Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2000-04-19
2001-09-11
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S496000
Reexamination Certificate
active
06286483
ABSTRACT:
TECHNICAL FIELD
The present invention relates to fuel injectors. More particularly, the present invention relates to hydraulically-actuated, electronically--controlled unit injectors (HEUI injectors).
BACKGROUND OF THE INVENTION
The prior art injectors (baseline) used here for references are the hydraulicallyactuated, electronically-controlled unit injectors described in the following references, which are incorporated herein by reference: SAE paper 930270 and U.S. Pat. Nos. 5,720,261, 5,597,118, and 5,826,562.
The first three above referenced injectors (SAE paper 930270 and U.S. Pat. Nos. 5,720,261, and 5,597,118) do not have any delay device between the control valve and the intensifier. The flow of actuation liquid into the intensifier piston chamber occurs almost immediately after the control valve opens.
The injector of U.S. Pat. No. 5,826,562 delays and limits the initial flow to the intensifier piston by adding throttle slots or a groove on top of the intensifier piston. The opening of the flow passage to the intensifier is controlled by the intensifier piston motion. In the invention of U.S. Pat. No. 5,826,562, flow to the intensifier chamber depends on the traveling velocity of the intensifier. If intensifier can not move fast enough, the flow area then cannot open up. If the flow area cannot open Lip, the intensifier cannot travel faster. This contradiction is the source of a serious limitation of an injector made according to the '562 patent.
Referring to the drawings,
FIGS. 7 and 7
a
show a prior art fuel injector
350
. The prior art fuel injector
350
is typically mounted to an engine block and injects a controlled pressurized volume of fuel into a combustion chamber (not shown). The prior art injector
350
of the present invention is typically used to inject diesel fuel into a compression ignition engine, although it is to be understood that the injector could also be used in a spark ignition engine or any other system that requires the injection of a fluid.
The fuel injector
350
has an injector housing
352
that is typically constructed from a plurality of individual parts. The housing
352
includes an outer casing
354
that contains block members
356
,
358
, and
360
(not shown). The outer casing
354
has a fuel port
364
that is coupled to a fuel pressure chamber
366
by a fuel passage
368
. A first check valve
370
is located within fuel passage
368
to prevent a reverse flow of fuel from the pressure chamber
366
to the fuel port
364
. The pressure chamber
366
is coupled to a nozzle
372
through fuel passage
374
. A second check valve
376
is located within the fuel passage
374
to prevent a reverse flow of fuel from the nozzle
372
to the pressure chamber
366
.
The flow of fuel through the nozzle
372
is controlled by a needle valve
378
that is biased into a closed position by spring
380
located within a spring chamber
381
. The needle valve
378
has a shoulder
382
above the location where the passage
374
enters the nozzle
378
. When fuel flows into the passage
374
the pressure of the fuel applies a force on the shoulder
382
. The shoulder force lifts the needle valve
378
away from the nozzle openings
372
and allows fuel to be discharged from the injector
350
.
A passage
383
may be provided between the spring chamber
381
and the fuel passage
368
to drain any fuel that leaks into the chamber
381
. The drain passage
383
prevents the build up of a hydrostatic pressure within the chamber
381
which could create a counteractive force on the needle valve
378
and degrade the performance of the injector
350
.
The volume of the pressure chamber
366
is varied by an intensifier piston
384
. The intensifier piston
384
extends through a bore
386
of block
360
and into a first intensifier chamber
388
located within an upper valve block
390
. The piston
384
includes a shaft member
392
which has a shoulder
394
that is attached to a head member
396
. The shoulder
394
is retained in position by clamp
398
that fits within a corresponding groove
400
in the head member
396
. The head member
396
has a cavity which defines a second intensifier chamber
402
.
The first intensifier chamber
388
is in fluid communication with a first intensifier passage
404
that extends through block
390
. Likewise, the second intensifier chamber
402
is in fluid communication with a second intensifier passage
406
.
The block
390
also has a supply working passage
408
that is in fluid communication with a supply working port
410
. The supply port
410
is typically coupled to a system that supplies a working fluid which is used to control the movement of the intensifier piston
384
. The working fluid is typically a hydraulic fluid that circulates in a closed system separate from the fuel. Alternatively the fuel could also be used as the working fluid. Both the outer body
354
and block
390
have a number of outer grooves
412
which typically retain O-rings (not shown) that seal the injector
350
against the engine block. Additionally, block
362
and outer shell
354
may be sealed to block
390
by O-ring
414
.
Block
360
has a passage
416
that is in fluid communication with the fuel port
364
. The passage
416
allows any fuel that leaks from the pressure chamber
366
between the block
362
and piston
384
to be drained back into the fuel port
364
. The passage
416
prevents fuel from leaking into the first intensifier chamber
388
.
The flow of working fluid into the intensifier chambers
388
and
402
can be controlled by a four-way solenoid control valve
418
. The control valve
418
has a spool
420
that moves within a valve housing
422
. The valve housing
422
has openings connected to the passages
404
,
406
and
408
and a drain port
424
. The spool
420
has an inner chamber
426
and a pair of spool ports that can be coupled to the drain ports
424
. The spool
420
also has an outer groove
432
. The ends of the spool
420
have openings
434
which provide fluid communication between the inner chamber
426
and the valve chamber
434
of the housing
422
. The openings
434
maintain the hydrostatic balance of the spool
420
.
The valve spool
420
is moved between the first closed position shown in
FIG. 7 and a
second open position shown in
FIG. 7
a
by a first solenoid
438
and a second solenoid
440
. The solenoids
438
and
440
are typically coupled to a controller which controls the operation of the injector. When the first solenoid
438
is energized, the spool
420
is pulled to the first position, wherein the first groove
432
allows the working fluid to flow from the supply working passage
408
into the first intensifier chamber
388
and the fluid flows from the second intensifier chamber
402
into the inner chamber
426
and out the drain port
424
. When the second solenoid
440
is energized the spool
420
is pulled to the second position, wherein the first groove
432
provides fluid communication between the supply working passage
408
and the second intensifier chamber
402
and between the first intensifier chamber
388
and the drain port
424
.
The groove
432
and passages
428
are preferably constructed so that the initial port is closed before the final port is opened. For example, when the spool
420
moves from the first position to the second position, the portion of the spool adjacent to the groove
432
initially blocks the first passage
404
before the passage
428
provides fluid communication between the first passage
404
and the drain port
424
. Delaying the exposure of the ports reduces the pressure surges in the system and provides an injector which has more predictable firing points on the fuel injection curve.
The spool
420
typically engages a pair of bearing surfaces
442
in the valve housing
422
. Both the spool
420
and the housing
422
are preferably constructed from a magnetic material such as a hardened
52100
or
440
c steel, so that the hysteresis of the material will maintain the spool
420
in e
Lei Ning
Thuente John F.
Yang Xilin
Calfa Jeffrey P.
Dennis Kelly Sullivan
Hernandez Gilberto
International Truck and Engine Corporation
Moulis Thomas N.
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