Fluid sprinkling – spraying – and diffusing – Processes – Of fuel injection
Reexamination Certificate
2002-04-18
2003-12-02
Ganey, Steven J. (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Processes
Of fuel injection
C239S088000, C239S092000, C239S533900
Reexamination Certificate
active
06655603
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to fuel injectors, and more specifically to reverse flow check valves within fuel injectors.
BACKGROUND
Occasionally, an injector nozzle of a fuel injector will become leaky, and after an injection event, allow hot combustion gases from the engine cylinder to leak past the nozzle outlet and travel upwards into the nozzle supply passage of the fuel injector. If the gases are permitted to continue to travel upwards and reach the fuel pressurization chamber, the fuel injector will inject less than a predicted amount of fuel, and can eventually be unable to pressurize fuel and inject it into the engine cylinder.
Typically, gases have been blocked from the fuel pressurization chamber by reverse flow check valve assemblies having a variety of structures. One example of such a check valve assembly is shown in co-owned U.S. Pat. No. 5,287,838 issued to Wells on Feb. 22, 1994. The function of the check valve assembly is to permit communication of high pressure fuel from the fuel pressurization chamber to the nozzle outlet of the fuel injector during an injection phase, but to prevent communication (i.e., reverse flow) of engine cylinder combustion gas from the nozzle to the fuel pressurization chamber at the end of an injection event and during a non-injection phase if the nozzle of the fuel injector becomes leaky.
Referring to
FIG. 1
, there is shown a partial sectioned side diagrammatic view of a fuel injector
10
according to the above identified patent. The fuel injector
10
consists of an injector body
11
that includes a barrel
33
separated from a stop component
42
by a relatively thin plate
50
. A plunger
13
is movably positioned along a centerline
12
within the injector body
11
. The plunger
13
, the barrel
33
and the plate
50
define a fuel pressurization chamber
14
that is fluidly connected to a fuel tank (not shown) via a fuel supply line
30
. When the plunger
13
is driven downward, it advances along the centerline
12
in order to pressurize fuel delivered from the fuel tank (not shown) via the fuel supply line
30
. A check valve
32
is positioned within the fuel supply line
30
. The check valve
32
is in its closed position in which it blocks fluid communication between the fuel pressurization chamber
14
and the fuel supply line
30
when the plunger
13
is advancing downward and increasing the pressure within the fuel pressurization chamber
14
. When the plunger
13
is returning to its upward position, the pressure within the pressurization chamber
14
decreases such that the check valve
32
opens and low pressure fuel within the fuel supply line
30
can flow past the check valve
32
and into the fuel pressurization chamber
14
.
The injector body
11
defines a nozzle supply passage
15
, a nozzle outlet
17
, and a guide bore
54
. A needle valve is positioned in the injector body
11
and has a needle valve member
20
that is movable between a first position, in which the nozzle outlet
17
is open, and a second position, in which the nozzle outlet
17
is closed. The needle valve member
20
has an opening hydraulic surface
21
that is exposed to fluid pressure within the nozzle supply passage
15
, but is biased toward a closed position by a compressed spring
22
. When the needle valve member
20
is in its open position, a stop surface of the needle valve member
20
is in contact with the stop component
42
, and the nozzle outlet
17
is opened to allow pressurized fuel to be injected into the engine cylinder (not shown).
The fuel pressurization chamber
14
is fluidly connected to the nozzle outlet
17
via the nozzle supply passage
15
, which includes the guide bore
54
. Positioned within the guide bore
54
, there is a reverse flow check valve assembly that includes a reverse flow check
52
, the plate
50
, and the stop component
42
. The reverse flow check
52
is preferably a flat circular plate and defines a flow passage
53
. The flow passage
53
is preferably cylindrical and centrally positioned within the reverse flow check
52
and is fluidly connected to the nozzle supply passage
15
. The plate
50
, which is preferably flat, is positioned between the barrel
33
and the stop component
42
and defines a pair of kidney-shaped or crescent-shaped holes
51
, which are fluidly connected to the fuel pressurization chamber
14
. The flow passage
53
of the reverse flow check
52
is radially inwardly spaced from the kidney holes
51
of the plate
50
and is arranged so that the nozzle supply passage
15
is blocked from the pressurization chamber
14
when the reverse flow check
52
and the plate
50
are in contact. The reverse flow check
52
is movable between an open position and closed position. When in its open position, as shown, the reverse flow check
52
is in contact with the stop component
42
, and the fuel pressurization chamber
14
is fluidly connected to the nozzle supply passage
15
via the kidney holes
51
of the plate
50
and the flow passage
53
of the reverse flow check
52
.
Prior to an injection event, the plunger
13
is driven downward by a hydraulic intensifier piston or a tappet along a centerline
12
of the fuel injector
10
toward its downward position. This greatly increases the pressure within the upper portion of the nozzle supply passage
15
which includes the fuel pressurization chamber
14
and the lower portion of the nozzle supply passage
15
. The increased pressure within the fuel pressurization chamber
14
will also close the check valve
32
, blocking fluid communication between the fuel pressurization chamber
14
and the fuel tank (not shown) via the fuel supply line
30
. The reverse flow check
52
will be in its first, or open, position, and in contact with the stop component
42
. Thus, the pressurized fuel will flow from the fuel pressurization chamber
14
through kidney holes
51
within the plate
50
and through the flow passage
53
of the reverse flow check
52
to the lower portion of the nozzle supply passage
15
. Thus, during an injection event, the fuel pressurization chamber
14
is fluid connected to the lower portion of the nozzle supply passage
15
.
Shortly before the desired amount of pressurized fuel is injected into the engine cylinder via the nozzle outlet
17
of the fuel injector
10
, the plunger
13
will stop moving downward, resulting in a fuel pressure drop to below valve closing pressure. This causes the needle valve member
20
to move to its closed position under the action of spring
22
. Towards the end of the movement of the needle valve member
20
to its closed position, there is a reverse flow of pressurized fuel within the lower portion of the nozzle supply passage
15
. The reverse flow of fuel will lift the reverse flow check
52
out of contact with the stop component
42
. The reverse flow check
52
will be lifted upward until it is in contact with the plate
50
and, thus, in its second, or closed, position. Due to the positioning and placement of the kidney holes
51
of the plate
50
and the flow passage
53
of the reverse flow check
52
, fluid communication between the fuel pressurization chamber
14
and the nozzle supply passage
15
will be blocked. Gas ingestion can occur over a brief instant as the needle valve member
20
is not yet closed while fuel pressure has dropped below cylinder pressure. If any engine cylinder combustion gases enter through the nozzle outlet
17
into the lower portion of the nozzle supply passage
15
, they will be blocked from fluid communication with the fuel pressurization chamber
14
when the reverse flow check
52
is in its closed position. Thus, the prior injector prevents gas from being trapped within the fuel pressurization chamber
14
by utilizing the reverse flow check
52
, the plate
51
, and the stop component
42
.
The hydraulic pressure acting on the plunger
13
is then reduced allowing the plunger
13
to retract along the centerline
12
to its upward position under the action of its biasing spring
16
. A
Ayanji Sudhindra K.
Haji Goudarz
Long Michael C.
Nan Xinshuang
Thaker Hrishikesh D.
Caterpillar Inc
Ganey Steven J.
Liell & McNeil
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