Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2000-01-13
2001-05-01
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S467000, C123S514000, C123S458000, C417S540000
Reexamination Certificate
active
06223725
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high-pressure fuel supply assembly used in a cylinder-injected engine, for example.
2. Description of the Related Art
FIG. 6
is a block diagram showing a construction of a conventional high-pressure fuel supply assembly
100
, and
FIG. 7
is a partially cut away general cross section of the high-pressure fuel supply assembly
100
.
This high-pressure fuel supply assembly
100
includes:
a low-pressure regulator for pressurizing low-pressure fuel to a predetermined pressure, the low-pressure regulator being disposed in a low-pressure fuel intake passage
3
through which flows low-pressure fuel conveyed by a low-pressure fuel pump
2
within a fuel tank
1
;
a low-pressure damper
5
for absorbing surges in the low-pressure fuel, the low-pressure damper
5
being disposed in the low-pressure fuel intake passage
3
;
a high-pressure fuel pump
6
for pressurizing low-pressure fuel from the low-pressure damper
5
and discharging it into a high-pressure fuel discharge passage
7
;
a high-pressure damper
8
for absorbing surges in the high-pressure fuel flowing through the high-pressure fuel discharge passage
7
;
a high-pressure regulator
10
for adjusting high-pressure fuel to a predetermined pressure, the high-pressure regulator
10
being disposed in a branch passage
9
branching from the high-pressure fuel discharge passage
7
at a branch portion
18
; and
an orifice
11
disposed in the high-pressure fuel discharge passage
7
between the high-pressure damper
8
and the branch portion
18
. Moreover,
12
are filters, and
17
is a drainage pipe connecting the high-pressure regulator
10
to the fuel tank
1
.
The above high-pressure fuel pump
6
includes: a valve assembly
20
for opening and closing the low-pressure fuel intake passage
3
and the high-pressure fuel discharge passage
7
; and a high-pressure fuel supply body
21
for pressurizing low-pressure fuel from the low-pressure fuel intake passage
3
and discharging it into the high-pressure fuel discharge passage
7
.
FIG. 8
is a cross section of the valve assembly
20
, the valve assembly
20
including: a first plate
22
; a second plate
23
; and a thin, flat valve main body
19
positioned between the first and second plates
22
and
23
. A first fuel inlet
24
connected to the low-pressure fuel intake passage
3
and a first fuel outlet
25
connected to the high-pressure fuel discharge passage
7
are formed in the first plate
22
, the inside dimensions of the first fuel outlet
25
being larger than the inside dimensions of the first fuel inlet
24
. A second fuel inlet
26
having inside dimensions larger than those of the first fuel inlet
24
and a second fuel outlet
27
having inside dimensions smaller than those of the first fuel outlet
25
are formed in the second plate
23
. The valve main body
19
is provided with: an intake-side tongue
28
interposed between the first fuel inlet
24
and the second fuel inlet
26
; and a discharge-side tongue
29
interposed between the first fuel outlet
25
and the second fuel outlet
27
.
The high-pressure fuel supply body
21
includes:
a casing
30
housing the valve assembly
20
inside a first recess
30
a;
a cylindrical sleeve
31
housed in surface contact with the second plate
23
of the valve assembly
20
;
a piston
33
slidably inserted inside the sleeve
31
forming a fuel pressurization chamber
32
in cooperation with the sleeve
31
; and
a first spring
36
disposed between a recessed bottom surface
34
of the piston
33
and a holder
35
, the spring
36
applying force to the piston
33
in a direction which expands the volume of the fuel pressurization chamber
32
.
The high-pressure fuel supply body
21
also includes:
a housing
37
fitted over the sleeve
31
;
a ring-shaped securing member
38
securing the valve assembly
20
, the sleeve
31
, and the housing
37
inside the first recess
30
a
of the casing
30
by fitting over the housing
37
and engaging the first recess
30
a
of the casing
30
by means of a male thread portion formed on an outer circumferential surface of the securing member
38
;
a metal bellows
40
disposed between the housing
37
and a receiving portion
39
;
a second spring
41
compressed and disposed around the outside of the bellows
40
between the housing
37
and a holder
42
; and
a bracket
43
disposed to surround the second spring
41
, the bracket
43
being secured to the casing
30
by a bolt (not shown).
The high-pressure fuel supply body
21
also includes:
a tappet
44
slidably disposed in a slide bore
43
a
in an end portion of the bracket
43
;
a pin
45
rotatably suspended to follow the shape of a cam (not shown) as a cam shaft rotates and to reciprocate the piston
33
; and
a bush
46
and a cam roller
47
each rotatably fitted onto the pin
45
.
The above high-pressure damper
8
is screwed into a second recess
30
b
in the casing
30
. The high-pressure damper
8
includes:
a first case
50
;
a second case
51
disposed opposite the first case
50
, the second case
51
forming a space in cooperation with the first case
50
; and
a thin, flat disk-shaped stainless steel diaphragm
54
dividing the space into a back-pressure chamber
52
charged with high-pressure gas and a buffer chamber
53
. The diaphragm
54
moves so that the pressure of the fuel flowing into the buffer chamber
53
from the high-pressure fuel discharge passage
7
is equalized with the pressure of the high-pressure gas in the back-pressure chamber
52
, thereby changing the volume inside the buffer chamber and absorbing surges in the fuel in the high-pressure fuel discharge passage
7
.
In a high-pressure fuel supply assembly
100
having the above construction, the piston
33
is reciprocated by the rotation of the cam secured to the cam shaft of an engine (not shown) by means of the cam roller
47
, the bush
46
, the pin
45
, and the tappet
44
.
When the piston
33
is descending (during the fuel intake stroke), the volume of the inside of the fuel pressurization chamber
32
increases and the pressure inside the fuel pressurization chamber
32
decreases. When the pressure inside the fuel pressurization chamber
32
falls below the pressure at the first fuel inlet
24
, the intake-side tongue
28
of the valve main body
19
bends towards the second fuel inlet
26
, allowing fuel in the low-pressure fuel supply passage
3
to flow through the first fuel inlet
24
into the fuel pressurization chamber
32
.
When the piston
33
is ascending (during the fuel discharge stroke), the pressure inside the fuel pressurization chamber
32
increases, and when the pressure inside the fuel pressurization chamber
32
rises above the pressure at the first fuel outlet
25
, the discharge-side tongue
29
of the valve main body
19
bends towards the first fuel outlet
25
, allowing fuel in the fuel pressurization chamber
32
to flow through the first fuel outlet
25
and the high-pressure fuel discharge passage
7
into the high-pressure damper
8
, where fuel pressure surges are absorbed. Fuel pressure surges in the high-pressure fuel are additionally absorbed by the orifice
11
which is disposed downstream from the high-pressure damper
8
. After surges have been removed, the high-pressure fuel is supplied to a delivery pipe
13
via a fuel discharge port
15
and a high-pressure pipe
16
formed in an end portion of the high-pressure fuel discharge passage
7
, and thereafter supplied to each of the cylinders (not shown) of the engine via the fuel injection valves
14
.
In a high-pressure fuel supply assembly
100
of the above construction, the high-pressure damper
8
and the orifice
11
are provided to stabilize the amount of fuel injected by the fuel injection valves
14
and to prevent amplification of surges due to resonation of the delivery pipe
13
which results from fuel pressure surges in the high-pressure fuel discharged from the high-pressure fuel pump
6
.
FIG. 9
shows data obtained experimen
Onishi Yoshihiko
Tochiyama Shigenobu
Mitsubishi Denki & Kabushiki Kaisha
Moulis Thomas N.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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