Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1999-07-07
2001-08-21
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S486000, C701S105000
Reexamination Certificate
active
06276337
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a common-rail fuel-injection system in which fuel supplied under high pressure from a common rail is injected under pressure into the combustion chambers of engines.
2. Description of the Prior Art
The various types of fuel-injection systems for engines include a common-rail fuel-injection system in which the fuel stored under high-pressure in the common rail is applied to the injectors, which are in turn actuated by making use of a part of the high-pressure fuel as a working fluid to thereby spray the fuel applied from the common rail into the combustion chambers out of discharge orifices formed at the distal ends of the injectors.
Referring to
FIG. 5
where an example of a conventional common-rail fuel-injection system is illustrated schematically, a fuel feed pump
6
draws fuel from a fuel tank
4
through a fuel filter
5
and forces it under a preselected intake pressure to a high-pressure, fuel-supply pump
8
through a fuel line
7
. The high-pressure, fuel-supply pump
8
is, for example, a fuel-supply plunger pump driven by the engine, which subjects the fuel to a high pressure determined depending on the engine operating conditions, and supplies the pressurized fuel into the common rail
2
through another fuel line
9
. The fuel, thus supplied, is stored in the common rail
2
at the preselected high pressure and forced to the injectors
1
through injection lines
3
from the common rail
2
. The engine illustrated is a six-cylinder engine. The injectors
1
are arranged in combustion chambers, one to each chamber, of a multi-cylinder engine, for example, a six-cylinder engine in FIG.
5
.
Excess fuel from the high-pressure, fuel-supply pump
8
is allowed to flow back to the fuel tank
4
through a fuel-return line
10
. The unconsumed fuel remaining in each injector
1
out of the fuel fed from the common rail
2
into the injectors
1
may return to the fuel tank
4
through a fuel-recovery line
11
. The controller unit
12
is supplied with various signals from sensors monitoring the engine operating conditions, such as a crankshaft position sensor for detecting the engine rpm Ne, an accelerator pedal sensor for detecting the depression Ac of an accelerator pedal, a high-pressure fuel temperature sensor and the like. In addition, the sensors for monitoring the engine operating conditions include an engine coolant temperature sensor, an intake manifold pressure sensor and the like. The controller unit
12
is also supplied with a detected signal as to fuel pressure in common-rail
2
, which is transmitted from a pressure sensor
13
installed in the common rail
2
.
The controller unit
12
may regulate the fuel injection characteristics of the injectors
1
, including the injection timing and the quantity of fuel injected, depending on the applied signals, so as to operate the engine with the optimum injection timing and quantity of fuel injected per cycle in conformity with the present engine operating conditions, thereby allowing the engine to operate as fuel-efficiently as possible. The quantity of fuel injected per cycle is determined by the combination of injection duration with the injection pressure of the fuel sprayed out of the injectors. The injection pressure is substantially equal to the common rail pressure controlled by operating a flow-rate control valve
14
, which is to regulate the quantity of high-pressure fuel delivered to the common rail
2
. In case the injection of fuel out of the injectors
1
consumes the fuel in the common rail
2
or it is required to alter the quantity of fuel injected, the controller unit
12
actuates the fuel flow-rate control valve
14
, which in turn regulates the quantity of fuel delivered from the high-pressure, fuel-supply pump
8
to the common rail
2
whereby the common rail pressure returns to the preselected fuel pressure.
Referring to
FIG. 6
, the injector
1
is comprised of an injector body
21
, and an injection nozzle
22
mounted to the injector body
21
and formed therein with an axial bore
23
in which a needle value
24
is fitted for sliding movement. The high-pressure fuel applied to the individual injector
1
from the common rail
2
through the associated injection line
3
fills fuel passages
31
,
32
and a fuel pocket
33
formed in the injector body
21
. The high-pressure fuel further reaches around the needle valve
24
in the axial bore
23
. Therefore, the instant the needle valve
24
is lifted to open discharge orifices
25
at the distal end of the injection nozzle
22
, the fuel is injected out of the discharge orifices
25
into the combustion chamber. Provided at the distal end of the injection nozzle
22
is a fuel sac
26
to which are opened the discharge orifices
25
. The needle valve
24
has a tapered end
27
that moves upwards off or downwards against a tapered surface
28
inside the injection nozzle
22
whereby the fuel injection starts or ceases.
The injector
1
is provided with a needle-valve lift mechanism of pressure-control chamber type in order to adjust the lift of the needle valve
24
. The high-pressure fuel fed from the common rail
2
is partly admitted into a pressure-control chamber
40
, which is formed inside the injector
1
, past a fuel passage
35
branching away from the fuel passage
31
and a fuel passage
36
reduced in cross-sectioned area. The injector
1
has at the head section thereof a solenoid-operated valve
15
, which constitutes an electronically-operated actuator to control the outflow of working fluid, or fuel from the pressure-control chamber
40
. The controller unit
12
makes the solenoid-operated valve
15
energize in compliance with the engine operating conditions, thereby adjusting the hydraulic pressure of the working fluid in the pressure-control chamber
40
to either the high pressure of the admitted high-pressure fuel or a low pressure released partially in the pressure-control chamber
40
. A control signal issued from the controller unit
12
is an exciting signal applied to a solenoid
38
of solenoid-operated valve
15
.
The solenoid-operated valve
15
includes an armature
39
having at its end a valve body
42
for opening and closing an egress of a fuel leakage path
41
. On energizing solenoid
38
, the armature
39
rises to open valve body
42
whereby the fuel in the pressure-control chamber
40
is allowed to discharge, resulting in relieving the high pressure of the fuel in the pressure-control chamber
40
. Although the valve body
42
is explained in the type of opening and closing the egress of the fuel leakage path
41
, it may be alternatively made of a poppet valve composed of a valve stem extending through the fuel leakage path
41
, and a tapered valve body provided at the end of the valve stem and having a valve face to make engagement with a valve seat at an ingress of the fuel leakage path
41
.
A control piston
44
is arranged for axial linear movement in an axial recess
43
formed in the injector body
21
of the injector
1
. Although the control piston
44
shown in the figure is formed integrally with the needle valve
24
, the control piston may be formed separately from the needle valve and combined therewith such that they may be energized so as to follow one another. When the solenoid-operated valve
15
is energized to cause the fuel pressure inside the pressure-control chamber
40
to decrease, the consequent force, acting on the control piston
44
to push it downward, is made less than the fuel pressure acting on both a tapered surface
34
exposed to the pocket
33
and the distal end of the needle valve
24
, whereby the control valve
44
moves upwards. As a result, the needle valve
24
lifts to allow the fuel to spray out of the discharge orifices
25
. The quantity of fuel injected per cycle is defined dependent on the fuel pressure in the fuel passages and both the amount and duration of lift of the needle valve
24
.
The common-rail fuel-injection system, or the pressure-balanc
Browdy and Neimark
Castro Arnold
Dolinar Andrew M.
Isuzu Motors Limited
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