Information
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Patent Grant
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6173699
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Patent Number
6,173,699
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Date Filed
Thursday, February 4, 199925 years ago
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Date Issued
Tuesday, January 16, 200123 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
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CPC
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US Classifications
Field of Search
US
- 123 446
- 123 496
- 123 506
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International Classifications
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Abstract
A hydraulically actuated fuel injector includes an injector body that defines an actuation fluid cavity and a nozzle outlet, and further defines a low pressure area and a fuel pressurization chamber in fluid communication with a spill passage. A pumping element is positioned in the injector body and moveable between a retracted position and an advanced position. The pumping element has a first end exposed to fluid pressure in the actuation fluid cavity and a second end exposed to fluid pressure in the fuel pressurization chamber. An electronic spill valve attached to the injector body is moveable between an open position in which the spill passage fluidly connects the fuel pressurization chamber to the low pressure area, and a closed position in which the spill passage is closed. Opening and closing of the spill valve during an injection event produces various rate shaping injection effects.
Description
TECHNICAL FIELD
The present invention relates generally to hydraulically-actuated fuel injectors, and more particularly to hydraulically-actuated fuel injectors having rate shaping through a fuel spillage valve.
BACKGROUND ART
Co-owned U.S. Pat. No. 5,492,098 to Hafner, et al., describes a hydraulically-actuated fuel injector having rate shaping through fuel spillage. Like many hydraulically-actuated fuel injectors, Hafner includes a pumping element or plunger that defines a portion of a fuel pressurization chamber. In order to produce a split injection at an idle condition, the Hafner, et al. plunger includes an annulus in fluid communication with the fuel pressurization chamber via several internal passageways. As the plunger is driven downward, the annulus comes briefly into registry with a spill passage defined by the injector body. When this occurs, fuel spills from the fuel pressurization chamber, and fuel pressure drops below a valve closing pressure sufficient to allow the nozzle needle valve to briefly close. In order to produce a split injection at idle, the plunger annulus is out of registry with the spill passage for the beginning and end portions of the plunger's stroke.
In part to increase the operating range of the Hafner, et al. injector, the actuation fluid pressure supplied to the injector is adjusted to be relatively low at idle but relatively high at rated conditions. These differing pressures allow the injector to inject a very small amount of fuel at idle, but a relatively large amount of fuel at a rated condition. This actuation fluid pressure difference also results in the plunger moving at significantly different rates at idle and rated conditions. Because the plunger moves relatively slowly at the idle condition, the plunger annulus is in registry with the spill passage for a sufficient duration that a split injection can occur; however, because the plunger moves so quickly at a rated condition, the plunger annulus moves past the spill passage so quickly that very little spillage occurs and no split injection takes place. Because of the stroke length limitations available for the Hafner, et al. plunger, it would be difficult to modify in a way that could produce a split injection, or other significant rate shaping completely across its operating range. Although the Hafner, et al. injector has performed magnificently for many years, there remains room for improvement in providing a broader possible range of rate shaping at various operating conditions.
The present invention is directed to providing more flexibility and control to rate shaping through fuel spillage in hydraulically-actuated fuel injectors.
DISCLOSURE OF THE INVENTION
A hydraulically-actuated fuel injector includes an injector body that defines an actuation fluid cavity and a nozzle outlet, and further defines a low pressure area and a fuel pressurization chamber in fluid communication with a spill passage. A pumping element is positioned in the injector body and moveable between a retracted position and an advanced position. The pumping element has a first end exposed to fluid pressure in the actuation fluid cavity and a second end exposed to fluid pressure in the fuel pressurization chamber. An electronic spill valve is attached to the injector body and moveable between an open position in which the spill passage fluidly connects the fuel pressurization chamber to the low pressure area, and a closed position in which the spill passage is closed.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a side sectioned diagrammatic view of a hydraulically-actuated fuel injector according to the present invention.
FIG. 2
is an enlarged side sectioned diagrammatic view of an electronic spill valve according to one aspect of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Referring now to
FIG. 1
, a hydraulically-actuated fuel injector
10
includes a control valve assembly
11
, a hydraulic pressurization assembly
12
, a nozzle assembly
13
, and a spill valve assembly
14
. These various sub-assemblies are made up of various components attached together in a manner well known in the art to produce an injector body
15
. Apart from defining various internal fluid flow passages and portions of these various sub-assemblies, injector body
15
defines a high pressure actuation fluid inlet
16
connected to a source of high pressure actuation fluid
20
via an actuation fluid supply line
21
. A low pressure actuation fluid drain
17
is connected to a volume of low pressure actuation fluid
23
, such as an oil pan, via a drain return line
22
. Finally, injector body
15
defines a fuel inlet
18
connected to a source of fuel
25
, preferably distillate diesel fuel, via a fuel supply line
24
. Thus, in the preferred embodiment, hydraulically-actuated fuel injector
10
uses two distinct fluids in its operation; an actuation fluid, such as lubricating oil is used as the hydraulic medium, and a second fluid, such as distillate diesel fuel, is used as the injected fuel fluid.
The control valve assembly
11
includes an electrical actuator, such as a solenoid
30
, and a moveable poppet valve member
31
. In this case, poppet valve member
31
is attached to the armature portion
36
of solenoid
30
via a conventional fastener
35
. Poppet valve member
31
is moveable between a lower high pressure seat
32
that closes actuation fluid inlet
16
and an upward low pressure seat
33
that closes low pressure actuation fluid drain
17
. When solenoid
30
is de-energized, a biasing spring
34
pushes poppet valve member
31
downward to close high pressure seat
32
and open low pressure seat
33
. When in this position, an actuation fluid cavity
37
defined by injector body
15
is opened to low pressure drain
17
. When solenoid
30
is energized, poppet valve member
31
is pulled upward against the action of biasing spring
34
to a position that closes low pressure seat
33
and opens high pressure seat
32
. When in this position, high pressure actuation fluid can flow from actuation fluid inlet
16
into actuation fluid cavity
37
to act on the top surface of a pumping element
48
.
The hydraulic pressurization assembly
12
includes a pumping element
48
, which is made up of an intensifier piston
40
and a plunger
44
. Intensifier piston
40
is positioned in a piston bore
42
, which is defined by injector body
15
, and is moveable between a retracted position as shown, and a downward advanced position. Intensifier piston
40
includes a hydraulic surface
41
that is exposed to fluid pressure in actuation fluid cavity
37
. Piston
40
is normally biased to its upward retracted position by a return spring
43
. Plunger
44
is connected to move with piston
40
, and moves in a plunger bore
45
defined by injector body
15
. Plunger bore
45
and a hydraulic surface
47
of plunger
44
define a fuel pressurization chamber
50
. Thus, pumping element
48
has an upper end exposed to fluid pressure in actuation fluid cavity
37
, and a lower end exposed to fluid pressure in fuel pressurization chamber
50
. In order to intensify the fuel pressure, hydraulic surface
41
is substantially larger than hydraulic surface
47
. When pumping element
48
is undergoing its downward pumping stroke, fuel is pressurized in fuel pressurization chamber
50
. When pumping element
48
is undergoing its upward return stroke between injection events, low pressure fuel is drawn into fuel pressurization chamber from fuel inlet
18
, through low pressure area
52
and past check valve
51
.
The nozzle assembly
13
includes a needle valve assembly
19
which includes a needle valve member
60
that is moveable between a downward closed position in which nozzle outlet
56
is blocked, and an upward opened position in which nozzle outlet
56
is open. Nozzle outlet
56
is fluidly connected to fuel pressurization chamber
50
via nozzle supply passage
53
and nozzle chamber
55
. Needle valve member
60
includes a needle portion
61
, a spacer portion
62
, and a stop portion
63
. Needle valve member
60
includes a lifting hydraulic surface
64
that is exposed to fluid pressure in nozzle chamber
55
. Needle valve member
60
is normally biased downward to its closed position by a biasing spring
65
. However, when fuel pressure acting on lifting hydraulic surface
64
is above a valve opening pressure, needle valve member
60
will lift against the action of biasing spring
65
to open nozzle outlet
56
.
Referring now in addition to
FIG. 2
, the spill valve assembly
14
includes a spool valve member
73
movably attached to an electrical actuator, such as a solenoid
70
, a piezo-electric actuator, or other suitable electronic device. Those skilled in the art will appreciate that spool valve member
73
could be another type of valve member, such as a ball or poppet. Spool valve member
73
is moveable between a closed position, as shown, in which spill passage
71
is closed, and a downward opened position in which spill passage
71
is open. In this downward position, an annulus
74
defined by spool valve member
73
opens nozzle supply passage
53
to low pressure fuel area
52
via spill passage
71
. When solenoid
70
is de-energized, spool valve member
73
is biased toward its upward closed position by a biasing spring
72
. In the preferred embodiment, these various components are fitted into a stop component
57
, which comprises a portion of injector body
15
.
INDUSTRIAL APPLICABILITY
Referring again to
FIGS. 1 and 2
, fuel injector
10
is shown with its various moveable components positioned as they would be just prior to an injection event. In particular, solenoids
30
and
70
are de-energized, poppet valve member
31
is in its downward position closing high pressure seat
32
, pumping element
48
is in its upward retracted position, spill spool valve member
73
is in its upward closed position, and needle valve member
60
is in its downward closed position to close nozzle outlet
56
. Each injection event is initiated by energizing solenoid
30
to move poppet valve member
31
upward to close low pressure seat
33
and open high pressure seat
32
. When this occurs, high pressure actuation fluid flows into actuation fluid cavity
37
from actuation fluid inlet
16
. This high pressure actuation fluid acts on hydraulic surface
41
and begins moving pumping element
48
(piston
40
and plunger
44
) downward for the pumping stroke. Downward movement of pumping element
48
closes check valve
51
and causes fuel pressure in fuel pressurization chamber
50
to quickly rise. When fuel pressure exceeds a valve opening pressure, needle valve member
60
lifts and the spray of fuel out of nozzle outlet
56
commences.
Each injection event is ended by de-energizing solenoid
30
. This causes poppet valve member
31
to move back downward to close high pressure seat
32
and open low pressure seat
33
. When this occurs, pressure acting on hydraulic surface
41
is relieved, and the pumping element
48
ceases its downward stroke. This in turn causes fuel pressure to rapidly drop below a valve closing pressure. When fuel pressure is sufficiently low, needle valve member
60
moves downward toward its closed position under the action of biasing spring
63
to close nozzle outlet
56
and end the injection event. Between injection events, return spring
43
pushes pumping element
48
upward toward its retracted position. When this occurs, fresh fuel is drawn into fuel pressurization chamber
50
past check valve
51
. At the same time, the used actuation fluid in actuation cavity
37
is expelled toward reservoir
23
past low pressure seat
33
and through low pressure actuation fluid drain
17
.
In order to extend fuel injector
10
's range of operation, it preferably has the ability to control actuation fluid pressure in source
20
. Thus, when it is desired to inject a relatively small amount of fuel, pressure in source
20
is relatively low, but pressure in source
20
is relatively high when it is desired to inject a relatively large amount of fuel, such as at a rated condition. While this flexibility allows fuel injector
10
to perform across the operational needs of most engines, there is often a desire to rate shape the injection at different engine operating conditions to produce certain desired results, such as reducing undesirable emissions, etc.
In order to introduce some rate shaping into injector
10
, spill valve assembly allows a control system to spill fuel during an injection event to produce certain rate shaping effects. In the preferred embodiment, the flow area past spill valve assembly
14
is about equal to the spill flow area in the previously described Hafner injector so that the present invention has the ability to produce a split injection at idle conditions. Recalling that in the Hafner injector, its mechanically opened spill passage is large to produce a split injection at idle, but is not sufficiently large enough to produce a split injection at a rated condition. In order to duplicate the performance of the previously described Hafner injector, the flow area through the fuel spillage valve would preferably have an area about equal to that of the previously described Hafner injector. Thus, the present invention would allow one to produce a split injection at idle by briefly energizing and de-energizing solenoid
70
during pumping element
48
's downward stroke. However, when the injector is operating at a rated condition, solenoid
70
would be left de-energized and no fuel spillage would occur.
In possible alternative embodiments, the flow area past spill valve assembly
14
could be adjusted such that the fuel injector would have the ability to produce boot shaped, or possibly split injections at rated operating conditions. In the case of a boot shaped injection, the flow area past spill valve assembly
14
would be such that fuel pressure would remain above the valve opening pressure, but would drop to reflect a lower fuel injection rate. Thus, for an appropriately sized spill valve assembly
14
, a boot shaped injection could be created by initially energizing solenoid
70
to open spill valve assembly
14
for a beginning portion of the injection event, and then closing spill valve assembly
14
for a remaining portion of an injection event. In the case of a possible split injection, the flow area past spill valve assembly
14
would preferably have to be large enough to cause the fuel pressure to drop below the valve closing pressure so that the needle valve member would briefly close. Such an injection event would be created by maintaining solenoid
70
de-energized for a beginning portion of an injection event, briefly energizing the solenoid to cause a brief spill, and then again de-energizing solenoid
70
to reclose the spill valve member to initiate a second half of a split injection event.
The above description is intended for illustrated purposes only, and is not intended to limit the scope of the present invention in any way. For instance, different electrical actuators could be substituted in for the solenoids described, the spill valve assembly could be relocated in the injector body, such as possibly the barrel portion of the fuel injector, and the flow areas through the spill valve member could be adjusted to produce different injection rate profiles. Thus, various modifications could be made to the disclosed embodiment without otherwise departing from the intended spirit and scope of the present invention, which is defined by the claims set forth below.
Claims
- 1. A hydraulically actuated fuel injector comprising:an injector body defining an actuation fluid cavity and a nozzle outlet, and further defining a low pressure area and a fuel pressurization chamber in fluid communication with a spill passage; a pumping element positioned in said injector body and being movable between a retracted position and an advanced position, and having a first end exposed to fluid pressure in said actuation fluid cavity and a second end exposed to fluid pressure in said fuel pressurization chamber; and an electronic spill valve attached to said injector body and being movable between an open position in which said spill passage fluidly connects said fuel pressurization chamber to said low pressure area and a closed position in which said spill passage is closed.
- 2. The hydraulically actuated fuel injector of claim 1 wherein said electronic spill valve includes an electrical actuator attached to a spill valve member.
- 3. The hydraulically actuated fuel injector of claim 1 wherein said spill passage opens into a nozzle supply passage that extends between said fuel pressurization chamber and said nozzle outlet; andsaid electronic spill valve includes a spool valve member.
- 4. The hydraulically actuated fuel injector of claim 1 wherein said electronic spill valve includes a solenoid and a spill valve member positioned in said injector body.
- 5. The hydraulically actuated fuel injector of claim 1 having an operating range and further comprising a needle valve assembly positioned in said injector body and defining a valve opening pressure; andsaid spill passage has a flow area sufficiently large to drop fuel pressure in said fuel pressurization chamber below said valve opening pressure over a portion of said operating range.
- 6. The hydraulically actuated fuel injector of claim 1 further comprising a needle valve member positioned in said injector body;said injector body including a stop component that defines a portion of said spill passage; and said needle valve member being movable between a closed position in which said nozzle outlet is closed, and an open position in which said needle valve member is in contact with said stop component.
- 7. The hydraulically actuated fuel injector of claim 1 further comprising an electronic control valve attached to said injector body and being movable between an on position in which said actuation fluid cavity is open to a source of high pressure actuation fluid, and an off position in which said actuation fluid cavity is open to a low pressure return.
- 8. The hydraulically actuated fuel injector of claim 1 wherein said injector body defines a fuel inlet connected to a source of fuel; andsaid injector body defines an actuation fluid inlet connected to a source of actuation fluid that is different from said fuel.
- 9. The hydraulically actuated fuel injector of claim 1 wherein said first end has a first hydraulic surface and said second end has a second hydraulic surface; andsaid first hydraulic surface is greater than said second hydraulic surface.
- 10. A hydraulically actuated fuel injector comprising:an injector body defining an actuation fluid cavity and a nozzle outlet, and further defining a low pressure area and a fuel pressurization chamber in fluid communication with a spill passage; a pumping element positioned in said injector body and being movable between a retracted position and an advanced position, and having a first end exposed to fluid pressure in said actuation fluid cavity and a second end exposed to fluid pressure in said fuel pressurization chamber; an electronic spill valve positioned in said injector body and including a spill valve member movable between an open position in which said spill passage fluidly connects said fuel pressurization chamber to said low pressure area and a closed position in which said spill passage is closed; a fuel inlet being connected to a source of low pressure fuel; and an actuation fluid inlet being connected to a source of high pressure actuation fluid that is different from fuel.
- 11. The hydraulically actuated fuel injector of claim 10 wherein said electronic spill valve includes an electrical actuator attached to a spill valve member.
- 12. The hydraulically actuated fuel injector of claim 11 wherein said electrical actuator is a solenoid; andsaid spill valve member is a spool valve member.
- 13. The hydraulically actuated fuel injector of claim 12 wherein said spill passage opens into a nozzle supply passage that extends between said fuel pressurization chamber and said nozzle outlet.
- 14. The hydraulically actuated fuel injector of claim 12 having an operating range and further comprising a needle valve assembly positioned in said injector body and defining a valve opening pressure; andsaid spill passage has a flow area sufficiently large to drop fuel pressure in said fuel pressurization chamber below said valve opening pressure over a portion of said operating range.
- 15. The hydraulically actuated fuel injector of claim 12 further comprising a needle valve member positioned in said injector body;said injector body including a stop component that defines a portion of said spill passage; and said needle valve member being movable between a closed position in which said nozzle outlet is closed, and an open position in which said needle valve member is in contact with said stop component.
- 16. The hydraulically actuated fuel injector of claim 12 further comprising an electronic control valve attached to said injector body and being movable between an on position in which said actuation fluid cavity is open to said source of high pressure actuation fluid, and an off position in which said actuation fluid cavity is open to a low pressure return.
- 17. The hydraulically actuated fuel injector of claim 12 wherein said first end has a first hydraulic surface and said second end has a second hydraulic surface; andsaid first hydraulic surface is greater than said second hydraulic surface.
- 18. A hydraulically actuated fuel injector comprising:an injector body defining an actuation fluid cavity and a nozzle outlet, and further defining a low pressure area and a fuel pressurization chamber in fluid communication with a spill passage; an electronic control valve attached to said injector body and being movable between an on position in which said actuation fluid cavity is open to a source of high pressure actuation fluid, and an off position in which said actuation fluid cavity is open to a low pressure return; a pumping element positioned in said injector body and being movable between a retracted position and an advanced position, and having a first hydraulic surface exposed to fluid pressure in said actuation fluid cavity and a second hydraulic surface exposed to fluid pressure in said fuel pressurization chamber; an electronic spill valve positioned in said injector body and including a spill valve member movable between an open position in which said spill passage fluidly connects said fuel pressurization chamber to said low pressure area and a closed position in which said spill passage is closed; said first hydraulic surface being greater than said second hydraulic surface; a fuel inlet being connected to a source of low pressure fuel; and a actuation fluid inlet being connected to said source of high pressure actuation fluid, which is different from fuel.
- 19. The hydraulically actuated fuel injector of claim 18 wherein said electronic spill valve includes a solenoid attached to a spool valve member.
- 20. The hydraulically actuated fuel injector of claim 19 having an operating range that includes an idle condition, and further comprising a needle valve assembly positioned in said injector body and defining a valve opening pressure; andsaid spill passage has a flow area sufficiently large to drop fuel pressure in said fuel pressurization chamber below said valve opening pressure when operating at said idle condition.
US Referenced Citations (20)
Foreign Referenced Citations (1)
Number |
Date |
Country |
2 266 933 |
Nov 1993 |
GB |