Unitized injector modified for ultrasonically stimulated...

Fluid sprinkling – spraying – and diffusing – Including valve means in flow line – Reciprocating

Reexamination Certificate

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C239S102100, C239S102200, C239S585500, C239S088000, C239S096000

Reexamination Certificate

active

06663027

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an apparatus and method for injecting fuel into a combustion chamber and in particular to a unitized fuel injector for engines that use overhead cams to actuate the injectors.
Diesel engines for locomotives use unitized fuel injectors that are actuated by overhead cams. One such typical conventional unitized injector is schematically represented in FIG.
1
A and is generally designated by the numeral
10
. This unitized injector
10
includes a valve body
11
that is disposed in an injector nut
29
. The valve body
11
houses a needle valve that can be biased in the valve's closed position to prevent the injector from injecting fuel into one of the engine's combustion chambers, which is generally designated by the numeral
20
.
As shown in
FIG. 1B
, which depicts an expanded cross-sectional view of a portion of the valve body
11
of
FIG. 1A
, the needle valve includes a conically shaped valve seat
12
that is defined in the hollowed interior of the valve body
11
and can be mated with and against a conically shaped tip
13
at one end of a needle
14
. The hollowed interior of the valve body
11
further defines a fuel pathway
15
connecting to a fuel reservoir
16
and a discharge plenum
17
, which is disposed downstream of the needle valve. Each of several exit channels
18
typically is connected to the discharge plenum
17
by an entrance orifice
19
and to the combustion chamber
20
by an exit orifice
21
at each opposite end of each exit channel
18
. The needle valve controls whether fuel is permitted to flow from the storage reservoir
16
into the discharge plenum
17
and through the exit channels
18
into the combustion chamber
20
.
As shown in
FIG. 1B
, the conically shaped tip
13
at one end of needle
14
, which is housed in the hollowed interior of the valve body
11
, is biased into sealing contact with valve seat
12
by a spring
22
(FIG.
1
A). As shown in
FIG. 1A
, a cage
28
houses spring
22
so as to be disposed to apply its biasing force against the opposite end of the needle
14
. A fuel pump
23
is disposed above the spring-biased end of the needle
14
and in axial alignment with the needle
14
. Another spring
24
biases a cam follower
25
that is disposed above and in axial alignment with each of the fuel pump
23
and the spring-biased end of the needle
14
. The cam follower
25
engages the plunger
26
that produces the pump's pumping action that forces pressurized fuel into the valve body
11
of the injector. An overhead cam
27
cyclically actuates the cam follower
25
to overcome the biasing force of spring
24
and press down on the plunger
26
, which accordingly actuates the fuel pump
23
. The fuel that is pumped into the valve body
11
via actuation of the pump
23
hydraulically lifts the conically shaped tip
13
of the needle
14
away from contact with the valve seat
12
and so opens the needle valve and forces a charge of fuel out of the exit orifices
21
of the injector
10
and into the combustion chamber
20
that is served by the injector.
However, the injector's exit orifices can become fouled and thereby adversely affect the amount of fuel that is able to enter the combustion chamber. Moreover, improving the fuel efficiency of these engines is desirable as is reducing unwanted emissions from the combustion process performed by such engines.
The goal of achieving more efficient combustion, which increases power and reduces pollution from the combustion process thereby improving the performance of injectors, has largely been sought to be accomplished by decreasing the size of the injector's exit orifices and/or increasing the pressure of the liquid fuel supplied to the exit orifice. Each of these solutions aims to increase the velocity of the fuel that exits the orifices of the injector.
However, these solutions introduce problems of their own such as: the need to use exotic metals; lubricity problems; the need to micro inch finish moving parts; the need to contour internal fuel passages; high cost; and direct injection. For example, the reliance on smaller orifices means that the orifices are more easily fouled. The reliance on higher pressures in the range of 1500 bar to 2000 bar means that exotic metals must be used that are strong enough to withstand these pressures without contorting in a manner that changes the characteristics of the injector if not destroying it altogether. Such exotic metals increase the cost of the injector. The higher pressures also create lubricity problems that cannot be solved by relying on additives in the fuel for lubrication of the injector's moving parts. Other means of lubricity such as applying a micro inch finish on the moving metal parts is required at great expense. Such higher pressures also create wear problems in the internal passages of the injector that must be counteracted by contouring the passages, which requires machining that is costly to perform. These wear problems also erode the exit orifices, and such erosion changes the character of the injector's plume over time and affects performance. Moreover, to achieve the higher pressures, the fuel pump must be localized with the injector for direct injection rather than disposed remotely from the injector.
Using ultrasonic energy to improve atomization of fuel injected into a combustion chamber is known, and advances in this field have been made as is evidenced by commonly owned U.S. Pat. Nos. 5,803,106; 5,868,153 and 6,053,424, which are hereby incorporated herein by this reference. These typically involve attaching an ultrasonic transducer on one end of an ultrasonic horn while the opposite end of the horn is immersed in the fuel in the vicinity of the injector's exit orifices and caused to vibrate at ultrasonic frequencies. However, unitized fuel injectors cannot be fitted with such ultrasonic transducers because of the disposition of the fuel pump, cam follower and overhead cam in axial alignment with the needle.
SUMMARY
Objects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
In a presently preferred embodiment of the present invention, the standard unitized injector actuated by overhead cams is retrofitted with a needle that has an elongated portion that is composed of magnetostrictive material. The portion of the injector's body surrounding the magnetostrictive portion of the retrofitted needle may be hollowed out and provided with an annular shaped insert that defines a wall surrounding the magnetostrictive portion of the retrofitted needle. This wall is composed of material that is transparent to magnetic fields oscillating at ultrasonic frequencies, and ceramic material can be used to compose the annular-shaped insert.
The exterior of the wall is surrounded by a coil that is capable of inducing a changing magnetic field in the region occupied by the magnetostrictive portion and thus causing the magnetostrictive portion to vibrate at ultrasonic frequencies. This vibration causes the tip of the needle, which is disposed in the liquid fuel near the entrance to the discharge plenum and the channels leading to the injector's exit orifices, to vibrate at ultrasonic frequencies and therefore subjects the fuel to these ultrasonic vibrations. The ultrasonic stimulation of the fuel as it leaves the exit orifices permits the injector to achieve the desired performance while operating at lower pressures and larger exit orifices than the conventional solutions that are aimed at increasing the velocity of the fuel exiting the injector.
In accordance with the present invention, a control is provided for actuation of the ultrasonically oscillating signal. The control is configured so that the actuation of the ultrasonically oscillating signal that is provided to the coil only occurs when the overhead cams are actuating the injector so as to allow fuel to flow through the in

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