Fluid sprinkling – spraying – and diffusing – Processes – Of fuel injection
Reexamination Certificate
1999-08-11
2001-05-29
Michalsky, Gerald A. (Department: 3753)
Fluid sprinkling, spraying, and diffusing
Processes
Of fuel injection
C137S625640, C239S096000
Reexamination Certificate
active
06237857
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to fuel injectors, and more particularly to valves for controlling hydraulically actuated fuel injectors.
BACKGROUND AND SUMMARY
Known hydraulically-actuated fuel injection systems and/or components are shown, for example, in U.S. Pat. Nos. 5,687,693 and 5,738,075 issued to Chen and Hafner et al. on Nov. 18, 1997 and Apr. 14, 1998, respectfully.
In these hydraulically actuated fuel injectors, a spring biased needle check opens to commence fuel injection when pressure is raised by an intensifier piston/plunger assembly to a valve opening pressure. The intensifier piston is acted upon by a relatively high pressure actuation fluid, such as engine lubricating oil, when an actuator driven actuation fluid control valve, for example a solenoid driven actuation fluid control valve, opens the injector's high pressure inlet.
Injection is ended by operating the actuator to release pressure above the intensifier piston. This in turn causes a drop in fuel pressure causing the needle check to close under the action of its return spring and end injection.
Recently, Caterpillar Inc. has developed a new generation of fuel injectors, such as the HEUI-B™ fuel injector, that feature direct control of the spring biased needle check valve. In these fuel injectors, even when fuel pressure has been raised by the intensifier piston to the valve opening pressure, the check valve can be kept shut (or quickly shut if it is open) by applying high pressure hydraulic fluid directly to the back of the needle check valve.
A critical component of both types of hydraulically actuated fuel injector is the actuation fluid control valve, which admits the high pressure actuating fluid to the injector. In the HEUI-B™ type injectors the actuation fluid control valve is especially critical because it must be able to control both the intensifier piston and the check valve.
In a yet-to-be-released HEUI-B™ fuel injector described in co-pending patent application Ser. No. 09/1358,990 filed Jul. 22, 1999 and entitled “Hydraulically Actuated Fuel Injector with Seated Pin Actuator” a two-way valve is used both to apply direct control on the check valve, and also to operate the spool valve that controls actuation of an intensifier piston.
Embodiments of the HEUI-B™ type injectors with a seated pin actuator valve are described below with reference to
FIGS. 1-3
. The fuel injector
10
utilizes an actuation fluid control valve including a single attractive two-way solenoid
12
. An armature assembly includes an actuation valve member
14
attached with an armature
16
. The solenoid
12
pulls the armature assembly upward in an actuator bore
18
. An actuator spring
20
biases the armature
16
and the attached actuation valve member
14
downward.
High-pressure actuation fluid from a hydraulic fluid source, such as a common rail (not shown) that feeds a number of fuel injectors for example, enters the fuel injector
10
through an actuation fluid inlet
22
. A fluid entry chamber
24
(
FIG. 2
) in the actuation fluid control valve is always exposed to the high pressure actuation fluid, as is an upper end hydraulic surface
26
(
FIG. 3
) of a spool valve member
28
that is slidable up and down in a spool valve bore
30
.
The actuation fluid control valve operates as follows. At a first position the solenoid
12
is de-energized and the actuator spring
20
pushes the valve member
14
downward to mate with a drain seat
32
. In this position high-pressure actuation fluid flows from the fluid entry chamber
24
into a check control cavity
34
.
The high-pressure actuation fluid in the check control cavity
34
flows down into a check control chamber
36
, at which time the high pressure actuation fluid together with a check spring
38
act on a closing hydraulic surface
40
of a check valve member
42
to close nozzle outlets
44
of a nozzle
46
. This keeps fuel in a nozzle chamber
48
from being injected into an engine for example.
The high pressure actuation fluid in the check control cavity
34
also flows into a side passage
50
where it acts against a lower end hydraulic surface
52
of the spool valve member
28
. This balances the hydraulic fluid pressure against the upper end hydraulic surface
26
of the spool valve member
28
, so that a spool valve spring
54
can keep the spool valve member
28
in an up position that closes off an intensifier control passage
56
from the source of high pressure actuation fluid, while opening the intensifier control passage
56
to a low pressure hydraulic fluid drain
58
.
When the solenoid
12
is energized it pulls the actuation valve member
14
upward against an inlet seat
60
. This closes off the check control cavity
34
from the source of high-pressure hydraulic fluid in the fluid entry chamber
24
, while opening the check control cavity
34
to a low-pressure actuator fluid drain
62
. This reduces fluid pressure in the check control chamber
36
so that only the force of the check spring
38
is acting on the closing hydraulic surface
40
of the check valve member
42
.
This also reduces fluid pressure against the lower end hydraulic surface
52
of the spool valve member
28
. When this happens, the force of the high pressure actuation fluid on the upper end hydraulic surface
26
of the spool valve member
28
overcomes the force of the spool valve spring
54
and pushes the spool valve member
28
downward. This closes off the intensifier control passage
56
from the hydraulic fluid drain
58
, while opening the intensifier control passage
56
to the source of high-pressure actuation fluid.
The high pressure actuation fluid in the intensifier control passage
56
pushes down on an intensifier piston
64
, pressurizing fuel in a fuel pressurization chamber
66
that has entered from a fuel inlet
68
connected to a source of low pressure fuel (not shown). The highly pressurized fuel flows through a connection passage
70
to the nozzle chamber
48
until fuel pressure in the nozzle chamber
48
is high enough to overcome the bias of the check spring
38
and push the check valve member
42
upward, which opens the nozzle outlets
44
and allows the fuel in the nozzle chamber
48
to be injected from the fuel injector
10
.
To terminate fuel injection the actuator
12
is de-energized, allowing the actuator spring
20
to move the actuation valve member
14
back to the first position. In this position the check control cavity
34
is closed off from the actuator fluid drain
62
, and is fluidly connected to high-pressure actuation fluid from the actuation fluid inlet
22
. This causes high pressure actuation fluid to be applied to the lower end hydraulic surface
52
of the spool valve member
28
, once again balancing the force of the high pressure actuation fluid against the upper end hydraulic surface
26
of the spool valve member
28
.
The bias provided by the spool valve spring
54
can now move the spool valve member
28
upward to cut off the supply of high pressure actuation fluid from the intensifier control passage
56
and to relieve the pressure in the intensifier control passage
56
by exposing it to the hydraulic fluid drain
58
. Bias provided by a plunger spring
72
is now able to push the intensifier piston
64
upward. This reduces the pressure of the fuel in the fuel pressurization chamber
66
, and hence in the nozzle chamber
48
, allowing the bias provided by the check spring
38
to push the check valve member
42
toward its closed position.
However, it takes some time for the high-pressure actuation fluid to move the spool valve member
28
to relieve pressure against the intensifier piston
64
. The high pressure actuation fluid in the check control cavity
34
reaches the check control chamber
36
and acts upon the low mass check valve member
42
much more quickly. Even though the nozzle chamber
48
still contains highly pressurized fuel, the combination of the increased pressure in the check control chamber
36
and the bias provided by the check spring
38
overcomes
Ausman Thomas G.
Satapathy Manas R.
Schuricht Scott R.
Bram Eric M.
Caterpillar Inc.
Michalsky Gerald A.
LandOfFree
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