Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1999-06-28
2001-06-26
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S480000
Reexamination Certificate
active
06250285
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a common-rail, fuel-injection system in which fuel under high-pressure in a common rail is injected into the combustion chambers of engines.
2. Description of the Prior Art
Among various types of fuel-injection systems for engines is conventionally well-known 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 tips of the injectors.
An example of a conventional common-rail, fuel-injection system will be explained below with reference to
FIG. 9. 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 of, for example, a fuel-supply plunger pump driven by the engine, which intensifies 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. There are six injectors
1
, each to each cylinder, to spray the fuel into the combustion chambers formed in the cylinders. The engine is not limited to the six-cylinder type, but may be the four-cylinder engine.
The fuel relieved from the high-pressure, fuel-supply pump
8
is allowed to flow back the fuel tank
4
through a fuel-return line
10
. The unconsumed fuel remaining in each injector
1
out of the fuel fed through the fuel line
9
into the injectors
1
may return to the fuel tank
4
through a fuel-recovery line
11
. The controller unit
12
is applied with various signals of 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 applied with a detected signal as to a fuel pressure in a common-rail
2
, which is reported from a pressure sensor
13
installed in the common rail
2
.
The controller unit
12
may regulate the fuel injection characteristics on 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 optimal injection timing and quantity of fuel injected per cycle in conformity with the recent engine operating conditions, thereby allowing the engine to operate as fuel-efficient as possible. As the injection pressure of the fuel sprayed out of the injectors is substantially equal with the common rail pressure, the injection pressure defining, in combination with the injection duration, the quantity of fuel injected per cycle may be controlled by operating a fuel flow-rate control valve
14
, which is to regulate the quantity of high-pressure fuel supplied 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 delivery of the fuel from the high-pressure, fuel-supply pump
8
to the common rail
2
whereby the common rail pressure recovers the preselected fuel pressure. Regulating a duration during which the fuel flow-rate control valve
14
is open results in controlling the quantity of the fuel fed into the common rail
2
through the fuel line
9
out of the fuel discharged from the high-pressure, fuel-supply pump
8
.
Referring to
FIG. 10
, 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 vale
24
is fitted for a sliding movement. The high-pressure fuel applied to the individual injector
1
from the common rail
2
through the associated injection line
3
is allowed to flow into fuel passages
31
,
32
formed in the injector body
21
and communicated with the associated injection line
3
through a high-pressure fuel inlet coupling
30
. The high-pressure fuel further reaches the discharge orifices
25
, formed at the tip of the injection nozzle
22
, past a fuel sac
33
formed in the injection nozzle
22
and a clearance around the needle valve
24
fitted in the axial bore
23
. Therefore, the instant the needle valve
24
is lifted to open the discharge orifices
25
, the fuel is injected out of the discharge orifices
25
into the combustion chamber while the unconsumed fuel remaining in the injector
1
may return to the common rail
2
through a fuel-recovery line
11
.
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
. The injector
1
has at the head section thereof a solenoid-operated valve
15
, which constitutes an electronically-operated actuator to control the inflow/outflow of the high-pressure fuel with respect to 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 fuel pressure 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
. On energizing a solenoid
38
in the solenoid-operated valve
15
by an exciting signal, for example, a current value, which is a control signal applied from the controller unit
12
via a signaling line
37
, the armature
39
rises to open a valve
42
arranged at one end of a fuel-leakage path
41
. The fuel fed in the pressure-control chamber
40
is allowed to discharge past the opened valve
42
to thereby release partially the high fuel pressure.
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
. At the event the pressure-control chamber
40
is under the high pressure, the fuel pressure forces the needle valve
24
downward to close the discharge orifices
25
. When the solenoid-operated valve
15
is energized to cause the fuel pressure inside the pressure-control chamber
40
to reduce, the resultant force of the fuel pressure in the pressure-control chamber
40
with the spring force of the return spring
45
, acting on the control piston
44
so as to pushing it downward, is made less than the fuel pressure acting on both a tapered surface exposed to a fuel sac
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 actual quantity of fuel injected is calculated based on an amount of pressure drop occurring nearby the fuel injection. The controller unit
12
adjusts a duration during which the fuel-injection nozzle is held open, so as to make the found actual quantity of fuel injected a desired quantity of fuel to be injected conforming with the engine ope
Browdy & Neimark
Gimie Mahmoud M
Isuzu Motors Limited
Yuen Henry C.
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