is a further bore
48
, in which a piston
50
that is connected to the injection valve member
28
is guided tightly. The piston
50
, with its face end remote from the injection valve member
28
, defines a control pressure chamber
52
. The pressure chamber
40
has a communication
54
with the pump work chamber
22
, which communication is formed by a conduit extending through the pump body
14
and the valve body
26
. The communication
54
will hereinafter be called the pressure chamber communication
54
. From the pressure chamber communication
54
, a communication
56
with the control pressure chamber
52
branches off, so that the control pressure chamber
52
likewise communicates with the pump work chamber
22
. The communication
56
will hereinafter be called the control pressure chamber communication
56
.
The fuel injection system has a first electrically actuated control valve
60
, by which a communication
59
of the pump work chamber
22
with a relief chamber is controlled; the compression side of the feed pump
21
and thus at least indirectly the fuel tank
9
can serve as this relief chamber. The communication
59
will hereinafter be called the relief chamber communication
59
. The first control valve
60
is disposed upstream of the control pressure chamber communication
56
, leading to the control pressure chamber
52
, in the pressure chamber communication
54
.
The first control valve
60
has an actuator
61
, which may be an electromagnet or a piezoelectric actuator, which is triggered electrically and by which a valve member of the control valve
60
is movable. The first control valve
60
can be embodied as either pressure-equalized or non-pressure-equalized. In a first exemplary embodiment, shown in
FIG. 1
, the first control valve
60
is embodied as a 3/2-port directional-control valve, which can be switched back and forth between two switching positions. By means of the first control valve
60
, in a first switching position, the relief chamber communication
59
with the relief chamber
9
is opened, so that the pump work chamber
22
communicates with the relief chamber
9
, while the pressure chamber
40
and the control pressure chamber
52
are disconnected from the pump work chamber
22
. In a second switching position, by means of the first control valve
60
, the relief chamber communication
59
with the relief chamber
9
is disconnected, so that the pump work chamber
22
is disconnected from the relief chamber
9
, while the pressure chamber
40
and the control pressure chamber
52
communicate with the pump work chamber
22
. The first control valve
60
is switched between its two switching positions by an electric control unit
66
as a function of engine operating parameters.
For controlling the pressure in the control pressure chamber
52
, a second electrically actuated control valve
68
is provided, by which a communication
70
of the control pressure chamber
52
with a relief chamber, for instance at least indirectly the fuel tank
9
, is controlled. The communication
70
will hereinafter be called the relief chamber communication
70
. The second control valve
68
has an actuator
69
, which may be an electromagnet or a piezoelectric actuator and which is triggered electrically, and by which a valve member of the control valve
68
is movable. The second control valve
68
is preferably embodied as pressure-balanced. The second control valve
68
is embodied as a 2/2-port directional-control valve, by which in a first switching position, the relief chamber communication
70
of the control pressure chamber
52
with the relief chamber
9
is opened, and by which in a second switching position, the relief chamber communication
70
of the control pressure chamber
52
with the relief chamber
9
is disconnected. A throttle restriction
58
is provided in the control pressure chamber communication
56
of the control pressure chamber
52
with the pressure chamber communication
54
, and a further throttle restriction
71
is provided in the relief chamber communication
70
of the control pressure chamber
52
with the relief chamber
9
. Selection of the throttle restrictions
58
,
71
makes it possible to adjust the inflow of fuel into the control pressure chamber
52
and the outflow of fuel from the control pressure chamber
52
. The second control valve
68
is likewise controlled by the control unit
66
. The control of the control valves
60
,
68
by the control unit
66
is effected as a function of engine operating parameters, such as rpm, load, and temperature.
The function of the fuel injection system will now be explained. In the intake stroke of the pump piston
18
, fuel is delivered to the pump work chamber
22
by the feed pump
21
, with the first control valve
60
in its first switching position, in which the pump work chamber
22
communicates with the feed pump
21
and is disconnected from both the pressure chamber
40
and the control pressure chamber
52
. In the pumping stroke of the pump piston
18
, a fuel injection takes place in an injection cycle. The injection cycle begins with a preinjection, in which a slight fuel quantity is injected, at a relatively slight pressure. At the onset of the pumping stroke of the pump piston
18
, the first control valve
60
is put into its second switching position by the control unit
66
, so that the pump work chamber
22
is disconnected from the relief chamber
9
, and the pressure chamber
40
and the control pressure chamber
52
communicate with the pump work chamber
22
. The second control valve
68
is closed by the control unit
66
. Fuel is then pumped by the pump piston
18
into the pressure chamber
40
and the control pressure chamber
52
. The fuel injection valve
12
remains closed during this process, because of the pressure prevailing in the control pressure chamber
52
when the second control valve
68
is closed. After a certain length of time, the control unit
66
puts the first control valve
60
in its first switching position, so that the pump work chamber
22
communicates with the relief chamber
9
, and the pressure chamber
40
and the control pressure chamber
52
are disconnected from the pump work chamber
22
. Fuel thus continues to be stored under pressure in the pressure chamber
40
and the control pressure chamber
52
. At a predetermined instant, the control unit
66
opens the second control valve
68
, so that the control pressure chamber
52
is relieved, and the injection valve member
28
opens in response to the pressure prevailing in the pressure chamber
40
. The valve member is effected at the pressure level at which the fuel is stored in the pressure chamber
40
. For terminating the preinjection, the second control valve
68
is closed again by the control unit
66
, so that the injection valve member
28
closes as a consequence of the increased pressure in the control pressure chamber
52
. It is also possible for a plurality of preinjections to be effected at intervals from one another by correspondingly opening and closing the second control valve
68
.
In
FIG. 3
, the course of the pressure p at the injection openings
32
of the fuel injection valve
12
is plotted over the time t during one injection cycle. The preinjection corresponds to an injection phase marked I in FIG.
3
.
Alternatively, for the preinjection it can also be provided that the first control valve
60
is put in its second switching position at the onset of the pumping stroke of the pump piston
18
by the control unit
66
, so that with the second control valve
68
closed, the pump piston
18
pumps fuel into the pressure chamber
40
and the control pressure chamber
52
. At a certain instant, when a certain fuel quantity has been pumped into the pressure chamber
40
and the control pressure chamber
52
by the pump piston
18
, the first control valve
60
is put in its first switching position by the control unit
66
, so that the pump work chamber
22
is relieved, and the pressure chamber
40
and the control pressure chamber
52
are disconnected from the pump work chamber
22
, and fuel continues to be stored under pressure in the pressure chamber
40
and in the control pressure chamber
52
. At a predetermined instant, the control unit
66
opens the second control valve
68
, so that the control pressure chamber
52
is relieved, and the injection valve member
28
opens in response to the pressure prevailing in the pressure chamber
40
. The preinjection is terminated when the pressure in the pressure chamber
40
has dropped so sharply that the force exerted on the injection valve member
28
by the closing spring
44
is greater than the force exerted in the opening direction on the injection valve member
28
by the pressure prevailing in the pressure chamber
40
, and the injection valve member
28
closes.
As a further alternative, it can be provided that fuel is still stored in the pressure chamber
40
and in the control pressure chamber
52
, from a preceding injection cycle with the second control valve
68
closed, at a pressure which is sufficiently high to perform a preinjection by opening the second control valve
68
. At the onset of the pumping stroke of the pump piston
18
, the first control valve
60
can remain in its first switching position, since no fuel needs to be pumped into the pressure chamber
40
and the control pressure chamber
52
. The preinjection is terminated by the closure of the second control valve
68
and/or if the pressure in the pressure chamber
40
has dropped so much that the injection valve member
28
is closed by the closing spring
44
.
As still another alternative, it may be provided that the first control valve
60
is put in its second switching position by the control unit
66
at the onset of the pumping stroke of the pump piston
18
, so that the pump work chamber
22
is disconnected from the relief chamber
9
and communicates with the pressure chamber
40
and the control pressure chamber
52
. The cam
20
has a shape such that by it, over a first rotational angle range, a pumping stroke of the pump piston
18
is accomplished, so that by the pump piston
18
, fuel is pumped into the pressure chamber
40
and the control pressure chamber
52
while the second control valve
68
is closed. In an ensuing rotational angle range of the cam
20
, this cam is shaped such that no further pumping stroke of the pump piston
18
occurs. The speed C of the pump piston
18
in its reciprocating motion, effected by the cam
20
, over the rotational angle φ of the cam
20
is shown in
FIG. 4
; the speed in the stroke effected by the first rotational angle range is marked I, while the speed in the ensuing rotational angle range of the cam
20
is zero, and the speed in a stroke accomplished by a further rotational angle range of the cam
20
during a main injection is marked II. By means of the shape of the cam
20
in the first rotational angle range and by means of the resultant stroke of the pump piston
18
, the fuel quantity that is pumped by the pump piston
18
into the pressure chamber
40
and the control pressure chamber
52
is determined. For the preinjection, the second control valve
68
is opened by the control unit
66
, and the preinjection is terminated when the second control valve
68
is closed and/or when the pressure in the pressure chamber
40
has dropped so sharply that the injection valve member
28
is closed by the force of the closing spring
44
.
After the preinjection, the first control valve
60
is put in its second switching position by the control unit
66
, and the second control valve
68
is closed by the control unit
66
. In the pumping stroke of the pump piston
18
, high pressure is built up in the pressure chamber
40
and in the control pressure chamber
52
, but no injection can yet occur, as long as the second control valve
68
is still closed and high pressure still prevails in the control pressure chamber
52
. Once a predetermined pressure, at which the main injection is meant to begin, is reached in the pressure chamber
40
, the control unit
66
opens the second control valve
68
, so that the control pressure chamber
52
is relieved. The injection valve member
28
then opens in response to the pressure prevailing in the pressure chamber
40
, and the main injection begins. The main injection corresponds to an injection phase marked II in FIG.
3
. For terminating the main injection, the second control valve
68
is closed by the control unit
66
, so that the control pressure chamber
52
is disconnected from the relief chamber
9
, and a high pressure builds up in the control pressure chamber
52
, by which pressure the injection valve member
28
is closed. Additionally, upon termination of the main injection, the first control valve
60
can also be put in its first switching position by the control unit
66
.
By varying the instant of opening of the second control valve
68
by means of the control unit
66
, the pressure at which the main injection begins is also varied. The earlier the second control valve
68
is opened, the less is the pressure at which the main injection begins. The later the second control valve
68
is opened, the higher is the pressure at which the main injection begins. Because of the kinds of preinjection procedures explained above, it is possible, in the event of a variation of the pressure at which the main injection begins, to vary the spacing T between the preinjection and the main injection independently of this pressure. The pressure buildup for the main injection is controlled by the first control valve
60
. If the main injection is to begin at high pressure, then the first control valve
60
is switched over from its first switching position to its second switching position by the control unit
66
, at an early instant after the preinjection, so that a pressure buildup takes place. The spacing of the main injection from the preinjection is determined by the instant of opening of the second control valve
68
by the control unit
66
. If the main injection is to begin at a slight pressure, then the first control valve
60
is closed by the control unit
66
at a later instant after the preinjection, so that a correspondingly delayed pressure buildup takes place. The spacing of the main injection from the preinjection is determined once again by the instant of opening of the second control valve
68
.
Alternatively, it can also be provided that the second control valve
68
is already opened by the control unit
66
before the main injection begins, so that the control pressure chamber
52
is relieved. The first control valve
60
is put in its second switching position by the control unit
66
, and the main injection begins when the pressure in the pressure chamber
40
is so high that this pressure opens the injection valve member
28
counter to the force of the closing spring
44
. For terminating the main injection, the second control valve
68
is closed by the control unit
66
, and/or the first control valve
60
is put in its first switching position.
After the main injection, at least one postinjection can also take place. After the termination of the main injection, fuel can be stored in the pressure chamber
40
and in the control pressure chamber
52
while the second control valve
68
is closed and the first control valve
60
is in its first switching position. The level of the pressure at which the fuel is stored is determined by the instant of closure of the second control valve
68
upon the termination of the main injection. The earlier the second control valve
68
is closed, the higher is the pressure at which the fuel is stored in the pressure chamber
40
and in the control pressure chamber
52
. For a postinjection, the second control valve
68
is opened again by the control unit
66
, so that the control pressure chamber
52
is relieved again and the injection valve member
28
opens. The postinjection is equivalent to an injection phase marked III in FIG.
3
. The postinjection is terminated by the closure of the second control valve
68
by the control unit
66
. It is also possible for a plurality of successive postinjections to take place. The fuel injected in the postinjection need not be pumped by the pump piston
18
at the instant of the postinjection but instead is withdrawn from the pressure chamber
40
and the control pressure chamber
52
, into which the fuel had already been pumped by the pump piston
18
in an earlier phase of the pumping stroke of the pump piston. The first control valve
60
can remain in its first switching position after the termination of the main injection.
For the postinjection, alternatively, the first control valve
60
can also be put in its second switching position by the control unit
66
, so that fuel is pumped into the pressure chamber
40
by the pump piston
18
. If fuel from the preceding main injection is still stored in the pressure chamber
40
and the control pressure chamber
52
, then only some of the fuel quantity required for the postinjection has to be pumped by the pump piston
18
during the postinjection. If with the second control valve
68
open and the control pressure chamber
52
thus relieved the pressure in the pressure chamber
40
is high enough that the opening force on the injection valve member
28
is greater than the closing force acting on it, the postinjection begins. The postinjection is terminated by the closure of the second control valve
68
by the control unit
66
and/or if the pressure in the pressure chamber
40
has dropped so sharply that the closing force on the injection valve member
28
is greater than the opening force, generated by the pressure in the pressure chamber
40
, and the injection valve member
28
closes.
After the termination of the postinjection or the main injection, if no postinjection is contemplated, fuel can still be stored under pressure in the pressure chamber
40
and in the control pressure chamber
52
, with which fuel, a preinjection can be effected in the ensuing injection cycle, as indicated above. This requires effective sealing of the pressure chamber
40
and the control pressure chamber
52
, so that there will be no substantial pressure drop from leakage. At low engine rpm, when the duration of an injection cycle is correspondingly long, the pressure in the pressure chamber
40
and in the control pressure chamber
52
can drop sharply because of leakage, but the pressure is preferably kept at least at the pressure level generated by the feed pump
21
. It may also be provided that to terminate the main injection or the postinjection, the second control valve
68
is closed by the control unit
66
and remains closed until such time as the pressure in the pressure chamber
40
has dropped from leakage so sharply that the injection valve member
28
can no longer open, even when the second control valve
68
is open. Next, the second control valve
68
is briefly opened, so that the pressure chamber
40
and the control pressure chamber
52
are relieved.
In
FIG. 2
, the fuel injection system is shown in a second exemplary embodiment, in which compared to the first exemplary embodiment only the embodiment of the first control valve
160
is modified. The first control valve
160
is embodied as a 3/3-port directional-control valve and can be switched among three switching positions. In a first switching position of the control valve
160
, the pump work chamber
22
is made by the control valve to communicate with the feed pump
21
or the relief chamber
9
, and the pressure chamber
40
and the control pressure chamber
52
are disconnected from the pump work chamber
22
. In a second switching position of the control valve
160
, this valve disconnects the pump work chamber
22
from the feed pump
21
or the relief chamber
9
and causes the pressure chamber
40
and the control pressure chamber
52
to communicate with the pump work chamber
22
. In a third switching position of the control valve
160
, by means of it the pump work chamber
22
communicates with the feed pump
21
or the relief chamber
9
, and the pressure chamber
40
and the control pressure chamber
52
likewise communicate with the feed pump
21
or the relief chamber
9
. The first switching position of the control valve
160
thus has the same function as the first switching position of the control valve
60
of the first exemplary embodiment, and the second switching position of the control valve
160
has the same function as the second switching position of the control valve
60
of the first exemplary embodiment. The mode of operation, explained above in conjunction with the first exemplary embodiment, of the fuel injection system can thus also be achieved with the control valve
160
of the second exemplary embodiment. With the third switching position of the control valve
160
, a relief of the pump work chamber
22
and also of the pressure chamber
40
and the control pressure chamber
52
is made possible. It may be provided that for terminating a fuel injection, that is, the preinjection and/or the main injection and/or the postinjection, the first control valve
160
is put in its third switching position by the control unit
66
, as a result of which a rapid relief of the pressure chamber
40
and the control pressure chamber
52
is achieved, and thus also a fast closure of the injection valve member
28
for terminating the fuel injection. For switching over the first control valve
160
, it may be provided that its actuator
161
is supplied with current at different current levels by the control unit
66
. When the actuator
161
is without current, the control valve
160
is in its first switching position; when the actuator
161
is supplied with an elevated current level, the control valve
160
is switched over to its third switching position; and when the actuator
161
is supplied with a still further-increased current level, the control valve
160
is switched over to its second switching position.
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 system for an internal combustion engine, comprisingone high-pressure fuel pump (10) and one fuel injection valve (12) communicating with the high pressure pump for each cylinder of the engine, the high-pressure fuel pump (10) having a pump piston (18) driven by the engine in a reciprocating motion and defining a pump work chamber (22) that can be made to communicate with a pressure chamber (40) of the fuel injection valve (12), the fuel injection valve (12) having an injection valve member (28) by which at least one injection opening (32) is controlled and which is movable, by the pressure prevailing in the pressure chamber (40), counter to a closing force (44) in an opening direction (29) for uncovering the at least one injection opening (32), a first electrically actuated control valve (60; 160), which can be switched back and forth between at least two switching positions and by which at least indirectly a communication (59) of the pump work chamber (22) with a relief chamber (9; 21) is controlled, and a second electrically actuated control valve (68), by which the pressure prevailing in a control pressure chamber (52) is controlled, by which pressure the injection valve member (28) is urged at least indirectly in the closing direction, the pump work chamber (22) communicating with the relief chamber (9; 21), while the pressure chamber (40) and the control pressure chamber (52) are disconnected from the pump work chamber (22) in a first switching position of the first control valve (60; 160), and the pump work chamber (22) is disconnected from the relief chamber (9; 21), while the pressure chamber (40) and the control pressure chamber (52) communicate with the pump work chamber (22) that in a second switching position of the first control valve (60; 160).
- 2. The fuel injection system in accordance with claim 1, wherein the first control valve (60) is embodied as a 3/2-port directional-control valve, which can be switched back and forth only between the first and second switching positions.
- 3. The fuel injection system in accordance with claim 1, wherein the first control valve (160) is embodied as a 3/3-port directional-control valve, which can additionally be switched back and forth into a third switching position, in which the pump work chamber (22) communicates with the relief chamber (9; 21), and the pressure chamber (40) and the control pressure chamber (52) communicate with the relief chamber (9).
- 4. The fuel injection system in accordance with claim 1, wherein a relief chamber communication (70) of the control pressure chamber (52) with the relief chamber (9) is controlled by the second control valve (68); and wherein the control pressure chamber (52) has a control pressure chamber communication with the pressure chamber communication (54), the control pressure chamber communication leading away from the pressure chamber communication (54) of the pump work chamber (22) with the pressure chamber (40), downstream of the first control valve (60; 160).
- 5. The fuel injection system in accordance with claim 2, wherein a relief chamber communication (70) of the control pressure chamber (52) with the relief chamber (9) is controlled by the second control valve (68); and wherein the control pressure chamber (52) has a control pressure chamber communication with the pressure chamber communication (54), the control pressure chamber communication leading away from the pressure chamber communication (54) of the pump work chamber (22) with the pressure chamber (40), downstream of the first control valve (60; 160).
- 6. The fuel injection system in accordance with claim 3, wherein a relief chamber communication (70) of the control pressure chamber (52) with the relief chamber (9) is controlled by the second control valve (68); and wherein the control pressure chamber (52) has a control pressure chamber communication with the pressure chamber communication (54), the control pressure chamber communication leading away from the pressure chamber communication (54) of the pump work chamber (22) with the pressure chamber (40), downstream of the first control valve (60; 160).
- 7. The fuel injection system in accordance with claim 4, further comprising a throttle restriction (58; 71) in the relief chamber communication (70) of the control pressure chamber (52) with the relief chamber (9) and/or in the control pressure chamber communication (56) of the control pressure chamber (52) with the pressure chamber communication (54).
- 8. The fuel injection system in accordance with claim 4, wherein, at the onset of a pumping stroke of the pump piston (18), the first control valve (60) is put in its second switching position and the second control valve (68) is closed, so that fuel is pumped into the pressure chamber (40) and the control pressure chamber (52); wherein in the course of the pumping stroke of the pump piston (18), the first control valve (60; 160) is put in its first switching position; and wherein for at least one preinjection, the second control valve (68) is opened, so that the control pressure chamber (52) is relieved, and the injection valve member (28) opens in response to the pressure prevailing in the pressure chamber (40).
- 9. The fuel injection system in accordance with claim 7, wherein, at the onset of a pumping stroke of the pump piston (18), the first control valve (60) is put in its second switching position and the second control valve (68) is closed, so that fuel is pumped into the pressure chamber (40) and the control pressure chamber (52); wherein in the course of the pumping stroke of the pump piston (18), the first control valve (60; 160) is put in its first switching position; and wherein for at least one preinjection, the second control valve (68) is opened, so that the control pressure chamber (52) is relieved, and the injection valve member (28) opens in response to the pressure prevailing in the pressure chamber (40).
- 10. The fuel injection system in accordance with claim 8, wherein, for terminating the at least one preinjection, the second control valve (68) is closed, so that the injection valve member (28) closes in response to the pressure prevailing in the control pressure chamber (52).
- 11. The fuel injection system in accordance with claim 8, wherein the at least one preinjection is terminated once the pressure prevailing in the pressure chamber (40) has dropped so sharply that the injection valve member (28) closes in response to the closing force (44).
- 12. The fuel injection system in accordance with claim 11, wherein the first control valve (60; 160), in the pumping stroke of the pump piston (18), is kept for a defined length of time in its second switching position, in order to pump a defined fuel quantity into the pressure chamber (40) and the control pressure chamber (52), so that in the at least one preinjection until the instant of closure of the injection valve member (28), a defined fuel quantity is injected.
- 13. The fuel injection system in accordance with claim 11, wherein the pump piston (18) is driven by a cam (20); wherein the cam (20), in a first rotational angle range, has a shape determined in such a way that the pump piston (18) executes a defined pumping stroke and pumps a defined fuel quantity into the pressure chamber (40) and the control pressure chamber (52), which quantity is injected in the preinjection; and wherein in an ensuing rotational angle range, the cam (20) has a form determined in such a way that the pump piston (18) executes no further pumping stroke.
- 14. The fuel injection system in accordance with claim 11, wherein during the pumping stroke of the pump piston (18) after the at least one preinjection, the first control valve (60; 160) is put in its second switching position; wherein the second control valve (68) is closed; and wherein for a subsequent main injection the second control valve (68) is opened, so that the control pressure chamber (52) is relieved, and the injection valve member (28) opens in response to the pressure prevailing in the pressure chamber (40).
- 15. The fuel injection system in accordance with 8, wherein, during the pumping stroke of the pump piston (18) after the at least one preinjection, the first control valve (60; 160) is put in its second switching position; wherein the second control valve (68) is opened, so that the control pressure chamber (52) is relieved; and wherein a subsequent main injection is effected when the pressure generated by the pump piston (18) in the pressure chamber (40) is so high that in response to it, the injection valve member (28) opens counter to the closing force (44).
- 16. The fuel injection system in accordance with claim 14, wherein, for terminating the main injection, the second control valve (68) is closed.
- 17. The fuel injection system in accordance with claim 15, wherein, for terminating the main injection, the second control valve (68) is closed.
- 18. The fuel injection system in accordance with claim 14, wherein, after the main injection, at least one postinjection is effected; that in the preceding main injection, by closure of the second control valve (68) and switching of the first control valve (60; 160) into its first switching position, fuel under pressure is stored in the pressure chamber (40) and in the control pressure chamber (52); and wherein for the postinjection, the second control valve (68) is opened, so that the control pressure chamber (52) is relieved, and the injection valve member (28) opens in response to the pressure prevailing in the pressure chamber (40).
- 19. The fuel injection system in accordance with claim 15, wherein, after the main injection, at least one postinjection is effected; that in the preceding main injection, by closure of the second control valve (68) and switching of the first control valve (60; 160) into its first switching position, fuel under pressure is stored in the pressure chamber (40) and in the control pressure chamber (52); and wherein for the postinjection, the second control valve (68) is opened, so that the control pressure chamber (52) is relieved, and the injection valve member (28) opens in response to the pressure prevailing in the pressure chamber (40).
- 20. The fuel injection system in accordance with claim 16, wherein, after the main injection, at least one postinjection is effected; that in the preceding main injection, by closure of the second control valve (68) and switching of the first control valve (60; 160) into its first switching position, fuel under pressure is stored in the pressure chamber (40) and in the control pressure chamber (52); and wherein for the postinjection, the second control valve (68) is opened, so that the control pressure chamber (52) is relieved, and the injection valve member (28) opens in response to the pressure prevailing in the pressure chamber (40).
- 21. The fuel injection system in accordance with claim 14, wherein, after the main injection, at least one postinjection is effected; wherein for pressure generation for the postinjection, the first control valve (60; 160) is put in its second switching position; and wherein for the postinjection, the second control valve (68) is opened.
- 22. The fuel injection system in accordance with claim 15, wherein, after the main injection, at least one postinjection is effected; wherein for pressure generation for the postinjection, the first control valve (60; 160) is put in its second switching position; and wherein for the postinjection, the second control valve (68) is opened.
- 23. The fuel injection system in accordance with claim 16, wherein, after the main injection, at least one postinjection is effected; wherein for pressure generation for the postinjection, the first control valve (60; 160) is put in its second switching position; and wherein for the postinjection, the second control valve (68) is opened.
- 24. The fuel injection system in accordance with claim 14, wherein, after the main injection or the postinjection, at the end of an injection cycle, fuel is stored in the pressure chamber (40) and in the control pressure chamber (52), with the second control valve (68) closed and the first control valve (60; 160) disposed in its first switching position, at such a high pressure that this pressure is sufficient, in a subsequent injection cycle with the second control valve (68) opened, to perform the preinjection.
- 25. The fuel injection system in accordance with claim 15, wherein, after the main injection or the postinjection, at the end of an injection cycle, fuel is stored in the pressure chamber (40) and in the control pressure chamber (52), with the second control valve (68) closed and the first control valve (60; 160) disposed in its first switching position, at such a high pressure that this pressure is sufficient, in a subsequent injection cycle with the second control valve (68) opened, to perform the preinjection.
- 26. The fuel injection system in accordance with claim 16, wherein, after the main injection or the postinjection, at the end of an injection cycle, fuel is stored in the pressure chamber (40) and in the control pressure chamber (52), with the second control valve (68) closed and the first control valve (60; 160) disposed in its first switching position, at such a high pressure that this pressure is sufficient, in a subsequent injection cycle with the second control valve (68) opened, to perform the preinjection.
- 27. The fuel injection system in accordance with claim 14, wherein, after the main injection or the postinjection, at the end of an injection cycle, the second control valve (68) is opened when the pressure in the pressure chamber (40) has dropped so sharply as a consequence of leakage that the force generated by this pressure on the injection valve member (28) in the opening direction (29) is less than the closing force (44) acting the injection valve member (28).
- 28. The fuel injection system in accordance with claim 15, wherein, after the main injection or the postinjection, at the end of an injection cycle, the second control valve (68) is opened when the pressure in the pressure chamber (40) has dropped so sharply as a consequence of leakage that the force generated by this pressure on the injection valve member (28) in the opening direction (29) is less than the closing force (44) acting the injection valve member (28).
- 29. The fuel injection system in accordance with claim 16, wherein, after the main injection or the postinjection, at the end of an injection cycle, the second control valve (68) is opened when the pressure in the pressure chamber (40) has dropped so sharply as a consequence of leakage that the force generated by this pressure on the injection valve member (28) in the opening direction (29) is less than the closing force (44) acting the injection valve member (28).
- 30. The fuel injection system in accordance with claim 2, a relief chamber communication (70) of the control pressure chamber (52) with the relief chamber (9) is controlled by the second control valve (68); wherein the control pressure chamber (52) has a control pressure chamber communication with the pressure chamber communication (54), the control pressure chamber communication leading away from the pressure chamber communication (54) of the pump work chamber (22) with the pressure chamber (40), downstream of the first control valve (60; 160), and wherein the first control valve (160) is put in its third switching position upon termination of a fuel injection.
Priority Claims (1)
Number |
Date |
Country |
Kind |
101 58 659 |
Nov 2001 |
DE |
|
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