Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1999-06-28
2001-04-03
Yeun, Henry C. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C239S124000
Reexamination Certificate
active
06209524
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel-injection apparatus adapted to direct-injection engines.
2. Description of the Prior Art
Of the various fuel-injection apparatus that have been conventionally developed, for example, the pressure-accumulated, fuel-injection apparatus is widely used, in which fuel stored in the common rail under pressure is injected into the combustion chambers by the closure and open of the solenoid-operated valves provided on the heads of the injectors. A fuel-injection apparatus, for example, shown in
FIG. 5
, has a needle valve
59
that is movable in a nozzle body
57
for a reciprocating manner to open and close discharge orifices
58
at the tip of the nozzle body
57
, the needle valve
59
being constantly urged by the action of a closing spring
60
to close the discharge orifices
58
.
The nozzle body
57
is provided therein with a fuel passage
62
for allowing the fuel fed under high pressure from the common rail to flow into a fuel sac
61
, a fuel passage
64
for allowing the fuel fed under high pressure from the common rail to flow into a balance chamber
63
, a fuel passage
67
for communicating the balance chamber
63
with a space
66
containing therein a solenoid-operated valve
65
to open and close the fuel passage
67
, a fuel-leak passage
70
for communicating the space
66
with an intermediate chamber
69
surrounding around a slender section
68
of the needle valve
59
, and a fuel discharge passage
71
for communicating the space
66
to a fuel reservoir.
The needle valve
59
has upper and lower sections arranged on the axially opposing end of the spender section
68
, the upper section being made greater in diameter, compared with the lower section. The needle valve
59
is subjected to the hydraulic pressure, or fuel pressure, of the high-pressure fuel forced into the fuel sac
61
, which acts so as to open the discharge orifice
58
, and at the same time subjected to the resultant force of the urging force of the closing spring
60
and the fuel pressure of high-pressure fuel in the balance chamber
63
, which acts so as to close the discharge orifice
58
. As the intermediate chamber
69
is exposed to the low fuel pressure acting through the fuel-leak passage
70
, the high-pressure fuel in the fuel sac
61
and balance chamber
63
may leak out through a clearance between the confronting needle valve
59
and the nozzle body
57
. The fuel leaked out in the intermediate chamber
69
is collected in the reservoir through the fuel-leak passage
70
, intermediate chamber
66
and fuel discharge passage
71
.
When energizing the solenoid-operated valve
65
, a valve body
72
of the solenoid-operated valve
65
is attracted to an electromagnet against an elastic force of a return spring
73
. At this event, the fuel passage
67
is open to the space
66
whereby the balance chamber
63
is relieved through the fuel passage
67
, resulting in the reduction in the fuel pressure therein. The force of fuel pressure acting on the fuel sac
61
is designed greater than the resultant force of the force of fuel pressure acting on the balance chamber
63
with the spring force and, therefore, the needle valve
59
moves upwards, resulting in opening the discharge orifice
58
as shown in FIG.
5
. In contrast, when deenergizing the solenoid-operated valve
65
, the valve body
72
moves downwards by the action of the return spring
73
to thereby close the space
66
at the fuel passage
67
. As a result, the resultant force of the elastic force of the spring
60
with the force of fuel pressure restored in the balance chamber
63
becomes greater than the force of fuel pressure acting in the fuel sac
61
to make the needle valve
59
move downwards thereby closing the discharge orifice
58
.
On the fuel-injection apparatus as described above, however, the fuel leaks constantly out from the intermediate chamber
69
through the fuel passage
67
, namely, the fuel is constantly under the static leakage, in addition to that the fuel leaks out from the balance chamber
63
to the space
66
through the fuel passage
67
at every actuation of the solenoid-operated valve
65
. Moreover, as seen from
FIG. 6
, the amount of static leakage of fuel increases with the increase of the common rail pressure. That is to say, as the pressure in the intermediate chamber
69
is constantly under the low pressure or the atmospheric pressure, the increase of the fuel pressure results in increasing the amount of the leakage of fuel from the fuel sac
61
and balance chamber
63
to the intermediate chamber
69
through the clearance between the confronting needle valve
59
and nozzle body
57
.
To cope with the problem as described just above, a fuel-injection apparatus was developed, which is disclosed in Japanese Patent Laid-Open No.77924/1998. The fuel-injection apparatus, as apparent from
FIG. 7
, has for its object to make sealing with the use of fuel pressure and is comprised of a body having fuel-discharge orifice equivalent to the reference number
58
, a needle valve
75
movable in a space
74
in the body in a reciprocating manner so as to open and close at its one axial end the fuel-discharge orifice, a balance chamber
76
in which the needle valve
75
is exposed at its axially opposite end serving as a pressure-supporting face to control the amount of lift of the needle valve
75
, a fuel-supply passage
77
for applying the fuel pressure to the balance chamber
76
, a fuel-discharge passage for relief of the fuel pressure in the balance chamber
76
, a valve
79
for opening and closing the fuel-discharge passage
78
, and an actuator for operating the valve
79
. The actuator-operated valve
79
is composed of a valve stem
80
extending through the fuel-discharge passage
78
into the balance chamber
76
, and a valve face provide at the tip of the valve stem
80
so as to make a contact with a valve seat formed at the ingress of the fuel-discharge passage
78
. The actuator-operated valve
79
is made of the valve stem
80
and valve body
81
that are formed integrally with each other.
When the actuator is not energized, a return spring
82
forces the valve stem
80
upwards through a spring shoe
83
while the valve face abuts against its associated valve seat and, therefore, the actuator-operated valve
79
closes the fuel-discharge passage
78
. On this event, the high-pressure fuel from the common rail is applied to the fuel sac, shown at
61
in FIG.
5
. The fuel in the sac forces the needle valve
75
to the direction of lift. Moreover, the fuel pressure applied to the balance chamber
76
through the fuel passage
77
acts on a pressure-support face
87
. At this instant, the resultant force of the spring force of a diaphragm spring
88
and the force of fuel pressure acting on the pressure-support face
87
of the needle valve
75
exceeds the force of fuel pressure applied in the fuel sac, which is exerted on the needle valve
75
to open the discharge orifice, so that the needle valve
75
is held closed to stop the fuel injection out of the discharge orifice.
The instant the actuator is energized, the valve stem
80
is forced downwards in
FIG. 7
against the compressed spring force of the return spring
82
, moving the valve face of the valve body
81
off its seat, whereby the actuator-operated valve
79
opens the fuel-discharge passage
78
. The fuel passage
77
has the effect of a kind of iris, which renders the flow of fuel in the fuel passage
77
smaller than that in the fuel-discharge passage
78
. Therefore, opening the fuel-discharge passage
78
results in relieving the balance chamber
76
of the fuel pressure to the space
74
. The instant the fuel pressure in the balance chamber
76
is relieved, the force to move the needle valve
75
towards opening overcomes the resultant force of the spring force of the diaphragm spring
88
and the fuel force acting on the pressure-support face
87
of the needle valve
75
, which urges the needle va
Browdy and Neimark
Gimie Mahmoud M
Isuzu Motors Limited
Yeun Henry C.
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