Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1999-09-09
2003-08-12
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S300000, C123S496000
Reexamination Certificate
active
06604507
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a fuel injector for use within an internal combustion engine. More particularly, the present invention relates to control of an injection event of a fuel injector by means of spill and/or bypass techniques.
BACKGROUND OF THE INVENTION
A fuel injector, particularly a fuel injector for use with a diesel engine, is required to very accurately discharge a quantity of fuel into a combustion chamber of an internal combustion engine over a wide range of engine operating conditions. The discharge of fuel typically occurs during a certain crank angle, such as, for example, 30 degrees, regardless of engine rotational speed.
While certain aspects of the invention described herein may be utilized with a number of different types of fuel injectors, including (HEUI) and mechanically-actuated, electronically-controlled unit injectors (MEUI) injectors of the types disclosed in the article, “Cat Gears up Next Generation Fuel Systems,”
Diesel Power,
August 1998, aspects of the invention are particularly suitable for use with a hydraulically-actuated fuel injector having a spool type control valve of the type disclosed in U.S. Pat. No. 5,460,329 (“the '329 patent”), and in Society of Automobile Engineers paper No. 1999-01-0196 entitled “
Application of Digital Valve Technology to Diesel Fuel Injection”.
FIG. 8
shows an exemplary prior art injector
160
controlled by a three-way spool control valve
162
. In this embodiment, an actuating fluid supply passage
108
in the injector body
90
is connected to a supply groove
163
in the control valve housing
165
and a working passage
106
connects an intensifier chamber
102
to a working groove
167
in the control valve housing
165
. The control valve housing further has a drain groove
169
to vent the actuating fluid from the injector. Movement of the spool
168
provides fluid communication between the working passage
106
and either the supply passage
108
or the drain
169
.
When the spool
168
connects the working passage
106
with the supply passage
108
, the pressure within the intensifier chamber
102
pushes the intensifier plunger
84
to pressurize fuel in the pressure chamber
86
. The pressurized fuel travels through passage
74
to the needle valve
72
and lifts the valve needle
78
so that fuel is ejected from the injector
160
. When the spool
168
connects the working passage
106
with the drain
169
, the force of the spring
166
moves the intensifier plunger
84
back to the original position while the fluid within the intensifier chamber
102
flows through the drain
169
.
The purpose of the control valve
162
in a hydraulically intensified fuel injector is to control the timing and flow of the hydraulic working fluid to the intensifier chamber
102
. The control valve
162
has only three different components: the spool
168
, the housing
165
, and two identical electromagnetic coils
138
and
180
. Beginning in the closed position, when the open coil
138
is energized by a voltage, the magnetic force generated causes the spool
168
to translate leftward towards the open coil
138
to connect the supply passage
108
to the working passage
106
. Once the spool
168
stops at the hard limit which is part of the coil assembly
138
, the voltage is discontinued. However, actuating fluid flow continues due to the spool position.
To end the fluid flow, the close coil
180
is energized by a voltage. The magnetic force generated by the close coil
180
causes the spool
168
to translate rightward towards the close coil
180
connecting the working passage
106
to the drain
169
.
Shifting the spool
168
of the control valve
162
from the closed position to the open position and a return shifting to the closed position is a round trip for the spool
168
. The minimum round trip time is the minimum time it takes for a complete round trip. Less than a complete round trip puts the control valve
162
in a region of unstable operation as will be further described below.
It may be desirable during a single injection cycle to provide for a relatively small pre-injection flow of fuel prior to the main injection event. The resulting injection flow profile is termed rate shaping or split pilot injection depending on whether one injection (rate shaping) or two injections (pilot injection) occur during the injection event. However, if the control valve does not make a complete round trip between the closed position and the open position and back to the closed position during the injection event, for example, if the control valve is retracted to the closed position before arriving at the open position, the fuel delivery commanded by such partial movement of the spool of the control valve is unstable and undesirable.
Accordingly, there is a need in the industry to eliminate the instabilities resulting from a partial translation of the spool of the control valve from the closed position toward the open position before retraction to the closed position.
Further, there is a need in the industry to continually improve the precise control of pilot injection and rate shaping to enhance the performance and emissions characteristics of engines utilizing fuel injectors.
An important consideration of a diesel fuel injector is its capability of delivering a small pilot injection of fuel (as small as 1 mm
3
) prior to the main injection event and its capability of controlling the shape of fuel delivery curve. Both have proved to be very difficult to achieve because of the following reasons:
For engine emission optimization, a very high-injection pressure is desired; therefore, the needle valve is subjected to a very high fuel pressure and it is easy to reach the needle valve full lift (full open) position when fuel is pressurized under the intensifier plunger
14
. However, for a small quantity of fuel delivery, the full lift position is not desirable since, at this position, the nozzle is full open and the controllability of the small quantity of fuel is accordingly very poor.
The position of the needle valve controls the opening area of injection nozzle orifice. For a small quantity of fuel delivery at high operating pressure, a very small needle valve lift, which only opens the nozzle orifice very slightly, is desired. This small lift is only needed during the pilot or rate shaping operation period when very small injection quantities are desired. For the main injection event, the needle valve should be able to reach its full lift position without any negative effect. Because of this, the controllability of the needle valve position during pilot or rate shaping operation becomes very important and also very difficult.
SUMMARY OF THE INVENTION
Various aspects of the invention described herein are intended to meet the aforementioned needs of the industry. One embodiment of the invention provides for a charge of pressurized fuel to the needle valve or check only when enough time has elapsed for the spool valve to make a round trip from the closed position to the open position and back to the closed position. A fuel injector of the such embodiment includes an intensifier, the intensifier having a plunger translatable in a cylinder between a retracted position and a full stroke position, the cylinder being defined by a cylinder wall, the cylinder wall defining in part a variable volume fuel pressure intensification chamber. The fuel injector further includes a spill port intersecting the cylinder wall, the spill port being open at the beginning of the injection event and closed by the intensifier plunger during the translating motion of the intensifier plunger for spilling fuel from the variable volume intensification chamber as desired. The present embodiment further includes a method of delaying the beginning of an injection event.
The present invention additionally is a fuel injector having an intensifier plunger, the intensifier plunger being translatable in a cylinder between a retracted position and a full stroke position, the cylinder being defined by a cylinder wall,
Arnold Steven C.
Lei Ning
Yang Xilin
Calfa Jeffrey P.
International Engine Intellectual Property Company LLC
Lukasik Susan L.
Miller Carl S.
Sullivan Dennis Kelly
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