Pumps – Expansible chamber type – Biasing means effects eduction stroke of abutment driven,...
Reexamination Certificate
2001-12-18
2003-12-02
Tyler, Cheryl J. (Department: 3746)
Pumps
Expansible chamber type
Biasing means effects eduction stroke of abutment driven,...
C417S470000
Reexamination Certificate
active
06655933
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel pump to be actuated by engine power.
2. Description of Related Art
Japanese Laid-Open Publication No. 2000-282994 discloses a prior art fuel pump which utilizes rotation of an eccentric cam by an engine by converting the rotation of the eccentric cam into reciprocating motion of a piston.
FIG. 6
of the accompanying drawings shows such a fuel pump
10
, and
FIG. 7
shows a detailed cross section of essential parts of the fuel pump shown in FIG.
6
. The fuel pump
10
includes a bottom body part
14
which is fixedly attached to a cylinder head cover
12
of an engine, a top body part
16
mounted on the bottom body part
14
, a cover
18
on the top body part
16
, and a piston
20
reciprocally mounted in the bottom body part
14
. As shown in
FIG. 6
, the cover
18
is positioned on top of the top body part
16
, and the bottom body part
14
is mounted under the top body part
16
.
The fuel pump
10
is to be arranged with a rotary shaft
22
positioned below the piston
20
and having an eccentric cam
24
. The shaft
22
is rotated by engine power, and the eccentric cam
24
is positioned at a tip of the piston
20
. A piston spring
26
is provided between the piston
20
and the bottom body part
14
, and urges the piston
20
toward the eccentric cam
24
so the piston remains in contact with the eccentric cam
24
. The piston
20
thus vertically reciprocates in the bottom body part
14
in response to the rotation of the eccentric cam
24
.
A diaphragm assembly
30
is coupled to the piston
20
, and includes a diaphragm
28
and a rod
32
coupled to the diaphragm
28
. An engagement member
36
has an elongated hole
34
along an axis thereof, and is fixedly attached to a tip of the rod
32
. Further, a pin
38
is fixedly attached to the piston
20
, and fits in the elongated hole
34
of the engagement member
36
.
The diaphragm
28
is sandwiched between the bottom body part
14
and the top body part
16
, and a seal such as a gasket is sandwiched between the top body part
16
and the cover
18
. In this state, the bottom body part
14
, the top body part
16
and the cover
18
are fixed together using a bolt
42
. A pump chamber
44
is defined by the top body part
16
and the diaphragm
28
, and is present near the top body part
16
. A diaphragm spring
46
is provided between the bottom body part
14
and the diaphragm
28
in order to continuously urge the diaphragm
28
toward the pump chamber
44
(i.e. toward a pump chamber pressurizing position).
An intake chamber
48
and a discharge chamber
50
are independently defined by the top body part
16
and the seal
40
. An intake path
52
is formed in the top body part
16
in order to connect the intake chamber
48
to the pump chamber
44
, and the intake path is opened and closed by an intake (one-way) valve
54
. Further, the top body part
16
has a discharge path
56
formed therein in order to connect the discharge chamber
48
to the pump chamber
44
. The discharge path
56
is opened and closed by a discharge (one-way) valve
58
.
In the fuel pump
10
, the piston
20
vertically reciprocates in response to the rotation of the eccentric cam
24
fixedly attached around the shaft
22
. When both the piston
20
and the diaphragm
28
are moved downward as shown in
FIG. 6
, the discharge. valve
58
closes the discharge path
56
. At the same time, the intake valve
54
is opened, so that fuel is introduced into the pump chamber
44
from the intake chamber
48
via the intake path
52
. Thereafter, when the piston
20
and the diaphragm
28
move upward, the intake valve
54
closes the intake path
52
, and the discharge valve
58
opens the discharge path
56
, so that the fuel is introduced into the discharge chamber
50
from the pump chamber
44
.
The piston spring
26
must be sufficiently strong so as to maintain the piston
20
continuously in contact with the eccentric cam
24
so that the piston
20
reliably follows the rotating eccentric cam
24
. The piston spring
26
is required for the downward movement of the diaphragm
28
toward a depressurizing position to effect a fuel intake action, and thus must have sufficient strength to overcome the resilient biasing force of the diaphragm spring
46
which resists the downward movement of the diaphragm
28
. Further, the larger the diaphragm
28
, the stronger must be the resiliency of the piston spring
26
. Still further, the more resilient the piston spring
26
must be, the more expensive of a material is generally required to form the piston spring, which inevitably makes the piston spring more expensive.
If the piston spring
26
is weakened, the piston
20
will sometimes fail to follow the eccentric cam
24
. In such a case, undesirable noises may be caused due to improper interaction between the piston
20
and the eccentric cam
24
. When the piston spring
26
is strengthened in order to overcome this problem, the pin
38
fixedly attached to the piston
20
may strike against the engagement member
36
fixedly attached to the rod
32
, thereby causing significant shocks and perhaps large knocking noises. Such striking contact will cause damage to the pin
38
at the contact point, as well as to the diaphragm
28
and components adjacent the rod
32
.
SUMMARY OF THE INVENTION
In order to overcome the foregoing problems of the related art, the present invention is intended to provide a fuel pump which does not require expensive material for a piston spring, reduces knocking noises and protects components near colliding portions against damage.
According to the invention, there is provided a fuel pump for pumping fuel in response to rotation of an eccentric cam, the fuel pump comprising: a fuel pump body having a pump chamber; a pumping member-movably provided at the pump chamber for pressurizing and depressurizing the pump chamber, the pumping member being movable between a first pumping member position and a second pumping member position; a piston movably mounted to the fuel pump body and being arranged to be operably engaged with the eccentric cam for movement between first and second ends of a piston stroke, the piston being operably coupled to the pumping member so that the pumping member is caused to move toward the first pumping member position due to the piston moving toward the first end of the piston stroke, and toward the second pumping member position due to the piston moving toward the second end of the piston stroke; a piston-following spring operably engaged with the piston to urge the piston toward the first end of the piston stroke; and a pumping member-moving spring operably engaged with the pumping member to urge the pumping member toward the first pumping member position.
The fuel pump further includes a pumping member spring mechanism urging the pumping member toward the second pumping member position, and the pumping member preferably comprises a diaphragm.
The fuel pump body comprises a first fuel pump body part, and a second fuel pump body part secured to the first fuel pump body part; and the diaphragm is sandwiched between the first and second fuel pump body parts.
The fuel pump further preferably includes a first engagement member coupled to the diaphragm; a second engagement member provided at the piston and being arranged for engagement with the first engagement member; and a plate member positioned between the first engagement member and the pump member-moving spring so as to be urged by the pump member-moving spring toward the first engagement member. The second engagement member is engageable with the first engagement member to limit an amount of movement of the first engagement member relative to the piston. Further, a rod preferably couples the first engagement member to the pumping member; the first engagement member comprises a pin fixed to the rod; and the second engagement member comprises an elongated groove provided in the piston, the pin being movably engaged in the elongated groove.
Mikuni Corporation
Solak Timothy P.
Tyler Cheryl J.
Wenderoth , Lind & Ponack, L.L.P.
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