Information
-
Patent Grant
-
6763809
-
Patent Number
6,763,809
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Date Filed
Wednesday, November 13, 200222 years ago
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Date Issued
Tuesday, July 20, 200420 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
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US Classifications
Field of Search
US
- 123 467
- 123 447
- 123 446
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International Classifications
-
Abstract
The fuel injection apparatus has a high-pressure fuel pump and a fuel injection valve connected to it for each cylinder of the engine. The high-pressure fuel pump has a pump piston, which is driven in a stroke motion by the engine and defines a pump working chamber, which is connected by means of a line to a pressure chamber of the fuel injection valve that is disposed separate from the high-pressure fuel pump in the engine and has an injection valve member, which is used to control at least one injection opening and can be moved by the pressure prevailing in the pressure chamber in an opening direction, counter to a closing force, in order to unblock the at least one injection opening. An electrically actuated control valve is provided in the fuel injection valve and at least indirectly controls a connection of the pump working chamber to a relief chamber, which can store pressurized fuel diverted by the control valve when this valve is open.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to an improved fuel injection apparatus for an internal combustion engine.
2. Description of the Prior Art
A fuel injection apparatus of the type with which this invention is concerned is known from EP 0 957 261 A1 which discloses a high-pressure fuel pump and a fuel injection valve connected to it for each cylinder of the internal combustion engine. The high-pressure fuel pump has a pump piston which the engine sets into a stroke motion and which defines a pump working chamber. The fuel injection valve has a pressure chamber connected to the pump working chamber and has an injection valve member, which controls at least one injection opening and which the pressure prevailing in the pressure chamber can move in an opening direction in order to unblock the at least one injection opening. The high-pressure fuel pump and the fuel injection valve are disposed separate from each other in the engine. The high-pressure fuel pump is provided with an electrically actuated control valve, which controls a connection of the pump working chamber and therefore of the line to a relief chamber, which function is at least indirectly fulfilled by the fuel tank. In this known fuel injection apparatus, it is disadvantageous that when the control valve is open, fuel delivered by the high-pressure fuel pump is diverted toward the fuel tank and in the subsequent intake stroke of the pump piston, this piston must aspirate the entire fuel quantity once again. This decreases the efficiency of the fuel injection apparatus. Furthermore, diverting fuel delivered by the pump piston toward the fuel tank produces pressure surges in the low-pressure system connected to it, which impairs the function and service life of the fuel injection apparatus.
OBJECT AND SUMMARY OF THE INVENTION
The fuel injection apparatus according to the invention has the advantage over the prior art that the control valve diverts fuel into the reservoir from which fuel is drawn in a subsequent intake stroke of the pump piston so that the pump working chamber only needs to aspirate part of the fuel quantity, which is required for the filling, from the fuel tank. Furthermore, no pressure surges are produced in the low-pressure region of the fuel injection apparatus when the control valve diverts the fuel into the reservoir.
Advantageous embodiments and modifications of the fuel injection apparatus according to the invention are disclosed. In one embodiment, the reservoir has a large enough volume to contain the fuel quantity that is diverted by the control valve, even when there is a smaller fuel injection quantity and therefore a greater diverted fuel quantity. Another modification permits a flexible control of the fuel injection in that the fuel injection valve can be closed when there is high pressure in 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
shows a schematic depiction of a fuel injection apparatus for an internal combustion engine, according to a first exemplary embodiment,
FIG. 2
shows a march of pressure at injection openings of a fuel injection valve of the fuel injection apparatus according to the first exemplary embodiment, and
FIG. 3
shows the fuel injection apparatus according to a second exemplary embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIGS. 1 and 3
show a fuel injection apparatus for an internal combustion engine of a motor vehicle. The fuel injection apparatus is embodied as a so-called unit pump system and for each cylinder of the engine, has a fuel pump
10
, a fuel injection valve
12
, and a line
14
that connects the fuel injection valve
12
to the fuel pump
10
. The fuel pump
10
has a pump piston
18
, which is guided in a sealed fashion in a cylinder bore
16
of a pump body
15
and is driven into a stroke motion counter to the force of a return spring
19
by a cam
20
of a camshaft of the engine. In the cylinder bore
16
, the pump piston
18
defines a pump working chamber
22
in which the pump piston
18
compresses fuel at high pressure. The pump working chamber
22
is supplied with fuel from the fuel tank
24
, for example by means of a low-pressure pump, not shown. The pump working chamber
22
has a connection
17
that leads to the fuel tank
24
and is provided with a check valve
21
, which opens toward the pump working chamber
22
and can be disposed in the pump body
15
.
The fuel injection valve
12
is disposed separate from the fuel pump
10
and is connected to the pump working chamber
22
by means of the line
14
. The fuel injection valve
12
has a valve body
26
, which can be comprised of several parts, in which a piston-shaped injection valve member
28
is guided so that it can move longitudinally in a bore
30
. In its end region oriented toward the combustion chamber of the cylinder of the engine, the valve body
26
has at least one, preferably several, injection openings
32
. In its end region oriented toward the combustion chamber, the injection valve member
28
has a for example approximately conical sealing surface
34
that cooperates with a valve seat
36
, which is embodied in the valve body
26
, and the injection openings
32
lead away from this valve seat
36
or branch off downstream of it. In the valve body
26
, between the injection valve member
28
and the bore
30
toward the valve seat
36
, there is an annular chamber
38
, which transitions by means of a radial expansion of the bore
30
into a pressure chamber
40
that encompasses the injection valve member
28
. In the vicinity of the pressure chamber
40
, the injection valve member
28
has a pressure shoulder
42
. A prestressed closing spring
44
acts on the end of the injection valve member
28
oriented away from the combustion chamber and presses the injection valve member
28
toward the valve seat
36
. The closing spring
44
is disposed in a spring chamber
46
of the valve body
26
, which chamber adjoins the bore
30
. At its end oriented away from the bore
30
in the valve body
26
, the spring chamber
46
can be adjoined by another bore
48
that has a control piston
50
guided in it in a sealed fashion, which is connected to the injection valve member
28
. With its end face oriented away from the spring chamber
46
, the piston
50
defines a control pressure chamber
52
in the valve body
26
.
The line
14
feeds into the valve body
26
and in it, leads into a conduit, which is embodied in the valve body
26
and leads to the pressure chamber
40
. Inside the valve body
26
, a conduit
54
branches off from the line
14
and leads to a reservoir
56
embodied in the valve body
26
. An electrically actuated control valve
58
controls the passage through the conduit
54
. Inside the valve body
26
, a conduit
60
that leads to the control pressure chamber
52
can also branch from the line
14
. The control pressure chamber
52
is also connected to the reservoir
56
by means of a conduit
62
.
The reservoir
56
can, for example, be embodied in a bore in the valve body
26
, which bore has a flexible boundary in the form of a reservoir piston
64
, which is supported by a prestressed return spring
65
. The reservoir
56
is dimensioned so that the volume that can be contained in the reservoir
56
is at least as great as the volume that the pump piston
18
of the high-pressure fuel pump
10
delivers during a delivery stroke.
In a first exemplary embodiment of the fuel injection apparatus shown in
FIG. 1
, an additional electrically actuated control valve
68
is provided, which controls the passage through the conduit
60
from the line
14
into the control pressure chamber
52
. Preferably a first throttle restriction
61
is provided in the conduit
60
and preferably a second throttle restriction
63
is provided in the conduit
62
from the control pressure chamber
52
to the reservoir
56
. The control pressure chamber
52
is continuously connected to the reservoir
56
by means of the conduit
62
. The inflow and outflow of fuel into and out of the control pressure chamber
52
can be adjusted or set in a suitable manner through appropriate dimensioning of the throttle restrictions
61
,
63
. The two control valves
58
and
68
can each have an electromagnetic actuator, a piezoelectric actuator, or some other fast-switching actuator. An electronic control device
70
controls the control valves
58
,
68
as a function of operating parameters of the engine. As shown in
FIG. 1
, the two control valves
58
,
68
can each be embodied as a 2/2-port directional-control valve, which can be switched between an open switched position, in which the passage through the conduit
60
or
62
is open, and a closed switched position, in which the passage through the conduit
60
or
62
is closed.
The function of the fuel injection apparatus according to the first exemplary embodiment will now be explained. During the intake stroke of the pump piston
18
, the first control valve
58
is disposed in its open switched position so that the connection of the line
14
to the reservoir
56
is open. The second control valve
68
is disposed in its closed switched position so that the control pressure chamber
52
is disconnected from the line
14
. Fuel stored under pressure in the reservoir
56
is supplied via the line
14
to the pump working chamber
22
until the reservoir
56
is emptied. The pressure in the reservoir
56
is therefore preferably higher than the pressure in the low-pressure region of the fuel injection apparatus upstream of the check valve
21
so that this check valve is closed until the reservoir
56
is empty. With another intake stroke, the pump piston
18
aspirates fuel from the fuel tank
24
when the check valve
21
is open. During the subsequent delivery stroke of the pump piston
18
, the check valve
21
closes and the pump piston
18
delivers fuel to the fuel injection valve
12
via the line
14
. During the delivery stroke of the pump piston
18
, the first control valve
58
can be disposed in its open switched position so that at first, fuel is delivered into the reservoir
56
and not enough high pressure can build up to produce a fuel injection. At the beginning of the fuel injection, the control device
70
then switches the first control valve
58
into its closed switched position so that the line
14
is disconnected from the reservoir
56
. It is also possible for the first control valve
58
to be brought into its closed switched position during the delivery of the pump piston
18
and for the second control valve
68
to be brought into its open switched position. The control pressure chamber
52
is then connected to the line
14
so that an increased pressure prevails in this control pressure chamber
52
, which keeps the fuel injection valve
12
closed by means of the control piston
50
. When the fuel injection is to begin, then the control device
70
moves the second control valve
68
into its closed switched position so that the control pressure chamber
52
is disconnected from the line
14
and only the pressure of the reservoir
56
prevails in this control pressure chamber
52
. When the pressure prevailing in the pressure chamber
40
of the fuel injection valve
12
generates a force on the injection valve member
28
that exceeds the force of the closing spring
44
and the compressive force acting on the control piston
50
, then this injection valve member
28
moves in the opening direction
29
and unblocks the injection openings
32
.
FIG. 2
shows the march of pressure at the injection openings
32
of the fuel injection valve
12
over time during an injection cycle. Due to the profile of the cam
20
, the fuel injection explained above occurs at a relatively low pressure and a small injection quantity during a preinjection phase labeled I in FIG.
2
.
In order to terminate the preinjection, the control device
70
moves the first control valve
58
into its open switched position so that the fuel delivered by the pump piston
18
travels into the reservoir
56
and the pressure in the pressure chamber
40
drops in such a way that the fuel injection valve
12
closes. Alternatively, the first control valve
58
can also remain in its closed switched position, wherein the control device
70
moves the second control valve
68
into its open switched position so that high pressure prevails in the control pressure chamber
52
and closes the fuel injection valve
12
by means of the control piston
50
.
Then, for a main injection of fuel, the control device
70
moves the first control valve
58
into its closed switched position so that the reservoir
56
is disconnected from the line and moves the second control valve
68
into its closed switched position so that the control pressure chamber
52
is disconnected from the line
14
. High pressure then builds up in the pressure chamber
40
of the fuel injection valve
12
in accordance with the profile of the cam
20
and the fuel injection valve
12
opens since the control pressure chamber
52
is pressure-relieved. Then an injection of fuel occurs in a main injection phase labeled II in FIG.
2
. The time at which the control device
70
switches the second control valve
68
into its closed switched position can influence the time and therefore the pressure at which the main injection begins. The later the second control valve
68
is closed, the higher the pressure at which the main injection begins. This is shown in
FIG. 2
by a march of pressure depicted with a dashed line.
In order to terminate the main injection, the control device
70
moves the second control valve
68
into its open switched position so that the control piston
50
closes the fuel injection valve
12
due to the high pressure prevailing in the control pressure chamber
52
. High pressure also prevails in the pressure chamber
40
due to the fact that the first control valve
58
remains in its closed switched position. For a secondary injection of fuel in a phase labeled III in
FIG. 2
, the control device
70
closes the second control valve
68
again so that the control pressure chamber
52
is pressure-relieved and the fuel injection valve
12
opens. In order to terminate the fuel injection, the control device
70
moves the first control valve
58
into its open switched position and moves the second control valve
68
into its open switched position or leaves it in its closed switched position.
When the first control valve
58
is open, fuel delivered by the pump piston
18
during its delivery stroke is diverted from the line
14
into the reservoir
56
. As an increasing fuel volume flows into the reservoir, the reservoir piston
64
moves counter to the force of the return spring
65
and the pressure in the reservoir
56
increases. If only a small quantity of fuel is injected during the fuel injection, which is the case for example when the engine is idling or is operating at a low load, then a large quantity of fuel is diverted into the reservoir
56
and a high pressure is produced in the reservoir
56
. During the subsequent intake stroke of the pump piston
18
, this piston consequently only has to aspirate a small quantity of fuel from the fuel tank
24
. If a large quantity of fuel is injected during the fuel injection, which is the case for example when the engine is operating at a high load, then only a small quantity of fuel is diverted into the reservoir
56
and a relatively low pressure is produced in the reservoir
56
. During the subsequent intake stroke of the pump piston
18
, this piston consequently has to aspirate a large quantity of fuel from the fuel tank
24
.
FIG. 3
shows the fuel injection apparatus according to a second exemplary embodiment in which the basic design is the same as in the first exemplary embodiment, and only the disposition of the second control valve
168
has been modified. The second control valve
168
is disposed in such a way that it controls the passage through the conduit
62
from the control pressure chamber
52
into the reservoir
56
. The control pressure chamber
52
is continuously connected to the line
14
by means of the conduit
60
with the throttle restriction
61
. The control device
70
controls the second control valve
168
during the fuel injection in a manner opposite from that of the control valve
68
in the first exemplary embodiment. In the starting position, the second control valve
168
is open so that the control pressure chamber
52
is connected to the reservoir
56
. If a fuel injection is to occur, then the control device
70
moves the second control valve
168
into its open switched position. In order to interrupt the fuel injection between the preinjection and the main injection or between the main injection and the secondary injection, the control device
70
moves the second control valve
168
into its closed switched position so that the control pressure chamber
52
is disconnected from the reservoir
56
and high pressure prevails in it.
In a simplified embodiment of the fuel injection apparatus, the second control valve
68
and/or
168
as well as the control piston
50
and the control pressure chamber
52
can be eliminated and solely the first control valve
58
is provided. In this case, the fuel injection is controlled only by means of the first control valve
58
, wherein during the delivery stroke of the pump piston
18
, when the control valve
58
is open, high pressure cannot build up in the pump working chamber
22
, the line
14
, and the pressure chamber
40
and consequently, no fuel injection takes place. When the control valve
58
is closed, high pressure can build up in the pressure chamber
40
and the fuel injection valve
12
opens when the force that the pressure in the pressure chamber
40
exerts on the injection valve member
28
in the opening direction
29
is greater than the force of the closing spring
44
. In order to interrupt or terminate the fuel injection, the control valve
58
is opened so that the pressure chamber
40
is pressure-relieved.
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 apparatus for an internal combustion engine, the apparatus comprisinga high-pressure fuel pump (10) and a fuel injection valve (12) connected to the pump (10) for each cylinder of the engine, the high-pressure fuel pump (10) having a pump piston (18) driven in a stroke motion by the engine and defining a pump working chamber (22), the fuel injection valve (12) having a pressure chamber (40) connected to the pump working chamber (22) by means of a line (14), the pressure chamber (40) being disposed separate from the high-pressure fuel pump (10) in the engine and having an injection valve member (28), which is used to control at least one injection opening (32) and which can be moved by the pressure prevailing in the pressure chamber (40) in an opening direction (29), counter to a closing force, in order to unblock the at least one injection opening (32), and, an electrically actuated control valve (58) which at least indirectly controls a connection (54) of the pump working chamber (22) to a relief chamber (56), the control valve (58) being disposed in the fuel injection valve (12) and the fuel injection valve (12) being provided with a reservoir (56) that functions as a relief chamber, which can store pressurized fuel diverted by the control valve (58) when this valve is open.
- 2. The fuel injection apparatus according to claim 1, wherein the volume of the reservoir (56) is at least as great as the volume that the pump piston (18) delivers during a delivery stroke.
- 3. The fuel injection apparatus according to claim 1, wherein the reservoir (56) has a flexible boundary (64).
- 4. The fuel injection apparatus according to claim 2, wherein the reservoir (56) has a flexible boundary (64).
- 5. The fuel injection apparatus according to claim 1, further comprisinga control pressure chamber (52), an additional electrically actuated control valve (68; 168) disposed in the fuel injection valve (12) and which controls the pressure prevailing in the control pressure chamber (52), the control pressure chamber (52) being defined by a control piston (50) that acts on the injection valve member (28) in a closing direction by means of the pressure prevailing in the control pressure chamber (52).
- 6. The fuel injection apparatus according to claim 2, further comprisinga control pressure chamber (52), an additional electrically actuated control valve (68; 168) disposed in the fuel injection valve (12) and which controls the pressure prevailing in the control pressure chamber (52) the control pressure chamber (52), being defined by a control piston (50) that acts on the injection valve member (28) in a closing direction by means of the pressure prevailing in the control pressure chamber (52).
- 7. The fuel injection apparatus according to claim 3, further comprisinga control pressure chamber (52), an additional electrically actuated control valve (68; 168) disposed in the fuel injection valve (12) and which controls the pressure prevailing in the control pressure chamber (52), the control pressure chamber (52) being defined by a control piston (50) that acts on the injection valve member (28) in a closing direction by means of the pressure prevailing in the control pressure chamber (52).
- 8. The fuel injection apparatus according to claim 4, further comprisinga control pressure chamber (52), an additional electrically actuated control valve (68; 168) disposed in the fuel injection valve (12) and which controls the pressure prevailing in the control pressure chamber (52), the control pressure chamber (52) being defined by a control piston (50) that acts on the injection valve member (28) in a closing direction by means of the pressure prevailing in the control pressure chamber (52).
- 9. The fuel injection apparatus according to claim 5, wherein the additional control valve (68) controls a connection (60) of the control pressure chamber (52) at least indirectly to the pump working chamber (22), wherein the control pressure chamber (52) has a continuously open connection (62) to the reservoir (56), and wherein a throttle restriction (61; 63) is preferably disposed in each of the connections (60; 62) of the control pressure chamber (52).
- 10. The fuel injection apparatus according to claim 6, wherein the additional control valve (68) controls a connection (60) of the control pressure chamber (52) at least indirectly to the pump working chamber (22), wherein the control pressure chamber (52) has a continuously open connection (62) to the reservoir (56), and wherein a throttle restriction (61; 63) is preferably disposed in each of the connections (60; 62) of the control pressure chamber (52).
- 11. The fuel injection apparatus according to claim 7, wherein the additional control valve (68) controls a connection (60) of the control pressure chamber (52) at least indirectly to the pump working chamber (22), wherein the control pressure chamber (52) has a continuously open connection (62) to the reservoir (56), and wherein a throttle restriction (61; 63) is preferably disposed in each of the connections (60; 62) of the control pressure chamber (52).
- 12. The fuel injection apparatus according to claim 8, wherein the additional control valve (68) controls a connection (60) of the control pressure chamber (52) at least indirectly to the pump working chamber (22), wherein the control pressure chamber (52) has a continuously open connection (62) to the reservoir (56), and wherein a throttle restriction (61; 63) is preferably disposed in each of the connections (60; 62) of the control pressure chamber (52).
- 13. The fuel injection apparatus according to claim 5, wherein the additional control valve (168) controls a connection (62) of the control pressure chamber (52) to the reservoir (56), wherein the control pressure chamber (52) has a continuously open connection (60) at least indirectly to the pump working chamber (22), and wherein a throttle restriction (61; 63) is preferably provided in each of the connections (60; 62) of the control pressure chamber (52).
- 14. The fuel injection apparatus according to claim 6, wherein the additional control valve (168) controls a connection (62) of the control pressure chamber (52) to the reservoir (56), wherein the control pressure chamber (52) has a continuously open connection (60) at least indirectly to the pump working chamber (22), and wherein a throttle restriction (61; 63) is preferably provided in each of the connections (60; 62) of the control pressure chamber (52).
- 15. The fuel injection apparatus according to claim 7, wherein the additional control valve (168) controls a connection (62) of the control pressure chamber (52) to the reservoir (56), wherein the control pressure chamber (52) has a continuously open connection (60) at least indirectly to the pump working chamber (22), and wherein a throttle restriction (61; 63) is preferably provided in each of the connections (60; 62) of the control pressure chamber (52).
- 16. The fuel injection apparatus according to claim 8, wherein the additional control valve (168) controls a connection (62) of the control pressure chamber (52) to the reservoir (56), wherein the control pressure chamber (52) has a continuously open connection (60) at least indirectly to the pump working chamber (22), and wherein a throttle restriction (61; 63) is preferably provided in each of the connections (60; 62) of the control pressure chamber (52).
- 17. The fuel injection apparatus according to claim 1, wherein the pump working chamber (22) in the high-pressure fuel pump (10) has a connection to a fuel tank (24) by means of a low-pressure region and this connection contains a check valve (21) that opens toward the pump working chamber (22).
- 18. The fuel injection apparatus according to claim 2, wherein the pump working chamber (22) in the high-pressure fuel pump (10) has a connection to a fuel tank (24) by means of a low-pressure region and this connection contains a check valve (21) that opens toward the pump working chamber (22).
- 19. The fuel injection apparatus according to claim 3, wherein the pump working chamber (22) in the high-pressure fuel pump (10) has a connection to a fuel tank (24) by means of a low-pressure region and this connection contains a check valve (21) that opens toward the pump working chamber (22).
- 20. The fuel injection apparatus according to claim 5, wherein the pump working chamber (22) in the high-pressure fuel pump (10) has a connection to a fuel tank (24) by means of a low-pressure region and this connection contains a check valve (21) that opens toward the pump working chamber (22).
Priority Claims (1)
Number |
Date |
Country |
Kind |
101 55 973 |
Nov 2001 |
DE |
|
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A |
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A |
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