Fluid sprinkling – spraying – and diffusing – Including valve means in flow line – Reciprocating
Reexamination Certificate
2002-12-18
2004-04-13
Mar, Michael (Department: 3747)
Fluid sprinkling, spraying, and diffusing
Including valve means in flow line
Reciprocating
C239S585400, C239S533900, C251S050000
Reexamination Certificate
active
06719224
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based on Japanese Patent Applications No. 2001-307355 filed on Oct. 3, 2001, No. 2001-308495 filed on Oct. 4, 2001, No. 2001-317688 filed on Oct. 16, 2001, No. 2001-384772 filed on Dec. 18, 2001 and No. 2002-14338 filed on Jan. 23, 2002 the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel injection system and a fuel injector in an internal combustion engine (hereinafter referred to simply as engine).
2. Related Art
For example, in the case of a common rail type fuel injection system applied to a diesel engine, there usually is employed a fuel injector having a two- or three-way solenoid valve. In connection with such a fuel injector, for example the technique disclosed in JP-A-9-42106 is well known. According to this technique, fuel of a high pressure is introduced into a pressure control chamber provided on an opposite-to-nozzle holes side of a valve element, and the valve element is actuated by allowing the high-pressure fuel present in the pressure control chamber to leak to a low pressure side at every fuel injection. However, in the case of the fuel injector disclosed in the above publication, there occurs leakage of the high-pressure fuel from the pressure control chamber at every fuel injection. There also is a problem that the number of components increases and the structure becomes complicated.
Recently there has been an increasing demand for reducing the cost of the fuel injector. To meet this demand, that is, for reducing the number of components which constitute the fuel injector, a study is being made about a direct-acting type fuel injector in which a valve element is actuated directly by an electromagnetic drive unit.
On the other hand, as an alternative to gas oil and taking the volatilizability, ignitability and combustibility of fuel or emission into account, there recently has been studied the use of liquefied gas fuels such as dimethyl ether (DME) and liquefied petroleum gas (LPG) with a cetane number improving additive incorporated therein. LPG as referred to herein means a liquefied petroleum gas with a cetane number improver incorporated therein unless otherwise specified. In case of using a liquefied gas fuel, the fuel is apt to vaporize because of a low boiling point and the amount of fuel leaking from the fuel injector tends to increase. Therefore, it becomes necessary to provide a recovery system for recovering fuel leaking from the fuel injector. For example, as is disclosed in JP-A-11-22590, it is necessary to provide a purge tank for the recovery of vaporized liquefied gas fuel and a compression pump for compressing and liquefying a gaseous liquefied gas fuel recovered into the purge tank. As a result, there arises the problem that the cost of the fuel injection system concerned increases. To solve this problem, as noted above, it is proposed to use, for example, such a direct acting type fuel injector
100
as shown in FIG.
10
and thereby decrease the amount of fuel leaking from the fuel injector
100
.
In the fuel injector
100
shown in
FIG. 10
, a valve element
101
extends vertically in the figure and an armature
102
is integrally provided at an upper end of the valve element
101
by laser welding for example. Holes
103
a
and
104
a
are formed in a casing
103
and a valve body
104
, respectively, and the valve element
101
is received into the holes
103
a
and
104
a
. A stator
105
is disposed in opposition to the armature
102
. When a coil
106
is energized and the armature
102
is thereby attracted to the stator
105
, the valve element
101
lifts upward in
FIG. 10
against the biasing force of a spring
107
, whereby nozzle holes
108
are opened and high-pressure fuel fed from a common rail system is injected from the nozzle holes
108
. In such a fuel injector
100
as shown in
FIG. 10
, the number of components is small and hence it is possible to attain the reduction of cost. Moreover, in the fuel injector
100
shown in
FIG. 10
, it is possible to decrease the amount of leaking fuel and therefore it becomes unnecessary to use a purge tank for the recovery of leaking fuel and a compression pump.
However, in the fuel injector
100
shown in
FIG. 10
, since the valve element
101
is actuated directly by an electromagnetic drive unit, it is necessary for the electromagnetic drive unit to actuate the valve member
101
against a force developed by an oil pressure acting on the valve element
101
. Accordingly, for enhancing the injection pressure of fuel injected from the fuel injector
100
, it is necessary to increase the size of the electromagnetic drive unit and thereby increase the driving force. However, the space ensured in an engine mounting portion is limited and therefore the size of the electromagnetic drive unit and that of the fuel injector
100
are limited. As a result, a maximum fuel injection pressure of about 30 MPa is a limit at present and a further increase of pressure is difficult.
For example, in connection with a common rail type fuel injection system for a diesel engine, there is known such a fuel injector as is disclosed in JP-A-10-18934. On the other hand, as a direct-acting type fuel injector there is proposed one illustrated in FIG.
16
. In the same figure, components equal to those illustrated in
FIG. 10
are identified by like reference numerals.
In an engine mounted on a vehicle, fuel injectors are replaced at every about 100,000 km running. In this case, for attaining the reduction of cost, it is proposed to remove a retaining nut
110
of a fuel injector
100
and replace only a nozzle portion
104
located at the tip of the injector. However, an armature
102
is fixed to a valve element
101
and the diameter of the armature
102
is usually larger than that of a hole
103
a
. This is for obtaining a satisfactory electromagnetic performance. Therefore, at the time of replacement of the nozzle portion
104
, not only the removal of the retaining nut
110
, but also a disassembling work for an electromagnetic solenoid portion
111
is required, resulting in that the maintainability is deteriorated. Thus, an improvement is desired.
FIG. 28
shows a fuel injector
100
in the related art. When a valve element
101
is opened, the valve member moves until abutment against a valve opening stopper
112
. At this time, the valve element
101
bounces as a reaction of its abutment against the stopper
112
. In many cases, for example the layout of intake/exhaust valves in an engine head portion requires the valve element
101
to be long, with the result that the valve member becomes heavy. Particularly, in the case of such a liquefied gas fuel as DME, the bounce of the valve element
101
becomes large. Such a bounce of the valve element
101
obstructs an accurate adjustment of fuel quantity.
In a fuel injector
100
shown in
FIG. 33
, when a valve element
101
opens, it strikes against a stopper
111
and bounces. Due to this bouncing during valve opening, an injection quantity Q becomes wavy relative to a pulse width T, thus making injection control difficult.
Further, when a coil
106
is de-energized, with loss in attraction of an armature
102
by a stator
105
, and the valve element
101
closes with the biasing force of a spring
107
, the valve element
101
strikes against a sheet portion of a nozzle body
104
and causes bouncing. Due to this bouncing in valve closing, there occurs re-injection (secondary injection) after the end of injection, thus resulting in deterioration of the injection characteristic.
On the other hand, in many cases, the valve element
101
is required to be long for example due to the layout of intake/exhaust valves in an engine head, resulting in that the valve element
101
becomes heavy and there occurs markedly such bouncing as referred to above.
Particularly in the case of such liquefied gas fuels as LPG and DME, since their viscosities are low, not only the bouncing of the valve elem
Enomoto Shigeiku
Goto Moriyasu
Kato Masaaki
Morita Tetsuo
Takeuchi Hisaharu
Gorman Darren
Mar Michael
Nippon Soken Inc.
Nixon & Vanderhye PC
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