Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2000-05-15
2002-11-05
Mohanty, Bibhu (Department: 3752)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S496000
Reexamination Certificate
active
06474304
ABSTRACT:
BACKGROUND OF THE INVENTION
This concept is directed to a double-acting, two-stage flow control valve (DATS Valve) for use as a hydraulic control device. The present invention has use generally as a hydraulic control device and may be used, for example, in a camless engine. Additionally, the present application is directed specifically at the use of the hydraulic control device in combination with an intensified, low-pressure, common rail fuel injector used in a hydraulically-actuated, electronically-controlled unit injection (HEUI) system for an internal combustion engine, particularly a diesel engine, and the method of operating the control valve to selectively achieve pilot injection, rate shaping injection, far split injection, and single shot injection modes of operation of the fuel injector.
THE PRIOR ART
The prior art injectors used here for reference are the hydraulically-actuated, electronically-controlled unit injectors described in the following references, which are incorporated herein by reference: SAE paper No. 930270, “HEUI—A New Direction for Diesel Fuel Systems,” and SAE paper No. 1999-01-0196, “Application of Digital Valve Technology to Diesel Fuel Injection” and U.S. Pat. Nos. 5,271,371, 5,479,901, 5,597,118, and 5,720,261, and 5,720,318.
A prior art HEUI injector
200
is depicted in prior art FIG.
1
. HEUI
200
consists of four main components: (1) control valve
202
; (2) intensifier
204
; (3) nozzle
206
; and (4) injector housing
208
.
The purpose of the control valve
202
is to initiate and end the injection process. Control valve
202
is comprised of a poppet valve
210
, having an attached armature
213
, and an electric control solenoid
212
. High pressure actuating oil from a high pressure rail
215
is supplied to the lower seat
214
of the poppet valve
210
through oil passageway
216
. To begin injection, the electric control solenoid
212
is energized moving the poppet valve
210
upward from the lower seat
214
to the upper seat
218
. This action admits high pressure oil to the spring cavity
220
and through the passage
222
to the piston chamber
223
of the intensifier
204
. Injection continues until the solenoid of the electric control
212
is de-energized and the poppet
210
moves from the upper seat
218
to lower seat
214
. Oil and fuel pressure then decrease as spent oil is ejected from the injector
200
through the open upper seat oil discharge
224
to the valve cover area of the internal combustion engine. The valve cover area is at ambient pressure.
The middle segment of the injector
200
includes the intensifier
204
. The intensifier
204
includes the hydraulic intensifier piston
236
, the plunger
228
, fuel chamber
230
, and the plunger return spring
232
.
Intensification of the fuel pressure to desired injection pressure levels is accomplished by the ratio of areas between the upper surface
234
of the intensifier piston
236
, acted on by the high pressure actuating oil and the lower surface
238
of the plunger
228
, acting on the fuel in chamber
230
. The intensification ratio can be tailored to achieve desired injection characteristics. Fuel is admitted to chamber
230
through passageway
240
past check valve
242
. Injection begins as the high pressure actuating oil is supplied to the upper surface
234
of the intensifier piston
236
.
As the intensifier piston
236
and plunger move downward responsive to the force exerted by the actuation oil, the pressure of the fuel in the chamber
230
below the plunger
228
rises dramatically. High pressure fuel flows in passageway
244
past check valve
246
to act upward on needle valve surface
248
. The upward force on surface
248
opens needle valve
250
and fuel is discharged from orifice
252
into the combustion chamber of the engine. The intensifier piston
236
continues to move downward until the solenoid of the electric control
212
is de-energized causing the poppet valve
210
to return to the lower seat
214
, thereby blocking actuating oil flow. The plunger return spring
232
returns the piston
236
and plunger
228
to their initial upward seated positions. As the plunger
228
returns upward, the plunger
228
draws replenishing fuel into the plunger chamber
230
across ball check valve
242
.
The nozzle
206
is typical of other diesel fuel system nozzles. The valve-closed-orifice style is shown, although a mini-sac version of the tip is also available. Fuel is supplied to the nozzle orifice
252
through internal passages. As fuel pressure increases, the nozzle needle
250
lifts from the lower seat
254
to its open position, thereby allowing fuel injection to occur. As fuel pressure decreases at the end of injection, the spring
256
returns the needle
250
to its closed position against the lower seat
254
.
FIGS. 2
a
,
2
b
,
2
c
, and
2
d
illustrate a prior art Digital Hydraulic Operating System (DHOS) injector and digital control valve operation. The intensifier and nozzle portions of the DHOS injector are similar to those of the HEUI injector and have been identified with the same reference numerals. However, in the DHOS injector, the poppet control valve
202
of the HEUI injector has been replaced by a spool type digital control valve
300
which is controlled by two solenoid coils
302
,
304
, the valve spool
306
which is made of magnetic material, being the armature. Thus, as illustrated in
FIG. 2
c
, when the coil
302
is energized to begin an injection event or engine cycle during which an injection occurs, the valve spool
306
is pulled toward the coil
302
thereby open a fluid connection between the hydraulic fluid (high pressure lube oil) supply passage
310
and the working fluid passages
312
to the intensifier chamber
223
within the injector while isolating the vent passages
314
. When the coil
302
is de-energized, the valve spool will remain in the open position shown in
FIG. 2
c
due to residual magnetism in the valve spool
306
.
To end the injection, the coil
304
is energized to pull the valve spool
306
rightward toward the coil
304
thereby establishing a fluid connection between the vent passages
314
and the working fluid passages
312
to the intensifier chamber
223
within the injector while isolating the hydraulic fluid supply passage
310
.
With either the HEUI or the DHOS injector, the size of the control valve normally is targeted for a single injection operation for achieving maximum injection pressure. And it is also sized for good performance at low temperature operation when hydraulic fluid is relatively viscous. Once the size of the control valve is selected, the fuel delivery quantity may be determined based on the actuation pressure and valve open duration (pulse width duration). The maximum fuel delivery for these type injectors could reach 200 mm
3
/stroke for full engine load condition. The minimum fuel delivery for engine at idle could be as small as 4 mm
3
/stroke. Especially for the DHOS injector, the digital valve is also responsible for pilot injection operation. The pilot injection quantity can be as small as 1 mm
3
/injection at maximum actuation pressure, approximately 3000 psi.
When a large size control valve is used for a small quantity of fuel delivery, significant performance variability is introduced during shot-to-shot and injector-to-injector operation. It is believed that this performance variability can be reduced if a smaller valve is used for small quantity operation and a large valve for full capacity operation.
SUMMARY OF THE INVENTION
The present invention is a valve for use generally as a hydraulic control device, such as, for example, in a camless internal combustion engine. One of the specific purposes of this invention is a control valve for a unit fuel injector, which can provide small flow when it is needed and can be switched to provide a larger flow rate when desired. Fundamentally, the control valve of the present invention has the ability to provide two-stage flow (high rate of flow and low rate of flow) with flexible controllab
Calfa Jeffrey P.
International Engine Intellectual Property Company, L.L.C.
Mohanty Bibhu
Powell Neil T.
Sullivan Dennis Kelly
LandOfFree
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