Pumps – Motor driven – Fluid motor
Reexamination Certificate
2000-08-28
2002-01-22
Koczo, Michael (Department: 3746)
Pumps
Motor driven
Fluid motor
C092S09800R, C092S1030SD
Reexamination Certificate
active
06340294
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a diaphragm type fuel pump which feeds fuel in response to reciprocations of a diaphragm.
2. Description of the Related Art
A diaphragm type fuel pump has been utilized as a fuel supply for feeding fuel to a fuel injector from a fuel tank. An example of such a fuel pump is shown in
FIG. 8
of the accompanying drawings.
A diaphragm type fuel pump
10
comprises: a first body
16
including a fuel introducing path
12
and a fuel discharging path
14
; a second body
18
arranged on one side of the first body
16
; a cover
20
arranged on the other side of the first body
16
; a diaphragm
22
sandwiched between the first and second bodies
16
and
18
; and a membrane
24
sandwiched between the first body
16
and the cover
20
.
A pump chamber
28
is formed between the diaphragm
22
and the first body
16
, while a pulse chamber
30
is formed between the diaphragm
22
and the second body
18
. The pump chamber
28
communicates with both the fuel introducing path
12
and fuel discharging path
14
of the first body
16
. The second body
18
is provided with a pulse introducing path
32
in order to introduce pulse pressure to the pulse chamber
30
. The pulse pressure is generated by an engine and is supplied to the pulse chamber
32
via the pulse introducing path
32
.
A fuel sucking chamber
34
communicating with a fuel tank (not shown) and a fuel discharging chamber
35
communicating with a fuel injector (not shown) are formed between the membrane
24
and the first body
16
. Between the membrane
24
and the cover
20
, a damping chamber
36
faces the fuel sucking chamber
34
via the membrane
24
, and a damping chamber
37
faces the fuel discharging chamber
35
via the membrane
24
.
The fuel sucking chamber
34
communicates with the pump chamber
28
via the fuel introducing path
12
of the first body
16
, while the fuel discharging chamber
35
communicates with the pump chamber
28
via the fuel discharging path
14
of the first body
16
. A check valve
38
is provided in the fuel introducing path
12
in order to feed fuel only to the pump chamber
28
from the fuel sucking chamber
38
. Further, a check valve
40
is provided in the fuel discharging path
14
in order to feed fuel only to the fuel discharging chamber
35
.
In this diaphragm type fuel pump
10
, pulse pressure generated in a crank chamber (not shown) of the engine is introduced into the pulse chamber
30
, thereby reciprocating the diaphragm
22
between the pump chamber
28
and the pulse chamber
30
. As a result, fuel introduced into the fuel sucking chamber
34
from the fuel tank is supplied to the fuel injector via the pump chamber
28
and the fuel discharging chamber
35
.
The diaphragm
22
is generally made of a rubber or synthetic resin material. The rubber material becomes hard at a low temperature, and tends not to reciprocate smoothly, thereby reducing the flow rate of the fuel pump. On the contrary, a synthetic resin material that remains flexible regardless of temperature variations has been utilized for snow mobiles or the like which are structured so as to be usable in very cold areas.
FIG. 9
shows the diaphragm
22
made of only synthetic resin in the related art. The diaphragm
22
is flat, and has openings
42
at four corners in which screws (not shown) are received in order to fixedly hold the first body
16
and two lids
18
and
20
.
At normal temperatures, the synthetic resin is hard compared with the rubber material, so that the synthetic resin diaphragm
22
is less flexible than the rubber diaphragm, and takes time to reciprocate. The fuel pump including a synthetic resin diaphragm
22
therefore suffers from a reduced flow rate compared with a fuel pump including a rubber diaphragm
22
.
It is well-known that the flow rate of the diaphragm type fuel pump depends upon a size of an effective diameter X (shown in
FIG. 8
) of the diaphragm
22
. The term “effective diameter” means a diameter of the diaphragm in which the pumping operation is performed. Referring to
FIG. 8
, the effective diameter X of the diaphragm
22
is equal to a diameter of an inner wall of the second body
18
constituting the cylindrical pulse chamber
30
.
FIG. 10
is a graph showing the relationship (N-Q characteristics) between the number N of pulses and flow rate Q of pumps
10
having the synthetic resin diaphragm
22
and two different effective diameters X. In
FIG. 10
, black squares ▪ denote the N-Q characteristics of a fuel pump having a relatively small effective diameter diaphragm (for a maximum flow rate of 42 L/H), and black circles &Circlesolid; denote the N-Q characteristics of a fuel pump having a relatively large effective diameter diaphragm (for a maximum flow rate of 72 L/H). Referring to the N-Q characteristics, it is understood that the effective diameter extensively affects the flow rate of the fuel pump.
In the related diaphragm type fuel pump
10
, a variety of second bodies
18
have been prepared in accordance with required flow rates of the fuel pump. Since the different flow rates mean the necessity of different effective diameters X, the second bodies
18
have been selected in accordance with the required flow rates. As a result, a plurality of dies have been required, which has caused an increase in manufacturing costs of fuel pumps.
The invention is intended to overcome the foregoing problems of the related art, and to provide a diaphragm type fuel pump that includes a single kind of body, meets requirements for a plurality of flow rates and can be manufactured at a reduced cost.
According to the present invention, at very low temperatures, the diaphragm of the fuel pump can assure strokes identical to those of the synthetic resin diaphragm of the related art and having an effective diameter X that is the same as that of the present invention. At normal temperatures, the diaphragm of the invention can assure large strokes compared with those of the synthetic resin diaphragm, and increases necessary flow rates. Therefore, the flow rates can be varied as desired only by exchanging the diaphragm but without replacing the second body. As a result, it is not necessary to prepare a plurality of dies, which is effective in promoting the use of just one type of second body and reducing manufacturing costs.
SUMMARY OF THE INVENTION
In order to accomplish the foregoing object of the invention, there is provided a diaphragm type fuel pump comprising: a fuel sucking chamber and a fuel discharging chamber; a first body having a fuel introducing path communicating with the fuel sucking chamber and a fuel discharging path communicating with the fuel discharging chamber; a diaphragm fixed to the first body using a second body; and a pump chamber constituted by the diaphragm and the first body and communicating with the fuel introducing path and the fuel discharging path. The diaphragm includes an outer diaphragm made of resin and having an opening formed within an effective diameter of the diaphragm, and an inner diaphragm arranged in the opening of the outer diaphragm. Further, the outer and inner diaphragms are mutually fixed using an elastic coupling member.
REFERENCES:
patent: 2307066 (1943-01-01), Paulus
patent: 2730131 (1956-01-01), Asp et al.
patent: 2764097 (1956-09-01), Browne
patent: 6173959 (2001-01-01), Oikawa et al.
Chiba Noriaki
Kubota Kenichi
Koczo Michael
Lorusso & Loud
Mikuni Adec Corporation
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