Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2002-11-06
2004-11-16
Gimie, Mahmoud (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S506000
Reexamination Certificate
active
06817340
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high-pressure fuel supply system used, for example, for a direct injection type internal combustion engine, and more particularly, it relates to a high-pressure fuel supply system including an electromagnetic valve arranged on a relief passage and controlled to be opened for a prescribed period on the discharge stroke of a fuel pump for controlling the amount of fuel discharged therefrom.
2. Description of the Related Art
FIG. 4
is a circuit diagram including a high-pressure fuel supply system
1
.
This high-pressure fuel supply system
1
includes a low-pressure damper
3
arranged on a low-pressure fuel suction passage
2
for absorbing the pulsation of a low-pressure fuel, a high-pressure fuel pump
5
for pressurizing the low-pressure fuel from a low-pressure damper
3
to discharge it to a high-pressure fuel discharge passage
4
, a relief passage
6
connecting between a suction side of the high-pressure fuel pump
5
and a pressurization chamber, and an electromagnetic valve
7
arranged on the relief passage
6
and being operated to open for adjusting the amount of fuel discharged from the high-pressure fuel pump
5
. The high-pressure fuel pump
5
has a suction valve
8
and a discharge valve
9
.
In the neighborhood of the high-pressure fuel supply system
1
, there are provided a fuel tank
10
, a low-pressure fuel pump
11
arranged in the fuel tank
10
, a low-pressure regulator
12
arranged on the low-pressure fuel suction passage
2
for regulating the low-pressure fuel at a constant pressure, a relief valve
15
arranged on a drain pipe
14
branched from the high-pressure fuel discharge passage
4
at a branch portion
13
, a delivery pipe
16
connected with the high-pressure fuel discharge passage
4
, a fuel injection valves
17
connected with the delivery pipe
16
, and a filter
18
connected with the low-pressure fuel pump
11
.
FIG. 5
is a cross sectional view of the high-pressure fuel supply system
1
of FIG.
4
.
The high-pressure fuel pump
5
of the high-pressure fuel supply system
1
includes a plate
21
having a fuel suction port
22
connected with the low-pressure fuel suction passage
2
and a fuel discharge port
23
connected with the high-pressure fuel discharge passage
4
, a sleeve
24
of a cylindrical shape, a valve disc
25
having the suction valve
8
and arranged between an upper end face of the sleeve
24
and the plate
21
, the discharge valve
9
arranged on the high-pressure fuel discharge passage
4
, a piston
26
slidably received in the sleeve
24
to define a fuel pressurization chamber
27
in cooperation with the sleeve
24
for pressurizing the fuel that flows into the fuel pressurization chamber
27
, and a spring
29
arranged under compression between a receiving portion
28
and a bracket
30
for urging the piston
26
in a direction to enlarge the volume of the fuel pressurization chamber
27
.
In addition, the high-pressure fuel pump
5
includes a casing
31
having the low-pressure fuel suction passage
2
and the high-pressure fuel discharge passage
4
, a housing
32
fixedly attached to the casing
31
, and a tappet
33
slidably arranged at a tip end of the housing
32
and adapted to be placed into abutting engagement with a cam
35
fixedly secured to a camshaft
34
for causing the piston
26
to reciprocate in accordance with the profile of the cam
35
.
FIG. 6
is an enlarged view of the electromagnetic valve
7
of FIG.
5
. The electromagnetic valve
7
includes a plunger
40
having a fuel passage
40
a
formed therein along the axis thereof, a body
41
of a cylindrical shape that is fitted in the casing
31
and a housing
44
and slidably receives the plunger
40
of a cylindrical shape, a valve seat
42
arranged in pressure contact with an end of the plunger
40
and welded to the body
41
, a stopper
43
fixedly mounted on the housing
44
for limiting the amount of lift of the plunger
40
upon opening thereof, a columnar armature
45
made of a magnetic material and welded to the plunger
40
, a columnar core
46
arranged in opposition to the armature
45
, a solenoid
47
wound around the core
46
, a spring
48
arranged under compression inside the core
46
for urging the plunger
40
in a direction toward the valve seat
42
and a seal member
200
made of non-magnetic material which is austenitic stainless steel and welded to the housing
44
and the core
46
.
Between the casing
31
and the housing
44
around the stopper
43
, there is arranged an elastic O ring
49
for sealing fuel and absorbing collision sounds generated when the plunger
40
collides with the stopper
43
.
With the high-pressure fuel supply system
1
as constructed above, the piston
26
is caused to reciprocate through the intermediary of the tappet
33
in accordance with the rotation of the cam
35
fixedly attached to the camshaft
34
of the engine.
When the piston
26
descends (on the fuel suction stroke), the volume of the fuel pressurization chamber
27
increases to reduce the pressure therein. As a result, the suction valve
8
is opened so that the fuel in the low-pressure fuel supply passage
2
flows into the fuel pressurization chamber
27
through the fuel suction port
22
.
When the piston
26
ascends (on the fuel discharge stroke), the pressure in the fuel pressurization chamber
27
increases to open the discharge valve
9
so that the fuel in the fuel pressurization chamber
27
is supplied to the delivery pipe
16
through the fuel discharge port
23
and the high-pressure fuel discharge passage
4
. Thereafter, the fuel is supplied to the fuel injection valves
17
which serve to inject the fuel to respective cylinders (not shown) of the engine.
In addition, when the solenoid
47
is energized, a closed magnetic circuit is formed by the core
46
, the yoke
70
, the housing
44
and the armature
45
, as a result of which magnetic attraction is generated between the armature
45
and the core
46
. In accordance with the magnetic attraction, the plunger
40
is caused to move away from the valve seat
42
against the resilient force of the spring
48
, thus opening the electromagnetic valve
7
. As a consequence, the relief passage
6
is placed in fluid communication with the fuel pressurization chamber
27
through the fuel passage
40
a
in the plunger
40
and the communication port
37
so that the pressure in the fuel pressurization chamber
27
is reduced to permit the discharge valve
9
to be closed, thereby stopping the supply of the high-pressure fuel to the fuel injection valves
17
.
On the other hand, when the solenoid
47
is deenergized, the magnetic attraction between the armature
45
and the core
46
rapidly decreases. When the magnetic attraction decreases below the resilient force of the spring
48
, the plunger
40
is caused to start moving in a direction toward the valve seat
42
under the action of the resilient force of the spring
48
so that it is placed in pressure contact with the valve seat
42
. Consequently, the electromagnetic valve
7
is closed to shut off the relief passage
6
.
FIG. 7
is a timing chart that shows the relation between the driving of the electromagnetic valve
7
and the suction and discharge strokes of the high-pressure fuel pump
5
. In
FIG. 7
, an upper portion represents the amount of plunger lift; a black painted portion represents an area where fuel is discharged from the high-pressure fuel pump
5
; and a lower portion represents the driving state of the electromagnetic valve
7
. As can be seen from this figure, the amount of fuel discharged from the high-pressure fuel pump
5
on the fuel discharge stroke can be adjusted by controlling the driving time of the electromagnetic valve
7
.
With the high-pressure fuel supply system
1
of the above configuration, the amount of lift of the plunger
40
is limited by the collision of the plunger
40
with the stopper
43
when the electromagnetic valve
7
is opened, and a collision
Onishi Yoshihiko
Tochiyama Sigenobu
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