Fluid sprinkling – spraying – and diffusing – Injection nozzle opened by relieving supply
Reexamination Certificate
2000-07-17
2001-07-10
Scherbel, David A. (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Injection nozzle opened by relieving supply
C239S088000, C239S090000, C251S129100, C251S030010
Reexamination Certificate
active
06257499
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel injector for an internal combustion engine.
2. Description of Related Art
Fuel injectors are used to introduce pressurized fuel into the combustion chamber of an internal combustion engine.
FIG. 1
shows a fuel injection system
10
of the prior art. The injection system includes a nozzle
12
that is coupled to a fuel port
14
through an intensifier chamber
16
. The intensifier chamber
16
contains an intensifier piston
18
which reduces the volume of the chamber
16
and increases the pressure of the fuel therein. The pressurized fuel is released into a combustion chamber through the nozzle
12
.
The intensifier piston
18
is stroked by a working fluid that is controlled by a poppet valve
20
. The working fluid enters the valve through port
22
. The poppet valve
20
is coupled to a solenoid
24
which can be energized to pull the valve into an open position. As shown in
FIG. 2
, when the solenoid
24
opens the poppet valve
20
, the working fluid applies a pressure to the intensifier piston
18
. The pressure of the working fluid moves the piston
18
and pressurizes the fuel. When the solenoid
24
is deenergized, springs
26
and
28
return the poppet valve
20
and the Intensifier piston
18
back to the original positions.
Spring return fuel injectors are relatively slow because of the slow response time of the poppet valve return spring. Additionally, the spring rate of the spring generates an additional force which must be overcome by the solenoid. Consequently the solenoid must be provided with enough current to overcome the spring force and the inertia of the valve. Higher currents generate additional heat and degrade the life and performance of the solenoid. Furthermore, the spring rate of the springs may change because of creep and fatigue. The change in spring rate will create varying results over the life of the injector.
Conventional fuel injectors typically incorporate a mechanical feature which determines the shape of the fuel curve. Mechanical rate shapers are relatively inaccurate and are susceptible to wear and fatigue. Additionally, fuel leakage into the spring chambers of the nozzle and the intensifier may create a hydrostatic pressure that will degrade the performance of the valve.
The graph of
FIG. 3
shows an ideal fuel injection rate for a fuel injector. To improve the efficiency of the engine, it is desirable to pre-inject fuel into the combustion chamber before the main discharge of fuel. As shown in phantom, the fuel curve should ideally be square so that the combustion chamber receives an optimal amount of fuel. Actual fuel injection curves have been found to be less than ideal, thereby contributing to the inefficiency of the engine. It is desirable to provide a high speed fuel injector that will supply a more optimum fuel curve than fuel injectors in the prior art.
As shown in
FIGS. 1 and 2
, the poppet valve constantly strikes the valve seat during the fuel injection cycles of the injector. Eventually the seat and the poppet valve will wear, so that the valve is not properly seated within the valve chamber. Improper valve seating may result in an early release of the working fluid into the intensifier chamber, causing the injector to prematurely inject fuel into the combustion chamber. It would be desirable to provide an injector valve that did not create wear between the working fluid control valve and the associated valve seat of the injector.
SUMMARY OP THE INVENTION
The present invention is a fuel injector which has a double solenoid three-way or four-way spool valve that controls the flow of a working fluid that is used to move an intensifier piston of the injector. The fuel injector includes a nozzle which is in fluid communication with a fuel port through a pressure chamber. The pressure chamber contains an intensifier piston which can move to decrease the volume of the chamber and increase the pressure of the fuel. The pressurized fuel is discharged into the combustion chamber of an engine through the nozzle of the injector.
The spool valve is moved by a pair of solenoids between a first position and a second position. Movement of the spool valve provides fluid communication between the intensifier piston and the working fluid ports of the injector, so that the working fluid strokes the intensifier piston. It has been found that the solenoid control valve of the present invention is very responsive and provides a more optimal fuel curve than injectors in the prior art. Additionally, the spool valve moves between bearing surfaces of a valve housing that are separate from the valve seats of the working fluid ports, thereby reducing wear on the seats and insuring a repeatable operation of the control valve.
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paten
Blakely , Sokoloff, Taylor & Zafman LLP
Ganey Steven J.
Scherbel David A.
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