Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2000-03-29
2001-02-27
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S357000
Reexamination Certificate
active
06192863
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a common-rail fuel-injection system and more particularly a common-rail fuel-injection system in which, on fuel injection into a combustion chamber, an auxiliary injection of a small amount of fuel is provided at any timing of soon before or after a main injection of major amount of fuel.
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 a high-injection pressure is maintained in the fuel discharge lines, and fuel-injection conditions such as a timing of fuel injection and an amount of fuel to be injected or injected are controlled depending on operating requirements of the engine. In accordance with the common-rail fuel-injection system, the fuel intensified in pressure by a fuel pump is stored in a common rail at desired pressures, and is injected into the combustion chambers through the injectors, which are arranged to the engine cylinders, each to each cylinder, with the fuel-injection conditions such as an amount of fuel to be delivered and a timing of fuel injection, which are regulated by a controller at the most suitable situations for the engine operating requirements.
A fuel pressure to ensure the injection pressure is maintained constantly in the fuel discharge lines extending from the common rail through injection lines to discharge orifices, which are formed at the distal ends of the injectors that are each provided with a solenoid valve to block or allow the discharge of fuel applied via the injection lines. The controller is to regulate both the fuel pressure in the common rail and the solenoid valves in the injectors to spray the high-pressure fuel out of the injectors under the desired fuel-injection conditions, which are the most suitable for the engine operating requirements. Of these common-rail fuel-injection systems, there is a type in which the actuation of the solenoid valves makes use of a part of the high-pressure fuel as a working fluid to operate the injectors.
An example of a conventional common-rail fuel-injection system will be explained below with reference to
FIG. 5. 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
of, for example, a variable stroke plunger type, through a fuel line
7
. The high-pressure, fuel-supply pump
8
is driven by the output of the engine, which intensifies the fuel to a high pressure desired depending on the engine operating requirements, and supplies the pressurized fuel into the common rail
2
through another fuel line
9
. The fuel-supply pump
8
is also provided with a fuel flow-rate control valve
14
, where the fuel pressure in the common rail
2
is maintained at the preselected high-pressure level. The fuel relieved from the fuel-supply pump
8
is allowed to flow back the fuel tank
4
through a fuel-return line
10
. 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
. The unconsumed fuel remaining in each injector
1
out of the fuel fed through the injection lines
3
into the injectors
1
may return to the fuel tank
4
through a fuel-recovery line
11
.
The controller
12
of an electronically-controlled unit is applied with various signals of sensors monitoring the engine operating conditions, such as a cylinder-identification sensor, a crankshaft position sensor for detecting the engine rpm Ne and top dead center TDC, a throttle-position sensor depending on the depression Ac of an accelerator pedal, an engine coolant temperature sensor, an intake manifold pressure sensor and the like. The controller
12
is also applied with a detected single as to a fuel pressure in a common-rail
2
, or a common-rail pressure, which is reported from a pressure sensor
13
installed in the common rail
2
. The controller unit
12
may regulate the fuel injection conditions on the injectors
1
such as the injection timing (the instant the injection starts and the duration of injection) and the amount of fuel injected or the others, depending on the signals issued from the sensors, to thereby operate the engine with the engine output, which is the most suitable for engine operating requirements. Although the injection of fuel out of the injectors
1
consumes the fuel in the common rail
2
, resulting in lowering the fuel pressure in the common rail
2
, the controller unit
12
actuates the fuel flow-rate control valve
14
of the fuel supply-pump
8
, 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 or ensures the fuel pressure that might be desired in accordance with the engine operating requirements.
The injector
1
constructed as shown in
FIG. 6
is installed through a hermetic sealing member in a port bored in a basement such as a cylinder head. The injector
1
is communicated at an upper section thereof with the associated injection line
3
through a high-pressure fuel inlet coupling
30
. The injector
1
is made therein with fuel passages
21
,
22
comprising a fuel-flow line in combination with the associated injection line
3
. The high-pressure fuel applied via the fuel passages
21
,
22
is allowed to reach a discharge orifice
25
through a fuel sac
23
and a clearance around the needle valve
24
. Thus, the instant the needle valve
24
is lifted to open the discharge orifice
25
, the fuel is injected out of the discharge orifice
25
into the combustion chamber.
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 injector
1
has at the head section thereof a solenoid-operated actuator
26
comprising a solenoid valve. A solenoid
28
of the solenoid-operated actuator
26
is applied with a control current through a signal line
27
, depending on a command pulse issued from the controller
12
. Upon energizing the solenoid
28
, an armature
29
is lifted to open a valve
32
arranged at one end of a fuel path
31
, so that the fuel pressure of fuel fed in a pressure-control chamber
30
via the fuel passages is relieved through the fuel path
31
. A control piston
34
is arranged for axial linear movement in an axial recess
33
formed in the injector
1
. As the resultant force of the reduced fuel pressure in the pressure-control chamber
30
with the spring force of a return spring
35
, acting on the control piston
34
to push it downward, is made less than the upward force exerted on the control piston
34
owing to the fuel pressure acting on a tapered surface
36
exposed to the fuel sac
23
, the control piston
34
moves upwards. As a result, the needle valve
24
lifts to allow the fuel to spray out of the discharge orifice
25
. It will be understood that a timing of fuel injection is defined by the instant the needle valve
24
starts lifting while the amount 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
.
It is commonly found that the relation of the amount of fuel injected out of the injector
1
with the pulse width of command pulse issued from the controller
12
is mapped or plotted for various choices of a parameter: the common-rail pressure Pr. With the common-rail pressure Pr being at constant, the amount of fuel injected increases in proportion to the command pulse becoming large in pulse width. In contrast, on the pulse width being kept at constant, the higher the common-rail pressure Pr is, the greater is the amount of fuel injected per cycle. On the other hand, the fuel injection usually starts or ceases with a fixed time lag after the fall time and rise time of the command pulse. Thus, the inj
Browdy and Neimark
Isuzu Motors Limited
Miller Carl S.
LandOfFree
Common-rail fuel-injection system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Common-rail fuel-injection system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Common-rail fuel-injection system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2606668