Pumps – With condition responsive pumped fluid control – Pressure responsive relief or bypass valve
Reexamination Certificate
2001-11-20
2003-06-17
Koczo, Michael (Department: 3746)
Pumps
With condition responsive pumped fluid control
Pressure responsive relief or bypass valve
C417S395000
Reexamination Certificate
active
06579074
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field Of The Invention
The present invention relates to a diaphragm type fuel pump in which fuel is introduced and discharged in accordance with strokes of a diaphragm.
2. Description Of Related Art
A diaphragm type fuel pump has been used up to now in order to introduce fuel into a fuel injector from a fuel tank. In the fuel pump, a diaphragm is operated using pulsating pressure of an engine in order to introduce and discharge fuel. Depending on the type of engine, fuel discharge pressure can sometimes become too large. Therefore, there are some diaphragm type fuel pumps provided with a fuel pressure regulating mechanism.
Japanese Patent Laid-Open No. Hei 11-201043 discloses a diaphragm type fuel pump including a fuel pressure regulating mechanism. Referring to
FIG. 9
of the accompanying drawing figures, a fuel pump
70
includes: a fuel intake chamber
71
; a fuel discharge chamber
72
; a pump chamber
73
; a fuel intake path
74
for introducing fuel from a fuel tank (not shown) to the fuel intake chamber
71
; and a fuel discharge path
75
for discharging fuel to a fuel injector and or the like (not shown). Further, a fuel pressure regulating mechanism
76
is provided in the fuel discharge chamber
72
. A fuel return pipe
77
connects the fuel pressure regulating mechanism
76
and the fuel intake chamber
71
. The pressure regulating mechanism
76
is positioned outside the fuel pump
70
, and returns the fuel from the fuel discharge chamber
72
to the fuel intake chamber
71
via the fuel return pipe
77
whenever the fuel pressure in the fuel discharge chamber
72
exceeds a predetermined value.
FIGS. 10 and 11
show a diaphragm type fuel pump
80
including a fuel pressure regulating mechanism (i.e., constituted of spill valve
96
and spring
98
) which is structurally different from the fuel pressure regulating mechanism
76
of the fuel pump
70
shown in
FIG. 9. A
body
81
of the fuel pump
80
includes a partition wall
82
, which defines, together with a diaphragm
84
, a fuel intake chamber
86
and a fuel discharge chamber
88
. Fuel is introduced into the fuel intake chamber
86
via a fuel intake path
90
, and is discharged from the fuel discharge chamber
88
via a fuel discharge path
92
. A path
94
is formed in the partition wall
82
in order to connect the fuel intake chamber
86
and the fuel discharge chamber
88
. A spill valve (ball valve)
96
and a spring
98
are provided in the fuel intake chamber
86
in order to open and close the path
94
.
Further, a cylindrical guide
99
is provided in the fuel intake chamber
86
in order that the spill valve
96
and the spring
98
move in a predetermined axial direction. The fuel intake path
90
, fuel discharge path
92
, path
94
and cylindrical guide
99
are substantially coaxial. A valve seat
100
is positioned at one end of the path
94
which is formed in the partition wall
82
and opens to the fuel intake chamber
86
.
When a pressure in the fuel discharge chamber
88
is equal or less than the predetermined value, the spill valve
96
is pushed by the spring
98
, sits on the valve seat
100
and closes the path
94
, so that no fuel is returned to the fuel intake chamber
86
from the fuel discharge chamber
88
. Otherwise, the pressure larger than the predetermined value pushes the spill valve
96
toward the fuel intake chamber
86
against the spring
98
and the pressure in the fuel intake chamber
86
, thereby opening the path
94
. Therefore, the high pressure fuel in the fuel discharge chamber
88
is returned to the fuel intake chamber
86
, thus regulating the pressure of the fuel discharged via the fuel discharge path
92
.
In the fuel pump shown in
FIG. 9
, the fuel pressure regulating mechanism
76
is arranged further out than the outer diameter D of the pump chamber
73
(shown by a dashed circle), which means that the fuel pump
70
is enlarged and becomes heavy because of the pressure regulating mechanism
76
, and there is a problem related to fitting of the fuel pump
70
.
Further, the fuel pump
70
should be provided with a fuel return pipe
77
running over an exterior thereof, which would lead to an increase in the cost of the fuel pump
70
and a problem of fitting.
In the diaphragm type fuel pump
80
of
FIGS. 10 and 11
, the fuel pressure regulating mechanism constituted by the spill valve
96
and the spring
98
is housed in the fuel intake chamber
86
, which is effective in making the fuel pump
80
compact.
However, this fuel pump seems to suffer from the following three problems.
(1) Since the valve seat
100
at the opening of the path
94
near the fuel intake chamber
86
is positioned behind the cylindrical guide
99
, the valve seat
100
is far from the fuel intake path
90
in the body
81
, which makes it difficult to perform surface treatment of the valve seat
100
and to check plane accuracy thereof.
(2) Both the fuel intake path
90
and the path
94
are linearly positioned with the spill valve
96
interposed therebetween. Fuel flowing through the fuel intake path
90
and fuel flowing through the path
94
may adversely affect the operation of the spill valve
96
, or may interfere with each other.
(3) The spring
98
may become long depending upon a mounting structure, which would cause variations in the dimensions of the spring
98
. This would lead to varying performances of the spring
98
.
Because of the above-described problems with respect to the fuel pressure regulating mechanisms of the foregoing fuel pumps
70
and
80
, it is difficult to have the fuel pumps
70
and
80
function as desired and assure reliable performance.
SUMMARY OF THE INVENTION
The invention is devised in order to overcome the foregoing problems of the related art, and provides a compact diaphragm type fuel pump whose performance is reliable.
In order to accomplish the foregoing objects of the present invention, a diaphragm type fuel pump is provided which comprises; a fuel intake chamber; a fuel discharge chamber; a pump body; a diaphragm; a pump chamber; a return path; and a pressure control mechanism. The pump body has a fuel intake path communicating with the fuel intake chamber and a fuel discharge path communicating with the fuel discharge chamber. The diaphragm is fixedly attached to the pump body via a bottom body. The pump chamber is defined by the diaphragm and the pump body and communicates with the fuel intake path and the fuel discharge path. The return path connects the fuel intake chamber and the fuel discharge chamber. The pressure control mechanism is for returning fuel from the fuel discharge chamber to the fuel intake chamber via the return path when pressure in the fuel discharge chamber exceeds a predetermined value. The return path is formed in the pump body. A cavity is formed between outer and inner parts of the pump body, communicates with the return path via one end thereof and with the fuel intake or discharge chamber via the other end thereof and perpendicularly extends to the diaphragm. The pressure regulating mechanism is housed in the cavity, and is positioned inside an outer diameter of the pump chamber.
REFERENCES:
patent: 1848546 (1932-03-01), Redmond
patent: 2146398 (1939-02-01), Lafferty
patent: 2405466 (1946-08-01), Tabb
patent: 2942550 (1960-06-01), Carter
patent: 3386388 (1968-06-01), Rosenberg
patent: 4807573 (1989-02-01), Schierling et al.
patent: 6340294 (2002-01-01), Kubota et al.
patent: 11-201043 (1999-07-01), None
Koczo Michael
Mikuni Adec Corporation
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