Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2000-01-11
2001-04-10
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S495000
Reexamination Certificate
active
06213094
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high-pressure fuel pump installed in a high-pressure fuel supply assembly used in a cylinder-injected engine, for example.
2. Description of the Related Art
FIG. 5
is a block diagram of a conventional high-pressure fuel supply assembly
100
, and
FIG. 6
is a cross section thereof. This high-pressure fuel supply assembly
100
includes: a low-pressure damper
2
for absorbing surges in low-pressure fuel, the low-pressure damper
2
being connected to a low-pressure fuel intake passage
1
through which flows low-pressure fuel from a low-pressure fuel pump (not shown); a high-pressure fuel pump
3
for pressurizing low-pressure fuel from the low-pressure damper
2
; a high-pressure damper
5
for absorbing surges in the high-pressure fuel flowing through a high-pressure fuel discharge passage
4
connected to the high-pressure fuel pump
3
; and a check valve for improving the starting of an engine by maintaining fuel in delivery pipes
8
at high pressure even when the engine is stopped, the check valve being disposed between the high-pressure damper
5
and a fuel supply port
7
and opening when the fuel pressure on the delivery pipe
8
side is lower than the fuel pressure on the high-pressure damper
5
side. Moreover, in the drawings,
17
is a passage connecting to a high-pressure regulator (not shown) from between the fuel supply port
7
and the delivery pipe
8
.
The above low-pressure damper
2
is mounted in a first recess
10
a
in a casing
10
. The low-pressure damper
2
includes: a cylindrical holder
14
; a base
13
having a ball
11
disposed in a bore
12
; and a metal bellows
15
disposed inside the holder
14
.
The above high-pressure fuel pump
3
includes: a valve assembly
20
for opening and closing the low-pressure fuel intake passage
1
and the high-pressure fuel discharge passage
4
; and a high-pressure fuel supply body
21
for pressurizing low-pressure fuel and discharging it into the high-pressure fuel discharge passage
4
.
FIG. 7
is a cross section of the valve assembly
20
, the valve assembly
20
being composed of 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
1
and a first fuel outlet
25
connected to the high-pressure fuel discharge passage
4
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
10
housing the valve assembly
20
inside a second recess
10
b;
a cylindrical sleeve
30
housed in surface contact with the second plate
23
of the valve assembly
20
; a piston
33
slidably inserted inside the sleeve
30
forming a fuel pressurization chamber
32
in cooperation with the sleeve
30
; 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
30
; a ring-shaped securing member
38
securing the valve assembly
20
, the sleeve
30
, and the housing
37
inside the second recess
10
b
of the casing
10
by fitting over the housing
37
and engaging the second recess
10
b
of the casing
10
by 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
10
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 in the tappet
44
; a bush
46
rotatably disposed on the pin
45
; and a cam roller
47
rotatably disposed on the bush
46
, the cam roller
47
contacting a cam (not shown) secured to a cam shaft (not shown), following the shape thereof, and reciprocating the piston
33
.
The above high-pressure damper
5
is screwed into a third recess
10
c
in the casing
10
. The high-pressure damper
5
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
4
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
4
.
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
1
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 fuel discharge passage
4
into the high-pressure damper
5
, where fuel pressure surges are absorbed. High-pressure fuel is then supplied to the delivery pipes
8
via the check valve
6
and the fuel supply port
7
, and thereafter supplied to the fuel injection valves
9
, which inject fuel into each of the cylinders (not shown) of the engine.
In the high-pressure fuel pump
3
of the high-pressure fuel supply assembly
100
of the above construction, the housing
37
, the sleeve
30
, and the valve assembly
20
are held inside the second recess
10
b
by the securing member
38
. Because the securing member
38
presses on an outer circumferential portion of the housing
37
, the valve assembly
20
is subjected to a large load from the casing
10
at an outer circumferential portion of the valve assembly
20
, and to an extremely small load at a central portion of the valve assembly
20
.
FIG. 6
shows the distribution of the load at that time, and it can be seen that
Arima Takemi
Morikaku Hideki
Ojima Kouichi
Onishi Yoshihiko
Mitsubishi Denki & Kabushiki Kaisha
Moulis Thomas N.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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