Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1999-02-16
2001-05-29
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S486000, C123S478000
Reexamination Certificate
active
06237567
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel-injection system having injectors that may inject fuel in accordance with fuel-injection characteristics, which is dependent on operating conditions of an engine.
2. Description of the Prior Art
A fuel-injection system has been well known in which an injector is provided with a needle valve movable in an injector body in a reciprocating manner to open and close injection holes, and a solenoid-operated valve having an electromagnetic actuator that is applied with an actuating current so as to control a hydraulically actuated fluid for driving the needle valve upwards and downwards, whereby the fuel to be injected out of the injector is regulated in injection timing and volume of injected fuel per cycle by a controller unit in response to the operating conditions of the engine.
There have been conventionally known two types of the injector used in the fuel-injection system, one of which is comprised of a solenoid-operated valve to control an ingress of the hydraulically actuated fluid, or hydraulic oil, into the injector body, and a boosting piston to pressurize the fuel in an intensified chamber, whereby the pressurized fuel makes the needle valve move so as to inject the pressurized fuel through the injection holes that have been free from the needle valve. Another type of the injector operates so as to regulate an ingress and egress of the highly pressurized fuel, which is accumulated in a common fuel supply rail, to a controlled pressure chamber in the injector body, whereby the pressurized fuel makes the needle valve move so as to inject the pressurized fuel through the injection holes that have been free from the needle valve.
FIG. 7
shows a prior fuel-injection system in which is incorporated the former type of the injector. The multicylinder engines, for example, four-cylinder or six-cylinder engine, have been dominated in most modern engines to attain the high horsepower. The injectors are each assigned to each cylinder to inject the fuel into the combustion chamber. In the fuel-injection system in
FIG. 7
, the fuel may be fed from a fuel tank
52
to a common fuel supply rail
51
through a fuel filter
54
by the driving of a fuel pump
53
. The common fuel supply rail
51
is communicated with each of the injectors
1
. It will be thus understood that the injectors
1
are constantly supplied with the fuel of the required pressure at their fuel inlets
11
and fuel outlets
12
through the common fuel supply rail
51
. The unconsumed fuel remaining in each injector
1
may return to the fuel tank
52
through a recovery line
55
.
The injectors
1
are supplied with the hydraulically actuating fluid, or high-pressurized oil, from a high-pressure fluid manifold
56
through a solenoid-operated valve
10
. The high-pressure fluid manifold
56
is fed with the fluid in a fluid reservoir
57
through a fluid supply line
61
by the driving of a fluid pump
58
. There are provided a fluid cooler
59
and a fluid filter
60
midway in the fluid supply line
61
. Moreover the fluid supply line
61
is branched into a lubricant line
67
communicating with an oil gallery
62
and a hydraulic fluid line
66
communicated with pressure chambers
8
, shown in
FIG. 8
, in the injectors
1
. A hydraulic pump
63
is provided in the hydraulic fluid line
66
while a flow control valve
64
regulates the fluid supply to the high-pressure fluid manifold
56
from the hydraulic pump
63
. A controller unit
50
is to control both of the flow control valve
64
and solenoids
10
of the injectors
1
. The controller unit
50
is applied with data indicative of the operating conditions of an engine, that is, rotational frequencies detected by a rotational frequency sensor
68
, throttle valve openings detected by a accelerometer
69
and crankshaft angles detected by a crank angle sensor
70
. The controller unit
50
is also input with a hydraulic pressure in the high-pressure manifold
56
, which is detected by a pressure sensor
71
in the high-pressure fluid manifold
56
. The crank angles detected by the crank angle sensor
70
are available to control the beginning and duration of the electric conduction of the actuating current per cycle, in cooperation with signals from sensors indicative that a piston has reached the top dead center or the pre-determined position just before the top dead center of the compression phase at any standard cylinder or each cylinder.
FIG. 8
is an axial cross-sectioned view showing an exemplary injector
1
incorporated in the fuel-injection system in FIG.
7
. The injector
1
is comprised of a nozzle body
2
formed at a distal end thereof with fuel-injection holes
13
, a solenoid body
3
having mounted thereon a solenoid
15
serving as the electromagnetic actuator, an injector body
4
and a fuel supply body
5
. The injector
1
further includes an intensified chamber supplied with fuel from the common fuel supply rail
51
, a pressure chamber
8
supplied with a hydraulically actuating fluid, a boosting piston
9
actuated by the hydraulically actuated fluid from the pressure chamber
8
to apply the pressure to the fuel in the intensified chamber
7
, a return spring
17
for forcing the boosting piston
9
to return to its neutral position, and a casing
6
having a fuel inlet
11
and a fuel outlet
12
, which are communicated with the common fuel supply rail
51
to thereby provide a fuel chamber in the casing
6
. In the injector
1
described just above, a needle valve
23
may move upwards and downwards by the action of the fuel pressure from the intensified chamber
7
to thereby open and close the injection holes
13
. A solenoid-operated valve
10
has a valve body
16
that is actuated by the solenoid
15
to regulate the hydraulically actuated fluid supplied to the pressure chamber
8
. The boosting piston
9
is composed of a radially-enlarged portion
25
and a radially-reduced portion
24
, the former portion
25
being arranged for reciprocating movement in a first concave
26
in the injector body
4
and provided with a bottom face to define partially the pressure chamber
8
, and the latter portion
24
being arranged for reciprocating movement in a second concave
27
and provided with a bottom face to define partially the intensified chamber
7
.
FIG. 9
illustrates fuel-injection characteristics in the injectors, which are expressed as the coordinate relation of an actuating pulse width Pw versus an volume Q of fuel injected per cycle with taking a parameter of a hydraulic pressure in the high-pressure fluid manifold
56
, or a rail pressure Pr. These characteristics may be obtained by the measurement of the volume Q of injected fuel per cycle with respect to the actuating pulse width Pw that is at least longer or equal to a pre-determined width. According to the characteristics, it will be seen that, as the actuating pulse width Pw increases, the duration when the injection holes are open becomes longer and then the volume Q of injected fuel per cycle increases. It will be further understood that the higher the rail pressure Pr is, the higher is the speed of opening the injection holes and the greater is the fuel-injection ratio so that the volume of injected fuel increases.
Disclosed in Japanese Patent Laid-Open No. 49591/1996 is an exemplary fuel-injection system, likewise with the system described above with reference to
FIG. 7
, and an injector adapted to be used in the system. The injector in the above citation is composed of a control valve, an intensifier and a nozzle. Moreover, Published Japanese translations on PCT international publication No. 511527/1994 discloses a similar fuel-injection system and an injector therefor. In these prior fuel-injection systems, controlling the electric conduction timing and duration to the electromagnetic actuator makes the fuel-injection start at the desired beginning of the fuel-injection and continue for the desired duration with the desired fuel-injection pressure, whereby th
Nakano Futoshi
Saiki Suzuhiro
Uchiyama Tadashi
Browdy & Neimark
Isuzu Motors Limited
Moulis Thomas N.
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